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/* Copyright (C) 2001-2022 Free Software Foundation, Inc.
Contributed by Jakub Jelinek <jakub@redhat.com>.
This file is part of GCC.
GCC 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, or (at your option)
any later version.
GCC 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.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* Locate the FDE entry for a given address, using PT_GNU_EH_FRAME ELF
segment and dl_iterate_phdr to avoid register/deregister calls at
DSO load/unload. */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
#include "tconfig.h"
#include "tsystem.h"
#if !defined(inhibit_libc) && !defined(__OpenBSD__)
#include <elf.h> /* Get DT_CONFIG. */
#endif
#include "coretypes.h"
#include "tm.h"
#include "libgcc_tm.h"
#include "dwarf2.h"
#include "unwind.h"
#define NO_BASE_OF_ENCODED_VALUE
#include "unwind-pe.h"
#include "unwind-dw2-fde.h"
#include "unwind-compat.h"
#include "gthr.h"
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \
|| (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG)))
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(__BIONIC__)
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(TARGET_DL_ITERATE_PHDR) \
&& defined(__linux__)
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(TARGET_DL_ITERATE_PHDR) \
&& (defined(__DragonFly__) || defined(__FreeBSD__))
# define ElfW __ElfN
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(TARGET_DL_ITERATE_PHDR) \
&& (defined(__OpenBSD__) || defined(__NetBSD__))
# define ElfW(type) Elf_##type
# define USE_PT_GNU_EH_FRAME
#endif
#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \
&& defined(TARGET_DL_ITERATE_PHDR) \
&& defined(__sun__) && defined(__svr4__)
# define USE_PT_GNU_EH_FRAME
#endif
#if defined(USE_PT_GNU_EH_FRAME)
#include <link.h>
#ifndef __RELOC_POINTER
# define __RELOC_POINTER(ptr, base) ((ptr) + (base))
#endif
static const fde * _Unwind_Find_registered_FDE (void *pc, struct dwarf_eh_bases *bases);
#define _Unwind_Find_FDE _Unwind_Find_registered_FDE
#include "unwind-dw2-fde.c"
#undef _Unwind_Find_FDE
#ifndef PT_GNU_EH_FRAME
#define PT_GNU_EH_FRAME (PT_LOOS + 0x474e550)
#endif
#ifdef CRT_GET_RFIB_DATA
#define NEED_DBASE_MEMBER 1
#else
#define NEED_DBASE_MEMBER 0
#endif
struct unw_eh_callback_data
{
_Unwind_Ptr pc;
#if NEED_DBASE_MEMBER
void *dbase;
#endif
const struct unw_eh_frame_hdr *hdr;
int check_cache;
};
/* Returns DATA->dbase if available, else NULL. */
static inline _Unwind_Ptr
unw_eh_callback_data_dbase (const struct unw_eh_callback_data *data
__attribute__ ((unused)))
{
#if NEED_DBASE_MEMBER
return (_Unwind_Ptr) data->dbase;
#else
return 0;
#endif
}
struct unw_eh_frame_hdr
{
unsigned char version;
unsigned char eh_frame_ptr_enc;
unsigned char fde_count_enc;
unsigned char table_enc;
};
#define FRAME_HDR_CACHE_SIZE 8
static struct frame_hdr_cache_element
{
_Unwind_Ptr pc_low;
_Unwind_Ptr pc_high;
#if defined __FRV_FDPIC__ || defined __BFIN_FDPIC__
struct elf32_fdpic_loadaddr load_base;
#else
_Unwind_Ptr load_base;
#endif
const ElfW(Phdr) *p_eh_frame_hdr;
const ElfW(Phdr) *p_dynamic;
struct frame_hdr_cache_element *link;
