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elf.c
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/* elf.c -- Get debug data from an ELF file for backtraces.
Copyright (C) 2012-2021 Free Software Foundation, Inc.
Written by Ian Lance Taylor, Google.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
(1) Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
(2) Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
(3) The name of the author may not be used to
endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
#include "config.h"
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#ifdef HAVE_DL_ITERATE_PHDR
#ifdef HAVE_LINK_H
#include <link.h>
#endif
#ifdef HAVE_SYS_LINK_H
#include <sys/link.h>
#endif
#endif
#include "backtrace.h"
#include "internal.h"
#ifndef S_ISLNK
#ifndef S_IFLNK
#define S_IFLNK 0120000
#endif
#ifndef S_IFMT
#define S_IFMT 0170000
#endif
#define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
#endif
#ifndef __GNUC__
#define __builtin_prefetch(p, r, l)
#define unlikely(x) (x)
#else
#define unlikely(x) __builtin_expect(!!(x), 0)
#endif
#if !defined(HAVE_DECL_STRNLEN) || !HAVE_DECL_STRNLEN
/* If strnlen is not declared, provide our own version. */
static size_t
xstrnlen (const char *s, size_t maxlen)
{
size_t i;
for (i = 0; i < maxlen; ++i)
if (s[i] == '\0')
break;
return i;
}
#define strnlen xstrnlen
#endif
#ifndef HAVE_LSTAT
/* Dummy version of lstat for systems that don't have it. */
static int
xlstat (const char *path ATTRIBUTE_UNUSED, struct stat *st ATTRIBUTE_UNUSED)
{
return -1;
}
#define lstat xlstat
#endif
#ifndef HAVE_READLINK
/* Dummy version of readlink for systems that don't have it. */
static ssize_t
xreadlink (const char *path ATTRIBUTE_UNUSED, char *buf ATTRIBUTE_UNUSED,
size_t bufsz ATTRIBUTE_UNUSED)
{
return -1;
}
#define readlink xreadlink
#endif
#ifndef HAVE_DL_ITERATE_PHDR
/* Dummy version of dl_iterate_phdr for systems that don't have it. */
#define dl_phdr_info x_dl_phdr_info
#define dl_iterate_phdr x_dl_iterate_phdr
struct dl_phdr_info
{
uintptr_t dlpi_addr;
const char *dlpi_name;
};
static int
dl_iterate_phdr (int (*callback) (struct dl_phdr_info *,
size_t, void *) ATTRIBUTE_UNUSED,
void *data ATTRIBUTE_UNUSED)
{
return 0;
}
#endif /* ! defined (HAVE_DL_ITERATE_PHDR) */
/* The configure script must tell us whether we are 32-bit or 64-bit
ELF. We could make this code test and support either possibility,
but there is no point. This code only works for the currently
running executable, which means that we know the ELF mode at
configure time. */
#if BACKTRACE_ELF_SIZE != 32 && BACKTRACE_ELF_SIZE != 64
#error "Unknown BACKTRACE_ELF_SIZE"
#endif
/* <link.h> might #include <elf.h> which might define our constants
with slightly different values. Undefine them to be safe. */
#undef EI_NIDENT
#undef EI_MAG0
#undef EI_MAG1
#undef EI_MAG2
#undef EI_MAG3
#undef EI_CLASS
#undef EI_DATA
#undef EI_VERSION
#undef ELF_MAG0
#undef ELF_MAG1
#undef ELF_MAG2
#undef ELF_MAG3
#undef ELFCLASS32
#undef ELFCLASS64
#undef ELFDATA2LSB
#undef ELFDATA2MSB
#undef EV_CURRENT
#undef ET_DYN
#undef EM_PPC64
#undef EF_PPC64_ABI
#undef SHN_LORESERVE
#undef SHN_XINDEX
#undef SHN_UNDEF
#undef SHT_PROGBITS
#undef SHT_SYMTAB
#undef SHT_STRTAB
#undef SHT_DYNSYM
#undef SHF_COMPRESSED
