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gnu / binutils-gdb / 2786ef85faf16c13029548832c4e4b025bf2624c / . / gdb / arm-tdep.c
blob: d7493f15700a9472b59c825151d7080144db1fac [file] [log] [blame]
/* Common target dependent code for GDB on ARM systems.
Copyright (C) 1988-2021 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include <ctype.h> /* XXX for isupper (). */
#include "frame.h"
#include "inferior.h"
#include "infrun.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "dis-asm.h" /* For register styles. */
#include "disasm.h"
#include "regcache.h"
#include "reggroups.h"
#include "target-float.h"
#include "value.h"
#include "arch-utils.h"
#include "osabi.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "trad-frame.h"
#include "objfiles.h"
#include "dwarf2/frame.h"
#include "gdbtypes.h"
#include "prologue-value.h"
#include "remote.h"
#include "target-descriptions.h"
#include "user-regs.h"
#include "observable.h"
#include "count-one-bits.h"
#include "arch/arm.h"
#include "arch/arm-get-next-pcs.h"
#include "arm-tdep.h"
#include "gdb/sim-arm.h"
#include "elf-bfd.h"
#include "coff/internal.h"
#include "elf/arm.h"
#include "record.h"
#include "record-full.h"
#include <algorithm>
#include "producer.h"
#if GDB_SELF_TEST
#include "gdbsupport/selftest.h"
#endif
static bool arm_debug;
/* Print an "arm" debug statement. */
#define arm_debug_printf(fmt, ...) \
debug_prefixed_printf_cond (arm_debug, "arm", fmt, ##__VA_ARGS__)
/* Macros for setting and testing a bit in a minimal symbol that marks
it as Thumb function. The MSB of the minimal symbol's "info" field
is used for this purpose.
MSYMBOL_SET_SPECIAL Actually sets the "special" bit.
MSYMBOL_IS_SPECIAL Tests the "special" bit in a minimal symbol. */
#define MSYMBOL_SET_SPECIAL(msym) \
MSYMBOL_TARGET_FLAG_1 (msym) = 1
#define MSYMBOL_IS_SPECIAL(msym) \
MSYMBOL_TARGET_FLAG_1 (msym)
struct arm_mapping_symbol
{
CORE_ADDR value;
char type;
bool operator< (const arm_mapping_symbol &other) const
{ return this->value < other.value; }
};
typedef std::vector<arm_mapping_symbol> arm_mapping_symbol_vec;
struct arm_per_bfd
{
explicit arm_per_bfd (size_t num_sections)
: section_maps (new arm_mapping_symbol_vec[num_sections]),
section_maps_sorted (new bool[num_sections] ())
{}
DISABLE_COPY_AND_ASSIGN (arm_per_bfd);
/* Information about mapping symbols ($a, $d, $t) in the objfile.
The format is an array of vectors of arm_mapping_symbols, there is one
vector for each section of the objfile (the array is index by BFD section
index).
For each section, the vector of arm_mapping_symbol is sorted by
symbol value (address). */
std::unique_ptr<arm_mapping_symbol_vec[]> section_maps;
/* For each corresponding element of section_maps above, is this vector
sorted. */
std::unique_ptr<bool[]> section_maps_sorted;
};
/* Per-bfd data used for mapping symbols. */
static bfd_key<arm_per_bfd> arm_bfd_data_key;
/* The list of available "set arm ..." and "show arm ..." commands. */
static struct cmd_list_element *setarmcmdlist = NULL;
static struct cmd_list_element *showarmcmdlist = NULL;
/* The type of floating-point to use. Keep this in sync with enum
arm_float_model, and the help string in _initialize_arm_tdep. */
static const char *const fp_model_strings[] =
{
"auto",
"softfpa",
"fpa",
"softvfp",
"vfp",
NULL
};
/* A variable that can be configured by the user. */
static enum arm_float_model arm_fp_model = ARM_FLOAT_AUTO;
static const char *current_fp_model = "auto";
/* The ABI to use. Keep this in sync with arm_abi_kind. */
static const char *const arm_abi_strings[] =
{
"auto",
"APCS",
"AAPCS",
NULL
};
/* A variable that can be configured by the user. */
static enum arm_abi_kind arm_abi_global = ARM_ABI_AUTO;
static const char *arm_abi_string = "auto";
/* The execution mode to assume. */
static const char *const arm_mode_strings[] =
{
"auto",
"arm",
"thumb",
NULL
};
static const char *arm_fallback_mode_string = "auto";
static const char *arm_force_mode_string = "auto";
/* The standard register names, and all the valid aliases for them. Note
that `fp', `sp' and `pc' are not added in this alias list, because they
have been added as builtin user registers in
std-regs.c:_initialize_frame_reg. */
static const struct
{
const char *name;
int regnum;
} arm_register_aliases[] = {
/* Basic register numbers. */
{ "r0", 0 },
{ "r1", 1 },
{ "r2", 2 },
{ "r3", 3 },
{ "r4", 4 },
{ "r5", 5 },
{ "r6", 6 },
{ "r7", 7 },
{ "r8", 8 },
{ "r9", 9 },
{ "r10", 10 },
{ "r11", 11 },
{ "r12", 12 },
{ "r13", 13 },
{ "r14", 14 },
{ "r15", 15 },
/* Synonyms (argument and variable registers). */
{ "a1", 0 },
{ "a2", 1 },
{ "a3", 2 },
{ "a4", 3 },
{ "v1", 4 },
{ "v2", 5 },
{ "v3", 6 },
{ "v4", 7 },
{ "v5", 8 },
{ "v6", 9 },
{ "v7", 10 },
{ "v8", 11 },
/* Other platform-specific names for r9. */
{ "sb", 9 },
{ "tr", 9 },
/* Special names. */
{ "ip", 12 },
{ "lr", 14 },
/* Names used by GCC (not listed in the ARM EABI). */
{ "sl", 10 },
/* A special name from the older ATPCS. */
{ "wr", 7 },
};
static const char *const arm_register_names[] =
{"r0", "r1", "r2", "r3", /* 0 1 2 3 */
"r4", "r5", "r6", "r7", /* 4 5 6 7 */
"r8", "r9", "r10", "r11", /* 8 9 10 11 */
"r12", "sp", "lr", "pc", /* 12 13 14 15 */
"f0", "f1", "f2", "f3", /* 16 17 18 19 */
"f4", "f5", "f6", "f7", /* 20 21 22 23 */
"fps", "cpsr" }; /* 24 25 */
/* Holds the current set of options to be passed to the disassembler. */
static char *arm_disassembler_options;
/* Valid register name styles. */
static const char **valid_disassembly_styles;
/* Disassembly style to use. Default to "std" register names. */
static const char *disassembly_style;
/* All possible arm target descriptors. */
static struct target_desc *tdesc_arm_list[ARM_FP_TYPE_INVALID];
static struct target_desc *tdesc_arm_mprofile_list[ARM_M_TYPE_INVALID];
/* This is used to keep the bfd arch_info in sync with the disassembly
style. */
static void set_disassembly_style_sfunc (const char *, int,
struct cmd_list_element *);
static void show_disassembly_style_sfunc (struct ui_file *, int,
struct cmd_list_element *,
const char *);
static enum register_status arm_neon_quad_read (struct gdbarch *gdbarch,
readable_regcache *regcache,
int regnum, gdb_byte *buf);
static void arm_neon_quad_write (struct gdbarch *gdbarch,
struct regcache *regcache,
int regnum, const gdb_byte *buf);
static CORE_ADDR
arm_get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self);
/* get_next_pcs operations. */
static struct arm_get_next_pcs_ops arm_get_next_pcs_ops = {
arm_get_next_pcs_read_memory_unsigned_integer,
arm_get_next_pcs_syscall_next_pc,
arm_get_next_pcs_addr_bits_remove,
arm_get_next_pcs_is_thumb,
NULL,
};
struct arm_prologue_cache
{
/* The stack pointer at the time this frame was created; i.e. the
caller's stack pointer when this function was called. It is used
to identify this frame. */
CORE_ADDR prev_sp;
/* The frame base for this frame is just prev_sp - frame size.
FRAMESIZE is the distance from the frame pointer to the
initial stack pointer. */
int framesize;
/* The register used to hold the frame pointer for this frame. */
int framereg;
/* Saved register offsets. */
trad_frame_saved_reg *saved_regs;
};
namespace {
/* Abstract class to read ARM instructions from memory. */
class arm_instruction_reader
{
public:
/* Read a 4 bytes instruction from memory using the BYTE_ORDER endianness. */
virtual uint32_t read (CORE_ADDR memaddr, bfd_endian byte_order) const = 0;
};
/* Read instructions from target memory. */
class target_arm_instruction_reader : public arm_instruction_reader
{
public:
uint32_t read (CORE_ADDR memaddr, bfd_endian byte_order) const override
{
return read_code_unsigned_integer (memaddr, 4, byte_order);
}
};
} /* namespace */
static CORE_ADDR arm_analyze_prologue
(struct gdbarch *gdbarch, CORE_ADDR prologue_start, CORE_ADDR prologue_end,
struct arm_prologue_cache *cache, const arm_instruction_reader &insn_reader);
/* Architecture version for displaced stepping. This effects the behaviour of
certain instructions, and really should not be hard-wired. */
#define DISPLACED_STEPPING_ARCH_VERSION 5
/* See arm-tdep.h. */
bool arm_apcs_32 = true;
/* Return the bit mask in ARM_PS_REGNUM that indicates Thumb mode. */
int
arm_psr_thumb_bit (struct gdbarch *gdbarch)
{
if (gdbarch_tdep (gdbarch)->is_m)
return XPSR_T;
else
return CPSR_T;
}
/* Determine if the processor is currently executing in Thumb mode. */
int
arm_is_thumb (struct regcache *regcache)
{
ULONGEST cpsr;
ULONGEST t_bit = arm_psr_thumb_bit (regcache->arch ());
cpsr = regcache_raw_get_unsigned (regcache, ARM_PS_REGNUM);
return (cpsr & t_bit) != 0;
}
/* Determine if FRAME is executing in Thumb mode. */
int
arm_frame_is_thumb (struct frame_info *frame)
{
CORE_ADDR cpsr;
ULONGEST t_bit = arm_psr_thumb_bit (get_frame_arch (frame));
/* Every ARM frame unwinder can unwind the T bit of the CPSR, either
directly (from a signal frame or dummy frame) or by interpreting
the saved LR (from a prologue or DWARF frame). So consult it and
trust the unwinders. */
cpsr = get_frame_register_unsigned (frame, ARM_PS_REGNUM);
return (cpsr & t_bit) != 0;
}
/* Search for the mapping symbol covering MEMADDR. If one is found,
return its type. Otherwise, return 0. If START is non-NULL,
set *START to the location of the mapping symbol. */
static char
arm_find_mapping_symbol (CORE_ADDR memaddr, CORE_ADDR *start)
{
struct obj_section *sec;
/* If there are mapping symbols, consult them. */
sec = find_pc_section (memaddr);
if (sec != NULL)
{
arm_per_bfd *data = arm_bfd_data_key.get (sec->objfile->obfd);
if (data != NULL)
{
unsigned int section_idx = sec->the_bfd_section->index;
arm_mapping_symbol_vec &map
= data->section_maps[section_idx];
/* Sort the vector on first use. */
if (!data->section_maps_sorted[section_idx])
{
std::sort (map.begin (), map.end ());
data->section_maps_sorted[section_idx] = true;
}
arm_mapping_symbol map_key = { memaddr - sec->addr (), 0 };
arm_mapping_symbol_vec::const_iterator it
= std::lower_bound (map.begin (), map.end (), map_key);
/* std::lower_bound finds the earliest ordered insertion
point. If the symbol at this position starts at this exact
address, we use that; otherwise, the preceding
mapping symbol covers this address. */
if (it < map.end ())
{
if (it->value == map_key.value)
{
if (start)
*start = it->value + sec->addr ();
return it->type;
}
}
if (it > map.begin ())
{
arm_mapping_symbol_vec::const_iterator prev_it
= it - 1;
if (start)
*start = prev_it->value + sec->addr ();
return prev_it->type;
}
}
}
return 0;
}
/* Determine if the program counter specified in MEMADDR is in a Thumb
function. This function should be called for addresses unrelated to
any executing frame; otherwise, prefer arm_frame_is_thumb. */
int
arm_pc_is_thumb (struct gdbarch *gdbarch, CORE_ADDR memaddr)
{
struct bound_minimal_symbol sym;
char type;
arm_displaced_step_copy_insn_closure *dsc = nullptr;
if (gdbarch_displaced_step_copy_insn_closure_by_addr_p (gdbarch))
dsc = ((arm_displaced_step_copy_insn_closure * )
gdbarch_displaced_step_copy_insn_closure_by_addr
(gdbarch, current_inferior (), memaddr));
/* If checking the mode of displaced instruction in copy area, the mode
should be determined by instruction on the original address. */
if (dsc)
{
displaced_debug_printf ("check mode of %.8lx instead of %.8lx",
(unsigned long) dsc->insn_addr,
(unsigned long) memaddr);
memaddr = dsc->insn_addr;
}
/* If bit 0 of the address is set, assume this is a Thumb address. */
if (IS_THUMB_ADDR (memaddr))
return 1;
/* If the user wants to override the symbol table, let him. */
if (strcmp (arm_force_mode_string, "arm") == 0)
return 0;
if (strcmp (arm_force_mode_string, "thumb") == 0)
return 1;
/* ARM v6-M and v7-M are always in Thumb mode. */
if (gdbarch_tdep (gdbarch)->is_m)
return 1;
/* If there are mapping symbols, consult them. */
type = arm_find_mapping_symbol (memaddr, NULL);
if (type)
return type == 't';
/* Thumb functions have a "special" bit set in minimal symbols. */
sym = lookup_minimal_symbol_by_pc (memaddr);
if (sym.minsym)
return (MSYMBOL_IS_SPECIAL (sym.minsym));
/* If the user wants to override the fallback mode, let them. */
if (strcmp (arm_fallback_mode_string, "arm") == 0)
return 0;
if (strcmp (arm_fallback_mode_string, "thumb") == 0)
return 1;
/* If we couldn't find any symbol, but we're talking to a running
target, then trust the current value of $cpsr. This lets
"display/i $pc" always show the correct mode (though if there is
a symbol table we will not reach here, so it still may not be
displayed in the mode it will be executed). */
if (target_has_registers ())
return arm_frame_is_thumb (get_current_frame ());
/* Otherwise we're out of luck; we assume ARM. */
return 0;
}
/* Determine if the address specified equals any of these magic return
values, called EXC_RETURN, defined by the ARM v6-M, v7-M and v8-M
architectures.
