gdb/arc-linux-tdep.c

/* Target dependent code for GNU/Linux ARC.

   Copyright 2020 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/>.  */

/* GDB header files.  */
#include "defs.h"
#include "linux-tdep.h"
#include "objfiles.h"
#include "opcode/arc.h"
#include "osabi.h"
#include "solib-svr4.h"

/* ARC header files.  */
#include "opcodes/arc-dis.h"
#include "arc-linux-tdep.h"
#include "arc-tdep.h"
#include "arch/arc.h"

#define REGOFF(offset) (offset * ARC_REGISTER_SIZE)

/* arc_linux_core_reg_offsets[i] is the offset in the .reg section of GDB
   regnum i.  Array index is an internal GDB register number, as defined in
   arc-tdep.h:arc_regnum.

   From include/uapi/asm/ptrace.h in the ARC Linux sources.  */

/* The layout of this struct is tightly bound to "arc_regnum" enum
   in arc-tdep.h.  Any change of order in there, must be reflected
   here as well.  */
static const int arc_linux_core_reg_offsets[] = {
  /* R0 - R12.  */
  REGOFF (22), REGOFF (21), REGOFF (20), REGOFF (19),
  REGOFF (18), REGOFF (17), REGOFF (16), REGOFF (15),
  REGOFF (14), REGOFF (13), REGOFF (12), REGOFF (11),
  REGOFF (10),

  /* R13 - R25.  */
  REGOFF (37), REGOFF (36), REGOFF (35), REGOFF (34),
  REGOFF (33), REGOFF (32), REGOFF (31), REGOFF (30),
  REGOFF (29), REGOFF (28), REGOFF (27), REGOFF (26),
  REGOFF (25),

  REGOFF (9),			/* R26 (GP) */
  REGOFF (8),			/* FP */
  REGOFF (23),			/* SP */
  ARC_OFFSET_NO_REGISTER,	/* ILINK */
  ARC_OFFSET_NO_REGISTER,	/* R30 */
  REGOFF (7),			/* BLINK */

  /* R32 - R59.  */
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
  ARC_OFFSET_NO_REGISTER,

  REGOFF (4),			/* LP_COUNT */
  ARC_OFFSET_NO_REGISTER,	/* RESERVED */
  ARC_OFFSET_NO_REGISTER,	/* LIMM */
  ARC_OFFSET_NO_REGISTER,	/* PCL */

  REGOFF (39),			/* PC  */
  REGOFF (5),			/* STATUS32 */
  REGOFF (2),			/* LP_START */
  REGOFF (3),			/* LP_END */
  REGOFF (1),			/* BTA */
  REGOFF (6)			/* ERET */
};

/* Implement the "cannot_fetch_register" gdbarch method.  */

static int
arc_linux_cannot_fetch_register (struct gdbarch *gdbarch, int regnum)
{
  /* Assume that register is readable if it is unknown.  */
  switch (regnum)
    {
    case ARC_ILINK_REGNUM:
    case ARC_RESERVED_REGNUM:
    case ARC_LIMM_REGNUM:
      return true;
    case ARC_R30_REGNUM:
    case ARC_R58_REGNUM:
    case ARC_R59_REGNUM:
      return !arc_mach_is_arcv2 (gdbarch);
    }
  return (regnum > ARC_BLINK_REGNUM) && (regnum < ARC_LP_COUNT_REGNUM);
}

/* Implement the "cannot_store_register" gdbarch method.  */

static int
arc_linux_cannot_store_register (struct gdbarch *gdbarch, int regnum)
{
  /* Assume that register is writable if it is unknown.  */
  switch (regnum)
    {
    case ARC_ILINK_REGNUM:
    case ARC_RESERVED_REGNUM:
    case ARC_LIMM_REGNUM:
    case ARC_PCL_REGNUM:
      return true;
    case ARC_R30_REGNUM:
    case ARC_R58_REGNUM:
    case ARC_R59_REGNUM:
      return !arc_mach_is_arcv2 (gdbarch);
    }
  return (regnum > ARC_BLINK_REGNUM) && (regnum < ARC_LP_COUNT_REGNUM);
}