} frame_hdr_cache[FRAME_HDR_CACHE_SIZE];
static struct frame_hdr_cache_element *frame_hdr_cache_head;
/* Like base_of_encoded_value, but take the base from a struct
unw_eh_callback_data instead of an _Unwind_Context. */
static inline _Unwind_Ptr
base_from_cb_data (unsigned char encoding __attribute__ ((unused)),
_Unwind_Ptr dbase __attribute__ ((unused)))
{
#if NEED_DBASE_MEMBER
if (encoding == DW_EH_PE_omit)
return 0;
switch (encoding & 0x70)
{
case DW_EH_PE_absptr:
case DW_EH_PE_pcrel:
case DW_EH_PE_aligned:
return 0;
case DW_EH_PE_textrel:
return 0;
case DW_EH_PE_datarel:
return dbase;
default:
gcc_unreachable ();
}
#else /* !NEED_DBASE_MEMBER */
return 0;
#endif
}
static int
_Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
{
struct unw_eh_callback_data *data = (struct unw_eh_callback_data *) ptr;
const ElfW(Phdr) *phdr, *p_eh_frame_hdr, *p_dynamic;
long n, match;
#if defined __FRV_FDPIC__ || defined __BFIN_FDPIC__
struct elf32_fdpic_loadaddr load_base;
#else
_Unwind_Ptr load_base;
#endif
_Unwind_Ptr pc_low = 0, pc_high = 0;
struct ext_dl_phdr_info
{
ElfW(Addr) dlpi_addr;
const char *dlpi_name;
const ElfW(Phdr) *dlpi_phdr;
ElfW(Half) dlpi_phnum;
unsigned long long int dlpi_adds;
unsigned long long int dlpi_subs;
};
match = 0;
phdr = info->dlpi_phdr;
load_base = info->dlpi_addr;
p_eh_frame_hdr = NULL;
p_dynamic = NULL;
struct frame_hdr_cache_element *prev_cache_entry = NULL,
*last_cache_entry = NULL;
if (data->check_cache && size >= sizeof (struct ext_dl_phdr_info))
{
static unsigned long long adds = -1ULL, subs;
struct ext_dl_phdr_info *einfo = (struct ext_dl_phdr_info *) info;
/* We use a least recently used cache replacement policy. Also,
the most recently used cache entries are placed at the head
of the search chain. */
if (einfo->dlpi_adds == adds && einfo->dlpi_subs == subs)
{
/* Find data->pc in shared library cache.
Set load_base, p_eh_frame_hdr and p_dynamic
plus match from the cache and goto
"Read .eh_frame_hdr header." below. */
struct frame_hdr_cache_element *cache_entry;
for (cache_entry = frame_hdr_cache_head;
cache_entry;
cache_entry = cache_entry->link)
{
if (data->pc >= cache_entry->pc_low
&& data->pc < cache_entry->pc_high)
{
load_base = cache_entry->load_base;
p_eh_frame_hdr = cache_entry->p_eh_frame_hdr;
p_dynamic = cache_entry->p_dynamic;
/* And move the entry we're using to the head. */
if (cache_entry != frame_hdr_cache_head)
{
prev_cache_entry->link = cache_entry->link;
cache_entry->link = frame_hdr_cache_head;
frame_hdr_cache_head = cache_entry;
}
goto found;
}
last_cache_entry = cache_entry;
/* Exit early if we found an unused entry. */
if ((cache_entry->pc_low | cache_entry->pc_high) == 0)
break;
if (cache_entry->link != NULL)
prev_cache_entry = cache_entry;
}
}
else
{
adds = einfo->dlpi_adds;
subs = einfo->dlpi_subs;
/* Initialize the cache. Create a chain of cache entries,
with the final one terminated by a NULL link. */
int i;
for (i = 0; i < FRAME_HDR_CACHE_SIZE; i++)
{
frame_hdr_cache[i].pc_low = 0;
frame_hdr_cache[i].pc_high = 0;
frame_hdr_cache[i].link = &frame_hdr_cache[i+1];
}
frame_hdr_cache[i-1].link = NULL;
frame_hdr_cache_head = &frame_hdr_cache[0];
data->check_cache = 0;
}