#undef STT_OBJECT
#undef STT_FUNC
#undef NT_GNU_BUILD_ID
#undef ELFCOMPRESS_ZLIB
#undef ELFCOMPRESS_ZSTD
/* Basic types. */
typedef uint16_t b_elf_half; /* Elf_Half. */
typedef uint32_t b_elf_word; /* Elf_Word. */
typedef int32_t b_elf_sword; /* Elf_Sword. */
#if BACKTRACE_ELF_SIZE == 32
typedef uint32_t b_elf_addr; /* Elf_Addr. */
typedef uint32_t b_elf_off; /* Elf_Off. */
typedef uint32_t b_elf_wxword; /* 32-bit Elf_Word, 64-bit ELF_Xword. */
#else
typedef uint64_t b_elf_addr; /* Elf_Addr. */
typedef uint64_t b_elf_off; /* Elf_Off. */
typedef uint64_t b_elf_xword; /* Elf_Xword. */
typedef int64_t b_elf_sxword; /* Elf_Sxword. */
typedef uint64_t b_elf_wxword; /* 32-bit Elf_Word, 64-bit ELF_Xword. */
#endif
/* Data structures and associated constants. */
#define EI_NIDENT 16
typedef struct {
unsigned char e_ident[EI_NIDENT]; /* ELF "magic number" */
b_elf_half e_type; /* Identifies object file type */
b_elf_half e_machine; /* Specifies required architecture */
b_elf_word e_version; /* Identifies object file version */
b_elf_addr e_entry; /* Entry point virtual address */
b_elf_off e_phoff; /* Program header table file offset */
b_elf_off e_shoff; /* Section header table file offset */
b_elf_word e_flags; /* Processor-specific flags */
b_elf_half e_ehsize; /* ELF header size in bytes */
b_elf_half e_phentsize; /* Program header table entry size */
b_elf_half e_phnum; /* Program header table entry count */
b_elf_half e_shentsize; /* Section header table entry size */
b_elf_half e_shnum; /* Section header table entry count */
b_elf_half e_shstrndx; /* Section header string table index */
} b_elf_ehdr; /* Elf_Ehdr. */
#define EI_MAG0 0
#define EI_MAG1 1
#define EI_MAG2 2
#define EI_MAG3 3
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define ELFMAG0 0x7f
#define ELFMAG1 'E'
#define ELFMAG2 'L'
#define ELFMAG3 'F'
#define ELFCLASS32 1
#define ELFCLASS64 2
#define ELFDATA2LSB 1
#define ELFDATA2MSB 2
#define EV_CURRENT 1
#define ET_DYN 3
#define EM_PPC64 21
#define EF_PPC64_ABI 3
typedef struct {
b_elf_word sh_name; /* Section name, index in string tbl */
b_elf_word sh_type; /* Type of section */
b_elf_wxword sh_flags; /* Miscellaneous section attributes */
b_elf_addr sh_addr; /* Section virtual addr at execution */
b_elf_off sh_offset; /* Section file offset */
b_elf_wxword sh_size; /* Size of section in bytes */
b_elf_word sh_link; /* Index of another section */
b_elf_word sh_info; /* Additional section information */
b_elf_wxword sh_addralign; /* Section alignment */
b_elf_wxword sh_entsize; /* Entry size if section holds table */
} b_elf_shdr; /* Elf_Shdr. */
#define SHN_UNDEF 0x0000 /* Undefined section */
#define SHN_LORESERVE 0xFF00 /* Begin range of reserved indices */
#define SHN_XINDEX 0xFFFF /* Section index is held elsewhere */
#define SHT_PROGBITS 1
#define SHT_SYMTAB 2
#define SHT_STRTAB 3
#define SHT_DYNSYM 11
#define SHF_COMPRESSED 0x800
#if BACKTRACE_ELF_SIZE == 32
typedef struct
{
b_elf_word st_name; /* Symbol name, index in string tbl */
b_elf_addr st_value; /* Symbol value */
b_elf_word st_size; /* Symbol size */
unsigned char st_info; /* Symbol binding and type */
unsigned char st_other; /* Visibility and other data */
b_elf_half st_shndx; /* Symbol section index */
} b_elf_sym; /* Elf_Sym. */