From ARMv6-M Reference Manual B1.5.8
Table B1-5 Exception return behavior
EXC_RETURN Return To Return Stack
0xFFFFFFF1 Handler mode Main
0xFFFFFFF9 Thread mode Main
0xFFFFFFFD Thread mode Process
From ARMv7-M Reference Manual B1.5.8
Table B1-8 EXC_RETURN definition of exception return behavior, no FP
EXC_RETURN Return To Return Stack
0xFFFFFFF1 Handler mode Main
0xFFFFFFF9 Thread mode Main
0xFFFFFFFD Thread mode Process
Table B1-9 EXC_RETURN definition of exception return behavior, with
FP
EXC_RETURN Return To Return Stack Frame Type
0xFFFFFFE1 Handler mode Main Extended
0xFFFFFFE9 Thread mode Main Extended
0xFFFFFFED Thread mode Process Extended
0xFFFFFFF1 Handler mode Main Basic
0xFFFFFFF9 Thread mode Main Basic
0xFFFFFFFD Thread mode Process Basic
For more details see "B1.5.8 Exception return behavior"
in both ARMv6-M and ARMv7-M Architecture Reference Manuals.
In the ARMv8-M Architecture Technical Reference also adds
for implementations without the Security Extension:
EXC_RETURN Condition
0xFFFFFFB0 Return to Handler mode.
0xFFFFFFB8 Return to Thread mode using the main stack.
0xFFFFFFBC Return to Thread mode using the process stack. */
static int
arm_m_addr_is_magic (CORE_ADDR addr)
{
switch (addr)
{
/* Values from ARMv8-M Architecture Technical Reference. */
case 0xffffffb0:
case 0xffffffb8:
case 0xffffffbc:
/* Values from Tables in B1.5.8 the EXC_RETURN definitions of
the exception return behavior. */
case 0xffffffe1:
case 0xffffffe9:
case 0xffffffed:
case 0xfffffff1:
case 0xfffffff9:
case 0xfffffffd:
/* Address is magic. */
return 1;
default:
/* Address is not magic. */
return 0;
}
}
/* Remove useless bits from addresses in a running program. */
static CORE_ADDR
arm_addr_bits_remove (struct gdbarch *gdbarch, CORE_ADDR val)
{
/* On M-profile devices, do not strip the low bit from EXC_RETURN
(the magic exception return address). */
if (gdbarch_tdep (gdbarch)->is_m
&& arm_m_addr_is_magic (val))
return val;
if (arm_apcs_32)
return UNMAKE_THUMB_ADDR (val);
else
return (val & 0x03fffffc);
}
/* Return 1 if PC is the start of a compiler helper function which
can be safely ignored during prologue skipping. IS_THUMB is true
if the function is known to be a Thumb function due to the way it
is being called. */
static int
skip_prologue_function (struct gdbarch *gdbarch, CORE_ADDR pc, int is_thumb)
{
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
struct bound_minimal_symbol msym;
msym = lookup_minimal_symbol_by_pc (pc);
if (msym.minsym != NULL
&& BMSYMBOL_VALUE_ADDRESS (msym) == pc
&& msym.minsym->linkage_name () != NULL)
{
const char *name = msym.minsym->linkage_name ();
/* The GNU linker's Thumb call stub to foo is named
__foo_from_thumb. */
if (strstr (name, "_from_thumb") != NULL)
name += 2;
/* On soft-float targets, __truncdfsf2 is called to convert promoted
arguments to their argument types in non-prototyped
functions. */
if (startswith (name, "__truncdfsf2"))
return 1;
if (startswith (name, "__aeabi_d2f"))
return 1;
/* Internal functions related to thread-local storage. */
if (startswith (name, "__tls_get_addr"))
return 1;
if (startswith (name, "__aeabi_read_tp"))
return 1;
}
else
{
/* If we run against a stripped glibc, we may be unable to identify
special functions by name. Check for one important case,
__aeabi_read_tp, by comparing the *code* against the default
implementation (this is hand-written ARM assembler in glibc). */
if (!is_thumb
&& read_code_unsigned_integer (pc, 4, byte_order_for_code)
== 0xe3e00a0f /* mov r0, #0xffff0fff */
&& read_code_unsigned_integer (pc + 4, 4, byte_order_for_code)
== 0xe240f01f) /* sub pc, r0, #31 */
return 1;
}
return 0;
}
/* Extract the immediate from instruction movw/movt of encoding T. INSN1 is
the first 16-bit of instruction, and INSN2 is the second 16-bit of
instruction. */
#define EXTRACT_MOVW_MOVT_IMM_T(insn1, insn2) \
((bits ((insn1), 0, 3) << 12) \
| (bits ((insn1), 10, 10) << 11) \
| (bits ((insn2), 12, 14) << 8) \
| bits ((insn2), 0, 7))
/* Extract the immediate from instruction movw/movt of encoding A. INSN is
the 32-bit instruction. */
#define EXTRACT_MOVW_MOVT_IMM_A(insn) \
((bits ((insn), 16, 19) << 12) \
| bits ((insn), 0, 11))
/* Decode immediate value; implements ThumbExpandImmediate pseudo-op. */
static unsigned int
thumb_expand_immediate (unsigned int imm)
{
unsigned int count = imm >> 7;
if (count < 8)
switch (count / 2)
{
case 0:
return imm & 0xff;
case 1:
return (imm & 0xff) | ((imm & 0xff) << 16);
case 2:
return ((imm & 0xff) << 8) | ((imm & 0xff) << 24);
case 3:
return (imm & 0xff) | ((imm & 0xff) << 8)
| ((imm & 0xff) << 16) | ((imm & 0xff) << 24);
}
return (0x80 | (imm & 0x7f)) << (32 - count);
}
/* Return 1 if the 16-bit Thumb instruction INSN restores SP in
epilogue, 0 otherwise. */
static int
thumb_instruction_restores_sp (unsigned short insn)
{
return (insn == 0x46bd /* mov sp, r7 */
|| (insn & 0xff80) == 0xb000 /* add sp, imm */
|| (insn & 0xfe00) == 0xbc00); /* pop <registers> */
}
/* Analyze a Thumb prologue, looking for a recognizable stack frame
and frame pointer. Scan until we encounter a store that could
clobber the stack frame unexpectedly, or an unknown instruction.