/* For ARC Linux, breakpoints use the 16-bit TRAP_S 1 instruction, which
   is 0x3e78 (little endian) or 0x783e (big endian).  */

static const gdb_byte arc_linux_trap_s_be[] = { 0x78, 0x3e };
static const gdb_byte arc_linux_trap_s_le[] = { 0x3e, 0x78 };
static const int trap_size = 2;   /* Number of bytes to insert "trap".  */

/* Implement the "breakpoint_kind_from_pc" gdbarch method.  */

static int
arc_linux_breakpoint_kind_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pcptr)
{
  return trap_size;
}

/* Implement the "sw_breakpoint_from_kind" gdbarch method.  */

static const gdb_byte *
arc_linux_sw_breakpoint_from_kind (struct gdbarch *gdbarch,
				   int kind, int *size)
{
  *size = kind;
  return ((gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG)
	  ? arc_linux_trap_s_be
	  : arc_linux_trap_s_le);
}

/* Implement the "software_single_step" gdbarch method.  */

static std::vector<CORE_ADDR>
arc_linux_software_single_step (struct regcache *regcache)
{
  struct gdbarch *gdbarch = regcache->arch ();
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  struct disassemble_info di = arc_disassemble_info (gdbarch);

  /* Read current instruction.  */
  struct arc_instruction curr_insn;
  arc_insn_decode (regcache_read_pc (regcache), &di, arc_delayed_print_insn,
		   &curr_insn);
  CORE_ADDR next_pc = arc_insn_get_linear_next_pc (curr_insn);

  std::vector<CORE_ADDR> next_pcs;

  /* For instructions with delay slots, the fall thru is not the
     instruction immediately after the current instruction, but the one
     after that.  */
  if (curr_insn.has_delay_slot)
    {
      struct arc_instruction next_insn;
      arc_insn_decode (next_pc, &di, arc_delayed_print_insn, &next_insn);
      next_pcs.push_back (arc_insn_get_linear_next_pc (next_insn));
    }
  else
    next_pcs.push_back (next_pc);

  ULONGEST status32;
  regcache_cooked_read_unsigned (regcache, gdbarch_ps_regnum (gdbarch),
				 &status32);

  if (curr_insn.is_control_flow)
    {
      CORE_ADDR branch_pc = arc_insn_get_branch_target (curr_insn);
      if (branch_pc != next_pc)
	next_pcs.push_back (branch_pc);
    }
  /* Is current instruction the last in a loop body?  */
  else if (tdep->has_hw_loops)
    {
      /* If STATUS32.L is 1, then ZD-loops are disabled.  */
      if ((status32 & ARC_STATUS32_L_MASK) == 0)
	{
	  ULONGEST lp_end, lp_start, lp_count;
	  regcache_cooked_read_unsigned (regcache, ARC_LP_START_REGNUM,
					 &lp_start);
	  regcache_cooked_read_unsigned (regcache, ARC_LP_END_REGNUM, &lp_end);
	  regcache_cooked_read_unsigned (regcache, ARC_LP_COUNT_REGNUM,
					 &lp_count);

	  if (arc_debug)
	    {
	      debug_printf ("arc-linux: lp_start = %s, lp_end = %s, "
			    "lp_count = %s, next_pc = %s\n",
			    paddress (gdbarch, lp_start),
			    paddress (gdbarch, lp_end),
			    pulongest (lp_count),
			    paddress (gdbarch, next_pc));
	    }

	  if (next_pc == lp_end && lp_count > 1)
	    {
	      /* The instruction is in effect a jump back to the start of
		 the loop.  */
	      next_pcs.push_back (lp_start);
	    }
	}
    }

  /* Is this a delay slot?  Then next PC is in BTA register.  */
  if ((status32 & ARC_STATUS32_DE_MASK) != 0)
    {
      ULONGEST bta;
      regcache_cooked_read_unsigned (regcache, ARC_BTA_REGNUM, &bta);
      next_pcs.push_back (bta);
    }

  return next_pcs;
}

/* Implement the "skip_solib_resolver" gdbarch method.

   See glibc_skip_solib_resolver for details.  */

static CORE_ADDR
arc_linux_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  /* For uClibc 0.9.26+.

     An unresolved PLT entry points to "__dl_linux_resolve", which calls
     "_dl_linux_resolver" to do the resolving and then eventually jumps to
     the function.