#else /* BACKTRACE_ELF_SIZE != 32 */
typedef struct
{
b_elf_word st_name; /* Symbol name, index in string tbl */
unsigned char st_info; /* Symbol binding and type */
unsigned char st_other; /* Visibility and other data */
b_elf_half st_shndx; /* Symbol section index */
b_elf_addr st_value; /* Symbol value */
b_elf_xword st_size; /* Symbol size */
} b_elf_sym; /* Elf_Sym. */
#endif /* BACKTRACE_ELF_SIZE != 32 */
#define STT_OBJECT 1
#define STT_FUNC 2
typedef struct
{
uint32_t namesz;
uint32_t descsz;
uint32_t type;
char name[1];
} b_elf_note;
#define NT_GNU_BUILD_ID 3
#if BACKTRACE_ELF_SIZE == 32
typedef struct
{
b_elf_word ch_type; /* Compresstion algorithm */
b_elf_word ch_size; /* Uncompressed size */
b_elf_word ch_addralign; /* Alignment for uncompressed data */
} b_elf_chdr; /* Elf_Chdr */
#else /* BACKTRACE_ELF_SIZE != 32 */
typedef struct
{
b_elf_word ch_type; /* Compression algorithm */
b_elf_word ch_reserved; /* Reserved */
b_elf_xword ch_size; /* Uncompressed size */
b_elf_xword ch_addralign; /* Alignment for uncompressed data */
} b_elf_chdr; /* Elf_Chdr */
#endif /* BACKTRACE_ELF_SIZE != 32 */
#define ELFCOMPRESS_ZLIB 1
#define ELFCOMPRESS_ZSTD 2
/* Names of sections, indexed by enum dwarf_section in internal.h. */
static const char * const dwarf_section_names[DEBUG_MAX] =
{
".debug_info",
".debug_line",
".debug_abbrev",
".debug_ranges",
".debug_str",
".debug_addr",
".debug_str_offsets",
".debug_line_str",
".debug_rnglists"
};
/* Information we gather for the sections we care about. */
struct debug_section_info
{
/* Section file offset. */
off_t offset;
/* Section size. */
size_t size;
/* Section contents, after read from file. */
const unsigned char *data;
/* Whether the SHF_COMPRESSED flag is set for the section. */
int compressed;
};
/* Information we keep for an ELF symbol. */
struct elf_symbol
{
/* The name of the symbol. */
const char *name;
/* The address of the symbol. */
uintptr_t address;
/* The size of the symbol. */
size_t size;
};
/* Information to pass to elf_syminfo. */
struct elf_syminfo_data
{
/* Symbols for the next module. */
struct elf_syminfo_data *next;
/* The ELF symbols, sorted by address. */
struct elf_symbol *symbols;
/* The number of symbols. */
size_t count;
/* The name of the shared object (see dl_iterate_phdr's dlpi_name) */
const char* binary_file_name;
/* Base address/offset of the shared object (see dl_iterate_phdr's dlpi_addr) */
uintptr_t base_address;
};
/* A view that works for either a file or memory. */
struct elf_view
{
struct backtrace_view view;
int release; /* If non-zero, must call backtrace_release_view. */
};
/* Information about PowerPC64 ELFv1 .opd section. */
struct elf_ppc64_opd_data
{
/* Address of the .opd section. */
b_elf_addr addr;
/* Section data. */
const char *data;
/* Size of the .opd section. */
size_t size;
/* Corresponding section view. */
struct elf_view view;
};
/* Create a view of SIZE bytes from DESCRIPTOR/MEMORY at OFFSET. */
static int
elf_get_view (struct backtrace_state *state, int descriptor,
const unsigned char *memory, size_t memory_size, off_t offset,
uint64_t size, backtrace_error_callback error_callback,
void *data, struct elf_view *view)
{
if (memory == NULL)
{
view->release = 1;
return backtrace_get_view (state, descriptor, offset, size,