Return the last address which is definitely safe to skip for an
initial breakpoint. */
static CORE_ADDR
thumb_analyze_prologue (struct gdbarch *gdbarch,
CORE_ADDR start, CORE_ADDR limit,
struct arm_prologue_cache *cache)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
int i;
pv_t regs[16];
CORE_ADDR offset;
CORE_ADDR unrecognized_pc = 0;
for (i = 0; i < 16; i++)
regs[i] = pv_register (i, 0);
pv_area stack (ARM_SP_REGNUM, gdbarch_addr_bit (gdbarch));
while (start < limit)
{
unsigned short insn;
insn = read_code_unsigned_integer (start, 2, byte_order_for_code);
if ((insn & 0xfe00) == 0xb400) /* push { rlist } */
{
int regno;
int mask;
if (stack.store_would_trash (regs[ARM_SP_REGNUM]))
break;
/* Bits 0-7 contain a mask for registers R0-R7. Bit 8 says
whether to save LR (R14). */
mask = (insn & 0xff) | ((insn & 0x100) << 6);
/* Calculate offsets of saved R0-R7 and LR. */
for (regno = ARM_LR_REGNUM; regno >= 0; regno--)
if (mask & (1 << regno))
{
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
-4);
stack.store (regs[ARM_SP_REGNUM], 4, regs[regno]);
}
}
else if ((insn & 0xff80) == 0xb080) /* sub sp, #imm */
{
offset = (insn & 0x7f) << 2; /* get scaled offset */
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
-offset);
}
else if (thumb_instruction_restores_sp (insn))
{
/* Don't scan past the epilogue. */
break;
}
else if ((insn & 0xf800) == 0xa800) /* add Rd, sp, #imm */
regs[bits (insn, 8, 10)] = pv_add_constant (regs[ARM_SP_REGNUM],
(insn & 0xff) << 2);
else if ((insn & 0xfe00) == 0x1c00 /* add Rd, Rn, #imm */
&& pv_is_register (regs[bits (insn, 3, 5)], ARM_SP_REGNUM))
regs[bits (insn, 0, 2)] = pv_add_constant (regs[bits (insn, 3, 5)],
bits (insn, 6, 8));
else if ((insn & 0xf800) == 0x3000 /* add Rd, #imm */
&& pv_is_register (regs[bits (insn, 8, 10)], ARM_SP_REGNUM))
regs[bits (insn, 8, 10)] = pv_add_constant (regs[bits (insn, 8, 10)],
bits (insn, 0, 7));
else if ((insn & 0xfe00) == 0x1800 /* add Rd, Rn, Rm */
&& pv_is_register (regs[bits (insn, 6, 8)], ARM_SP_REGNUM)
&& pv_is_constant (regs[bits (insn, 3, 5)]))
regs[bits (insn, 0, 2)] = pv_add (regs[bits (insn, 3, 5)],
regs[bits (insn, 6, 8)]);
else if ((insn & 0xff00) == 0x4400 /* add Rd, Rm */
&& pv_is_constant (regs[bits (insn, 3, 6)]))
{
int rd = (bit (insn, 7) << 3) + bits (insn, 0, 2);
int rm = bits (insn, 3, 6);
regs[rd] = pv_add (regs[rd], regs[rm]);
}
else if ((insn & 0xff00) == 0x4600) /* mov hi, lo or mov lo, hi */
{
int dst_reg = (insn & 0x7) + ((insn & 0x80) >> 4);
int src_reg = (insn & 0x78) >> 3;
regs[dst_reg] = regs[src_reg];
}
else if ((insn & 0xf800) == 0x9000) /* str rd, [sp, #off] */
{
/* Handle stores to the stack. Normally pushes are used,
but with GCC -mtpcs-frame, there may be other stores
in the prologue to create the frame. */
int regno = (insn >> 8) & 0x7;
pv_t addr;
offset = (insn & 0xff) << 2;
addr = pv_add_constant (regs[ARM_SP_REGNUM], offset);
if (stack.store_would_trash (addr))
break;
stack.store (addr, 4, regs[regno]);
}
else if ((insn & 0xf800) == 0x6000) /* str rd, [rn, #off] */
{
int rd = bits (insn, 0, 2);
int rn = bits (insn, 3, 5);
pv_t addr;
offset = bits (insn, 6, 10) << 2;
addr = pv_add_constant (regs[rn], offset);
if (stack.store_would_trash (addr))
break;
stack.store (addr, 4, regs[rd]);
}
else if (((insn & 0xf800) == 0x7000 /* strb Rd, [Rn, #off] */
|| (insn & 0xf800) == 0x8000) /* strh Rd, [Rn, #off] */
&& pv_is_register (regs[bits (insn, 3, 5)], ARM_SP_REGNUM))
/* Ignore stores of argument registers to the stack. */
;
else if ((insn & 0xf800) == 0xc800 /* ldmia Rn!, { registers } */
&& pv_is_register (regs[bits (insn, 8, 10)], ARM_SP_REGNUM))
/* Ignore block loads from the stack, potentially copying
parameters from memory. */
;
else if ((insn & 0xf800) == 0x9800 /* ldr Rd, [Rn, #immed] */
|| ((insn & 0xf800) == 0x6800 /* ldr Rd, [sp, #immed] */
&& pv_is_register (regs[bits (insn, 3, 5)], ARM_SP_REGNUM)))
/* Similarly ignore single loads from the stack. */
;
else if ((insn & 0xffc0) == 0x0000 /* lsls Rd, Rm, #0 */
|| (insn & 0xffc0) == 0x1c00) /* add Rd, Rn, #0 */
/* Skip register copies, i.e. saves to another register
instead of the stack. */
;
else if ((insn & 0xf800) == 0x2000) /* movs Rd, #imm */
/* Recognize constant loads; even with small stacks these are necessary
on Thumb. */
regs[bits (insn, 8, 10)] = pv_constant (bits (insn, 0, 7));
else if ((insn & 0xf800) == 0x4800) /* ldr Rd, [pc, #imm] */
{
/* Constant pool loads, for the same reason. */
unsigned int constant;
CORE_ADDR loc;
loc = start + 4 + bits (insn, 0, 7) * 4;
constant = read_memory_unsigned_integer (loc, 4, byte_order);
regs[bits (insn, 8, 10)] = pv_constant (constant);
}
else if (thumb_insn_size (insn) == 4) /* 32-bit Thumb-2 instructions. */
{
unsigned short inst2;
inst2 = read_code_unsigned_integer (start + 2, 2,
byte_order_for_code);
if ((insn & 0xf800) == 0xf000 && (inst2 & 0xe800) == 0xe800)
{
/* BL, BLX. Allow some special function calls when
skipping the prologue; GCC generates these before
storing arguments to the stack. */
CORE_ADDR nextpc;
int j1, j2, imm1, imm2;
imm1 = sbits (insn, 0, 10);
imm2 = bits (inst2, 0, 10);
j1 = bit (inst2, 13);
j2 = bit (inst2, 11);
offset = ((imm1 << 12) + (imm2 << 1));
offset ^= ((!j2) << 22) | ((!j1) << 23);
nextpc = start + 4 + offset;
/* For BLX make sure to clear the low bits. */
if (bit (inst2, 12) == 0)
nextpc = nextpc & 0xfffffffc;
if (!skip_prologue_function (gdbarch, nextpc,
bit (inst2, 12) != 0))
break;
}
else if ((insn & 0xffd0) == 0xe900 /* stmdb Rn{!},
{ registers } */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
{
pv_t addr = regs[bits (insn, 0, 3)];
int regno;
if (stack.store_would_trash (addr))
break;
/* Calculate offsets of saved registers. */
for (regno = ARM_LR_REGNUM; regno >= 0; regno--)
if (inst2 & (1 << regno))
{
addr = pv_add_constant (addr, -4);
stack.store (addr, 4, regs[regno]);
}
if (insn & 0x0020)
regs[bits (insn, 0, 3)] = addr;
}
else if ((insn & 0xff50) == 0xe940 /* strd Rt, Rt2,
[Rn, #+/-imm]{!} */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
{
int regno1 = bits (inst2, 12, 15);
int regno2 = bits (inst2, 8, 11);
pv_t addr = regs[bits (insn, 0, 3)];
offset = inst2 & 0xff;
if (insn & 0x0080)
addr = pv_add_constant (addr, offset);
else
addr = pv_add_constant (addr, -offset);
if (stack.store_would_trash (addr))
break;
stack.store (addr, 4, regs[regno1]);
stack.store (pv_add_constant (addr, 4),
4, regs[regno2]);
if (insn & 0x0020)
regs[bits (insn, 0, 3)] = addr;
}
else if ((insn & 0xfff0) == 0xf8c0 /* str Rt,[Rn,+/-#imm]{!} */
&& (inst2 & 0x0c00) == 0x0c00
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
{
int regno = bits (inst2, 12, 15);
pv_t addr = regs[bits (insn, 0, 3)];
offset = inst2 & 0xff;
if (inst2 & 0x0200)
addr = pv_add_constant (addr, offset);
else
addr = pv_add_constant (addr, -offset);
if (stack.store_would_trash (addr))
break;
stack.store (addr, 4, regs[regno]);
if (inst2 & 0x0100)
regs[bits (insn, 0, 3)] = addr;
}
else if ((insn & 0xfff0) == 0xf8c0 /* str.w Rt,[Rn,#imm] */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
{
int regno = bits (inst2, 12, 15);
pv_t addr;
offset = inst2 & 0xfff;
addr = pv_add_constant (regs[bits (insn, 0, 3)], offset);
if (stack.store_would_trash (addr))
break;
stack.store (addr, 4, regs[regno]);
}
else if ((insn & 0xffd0) == 0xf880 /* str{bh}.w Rt,[Rn,#imm] */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Ignore stores of argument registers to the stack. */
;
else if ((insn & 0xffd0) == 0xf800 /* str{bh} Rt,[Rn,#+/-imm] */
&& (inst2 & 0x0d00) == 0x0c00
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Ignore stores of argument registers to the stack. */
;
else if ((insn & 0xffd0) == 0xe890 /* ldmia Rn[!],
{ registers } */
&& (inst2 & 0x8000) == 0x0000
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Ignore block loads from the stack, potentially copying
parameters from memory. */
;
else if ((insn & 0xff70) == 0xe950 /* ldrd Rt, Rt2,
[Rn, #+/-imm] */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Similarly ignore dual loads from the stack. */
;
else if ((insn & 0xfff0) == 0xf850 /* ldr Rt,[Rn,#+/-imm] */
&& (inst2 & 0x0d00) == 0x0c00
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Similarly ignore single loads from the stack. */
;
else if ((insn & 0xfff0) == 0xf8d0 /* ldr.w Rt,[Rn,#imm] */
&& pv_is_register (regs[bits (insn, 0, 3)], ARM_SP_REGNUM))
/* Similarly ignore single loads from the stack. */
;
else if ((insn & 0xfbf0) == 0xf100 /* add.w Rd, Rn, #imm */
&& (inst2 & 0x8000) == 0x0000)
{
unsigned int imm = ((bits (insn, 10, 10) << 11)
| (bits (inst2, 12, 14) << 8)
| bits (inst2, 0, 7));
regs[bits (inst2, 8, 11)]
= pv_add_constant (regs[bits (insn, 0, 3)],
thumb_expand_immediate (imm));
}
else if ((insn & 0xfbf0) == 0xf200 /* addw Rd, Rn, #imm */
&& (inst2 & 0x8000) == 0x0000)
{
unsigned int imm = ((bits (insn, 10, 10) << 11)
| (bits (inst2, 12, 14) << 8)
| bits (inst2, 0, 7));
regs[bits (inst2, 8, 11)]
= pv_add_constant (regs[bits (insn, 0, 3)], imm);
}
else if ((insn & 0xfbf0) == 0xf1a0 /* sub.w Rd, Rn, #imm */
&& (inst2 & 0x8000) == 0x0000)
{
unsigned int imm = ((bits (insn, 10, 10) << 11)
| (bits (inst2, 12, 14) << 8)
| bits (inst2, 0, 7));
regs[bits (inst2, 8, 11)]
= pv_add_constant (regs[bits (insn, 0, 3)],
- (CORE_ADDR) thumb_expand_immediate (imm));
}
else if ((insn & 0xfbf0) == 0xf2a0 /* subw Rd, Rn, #imm */
&& (inst2 & 0x8000) == 0x0000)
{
unsigned int imm = ((bits (insn, 10, 10) << 11)
| (bits (inst2, 12, 14) << 8)
| bits (inst2, 0, 7));
regs[bits (inst2, 8, 11)]
= pv_add_constant (regs[bits (insn, 0, 3)], - (CORE_ADDR) imm);
}
else if ((insn & 0xfbff) == 0xf04f) /* mov.w Rd, #const */
{
unsigned int imm = ((bits (insn, 10, 10) << 11)
| (bits (inst2, 12, 14) << 8)
| bits (inst2, 0, 7));
regs[bits (inst2, 8, 11)]
= pv_constant (thumb_expand_immediate (imm));
}
else if ((insn & 0xfbf0) == 0xf240) /* movw Rd, #const */
{
unsigned int imm
= EXTRACT_MOVW_MOVT_IMM_T (insn, inst2);
regs[bits (inst2, 8, 11)] = pv_constant (imm);
}
else if (insn == 0xea5f /* mov.w Rd,Rm */
&& (inst2 & 0xf0f0) == 0)
{
int dst_reg = (inst2 & 0x0f00) >> 8;
int src_reg = inst2 & 0xf;
regs[dst_reg] = regs[src_reg];
}
else if ((insn & 0xff7f) == 0xf85f) /* ldr.w Rt,<label> */
{
/* Constant pool loads. */
unsigned int constant;
CORE_ADDR loc;
offset = bits (inst2, 0, 11);
if (insn & 0x0080)
loc = start + 4 + offset;
else
loc = start + 4 - offset;
constant = read_memory_unsigned_integer (loc, 4, byte_order);
regs[bits (inst2, 12, 15)] = pv_constant (constant);
}
else if ((insn & 0xff7f) == 0xe95f) /* ldrd Rt,Rt2,<label> */