     So we look for the symbol `_dl_linux_resolver', and if we are there,
     gdb sets a breakpoint at the return address, and continues.  */
  struct bound_minimal_symbol resolver
    = lookup_minimal_symbol ("_dl_linux_resolver", NULL, NULL);

  if (arc_debug)
    {
      if (resolver.minsym != nullptr)
	{
	  CORE_ADDR res_addr = BMSYMBOL_VALUE_ADDRESS (resolver);
	  debug_printf ("arc-linux: skip_solib_resolver (): "
			"pc = %s, resolver at %s\n",
			print_core_address (gdbarch, pc),
			print_core_address (gdbarch, res_addr));
	}
      else
	{
	  debug_printf ("arc-linux: skip_solib_resolver (): "
			"pc = %s, no resolver found\n",
			print_core_address (gdbarch, pc));
	}
    }

  if (resolver.minsym != nullptr && BMSYMBOL_VALUE_ADDRESS (resolver) == pc)
    {
      /* Find the return address.  */
      return frame_unwind_caller_pc (get_current_frame ());
    }
  else
    {
      /* No breakpoint required.  */
      return 0;
    }
}

void
arc_linux_supply_gregset (const struct regset *regset,
			  struct regcache *regcache,
			  int regnum, const void *gregs, size_t size)
{
  gdb_static_assert (ARC_LAST_REGNUM
		     < ARRAY_SIZE (arc_linux_core_reg_offsets));

  const bfd_byte *buf = (const bfd_byte *) gregs;

  for (int reg = 0; reg <= ARC_LAST_REGNUM; reg++)
      if (arc_linux_core_reg_offsets[reg] != ARC_OFFSET_NO_REGISTER)
	regcache->raw_supply (reg, buf + arc_linux_core_reg_offsets[reg]);
}

void
arc_linux_supply_v2_regset (const struct regset *regset,
			    struct regcache *regcache, int regnum,
			    const void *v2_regs, size_t size)
{
  const bfd_byte *buf = (const bfd_byte *) v2_regs;

  /* user_regs_arcv2 is defined in linux arch/arc/include/uapi/asm/ptrace.h.  */
  regcache->raw_supply (ARC_R30_REGNUM, buf);
  regcache->raw_supply (ARC_R58_REGNUM, buf + REGOFF (1));
  regcache->raw_supply (ARC_R59_REGNUM, buf + REGOFF (2));
}

/* Populate BUF with register REGNUM from the REGCACHE.  */

static void
collect_register (const struct regcache *regcache, struct gdbarch *gdbarch,
		  int regnum, gdb_byte *buf)
{
  /* Skip non-existing registers.  */
  if ((arc_linux_core_reg_offsets[regnum] == ARC_OFFSET_NO_REGISTER))
    return;

  /* The address where the execution has stopped is in pseudo-register
     STOP_PC.  However, when kernel code is returning from the exception,
     it uses the value from ERET register.  Since, TRAP_S (the breakpoint
     instruction) commits, the ERET points to the next instruction.  In
     other words: ERET != STOP_PC.  To jump back from the kernel code to
     the correct address, ERET must be overwritten by GDB's STOP_PC.  Else,
     the program will continue at the address after the current instruction.
     */
  if (regnum == gdbarch_pc_regnum (gdbarch))
    regnum = ARC_ERET_REGNUM;
  regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
}

void
arc_linux_collect_gregset (const struct regset *regset,
			   const struct regcache *regcache,
			   int regnum, void *gregs, size_t size)
{
  gdb_static_assert (ARC_LAST_REGNUM
		     < ARRAY_SIZE (arc_linux_core_reg_offsets));

  gdb_byte *buf = (gdb_byte *) gregs;
  struct gdbarch *gdbarch = regcache->arch ();