error_callback, data, &view->view);
}
else
{
if ((uint64_t) offset + size > (uint64_t) memory_size)
{
error_callback (data, "out of range for in-memory file", 0);
return 0;
}
view->view.data = (const void *) (memory + offset);
view->view.base = NULL;
view->view.len = size;
view->release = 0;
return 1;
}
}
/* Release a view read by elf_get_view. */
static void
elf_release_view (struct backtrace_state *state, struct elf_view *view,
backtrace_error_callback error_callback, void *data)
{
if (view->release)
backtrace_release_view (state, &view->view, error_callback, data);
}
/* Compute the CRC-32 of BUF/LEN. This uses the CRC used for
.gnu_debuglink files. */
static uint32_t
elf_crc32 (uint32_t crc, const unsigned char *buf, size_t len)
{
static const uint32_t crc32_table[256] =
{
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
0x2d02ef8d
};
const unsigned char *end;
crc = ~crc;
for (end = buf + len; buf < end; ++ buf)
crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
return ~crc;
}
/* Return the CRC-32 of the entire file open at DESCRIPTOR. */
static uint32_t
elf_crc32_file (struct backtrace_state *state, int descriptor,
backtrace_error_callback error_callback, void *data)
{
struct stat st;
struct backtrace_view file_view;
uint32_t ret;
if (fstat (descriptor, &st) < 0)
{
error_callback (data, "fstat", errno);
return 0;
}
if (!backtrace_get_view (state, descriptor, 0, st.st_size, error_callback,
data, &file_view))
return 0;
ret = elf_crc32 (0, (const unsigned char *) file_view.data, st.st_size);
backtrace_release_view (state, &file_view, error_callback, data);
return ret;
}
/* A dummy callback function used when we can't find a symbol
table. */
void
elf_nosyms (struct backtrace_state *state ATTRIBUTE_UNUSED,
uintptr_t addr ATTRIBUTE_UNUSED,
backtrace_syminfo_callback callback ATTRIBUTE_UNUSED,
backtrace_error_callback error_callback, void *data)
{
error_callback (data, "no symbol table in ELF executable", -1);
}
/* A callback function used when we can't find any debug info. */
static int
elf_nodebug (struct backtrace_state *state, uintptr_t pc,
backtrace_full_callback callback,
backtrace_error_callback error_callback, void *data)
{
if (state->syminfo_fn != NULL && state->syminfo_fn != elf_nosyms)
{
struct backtrace_call_full bdata;
/* Fetch symbol information so that we can least get the
function name. */
bdata.full_callback = callback;
bdata.full_error_callback = error_callback;
bdata.full_data = data;
bdata.ret = 0;
state->syminfo_fn (state, pc, backtrace_syminfo_to_full_callback,
backtrace_syminfo_to_full_error_callback, &bdata);
return bdata.ret;
}
error_callback (data, "no debug info in ELF executable", -1);
return 0;
}
/* Compare struct elf_symbol for qsort. */
static int
elf_symbol_compare (const void *v1, const void *v2)
{
const struct elf_symbol *e1 = (const struct elf_symbol *) v1;
const struct elf_symbol *e2 = (const struct elf_symbol *) v2;
if (e1->address < e2->address)
return -1;
else if (e1->address > e2->address)
return 1;
else
return 0;
}
/* Compare an ADDR against an elf_symbol for bsearch. We allocate one
extra entry in the array so that this can look safely at the next
entry. */
static int
elf_symbol_search (const void *vkey, const void *ventry)
{