{
/* Constant pool loads. */
unsigned int constant;
CORE_ADDR loc;
offset = bits (inst2, 0, 7) << 2;
if (insn & 0x0080)
loc = start + 4 + offset;
else
loc = start + 4 - offset;
constant = read_memory_unsigned_integer (loc, 4, byte_order);
regs[bits (inst2, 12, 15)] = pv_constant (constant);
constant = read_memory_unsigned_integer (loc + 4, 4, byte_order);
regs[bits (inst2, 8, 11)] = pv_constant (constant);
}
else if (thumb2_instruction_changes_pc (insn, inst2))
{
/* Don't scan past anything that might change control flow. */
break;
}
else
{
/* The optimizer might shove anything into the prologue,
so we just skip what we don't recognize. */
unrecognized_pc = start;
}
start += 2;
}
else if (thumb_instruction_changes_pc (insn))
{
/* Don't scan past anything that might change control flow. */
break;
}
else
{
/* The optimizer might shove anything into the prologue,
so we just skip what we don't recognize. */
unrecognized_pc = start;
}
start += 2;
}
arm_debug_printf ("Prologue scan stopped at %s",
paddress (gdbarch, start));
if (unrecognized_pc == 0)
unrecognized_pc = start;
if (cache == NULL)
return unrecognized_pc;
if (pv_is_register (regs[ARM_FP_REGNUM], ARM_SP_REGNUM))
{
/* Frame pointer is fp. Frame size is constant. */
cache->framereg = ARM_FP_REGNUM;
cache->framesize = -regs[ARM_FP_REGNUM].k;
}
else if (pv_is_register (regs[THUMB_FP_REGNUM], ARM_SP_REGNUM))
{
/* Frame pointer is r7. Frame size is constant. */
cache->framereg = THUMB_FP_REGNUM;
cache->framesize = -regs[THUMB_FP_REGNUM].k;
}
else
{
/* Try the stack pointer... this is a bit desperate. */
cache->framereg = ARM_SP_REGNUM;
cache->framesize = -regs[ARM_SP_REGNUM].k;
}
for (i = 0; i < 16; i++)
if (stack.find_reg (gdbarch, i, &offset))
cache->saved_regs[i].set_addr (offset);
return unrecognized_pc;
}
/* Try to analyze the instructions starting from PC, which load symbol
__stack_chk_guard. Return the address of instruction after loading this
symbol, set the dest register number to *BASEREG, and set the size of
instructions for loading symbol in OFFSET. Return 0 if instructions are
not recognized. */
static CORE_ADDR
arm_analyze_load_stack_chk_guard(CORE_ADDR pc, struct gdbarch *gdbarch,
unsigned int *destreg, int *offset)
{
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
int is_thumb = arm_pc_is_thumb (gdbarch, pc);
unsigned int low, high, address;
address = 0;
if (is_thumb)
{
unsigned short insn1
= read_code_unsigned_integer (pc, 2, byte_order_for_code);
if ((insn1 & 0xf800) == 0x4800) /* ldr Rd, #immed */
{
*destreg = bits (insn1, 8, 10);
*offset = 2;
address = (pc & 0xfffffffc) + 4 + (bits (insn1, 0, 7) << 2);
address = read_memory_unsigned_integer (address, 4,
byte_order_for_code);
}
else if ((insn1 & 0xfbf0) == 0xf240) /* movw Rd, #const */
{
unsigned short insn2
= read_code_unsigned_integer (pc + 2, 2, byte_order_for_code);
low = EXTRACT_MOVW_MOVT_IMM_T (insn1, insn2);
insn1
= read_code_unsigned_integer (pc + 4, 2, byte_order_for_code);
insn2
= read_code_unsigned_integer (pc + 6, 2, byte_order_for_code);
/* movt Rd, #const */
if ((insn1 & 0xfbc0) == 0xf2c0)
{
high = EXTRACT_MOVW_MOVT_IMM_T (insn1, insn2);
*destreg = bits (insn2, 8, 11);
*offset = 8;
address = (high << 16 | low);
}
}
}
else
{
unsigned int insn
= read_code_unsigned_integer (pc, 4, byte_order_for_code);
if ((insn & 0x0e5f0000) == 0x041f0000) /* ldr Rd, [PC, #immed] */
{
address = bits (insn, 0, 11) + pc + 8;
address = read_memory_unsigned_integer (address, 4,
byte_order_for_code);
*destreg = bits (insn, 12, 15);
*offset = 4;
}
else if ((insn & 0x0ff00000) == 0x03000000) /* movw Rd, #const */
{
low = EXTRACT_MOVW_MOVT_IMM_A (insn);
insn
= read_code_unsigned_integer (pc + 4, 4, byte_order_for_code);
if ((insn & 0x0ff00000) == 0x03400000) /* movt Rd, #const */
{
high = EXTRACT_MOVW_MOVT_IMM_A (insn);
*destreg = bits (insn, 12, 15);
*offset = 8;
address = (high << 16 | low);
}
}
}
return address;
}
/* Try to skip a sequence of instructions used for stack protector. If PC
points to the first instruction of this sequence, return the address of
first instruction after this sequence, otherwise, return original PC.
On arm, this sequence of instructions is composed of mainly three steps,
Step 1: load symbol __stack_chk_guard,
Step 2: load from address of __stack_chk_guard,
Step 3: store it to somewhere else.
Usually, instructions on step 2 and step 3 are the same on various ARM
architectures. On step 2, it is one instruction 'ldr Rx, [Rn, #0]', and
on step 3, it is also one instruction 'str Rx, [r7, #immd]'. However,
instructions in step 1 vary from different ARM architectures. On ARMv7,
they are,
movw Rn, #:lower16:__stack_chk_guard
movt Rn, #:upper16:__stack_chk_guard
On ARMv5t, it is,
ldr Rn, .Label
....
.Lable:
.word __stack_chk_guard
Since ldr/str is a very popular instruction, we can't use them as
'fingerprint' or 'signature' of stack protector sequence. Here we choose
sequence {movw/movt, ldr}/ldr/str plus symbol __stack_chk_guard, if not
stripped, as the 'fingerprint' of a stack protector cdoe sequence. */
static CORE_ADDR
arm_skip_stack_protector(CORE_ADDR pc, struct gdbarch *gdbarch)
{
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
unsigned int basereg;
struct bound_minimal_symbol stack_chk_guard;
int offset;
int is_thumb = arm_pc_is_thumb (gdbarch, pc);
CORE_ADDR addr;
/* Try to parse the instructions in Step 1. */
addr = arm_analyze_load_stack_chk_guard (pc, gdbarch,
&basereg, &offset);
if (!addr)
return pc;
stack_chk_guard = lookup_minimal_symbol_by_pc (addr);
/* ADDR must correspond to a symbol whose name is __stack_chk_guard.
Otherwise, this sequence cannot be for stack protector. */
if (stack_chk_guard.minsym == NULL
|| !startswith (stack_chk_guard.minsym->linkage_name (), "__stack_chk_guard"))
return pc;
if (is_thumb)
{
unsigned int destreg;
unsigned short insn
= read_code_unsigned_integer (pc + offset, 2, byte_order_for_code);
/* Step 2: ldr Rd, [Rn, #immed], encoding T1. */
if ((insn & 0xf800) != 0x6800)
return pc;
if (bits (insn, 3, 5) != basereg)
return pc;
destreg = bits (insn, 0, 2);
insn = read_code_unsigned_integer (pc + offset + 2, 2,
byte_order_for_code);
/* Step 3: str Rd, [Rn, #immed], encoding T1. */
if ((insn & 0xf800) != 0x6000)
return pc;
if (destreg != bits (insn, 0, 2))
return pc;
}
else
{
unsigned int destreg;
unsigned int insn
= read_code_unsigned_integer (pc + offset, 4, byte_order_for_code);
/* Step 2: ldr Rd, [Rn, #immed], encoding A1. */
if ((insn & 0x0e500000) != 0x04100000)
return pc;
if (bits (insn, 16, 19) != basereg)
return pc;
destreg = bits (insn, 12, 15);
/* Step 3: str Rd, [Rn, #immed], encoding A1. */
insn = read_code_unsigned_integer (pc + offset + 4,
4, byte_order_for_code);
if ((insn & 0x0e500000) != 0x04000000)
return pc;
if (bits (insn, 12, 15) != destreg)
return pc;
}
/* The size of total two instructions ldr/str is 4 on Thumb-2, while 8
on arm. */
if (is_thumb)
return pc + offset + 4;
else
return pc + offset + 8;
}
/* Advance the PC across any function entry prologue instructions to
reach some "real" code.
The APCS (ARM Procedure Call Standard) defines the following
prologue:
mov ip, sp
[stmfd sp!, {a1,a2,a3,a4}]
stmfd sp!, {...,fp,ip,lr,pc}
[stfe f7, [sp, #-12]!]
[stfe f6, [sp, #-12]!]
[stfe f5, [sp, #-12]!]
[stfe f4, [sp, #-12]!]
sub fp, ip, #nn @@ nn == 20 or 4 depending on second insn. */
static CORE_ADDR
arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
CORE_ADDR func_addr, limit_pc;
/* See if we can determine the end of the prologue via the symbol table.
If so, then return either PC, or the PC after the prologue, whichever
is greater. */
if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
{
CORE_ADDR post_prologue_pc
= skip_prologue_using_sal (gdbarch, func_addr);
struct compunit_symtab *cust = find_pc_compunit_symtab (func_addr);
if (post_prologue_pc)
post_prologue_pc
= arm_skip_stack_protector (post_prologue_pc, gdbarch);
/* GCC always emits a line note before the prologue and another
one after, even if the two are at the same address or on the
same line. Take advantage of this so that we do not need to
know every instruction that might appear in the prologue. We
will have producer information for most binaries; if it is
missing (e.g. for -gstabs), assuming the GNU tools. */
if (post_prologue_pc
&& (cust == NULL
|| COMPUNIT_PRODUCER (cust) == NULL
|| startswith (COMPUNIT_PRODUCER (cust), "GNU ")
|| producer_is_llvm (COMPUNIT_PRODUCER (cust))))
return post_prologue_pc;
if (post_prologue_pc != 0)
{
CORE_ADDR analyzed_limit;
/* For non-GCC compilers, make sure the entire line is an
acceptable prologue; GDB will round this function's
return value up to the end of the following line so we
can not skip just part of a line (and we do not want to).
RealView does not treat the prologue specially, but does
associate prologue code with the opening brace; so this
lets us skip the first line if we think it is the opening
brace. */
if (arm_pc_is_thumb (gdbarch, func_addr))
analyzed_limit = thumb_analyze_prologue (gdbarch, func_addr,
post_prologue_pc, NULL);
else
analyzed_limit
= arm_analyze_prologue (gdbarch, func_addr, post_prologue_pc,
NULL, target_arm_instruction_reader ());
if (analyzed_limit != post_prologue_pc)
return func_addr;
return post_prologue_pc;
}
}
/* Can't determine prologue from the symbol table, need to examine
instructions. */
/* Find an upper limit on the function prologue using the debug
information. If the debug information could not be used to provide
that bound, then use an arbitrary large number as the upper bound. */
/* Like arm_scan_prologue, stop no later than pc + 64. */
limit_pc = skip_prologue_using_sal (gdbarch, pc);
if (limit_pc == 0)
limit_pc = pc + 64; /* Magic. */
/* Check if this is Thumb code. */
if (arm_pc_is_thumb (gdbarch, pc))
return thumb_analyze_prologue (gdbarch, pc, limit_pc, NULL);
else
return arm_analyze_prologue (gdbarch, pc, limit_pc, NULL,
target_arm_instruction_reader ());
}
/* *INDENT-OFF* */
/* Function: thumb_scan_prologue (helper function for arm_scan_prologue)
This function decodes a Thumb function prologue to determine:
1) the size of the stack frame
2) which registers are saved on it
3) the offsets of saved regs
4) the offset from the stack pointer to the frame pointer
A typical Thumb function prologue would create this stack frame
(offsets relative to FP)
old SP -> 24 stack parameters
20 LR
16 R7
R7 -> 0 local variables (16 bytes)
SP -> -12 additional stack space (12 bytes)
The frame size would thus be 36 bytes, and the frame offset would be
12 bytes. The frame register is R7.