  /* regnum == -1 means writing all the registers.  */
  if (regnum == -1)
    for (int reg = 0; reg <= ARC_LAST_REGNUM; reg++)
      collect_register (regcache, gdbarch, reg, buf);
  else if (regnum <= ARC_LAST_REGNUM)
    collect_register (regcache, gdbarch, regnum, buf);
  else
    gdb_assert_not_reached ("Invalid regnum in arc_linux_collect_gregset.");
}

void
arc_linux_collect_v2_regset (const struct regset *regset,
			     const struct regcache *regcache, int regnum,
			     void *v2_regs, size_t size)
{
  bfd_byte *buf = (bfd_byte *) v2_regs;

  regcache->raw_collect (ARC_R30_REGNUM, buf);
  regcache->raw_collect (ARC_R58_REGNUM, buf + REGOFF (1));
  regcache->raw_collect (ARC_R59_REGNUM, buf + REGOFF (2));
}

/* Linux regset definitions.  */

static const struct regset arc_linux_gregset = {
  arc_linux_core_reg_offsets,
  arc_linux_supply_gregset,
  arc_linux_collect_gregset,
};

static const struct regset arc_linux_v2_regset = {
  NULL,
  arc_linux_supply_v2_regset,
  arc_linux_collect_v2_regset,
};

/* Implement the `iterate_over_regset_sections` gdbarch method.  */

static void
arc_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
					iterate_over_regset_sections_cb *cb,
					void *cb_data,
					const struct regcache *regcache)
{
  /* There are 40 registers in Linux user_regs_struct, although some of
     them are now just a mere paddings, kept to maintain binary
     compatibility with older tools.  */
  const int sizeof_gregset = 40 * ARC_REGISTER_SIZE;

  cb (".reg", sizeof_gregset, sizeof_gregset, &arc_linux_gregset, NULL,
      cb_data);
  cb (".reg-arc-v2", ARC_LINUX_SIZEOF_V2_REGSET, ARC_LINUX_SIZEOF_V2_REGSET,
      &arc_linux_v2_regset, NULL, cb_data);
}

/* Implement the `core_read_description` gdbarch method.  */

static const struct target_desc *
arc_linux_core_read_description (struct gdbarch *gdbarch,
				 struct target_ops *target,
				 bfd *abfd)
{
  arc_arch_features features
    = arc_arch_features_create (abfd,
				gdbarch_bfd_arch_info (gdbarch)->mach);
  return arc_lookup_target_description (features);
}

/* Initialization specific to Linux environment.  */

static void
arc_linux_init_osabi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  if (arc_debug)
    debug_printf ("arc-linux: GNU/Linux OS/ABI initialization.\n");

  /* If we are using Linux, we have in uClibc
     (libc/sysdeps/linux/arc/bits/setjmp.h):

     typedef int __jmp_buf[13+1+1+1];    //r13-r25, fp, sp, blink

     Where "blink" is a stored PC of a caller function.
   */
  tdep->jb_pc = 15;

  linux_init_abi (info, gdbarch);

  /* Set up target dependent GDB architecture entries.  */
  set_gdbarch_cannot_fetch_register (gdbarch, arc_linux_cannot_fetch_register);
  set_gdbarch_cannot_store_register (gdbarch, arc_linux_cannot_store_register);
  set_gdbarch_breakpoint_kind_from_pc (gdbarch,
				       arc_linux_breakpoint_kind_from_pc);
  set_gdbarch_sw_breakpoint_from_kind (gdbarch,
				       arc_linux_sw_breakpoint_from_kind);
  set_gdbarch_fetch_tls_load_module_address (gdbarch,
					     svr4_fetch_objfile_link_map);
  set_gdbarch_software_single_step (gdbarch, arc_linux_software_single_step);
  set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
  set_gdbarch_skip_solib_resolver (gdbarch, arc_linux_skip_solib_resolver);
  set_gdbarch_iterate_over_regset_sections
    (gdbarch, arc_linux_iterate_over_regset_sections);
  set_gdbarch_core_read_description (gdbarch, arc_linux_core_read_description);

  /* GNU/Linux uses SVR4-style shared libraries, with 32-bit ints, longs
     and pointers (ILP32).  */
  set_solib_svr4_fetch_link_map_offsets (gdbarch,
					 svr4_ilp32_fetch_link_map_offsets);
}

/* Suppress warning from -Wmissing-prototypes.  */
extern initialize_file_ftype _initialize_arc_linux_tdep;

void
_initialize_arc_linux_tdep ()
{
  gdbarch_register_osabi (bfd_arch_arc, 0, GDB_OSABI_LINUX,
			  arc_linux_init_osabi);
}