const uintptr_t *key = (const uintptr_t *) vkey;
const struct elf_symbol *entry = (const struct elf_symbol *) ventry;
uintptr_t addr;
addr = *key;
if (addr < entry->address)
return -1;
else if (addr >= entry->address + entry->size)
return 1;
else
return 0;
}
/* Initialize the symbol table info for elf_syminfo. */
static int
elf_initialize_syminfo (struct backtrace_state *state,
uintptr_t base_address,
const unsigned char *symtab_data, size_t symtab_size,
const unsigned char *strtab, size_t strtab_size,
backtrace_error_callback error_callback,
void *data, struct elf_syminfo_data *sdata,
struct elf_ppc64_opd_data *opd,
const char *binary_filename)
{
size_t sym_count;
const b_elf_sym *sym;
size_t elf_symbol_count;
size_t elf_symbol_size;
struct elf_symbol *elf_symbols;
size_t i;
unsigned int j;
sym_count = symtab_size / sizeof (b_elf_sym);
/* We only care about function symbols. Count them. */
sym = (const b_elf_sym *) symtab_data;
elf_symbol_count = 0;
for (i = 0; i < sym_count; ++i, ++sym)
{
int info;
info = sym->st_info & 0xf;
if ((info == STT_FUNC || info == STT_OBJECT)
&& sym->st_shndx != SHN_UNDEF)
++elf_symbol_count;
}
elf_symbol_size = elf_symbol_count * sizeof (struct elf_symbol);
elf_symbols = ((struct elf_symbol *)
backtrace_alloc (state, elf_symbol_size, error_callback,
data));
if (elf_symbols == NULL)
return 0;
sym = (const b_elf_sym *) symtab_data;
j = 0;
for (i = 0; i < sym_count; ++i, ++sym)
{
int info;
info = sym->st_info & 0xf;
if (info != STT_FUNC && info != STT_OBJECT)
continue;
if (sym->st_shndx == SHN_UNDEF)
continue;
if (sym->st_name >= strtab_size)
{
error_callback (data, "symbol string index out of range", 0);
backtrace_free (state, elf_symbols, elf_symbol_size, error_callback,
data);
return 0;
}
elf_symbols[j].name = (const char *) strtab + sym->st_name;
/* Special case PowerPC64 ELFv1 symbols in .opd section, if the symbol
is a function descriptor, read the actual code address from the
descriptor. */
if (opd
&& sym->st_value >= opd->addr
&& sym->st_value < opd->addr + opd->size)
elf_symbols[j].address
= *(const b_elf_addr *) (opd->data + (sym->st_value - opd->addr));
else
elf_symbols[j].address = sym->st_value;
elf_symbols[j].address += base_address;
elf_symbols[j].size = sym->st_size;
++j;
}
backtrace_qsort (elf_symbols, elf_symbol_count, sizeof (struct elf_symbol),
elf_symbol_compare);
sdata->next = NULL;
sdata->symbols = elf_symbols;
sdata->count = elf_symbol_count;
sdata->binary_file_name = binary_filename;
sdata->base_address = base_address;
return 1;
}
/* Add EDATA to the list in STATE. */
static void
elf_add_syminfo_data (struct backtrace_state *state,
struct elf_syminfo_data *edata)
{
if (!state->threaded)
{
struct elf_syminfo_data **pp;
for (pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;
*pp != NULL;
pp = &(*pp)->next)
;
*pp = edata;
}
else
{
while (1)
{
struct elf_syminfo_data **pp;
pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;
while (1)
{
struct elf_syminfo_data *p;
p = backtrace_atomic_load_pointer (pp);
if (p == NULL)
break;
pp = &p->next;
}
if (__sync_bool_compare_and_swap (pp, NULL, edata))
break;
}
}
}
/* Return the symbol name and value for an ADDR. */
void
elf_syminfo (struct backtrace_state *state, uintptr_t addr,
backtrace_syminfo_callback callback,