The comments for thumb_skip_prolog() describe the algorithm we use
to detect the end of the prolog. */
/* *INDENT-ON* */
static void
thumb_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR prev_pc,
CORE_ADDR block_addr, struct arm_prologue_cache *cache)
{
CORE_ADDR prologue_start;
CORE_ADDR prologue_end;
if (find_pc_partial_function (block_addr, NULL, &prologue_start,
&prologue_end))
{
/* See comment in arm_scan_prologue for an explanation of
this heuristics. */
if (prologue_end > prologue_start + 64)
{
prologue_end = prologue_start + 64;
}
}
else
/* We're in the boondocks: we have no idea where the start of the
function is. */
return;
prologue_end = std::min (prologue_end, prev_pc);
thumb_analyze_prologue (gdbarch, prologue_start, prologue_end, cache);
}
/* Return 1 if the ARM instruction INSN restores SP in epilogue, 0
otherwise. */
static int
arm_instruction_restores_sp (unsigned int insn)
{
if (bits (insn, 28, 31) != INST_NV)
{
if ((insn & 0x0df0f000) == 0x0080d000
/* ADD SP (register or immediate). */
|| (insn & 0x0df0f000) == 0x0040d000
/* SUB SP (register or immediate). */
|| (insn & 0x0ffffff0) == 0x01a0d000
/* MOV SP. */
|| (insn & 0x0fff0000) == 0x08bd0000
/* POP (LDMIA). */
|| (insn & 0x0fff0000) == 0x049d0000)
/* POP of a single register. */
return 1;
}
return 0;
}
/* Implement immediate value decoding, as described in section A5.2.4
(Modified immediate constants in ARM instructions) of the ARM Architecture
Reference Manual (ARMv7-A and ARMv7-R edition). */
static uint32_t
arm_expand_immediate (uint32_t imm)
{
/* Immediate values are 12 bits long. */
gdb_assert ((imm & 0xfffff000) == 0);
uint32_t unrotated_value = imm & 0xff;
uint32_t rotate_amount = (imm & 0xf00) >> 7;
if (rotate_amount == 0)
return unrotated_value;
return ((unrotated_value >> rotate_amount)
| (unrotated_value << (32 - rotate_amount)));
}
/* Analyze an ARM mode prologue starting at PROLOGUE_START and
continuing no further than PROLOGUE_END. If CACHE is non-NULL,
fill it in. Return the first address not recognized as a prologue
instruction.
We recognize all the instructions typically found in ARM prologues,
plus harmless instructions which can be skipped (either for analysis
purposes, or a more restrictive set that can be skipped when finding
the end of the prologue). */
static CORE_ADDR
arm_analyze_prologue (struct gdbarch *gdbarch,
CORE_ADDR prologue_start, CORE_ADDR prologue_end,
struct arm_prologue_cache *cache,
const arm_instruction_reader &insn_reader)
{
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
int regno;
CORE_ADDR offset, current_pc;
pv_t regs[ARM_FPS_REGNUM];
CORE_ADDR unrecognized_pc = 0;
/* Search the prologue looking for instructions that set up the
frame pointer, adjust the stack pointer, and save registers.
Be careful, however, and if it doesn't look like a prologue,
don't try to scan it. If, for instance, a frameless function
begins with stmfd sp!, then we will tell ourselves there is
a frame, which will confuse stack traceback, as well as "finish"
and other operations that rely on a knowledge of the stack
traceback. */
for (regno = 0; regno < ARM_FPS_REGNUM; regno++)
regs[regno] = pv_register (regno, 0);
pv_area stack (ARM_SP_REGNUM, gdbarch_addr_bit (gdbarch));
for (current_pc = prologue_start;
current_pc < prologue_end;
current_pc += 4)
{
uint32_t insn = insn_reader.read (current_pc, byte_order_for_code);
if (insn == 0xe1a0c00d) /* mov ip, sp */
{
regs[ARM_IP_REGNUM] = regs[ARM_SP_REGNUM];
continue;
}
else if ((insn & 0xfff00000) == 0xe2800000 /* add Rd, Rn, #n */
&& pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
{
uint32_t imm = arm_expand_immediate (insn & 0xfff);
int rd = bits (insn, 12, 15);
regs[rd] = pv_add_constant (regs[bits (insn, 16, 19)], imm);
continue;
}
else if ((insn & 0xfff00000) == 0xe2400000 /* sub Rd, Rn, #n */
&& pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
{
uint32_t imm = arm_expand_immediate (insn & 0xfff);
int rd = bits (insn, 12, 15);
regs[rd] = pv_add_constant (regs[bits (insn, 16, 19)], -imm);
continue;
}
else if ((insn & 0xffff0fff) == 0xe52d0004) /* str Rd,
[sp, #-4]! */
{
if (stack.store_would_trash (regs[ARM_SP_REGNUM]))
break;
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -4);
stack.store (regs[ARM_SP_REGNUM], 4,
regs[bits (insn, 12, 15)]);
continue;
}
else if ((insn & 0xffff0000) == 0xe92d0000)
/* stmfd sp!, {..., fp, ip, lr, pc}
or
stmfd sp!, {a1, a2, a3, a4} */
{
int mask = insn & 0xffff;
if (stack.store_would_trash (regs[ARM_SP_REGNUM]))
break;
/* Calculate offsets of saved registers. */
for (regno = ARM_PC_REGNUM; regno >= 0; regno--)
if (mask & (1 << regno))
{
regs[ARM_SP_REGNUM]
= pv_add_constant (regs[ARM_SP_REGNUM], -4);
stack.store (regs[ARM_SP_REGNUM], 4, regs[regno]);
}
}
else if ((insn & 0xffff0000) == 0xe54b0000 /* strb rx,[r11,#-n] */
|| (insn & 0xffff00f0) == 0xe14b00b0 /* strh rx,[r11,#-n] */
|| (insn & 0xffffc000) == 0xe50b0000) /* str rx,[r11,#-n] */
{
/* No need to add this to saved_regs -- it's just an arg reg. */
continue;
}
else if ((insn & 0xffff0000) == 0xe5cd0000 /* strb rx,[sp,#n] */
|| (insn & 0xffff00f0) == 0xe1cd00b0 /* strh rx,[sp,#n] */
|| (insn & 0xffffc000) == 0xe58d0000) /* str rx,[sp,#n] */
{
/* No need to add this to saved_regs -- it's just an arg reg. */
continue;
}
else if ((insn & 0xfff00000) == 0xe8800000 /* stm Rn,
{ registers } */
&& pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
{
/* No need to add this to saved_regs -- it's just arg regs. */
continue;
}
else if ((insn & 0xfffff000) == 0xe24cb000) /* sub fp, ip #n */
{
uint32_t imm = arm_expand_immediate (insn & 0xfff);
regs[ARM_FP_REGNUM] = pv_add_constant (regs[ARM_IP_REGNUM], -imm);
}
else if ((insn & 0xfffff000) == 0xe24dd000) /* sub sp, sp #n */
{
uint32_t imm = arm_expand_immediate(insn & 0xfff);
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -imm);
}
else if ((insn & 0xffff7fff) == 0xed6d0103 /* stfe f?,
[sp, -#c]! */
&& gdbarch_tdep (gdbarch)->have_fpa_registers)
{
if (stack.store_would_trash (regs[ARM_SP_REGNUM]))
break;
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -12);
regno = ARM_F0_REGNUM + ((insn >> 12) & 0x07);
stack.store (regs[ARM_SP_REGNUM], 12, regs[regno]);
}
else if ((insn & 0xffbf0fff) == 0xec2d0200 /* sfmfd f0, 4,
[sp!] */
&& gdbarch_tdep (gdbarch)->have_fpa_registers)
{
int n_saved_fp_regs;
unsigned int fp_start_reg, fp_bound_reg;
if (stack.store_would_trash (regs[ARM_SP_REGNUM]))
break;
if ((insn & 0x800) == 0x800) /* N0 is set */
{
if ((insn & 0x40000) == 0x40000) /* N1 is set */
n_saved_fp_regs = 3;
else
n_saved_fp_regs = 1;
}
else
{
if ((insn & 0x40000) == 0x40000) /* N1 is set */
n_saved_fp_regs = 2;
else
n_saved_fp_regs = 4;
}
fp_start_reg = ARM_F0_REGNUM + ((insn >> 12) & 0x7);
fp_bound_reg = fp_start_reg + n_saved_fp_regs;
for (; fp_start_reg < fp_bound_reg; fp_start_reg++)
{
regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -12);
stack.store (regs[ARM_SP_REGNUM], 12,
regs[fp_start_reg++]);
}
}
else if ((insn & 0xff000000) == 0xeb000000 && cache == NULL) /* bl */
{
/* Allow some special function calls when skipping the
prologue; GCC generates these before storing arguments to
the stack. */
CORE_ADDR dest = BranchDest (current_pc, insn);
if (skip_prologue_function (gdbarch, dest, 0))
continue;
else
break;
}
else if ((insn & 0xf0000000) != 0xe0000000)
break; /* Condition not true, exit early. */
else if (arm_instruction_changes_pc (insn))
/* Don't scan past anything that might change control flow. */
break;
else if (arm_instruction_restores_sp (insn))
{
/* Don't scan past the epilogue. */
break;
}
else if ((insn & 0xfe500000) == 0xe8100000 /* ldm */
&& pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
/* Ignore block loads from the stack, potentially copying
parameters from memory. */
continue;
else if ((insn & 0xfc500000) == 0xe4100000
&& pv_is_register (regs[bits (insn, 16, 19)], ARM_SP_REGNUM))
/* Similarly ignore single loads from the stack. */
continue;
else if ((insn & 0xffff0ff0) == 0xe1a00000)
/* MOV Rd, Rm. Skip register copies, i.e. saves to another
register instead of the stack. */
continue;
else
{
/* The optimizer might shove anything into the prologue, if
we build up cache (cache != NULL) from scanning prologue,
we just skip what we don't recognize and scan further to
make cache as complete as possible. However, if we skip
prologue, we'll stop immediately on unrecognized
instruction. */
unrecognized_pc = current_pc;
if (cache != NULL)
continue;
else
break;
}
}
if (unrecognized_pc == 0)
unrecognized_pc = current_pc;
if (cache)
{
int framereg, framesize;
/* The frame size is just the distance from the frame register
to the original stack pointer. */
if (pv_is_register (regs[ARM_FP_REGNUM], ARM_SP_REGNUM))
{
/* Frame pointer is fp. */
framereg = ARM_FP_REGNUM;
framesize = -regs[ARM_FP_REGNUM].k;
}
else
{
/* Try the stack pointer... this is a bit desperate. */
framereg = ARM_SP_REGNUM;
framesize = -regs[ARM_SP_REGNUM].k;
}
cache->framereg = framereg;
cache->framesize = framesize;
for (regno = 0; regno < ARM_FPS_REGNUM; regno++)
if (stack.find_reg (gdbarch, regno, &offset))
cache->saved_regs[regno].set_addr (offset);
}
arm_debug_printf ("Prologue scan stopped at %s",
paddress (gdbarch, unrecognized_pc));
return unrecognized_pc;
}
static void
arm_scan_prologue (struct frame_info *this_frame,
struct arm_prologue_cache *cache)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR prologue_start, prologue_end;
CORE_ADDR prev_pc = get_frame_pc (this_frame);
CORE_ADDR block_addr = get_frame_address_in_block (this_frame);
/* Assume there is no frame until proven otherwise. */
cache->framereg = ARM_SP_REGNUM;
cache->framesize = 0;
/* Check for Thumb prologue. */
if (arm_frame_is_thumb (this_frame))
{
thumb_scan_prologue (gdbarch, prev_pc, block_addr, cache);
return;
}
/* Find the function prologue. If we can't find the function in
the symbol table, peek in the stack frame to find the PC. */
if (find_pc_partial_function (block_addr, NULL, &prologue_start,
&prologue_end))
{
/* One way to find the end of the prologue (which works well
for unoptimized code) is to do the following:
struct symtab_and_line sal = find_pc_line (prologue_start, 0);
if (sal.line == 0)
prologue_end = prev_pc;
else if (sal.end < prologue_end)
prologue_end = sal.end;
This mechanism is very accurate so long as the optimizer
doesn't move any instructions from the function body into the
prologue. If this happens, sal.end will be the last
instruction in the first hunk of prologue code just before
the first instruction that the scheduler has moved from
the body to the prologue.