}
/* Make sure struct dl_phdr_info is at least as big as we need. */
if (size < offsetof (struct dl_phdr_info, dlpi_phnum)
+ sizeof (info->dlpi_phnum))
return -1;
/* See if PC falls into one of the loaded segments. Find the eh_frame
segment at the same time. */
for (n = info->dlpi_phnum; --n >= 0; phdr++)
{
if (phdr->p_type == PT_LOAD)
{
_Unwind_Ptr vaddr = (_Unwind_Ptr)
__RELOC_POINTER (phdr->p_vaddr, load_base);
if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz)
{
match = 1;
pc_low = vaddr;
pc_high = vaddr + phdr->p_memsz;
}
}
else if (phdr->p_type == PT_GNU_EH_FRAME)
p_eh_frame_hdr = phdr;
#ifdef PT_SUNW_UNWIND
/* Sun ld emits PT_SUNW_UNWIND .eh_frame_hdr sections instead of
PT_SUNW_EH_FRAME/PT_GNU_EH_FRAME, so accept them as well. */
else if (phdr->p_type == PT_SUNW_UNWIND)
p_eh_frame_hdr = phdr;
#endif
else if (phdr->p_type == PT_DYNAMIC)
p_dynamic = phdr;
}
if (!match)
return 0;
if (size >= sizeof (struct ext_dl_phdr_info))
{
/* Move the cache entry we're about to overwrite to the head of
the list. If either last_cache_entry or prev_cache_entry are
NULL, that cache entry is already at the head. */
if (last_cache_entry != NULL && prev_cache_entry != NULL)
{
prev_cache_entry->link = last_cache_entry->link;
last_cache_entry->link = frame_hdr_cache_head;
frame_hdr_cache_head = last_cache_entry;
}
frame_hdr_cache_head->load_base = load_base;
frame_hdr_cache_head->p_eh_frame_hdr = p_eh_frame_hdr;
frame_hdr_cache_head->p_dynamic = p_dynamic;
frame_hdr_cache_head->pc_low = pc_low;
frame_hdr_cache_head->pc_high = pc_high;
}
found:
if (!p_eh_frame_hdr)
return 0;
/* Read .eh_frame_hdr header. */
data->hdr = (const struct unw_eh_frame_hdr *)
__RELOC_POINTER (p_eh_frame_hdr->p_vaddr, load_base);
#ifdef CRT_GET_RFIB_DATA
# if defined __i386__ || defined __nios2__
data->dbase = NULL;
if (p_dynamic)
{
/* For dynamically linked executables and shared libraries,
DT_PLTGOT is the gp value for that object. */
ElfW(Dyn) *dyn = (ElfW(Dyn) *)
__RELOC_POINTER (p_dynamic->p_vaddr, load_base);
for (; dyn->d_tag != DT_NULL ; dyn++)
if (dyn->d_tag == DT_PLTGOT)
{
data->dbase = (void *) dyn->d_un.d_ptr;
#if defined __linux__
/* On IA-32 Linux, _DYNAMIC is writable and GLIBC has
relocated it. */
#elif defined __sun__ && defined __svr4__
/* On Solaris 2/x86, we need to do this ourselves. */
data->dbase += load_base;
#endif
break;
}
}
# elif (defined __FRV_FDPIC__ || defined __BFIN_FDPIC__) && defined __linux__
data->dbase = load_base.got_value;
# else
# error What is DW_EH_PE_datarel base on this platform?
# endif
#endif
return 1;
}
/* Find the FDE for the program counter PC, in a previously located
PT_GNU_EH_FRAME data region. *BASES is updated if an FDE to return is
found. */
static const fde *
find_fde_tail (_Unwind_Ptr pc,
const struct unw_eh_frame_hdr *hdr,
_Unwind_Ptr dbase,
struct dwarf_eh_bases *bases)
{
const unsigned char *p = (const unsigned char *) (hdr + 1);
_Unwind_Ptr eh_frame;
struct object ob;
if (hdr->version != 1)
return NULL;
p = read_encoded_value_with_base (hdr->eh_frame_ptr_enc,
base_from_cb_data (hdr->eh_frame_ptr_enc,
dbase),
p, &eh_frame);
/* We require here specific table encoding to speed things up.
Also, DW_EH_PE_datarel here means using PT_GNU_EH_FRAME start
as base, not the processor specific DW_EH_PE_datarel. */
if (hdr->fde_count_enc != DW_EH_PE_omit
&& hdr->table_enc == (DW_EH_PE_datarel | DW_EH_PE_sdata4))
{
_Unwind_Ptr fde_count;
p = read_encoded_value_with_base (hdr->fde_count_enc,
base_from_cb_data (hdr->fde_count_enc,
dbase),
p, &fde_count);
/* Shouldn't happen. */
if (fde_count == 0)
return NULL;
if ((((_Unwind_Ptr) p) & 3) == 0)
{
struct fde_table {
signed initial_loc __attribute__ ((mode (SI)));
signed fde __attribute__ ((mode (SI)));
};
const struct fde_table *table = (const struct fde_table *) p;
size_t lo, hi, mid;
_Unwind_Ptr data_base = (_Unwind_Ptr) hdr;
fde *f;
unsigned int f_enc, f_enc_size;
_Unwind_Ptr range;
mid = fde_count - 1;
if (pc < table[0].initial_loc + data_base)
return NULL;
else if (pc < table[mid].initial_loc + data_base)
{
lo = 0;
hi = mid;
while (lo < hi)
{
mid = (lo + hi) / 2;
if (pc < table[mid].initial_loc + data_base)
hi = mid;
else if (pc >= table[mid + 1].initial_loc + data_base)
lo = mid + 1;
else
break;
}
gcc_assert (lo < hi);
}
f = (fde *) (table[mid].fde + data_base);
f_enc = get_fde_encoding (f);
f_enc_size = size_of_encoded_value (f_enc);
read_encoded_value_with_base (f_enc & 0x0f, 0,
&f->pc_begin[f_enc_size], &range);
_Unwind_Ptr func = table[mid].initial_loc + data_base;
if (pc < table[mid].initial_loc + data_base + range)
{
bases->tbase = NULL;
bases->dbase = (void *) dbase;
bases->func = (void *) func;
return f;
}
else
return NULL;
}
}
/* We have no sorted search table, so need to go the slow way.
As soon as GLIBC will provide API so to notify that a library has been
removed, we could cache this (and thus use search_object). */
ob.pc_begin = NULL;
ob.tbase = NULL;
ob.dbase = (void *) dbase;
ob.u.single = (fde *) eh_frame;
ob.s.i = 0;
ob.s.b.mixed_encoding = 1; /* Need to assume worst case. */
const fde *entry = linear_search_fdes (&ob, (fde *) eh_frame, (void *) pc);
if (entry != NULL)
{
_Unwind_Ptr func;
unsigned int encoding = get_fde_encoding (entry);
read_encoded_value_with_base (encoding,
base_from_cb_data (encoding, dbase),
entry->pc_begin, &func);
bases->tbase = NULL;
bases->dbase = (void *) dbase;
bases->func = (void *) func;
}
return entry;
}
const fde *
_Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
{
struct unw_eh_callback_data data;
const fde *ret;
ret = _Unwind_Find_registered_FDE (pc, bases);
if (ret != NULL)
return ret;
/* Use DLFO_STRUCT_HAS_EH_DBASE as a proxy for the existence of a glibc-style
_dl_find_object function. */
#ifdef DLFO_STRUCT_HAS_EH_DBASE
{
struct dl_find_object dlfo;
if (_dl_find_object (pc, &dlfo) == 0 && dlfo.dlfo_eh_frame != NULL)
return find_fde_tail ((_Unwind_Ptr) pc, dlfo.dlfo_eh_frame,
# if DLFO_STRUCT_HAS_EH_DBASE
(_Unwind_Ptr) dlfo.dlfo_eh_dbase,
# else
NULL,
# endif
bases);
else
return NULL;
}
#endif /* DLFO_STRUCT_HAS_EH_DBASE */
data.pc = (_Unwind_Ptr) pc;
#if NEED_DBASE_MEMBER
data.dbase = NULL;
#endif
data.check_cache = 1;
if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) <= 0)
return NULL;
_Unwind_Ptr dbase = unw_eh_callback_data_dbase (&data);
return find_fde_tail ((_Unwind_Ptr) pc, data.hdr, dbase, bases);
}
#else
/* Prevent multiple include of header files. */
#define _Unwind_Find_FDE _Unwind_Find_FDE
#include "unwind-dw2-fde.c"
#endif
#if defined (USE_GAS_SYMVER) && defined (SHARED) && defined (USE_LIBUNWIND_EXCEPTIONS)
alias (_Unwind_Find_FDE);
#endif