In order to make sure that we scan all of the prologue
instructions, we use a slightly less accurate mechanism which
may scan more than necessary. To help compensate for this
lack of accuracy, the prologue scanning loop below contains
several clauses which'll cause the loop to terminate early if
an implausible prologue instruction is encountered.
The expression
prologue_start + 64
is a suitable endpoint since it accounts for the largest
possible prologue plus up to five instructions inserted by
the scheduler. */
if (prologue_end > prologue_start + 64)
{
prologue_end = prologue_start + 64; /* See above. */
}
}
else
{
/* We have no symbol information. Our only option is to assume this
function has a standard stack frame and the normal frame register.
Then, we can find the value of our frame pointer on entrance to
the callee (or at the present moment if this is the innermost frame).
The value stored there should be the address of the stmfd + 8. */
CORE_ADDR frame_loc;
ULONGEST return_value;
/* AAPCS does not use a frame register, so we can abort here. */
if (gdbarch_tdep (gdbarch)->arm_abi == ARM_ABI_AAPCS)
return;
frame_loc = get_frame_register_unsigned (this_frame, ARM_FP_REGNUM);
if (!safe_read_memory_unsigned_integer (frame_loc, 4, byte_order,
&return_value))
return;
else
{
prologue_start = gdbarch_addr_bits_remove
(gdbarch, return_value) - 8;
prologue_end = prologue_start + 64; /* See above. */
}
}
if (prev_pc < prologue_end)
prologue_end = prev_pc;
arm_analyze_prologue (gdbarch, prologue_start, prologue_end, cache,
target_arm_instruction_reader ());
}
static struct arm_prologue_cache *
arm_make_prologue_cache (struct frame_info *this_frame)
{
int reg;
struct arm_prologue_cache *cache;
CORE_ADDR unwound_fp;
cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
arm_scan_prologue (this_frame, cache);
unwound_fp = get_frame_register_unsigned (this_frame, cache->framereg);
if (unwound_fp == 0)
return cache;
cache->prev_sp = unwound_fp + cache->framesize;
/* Calculate actual addresses of saved registers using offsets
determined by arm_scan_prologue. */
for (reg = 0; reg < gdbarch_num_regs (get_frame_arch (this_frame)); reg++)
if (cache->saved_regs[reg].is_addr ())
cache->saved_regs[reg].set_addr (cache->saved_regs[reg].addr ()
+ cache->prev_sp);
return cache;
}
/* Implementation of the stop_reason hook for arm_prologue frames. */
static enum unwind_stop_reason
arm_prologue_unwind_stop_reason (struct frame_info *this_frame,
void **this_cache)
{
struct arm_prologue_cache *cache;
CORE_ADDR pc;
if (*this_cache == NULL)
*this_cache = arm_make_prologue_cache (this_frame);
cache = (struct arm_prologue_cache *) *this_cache;
/* This is meant to halt the backtrace at "_start". */
pc = get_frame_pc (this_frame);
if (pc <= gdbarch_tdep (get_frame_arch (this_frame))->lowest_pc)
return UNWIND_OUTERMOST;
/* If we've hit a wall, stop. */
if (cache->prev_sp == 0)
return UNWIND_OUTERMOST;
return UNWIND_NO_REASON;
}
/* Our frame ID for a normal frame is the current function's starting PC
and the caller's SP when we were called. */
static void
arm_prologue_this_id (struct frame_info *this_frame,
void **this_cache,
struct frame_id *this_id)
{
struct arm_prologue_cache *cache;
struct frame_id id;
CORE_ADDR pc, func;
if (*this_cache == NULL)
*this_cache = arm_make_prologue_cache (this_frame);
cache = (struct arm_prologue_cache *) *this_cache;
/* Use function start address as part of the frame ID. If we cannot
identify the start address (due to missing symbol information),
fall back to just using the current PC. */
pc = get_frame_pc (this_frame);
func = get_frame_func (this_frame);
if (!func)
func = pc;
id = frame_id_build (cache->prev_sp, func);
*this_id = id;
}
static struct value *
arm_prologue_prev_register (struct frame_info *this_frame,
void **this_cache,
int prev_regnum)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
struct arm_prologue_cache *cache;
if (*this_cache == NULL)
*this_cache = arm_make_prologue_cache (this_frame);
cache = (struct arm_prologue_cache *) *this_cache;
/* If we are asked to unwind the PC, then we need to return the LR
instead. The prologue may save PC, but it will point into this
frame's prologue, not the next frame's resume location. Also
strip the saved T bit. A valid LR may have the low bit set, but
a valid PC never does. */
if (prev_regnum == ARM_PC_REGNUM)
{
CORE_ADDR lr;
lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
return frame_unwind_got_constant (this_frame, prev_regnum,
arm_addr_bits_remove (gdbarch, lr));
}
/* SP is generally not saved to the stack, but this frame is
identified by the next frame's stack pointer at the time of the call.
The value was already reconstructed into PREV_SP. */
if (prev_regnum == ARM_SP_REGNUM)
return frame_unwind_got_constant (this_frame, prev_regnum, cache->prev_sp);
/* The CPSR may have been changed by the call instruction and by the
called function. The only bit we can reconstruct is the T bit,
by checking the low bit of LR as of the call. This is a reliable
indicator of Thumb-ness except for some ARM v4T pre-interworking
Thumb code, which could get away with a clear low bit as long as
the called function did not use bx. Guess that all other
bits are unchanged; the condition flags are presumably lost,
but the processor status is likely valid. */
if (prev_regnum == ARM_PS_REGNUM)
{
CORE_ADDR lr, cpsr;
ULONGEST t_bit = arm_psr_thumb_bit (gdbarch);
cpsr = get_frame_register_unsigned (this_frame, prev_regnum);
lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
if (IS_THUMB_ADDR (lr))
cpsr |= t_bit;
else
cpsr &= ~t_bit;
return frame_unwind_got_constant (this_frame, prev_regnum, cpsr);
}
return trad_frame_get_prev_register (this_frame, cache->saved_regs,
prev_regnum);
}
static frame_unwind arm_prologue_unwind = {
"arm prologue",
NORMAL_FRAME,
arm_prologue_unwind_stop_reason,
arm_prologue_this_id,
arm_prologue_prev_register,
NULL,
default_frame_sniffer
};
/* Maintain a list of ARM exception table entries per objfile, similar to the
list of mapping symbols. We only cache entries for standard ARM-defined
personality routines; the cache will contain only the frame unwinding
instructions associated with the entry (not the descriptors). */
struct arm_exidx_entry
{
CORE_ADDR addr;
gdb_byte *entry;
bool operator< (const arm_exidx_entry &other) const
{
return addr < other.addr;
}
};
struct arm_exidx_data
{
std::vector<std::vector<arm_exidx_entry>> section_maps;
};
/* Per-BFD key to store exception handling information. */
static const struct bfd_key<arm_exidx_data> arm_exidx_data_key;
static struct obj_section *
arm_obj_section_from_vma (struct objfile *objfile, bfd_vma vma)
{
struct obj_section *osect;
ALL_OBJFILE_OSECTIONS (objfile, osect)
if (bfd_section_flags (osect->the_bfd_section) & SEC_ALLOC)
{
bfd_vma start, size;
start = bfd_section_vma (osect->the_bfd_section);
size = bfd_section_size (osect->the_bfd_section);
if (start <= vma && vma < start + size)
return osect;
}
return NULL;
}
/* Parse contents of exception table and exception index sections
of OBJFILE, and fill in the exception table entry cache.
For each entry that refers to a standard ARM-defined personality
routine, extract the frame unwinding instructions (from either
the index or the table section). The unwinding instructions
are normalized by:
- extracting them from the rest of the table data
- converting to host endianness
- appending the implicit 0xb0 ("Finish") code
The extracted and normalized instructions are stored for later
retrieval by the arm_find_exidx_entry routine. */
static void
arm_exidx_new_objfile (struct objfile *objfile)
{
struct arm_exidx_data *data;
asection *exidx, *extab;
bfd_vma exidx_vma = 0, extab_vma = 0;
LONGEST i;
/* If we've already touched this file, do nothing. */
if (!objfile || arm_exidx_data_key.get (objfile->obfd) != NULL)
return;
/* Read contents of exception table and index. */
exidx = bfd_get_section_by_name (objfile->obfd, ELF_STRING_ARM_unwind);
gdb::byte_vector exidx_data;
if (exidx)
{
exidx_vma = bfd_section_vma (exidx);
exidx_data.resize (bfd_section_size (exidx));
if (!bfd_get_section_contents (objfile->obfd, exidx,
exidx_data.data (), 0,
exidx_data.size ()))
return;
}
extab = bfd_get_section_by_name (objfile->obfd, ".ARM.extab");
gdb::byte_vector extab_data;
if (extab)
{
extab_vma = bfd_section_vma (extab);
extab_data.resize (bfd_section_size (extab));
if (!bfd_get_section_contents (objfile->obfd, extab,
extab_data.data (), 0,
extab_data.size ()))
return;
}
/* Allocate exception table data structure. */
data = arm_exidx_data_key.emplace (objfile->obfd);
data->section_maps.resize (objfile->obfd->section_count);
/* Fill in exception table. */
for (i = 0; i < exidx_data.size () / 8; i++)
{
struct arm_exidx_entry new_exidx_entry;
bfd_vma idx = bfd_h_get_32 (objfile->obfd, exidx_data.data () + i * 8);
bfd_vma val = bfd_h_get_32 (objfile->obfd,
exidx_data.data () + i * 8 + 4);
bfd_vma addr = 0, word = 0;
int n_bytes = 0, n_words = 0;
struct obj_section *sec;
gdb_byte *entry = NULL;
/* Extract address of start of function. */
idx = ((idx & 0x7fffffff) ^ 0x40000000) - 0x40000000;
idx += exidx_vma + i * 8;
/* Find section containing function and compute section offset. */
sec = arm_obj_section_from_vma (objfile, idx);
if (sec == NULL)
continue;
idx -= bfd_section_vma (sec->the_bfd_section);
/* Determine address of exception table entry. */
if (val == 1)
{
/* EXIDX_CANTUNWIND -- no exception table entry present. */
}
else if ((val & 0xff000000) == 0x80000000)
{
/* Exception table entry embedded in .ARM.exidx
-- must be short form. */
word = val;
n_bytes = 3;
}
else if (!(val & 0x80000000))
{
/* Exception table entry in .ARM.extab. */
addr = ((val & 0x7fffffff) ^ 0x40000000) - 0x40000000;
addr += exidx_vma + i * 8 + 4;
if (addr >= extab_vma && addr + 4 <= extab_vma + extab_data.size ())
{
word = bfd_h_get_32 (objfile->obfd,
extab_data.data () + addr - extab_vma);
addr += 4;
if ((word & 0xff000000) == 0x80000000)
{
/* Short form. */
n_bytes = 3;
}
else if ((word & 0xff000000) == 0x81000000
|| (word & 0xff000000) == 0x82000000)
{
/* Long form. */
n_bytes = 2;
n_words = ((word >> 16) & 0xff);
}
else if (!(word & 0x80000000))
{
bfd_vma pers;
struct obj_section *pers_sec;
int gnu_personality = 0;
/* Custom personality routine. */
pers = ((word & 0x7fffffff) ^ 0x40000000) - 0x40000000;
pers = UNMAKE_THUMB_ADDR (pers + addr - 4);
/* Check whether we've got one of the variants of the
GNU personality routines. */
pers_sec = arm_obj_section_from_vma (objfile, pers);
if (pers_sec)
{
static const char *personality[] =
{
"__gcc_personality_v0",
"__gxx_personality_v0",
"__gcj_personality_v0",
"__gnu_objc_personality_v0",
NULL
};
CORE_ADDR pc = pers + pers_sec->offset ();
int k;
for (k = 0; personality[k]; k++)
if (lookup_minimal_symbol_by_pc_name
(pc, personality[k], objfile))
{
gnu_personality = 1;
break;
}
}
/* If so, the next word contains a word count in the high
byte, followed by the same unwind instructions as the
pre-defined forms. */
if (gnu_personality
&& addr + 4 <= extab_vma + extab_data.size ())
{
word = bfd_h_get_32 (objfile->obfd,
(extab_data.data ()
+ addr - extab_vma));
addr += 4;
n_bytes = 3;
n_words = ((word >> 24) & 0xff);
}
}
}
}
/* Sanity check address. */
if (n_words)
if (addr < extab_vma
|| addr + 4 * n_words > extab_vma + extab_data.size ())
n_words = n_bytes = 0;
/* The unwind instructions reside in WORD (only the N_BYTES least
significant bytes are valid), followed by N_WORDS words in the
extab section starting at ADDR. */
if (n_bytes || n_words)
{
gdb_byte *p = entry
= (gdb_byte *) obstack_alloc (&objfile->objfile_obstack,
n_bytes + n_words * 4 + 1);
while (n_bytes--)
*p++ = (gdb_byte) ((word >> (8 * n_bytes)) & 0xff);
while (n_words--)
{
word = bfd_h_get_32 (objfile->obfd,
extab_data.data () + addr - extab_vma);
addr += 4;
*p++ = (gdb_byte) ((word >> 24) & 0xff);
*p++ = (gdb_byte) ((word >> 16) & 0xff);
*p++ = (gdb_byte) ((word >> 8) & 0xff);
*p++ = (gdb_byte) (word & 0xff);
}
/* Implied "Finish" to terminate the list. */
*p++ = 0xb0;
}
/* Push entry onto vector. They are guaranteed to always
appear in order of increasing addresses. */
new_exidx_entry.addr = idx;
new_exidx_entry.entry = entry;
data->section_maps[sec->the_bfd_section->index].push_back
(new_exidx_entry);
}
}
/* Search for the exception table entry covering MEMADDR. If one is found,
return a pointer to its data. Otherwise, return 0. If START is non-NULL,
set *START to the start of the region covered by this entry. */
static gdb_byte *
arm_find_exidx_entry (CORE_ADDR memaddr, CORE_ADDR *start)
{
struct obj_section *sec;
sec = find_pc_section (memaddr);
if (sec != NULL)
{
struct arm_exidx_data *data;
struct arm_exidx_entry map_key = { memaddr - sec->addr (), 0 };
data = arm_exidx_data_key.get (sec->objfile->obfd);
if (data != NULL)
{
std::vector<arm_exidx_entry> &map
= data->section_maps[sec->the_bfd_section->index];
if (!map.empty ())
{
auto idx = std::lower_bound (map.begin (), map.end (), map_key);
/* std::lower_bound finds the earliest ordered insertion
point. If the following symbol starts at this exact
address, we use that; otherwise, the preceding
exception table entry covers this address. */
if (idx < map.end ())
{
if (idx->addr == map_key.addr)
{
if (start)
*start = idx->addr + sec->addr ();
return idx->entry;
}
}
if (idx > map.begin ())
{
idx = idx - 1;
if (start)
*start = idx->addr + sec->addr ();
return idx->entry;
}
}
}
}
return NULL;
}
/* Given the current frame THIS_FRAME, and its associated frame unwinding
instruction list from the ARM exception table entry ENTRY, allocate and
return a prologue cache structure describing how to unwind this frame.
Return NULL if the unwinding instruction list contains a "spare",
"reserved" or "refuse to unwind" instruction as defined in section
"9.3 Frame unwinding instructions" of the "Exception Handling ABI
for the ARM Architecture" document. */
static struct arm_prologue_cache *
arm_exidx_fill_cache (struct frame_info *this_frame, gdb_byte *entry)
{
CORE_ADDR vsp = 0;
int vsp_valid = 0;
struct arm_prologue_cache *cache;
cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
for (;;)
{
gdb_byte insn;
/* Whenever we reload SP, we actually have to retrieve its
actual value in the current frame. */
if (!vsp_valid)
{
if (cache->saved_regs[ARM_SP_REGNUM].is_realreg ())
{
int reg = cache->saved_regs[ARM_SP_REGNUM].realreg ();
vsp = get_frame_register_unsigned (this_frame, reg);
}
else
{
CORE_ADDR addr = cache->saved_regs[ARM_SP_REGNUM].addr ();
vsp = get_frame_memory_unsigned (this_frame, addr, 4);
}
vsp_valid = 1;
}
/* Decode next unwind instruction. */
insn = *entry++;
if ((insn & 0xc0) == 0)
{
int offset = insn & 0x3f;
vsp += (offset << 2) + 4;
}
else if ((insn & 0xc0) == 0x40)
{
int offset = insn & 0x3f;
vsp -= (offset << 2) + 4;
}
else if ((insn & 0xf0) == 0x80)
{
int mask = ((insn & 0xf) << 8) | *entry++;
int i;
/* The special case of an all-zero mask identifies
"Refuse to unwind". We return NULL to fall back
to the prologue analyzer. */
if (mask == 0)
return NULL;
/* Pop registers r4..r15 under mask. */
for (i = 0; i < 12; i++)
if (mask & (1 << i))
{
cache->saved_regs[4 + i].set_addr (vsp);
vsp += 4;
}
/* Special-case popping SP -- we need to reload vsp. */
if (mask & (1 << (ARM_SP_REGNUM - 4)))
vsp_valid = 0;
}
else if ((insn & 0xf0) == 0x90)
{
int reg = insn & 0xf;
/* Reserved cases. */
if (reg == ARM_SP_REGNUM || reg == ARM_PC_REGNUM)
return NULL;
/* Set SP from another register and mark VSP for reload. */
cache->saved_regs[ARM_SP_REGNUM] = cache->saved_regs[reg];
vsp_valid = 0;
}
else if ((insn & 0xf0) == 0xa0)
{
int count = insn & 0x7;
int pop_lr = (insn & 0x8) != 0;
int i;
/* Pop r4..r[4+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[4 + i].set_addr (vsp);
vsp += 4;
}
/* If indicated by flag, pop LR as well. */
if (pop_lr)
{
cache->saved_regs[ARM_LR_REGNUM].set_addr (vsp);
vsp += 4;
}
}
else if (insn == 0xb0)
{
/* We could only have updated PC by popping into it; if so, it
will show up as address. Otherwise, copy LR into PC. */
if (!cache->saved_regs[ARM_PC_REGNUM].is_addr ())
cache->saved_regs[ARM_PC_REGNUM]
= cache->saved_regs[ARM_LR_REGNUM];
/* We're done. */
break;
}
else if (insn == 0xb1)
{
int mask = *entry++;
int i;
/* All-zero mask and mask >= 16 is "spare". */
if (mask == 0 || mask >= 16)
return NULL;
/* Pop r0..r3 under mask. */
for (i = 0; i < 4; i++)
if (mask & (1 << i))
{
cache->saved_regs[i].set_addr (vsp);
vsp += 4;
}
}
else if (insn == 0xb2)
{
ULONGEST offset = 0;
unsigned shift = 0;
do
{
offset |= (*entry & 0x7f) << shift;
shift += 7;
}
while (*entry++ & 0x80);
vsp += 0x204 + (offset << 2);
}
else if (insn == 0xb3)
{
int start = *entry >> 4;
int count = (*entry++) & 0xf;
int i;
/* Only registers D0..D15 are valid here. */
if (start + count >= 16)
return NULL;
/* Pop VFP double-precision registers D[start]..D[start+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_D0_REGNUM + start + i].set_addr (vsp);
vsp += 8;
}
/* Add an extra 4 bytes for FSTMFDX-style stack. */
vsp += 4;
}
else if ((insn & 0xf8) == 0xb8)
{
int count = insn & 0x7;
int i;
/* Pop VFP double-precision registers D[8]..D[8+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_D0_REGNUM + 8 + i].set_addr (vsp);
vsp += 8;
}
/* Add an extra 4 bytes for FSTMFDX-style stack. */
vsp += 4;
}
else if (insn == 0xc6)
{
int start = *entry >> 4;
int count = (*entry++) & 0xf;
int i;
/* Only registers WR0..WR15 are valid. */
if (start + count >= 16)
return NULL;
/* Pop iwmmx registers WR[start]..WR[start+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_WR0_REGNUM + start + i].set_addr (vsp);
vsp += 8;
}
}
else if (insn == 0xc7)
{
int mask = *entry++;
int i;
/* All-zero mask and mask >= 16 is "spare". */
if (mask == 0 || mask >= 16)
return NULL;
/* Pop iwmmx general-purpose registers WCGR0..WCGR3 under mask. */
for (i = 0; i < 4; i++)
if (mask & (1 << i))
{
cache->saved_regs[ARM_WCGR0_REGNUM + i].set_addr (vsp);
vsp += 4;
}
}
else if ((insn & 0xf8) == 0xc0)
{
int count = insn & 0x7;
int i;
/* Pop iwmmx registers WR[10]..WR[10+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_WR0_REGNUM + 10 + i].set_addr (vsp);
vsp += 8;
}
}
else if (insn == 0xc8)
{
int start = *entry >> 4;
int count = (*entry++) & 0xf;
int i;
/* Only registers D0..D31 are valid. */
if (start + count >= 16)
return NULL;
/* Pop VFP double-precision registers
D[16+start]..D[16+start+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_D0_REGNUM + 16 + start + i].set_addr (vsp);
vsp += 8;
}
}
else if (insn == 0xc9)
{
int start = *entry >> 4;
int count = (*entry++) & 0xf;
int i;
/* Pop VFP double-precision registers D[start]..D[start+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_D0_REGNUM + start + i].set_addr (vsp);
vsp += 8;
}
}
else if ((insn & 0xf8) == 0xd0)
{
int count = insn & 0x7;
int i;
/* Pop VFP double-precision registers D[8]..D[8+count]. */
for (i = 0; i <= count; i++)
{
cache->saved_regs[ARM_D0_REGNUM + 8 + i].set_addr (vsp);
vsp += 8;
}
}
else
{
/* Everything else is "spare". */
return NULL;
}
}
/* If we restore SP from a register, assume this was the frame register.
Otherwise just fall back to SP as frame register. */
if (cache->saved_regs[ARM_SP_REGNUM].is_realreg ())
cache->framereg = cache->saved_regs[ARM_SP_REGNUM].realreg ();
else
cache->framereg = ARM_SP_REGNUM;
/* Determine offset to previous frame. */
cache->framesize
= vsp - get_frame_register_unsigned (this_frame, cache->framereg);
/* We already got the previous SP. */
cache->prev_sp = vsp;
return cache;
}
/* Unwinding via ARM exception table entries. Note that the sniffer
already computes a filled-in prologue cache, which is then used
with the same arm_prologue_this_id and arm_prologue_prev_register
routines also used for prologue-parsing based unwinding. */
static int
arm_exidx_unwind_sniffer (const struct frame_unwind *self,
struct frame_info *this_frame,
void **this_prologue_cache)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
CORE_ADDR addr_in_block, exidx_region, func_start;
struct arm_prologue_cache *cache;
gdb_byte *entry;
/* See if we have an ARM exception table entry covering this address. */
addr_in_block = get_frame_address_in_block (this_frame);
entry = arm_find_exidx_entry (addr_in_block, &exidx_region);
if (!entry)
return 0;
/* The ARM exception table does not describe unwind information
for arbitrary PC values, but is guaranteed to be correct only
at call sites. We have to decide here whether we want to use
ARM exception table information for this frame, or fall back
to using prologue parsing. (Note that if we have DWARF CFI,
this sniffer isn't even called -- CFI is always preferred.)
Before we make this decision, however, we check whether we
actually have *symbol* information for the current frame.
If not, prologue parsing would not work anyway, so we might
as well use the exception table and hope for the best. */
if (find_pc_partial_function (addr_in_block, NULL, &func_start, NULL))
{
int exc_valid = 0;
/* If the next frame is "normal", we are at a call site in this
frame, so exception information is guaranteed to be valid. */
if (get_next_frame (this_frame)
&& get_frame_type (get_next_frame (this_frame)) == NORMAL_FRAME)
exc_valid = 1;
/* We also assume exception information is valid if we're currently
blocked in a system call. The system library is supposed to
ensure this, so that e.g. pthread cancellation works. */
if (arm_frame_is_thumb (this_frame))
{
ULONGEST insn;
if (safe_read_memory_unsigned_integer (get_frame_pc (this_frame) - 2,
2, byte_order_for_code, &insn)
&& (insn & 0xff00) == 0xdf00 /* svc */)
exc_valid = 1;
}
else
{
ULONGEST insn;
if (safe_read_memory_unsigned_integer (get_frame_pc (this_frame) - 4,
4, byte_order_for_code, &insn)
&& (insn & 0x0f000000) == 0x0f000000 /* svc */)
exc_valid = 1;
}
/* Bail out if we don't know that exception information is valid. */
if (!exc_valid)
return 0;
/* The ARM exception index does not mark the *end* of the region
covered by the entry, and some functions will not have any entry.
To correctly recognize the end of the covered region, the linker
should have inserted dummy records with a CANTUNWIND marker.
Unfortunately, current versions of GNU ld do not reliably do
this, and thus we may have found an incorrect entry above.
As a (temporary) sanity check, we only use the entry if it
lies *within* the bounds of the function. Note that this check
might reject perfectly valid entries that just happen to cover
multiple functions; therefore this check ought to be removed
once the linker is fixed. */
if (func_start > exidx_region)
return 0;
}
/* Decode the list of unwinding instructions into a prologue cache.
Note that this may fail due to e.g. a "refuse to unwind" code. */
cache = arm_exidx_fill_cache (this_frame, entry);
if (!cache)
return 0;
*this_prologue_cache = cache;
return 1;
}
struct frame_unwind arm_exidx_unwind = {
"arm exidx",
NORMAL_FRAME,
default_frame_unwind_stop_reason,
arm_prologue_this_id,
arm_prologue_prev_register,
NULL,
arm_exidx_unwind_sniffer
};
static struct arm_prologue_cache *
arm_make_epilogue_frame_cache (struct frame_info *this_frame)
{
struct arm_prologue_cache *cache;
int reg;
cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
/* Still rely on the offset calculated from prologue. */
arm_scan_prologue (this_frame, cache);
/* Since we are in epilogue, the SP has been restored. */
cache->prev_sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
/* Calculate actual addresses of saved registers using offsets
determined by arm_scan_prologue. */
for (reg = 0; reg < gdbarch_num_regs (get_frame_arch (this_frame)); reg++)
if (cache->saved_regs[reg].is_addr ())
cache->saved_regs[reg].set_addr (cache->saved_regs[reg].addr ()
+ cache->prev_sp);
return cache;
}
/* Implementation of function hook 'this_id' in
'struct frame_uwnind' for epilogue unwinder. */
static void
arm_epilogue_frame_this_id (struct frame_info *this_frame,
void **this_cache,
struct frame_id *this_id)
{
struct arm_prologue_cache *cache;
CORE_ADDR pc, func;
if (*this_cache == NULL)
*this_cache = arm_make_epilogue_frame_cache (this_frame);
cache = (struct arm_prologue_cache *) *this_cache;
/* Use function start address as part of the frame ID. If we cannot
identify the start address (due to missing symbol information),
fall back to just using the current PC. */
pc = get_frame_pc (this_frame);
func = get_frame_func (this_frame);
if (func == 0)
func = pc;
(*this_id) = frame_id_build (cache->prev_sp, pc);
}
/* Implementation of function hook 'prev_register' in
'struct frame_uwnind' for epilogue unwinder. */
static struct value *
arm_epilogue_frame_prev_register (struct frame_info *this_frame,
void **this_cache, int regnum)
{
if (*this_cache == NULL)
*this_cache = arm_make_epilogue_frame_cache (this_frame);
return arm_prologue_prev_register (this_frame, this_cache, regnum);
}
static int arm_stack_frame_destroyed_p_1 (struct gdbarch *gdbarch,
CORE_ADDR pc);
static int thumb_stack_frame_destroyed_p (struct gdbarch *gdbarch,
CORE_ADDR pc);
/* Implementation of function hook 'sniffer' in
'struct frame_uwnind' for epilogue unwinder. */
static int
arm_epilogue_frame_sniffer (const struct frame_unwind *self,
struct frame_info *this_frame,
void **this_prologue_cache)
{
if (frame_relative_level (this_frame) == 0)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
CORE_ADDR pc = get_frame_pc (this_frame);
if (arm_frame_is_thumb (this_frame))
return thumb_stack_frame_destroyed_p (gdbarch, pc);
else
return arm_stack_frame_destroyed_p_1 (gdbarch, pc);
}
else
return 0;
}
/* Frame unwinder from epilogue. */
static const struct frame_unwind arm_epilogue_frame_unwind =
{
"arm epilogue",
NORMAL_FRAME,
default_frame_unwind_stop_reason,
arm_epilogue_frame_this_id,
arm_epilogue_frame_prev_register,
NULL,
arm_epilogue_frame_sniffer,
};
/* Recognize GCC's trampoline for thumb call-indirect. If we are in a
trampoline, return the target PC. Otherwise return 0.
void call0a (char c, short s, int i, long l) {}
int main (void)
{
(*pointer_to_call0a) (c, s, i, l);
}
Instead of calling a stub library function _call_via_xx (xx is
the register name), GCC may inline the trampoline in the object
file as below (register r2 has the address of call0a).
.global main
.type main, %function
...
bl .L1
...
.size main, .-main
.L1:
bx r2
The trampoline 'bx r2' doesn't belong to main. */
static CORE_ADDR
arm_skip_bx_reg (struct frame_info *frame, CORE_ADDR pc)
{
/* The heuristics of recognizing such trampoline is that FRAME is
executing in Thumb mode and the instruction on PC is 'bx Rm'. */
if (arm_frame_is_thumb (frame))
{
gdb_byte buf[2];
if (target_read_memory (pc, buf, 2) == 0)
{
struct gdbarch *gdbarch = get_frame_arch (frame);
enum bfd_endian byte_order_for_code
= gdbarch_byte_order_for_code (gdbarch);
uint16_t insn
= extract_unsigned_integer (buf, 2, byte_order_for_code);
if ((insn & 0xff80) == 0x4700) /* bx <Rm> */
{
CORE_ADDR dest
= get_frame_register_unsigned (frame, bits (insn, 3, 6));
/* Clear the LSB so that gdb core sets step-resume
breakpoint at the right address. */
return UNMAKE_THUMB_ADDR (dest);
}
}
}
return 0;
}
static struct arm_prologue_cache *
arm_make_stub_cache (struct frame_info *this_frame)
{
struct arm_prologue_cache *cache;
cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
cache->prev_sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
return cache;
}
/* Our frame ID for a stub frame is the current SP and LR. */
static void
arm_stub_this_id (struct frame_info *this_frame,
void **this_cache,
struct frame_id *this_id)
{
struct arm_prologue_cache *cache;
if (*this_cache == NULL)
*this_cache = arm_make_stub_cache (this_frame);
cache = (struct arm_prologue_cache *) *this_cache;
*this_id = frame_id_build (cache->prev_sp, get_frame_pc (this_frame));
}
static int
arm_stub_unwind_sniffer (const struct frame_unwind *self,
struct frame_info *this_frame,
void **this_prologue_cache)
{
CORE_ADDR addr_in_block;
gdb_byte dummy[4];
CORE_ADDR pc, start_addr;
const char *name;
addr_in_block = get_frame_address_in_block (this_frame);
pc = get_frame_pc (this_frame);
if (in_plt_section (addr_in_block)
/* We also use the stub winder if the target memory is unreadable
to avoid having the prologue unwinder trying to read it. */
|| target_read_memory (pc, dummy, 4) != 0)
return 1;
if (find_pc_partial_function (pc, &name, &start_addr, NULL) == 0
&& arm_skip_bx_reg (this_frame, pc) != 0)
return 1;
return 0;
}
struct frame_unwind arm_stub_unwind = {
"arm stub",
NORMAL_FRAME,
default_frame_unwind_stop_reason,
arm_stub_this_id,
arm_prologue_prev_register,
NULL,
arm_stub_unwind_sniffer
};
/* Put here the code to store, into CACHE->saved_regs, the addresses
of the saved registers of frame described by THIS_FRAME. CACHE is
returned. */
static struct arm_prologue_cache *
arm_m_exception_cache (struct frame_info *this_frame)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
struct arm_prologue_cache *cache;
CORE_ADDR lr;
CORE_ADDR sp;
CORE_ADDR unwound_sp;
LONGEST xpsr;
uint32_t exc_return;
uint32_t process_stack_used;
uint32_t extended_frame_used;
uint32_t secure_stack_used;
cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);
/* ARMv7-M Architecture Reference "B1.5.6 Exception entry behavior"
describes which bits in LR that define which stack was used prior
to the exception and if FPU is used (causing extended stack frame). */
lr = get_frame_register_unsigned (this_frame, ARM_LR_REGNUM);
sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
/* Check EXC_RETURN indicator bits. */
exc_return = (((lr >> 28) & 0xf) == 0xf);
/* Check EXC_RETURN bit SPSEL if Main or Thread (process) stack used. */
process_stack_used = ((lr & (1 << 2)) != 0);
if (exc_return && process_stack_used)
{
/* Thread (process) stack used.
Potentially this could be other register defined by target, but PSP
can be considered a standard name for the "Process Stack Pointer".
To be fully aware of system registers like MSP and PSP, these could
be added to a separate XML arm-m-system-profile that is valid for
ARMv6-M and ARMv7-M architectures. Also to be able to debug eg a
corefile off-line, then these registers must be defined by GDB,
and also be included in the corefile regsets. */
int psp_regnum = user_reg_map_name_to_regnum (gdbarch, "psp", -1);
if (psp_regnum == -1)
{
/* Thread (process) stack could not be fetched,
give warning and exit. */
warning (_("no PSP thread stack unwinding supported."));
/* Terminate any further stack unwinding by refer to self. */
cache->prev_sp = sp;
return cache;
}
else
{
/* Thread (process) stack used, use PSP as SP. */
unwound_sp = get_frame_register_unsigned (this_frame, psp_regnum);
}
}
else
{
/* Main stack used, use MSP as SP. */
unwound_sp = sp;
}
/* The hardware saves eight 32-bit words, comprising xPSR,
ReturnAddress, LR (R14), R12, R3, R2, R1, R0. See details in
"B1.5.6 Exception entry behavior" in
"ARMv7-M Architecture Reference Manual". */
cache->saved_regs[0].set_addr (unwound_sp);
cache->saved_regs[1].set_addr (unwound_sp + 4);
cache->saved_regs[2].set_addr (unwound_sp + 8);
cache->saved_regs[3].set_addr (unwound_sp + 12);
cache->saved_regs[ARM_IP_REGNUM].set_addr (unwound_sp + 16);
cache->saved_regs[ARM_LR_REGNUM].set_addr (unwound_sp + 20);
cache->saved_regs[ARM_PC_REGNUM].set_addr (unwound_sp + 24);
cache->saved_regs[ARM_PS_REGNUM].set_addr (unwound_sp + 28);
/* Check EXC_RETURN bit FTYPE if extended stack frame (FPU regs stored)
type used. */
extended_frame_used = ((lr & (1 << 4)) == 0);
if (exc_return && extended_frame_used)
{
int i;
int fpu_regs_stack_offset;