backtrace_error_callback error_callback ATTRIBUTE_UNUSED,
void *data)
{
struct elf_syminfo_data *edata;
struct elf_symbol *sym = NULL;
if (!state->threaded)
{
for (edata = (struct elf_syminfo_data *) state->syminfo_data;
edata != NULL;
edata = edata->next)
{
sym = ((struct elf_symbol *)
bsearch (&addr, edata->symbols, edata->count,
sizeof (struct elf_symbol), elf_symbol_search));
if (sym != NULL)
break;
}
}
else
{
struct elf_syminfo_data **pp;
pp = (struct elf_syminfo_data **) (void *) &state->syminfo_data;
while (1)
{
edata = backtrace_atomic_load_pointer (pp);
if (edata == NULL)
break;
sym = ((struct elf_symbol *)
bsearch (&addr, edata->symbols, edata->count,
sizeof (struct elf_symbol), elf_symbol_search));
if (sym != NULL)
break;
pp = &edata->next;
}
}
if (sym == NULL)
callback(data, addr, NULL, 0, 0, NULL, 0);
else
callback(data, addr, sym->name, sym->address, sym->size, edata->binary_file_name, edata->base_address);
}
/* Return whether FILENAME is a symlink. */
static int
elf_is_symlink (const char *filename)
{
struct stat st;
if (lstat (filename, &st) < 0)
return 0;
return S_ISLNK (st.st_mode);
}
/* Return the results of reading the symlink FILENAME in a buffer
allocated by backtrace_alloc. Return the length of the buffer in
*LEN. */
static char *
elf_readlink (struct backtrace_state *state, const char *filename,
backtrace_error_callback error_callback, void *data,
size_t *plen)
{
size_t len;
char *buf;
len = 128;
while (1)
{
ssize_t rl;
buf = backtrace_alloc (state, len, error_callback, data);
if (buf == NULL)
return NULL;
rl = readlink (filename, buf, len);
if (rl < 0)
{
backtrace_free (state, buf, len, error_callback, data);
return NULL;
}
if ((size_t) rl < len - 1)
{
buf[rl] = '\0';
*plen = len;
return buf;
}
backtrace_free (state, buf, len, error_callback, data);
len *= 2;
}
}
#define SYSTEM_BUILD_ID_DIR "/usr/lib/debug/.build-id/"
/* Open a separate debug info file, using the build ID to find it.
Returns an open file descriptor, or -1.
The GDB manual says that the only place gdb looks for a debug file
when the build ID is known is in /usr/lib/debug/.build-id. */
static int
elf_open_debugfile_by_buildid (struct backtrace_state *state,
const char *buildid_data, size_t buildid_size,
backtrace_error_callback error_callback,
void *data)
{
const char * const prefix = SYSTEM_BUILD_ID_DIR;
const size_t prefix_len = strlen (prefix);
const char * const suffix = ".debug";
const size_t suffix_len = strlen (suffix);
size_t len;
char *bd_filename;
char *t;
size_t i;
int ret;
int does_not_exist;
len = prefix_len + buildid_size * 2 + suffix_len + 2;
bd_filename = backtrace_alloc (state, len, error_callback, data);
if (bd_filename == NULL)
return -1;
t = bd_filename;
memcpy (t, prefix, prefix_len);
t += prefix_len;
for (i = 0; i < buildid_size; i++)
{
unsigned char b;
unsigned char nib;
b = (unsigned char) buildid_data[i];
nib = (b & 0xf0) >> 4;
*t++ = nib < 10 ? '0' + nib : 'a' + nib - 10;
nib = b & 0x0f;
*t++ = nib < 10 ? '0' + nib : 'a' + nib - 10;
if (i == 0)
*t++ = '/';
}
memcpy (t, suffix, suffix_len);
t[suffix_len] = '\0';
ret = backtrace_open (bd_filename, error_callback, data, &does_not_exist);
backtrace_free (state, bd_filename, len, error_callback, data);
/* gdb checks that the debuginfo file has the same build ID note.
That seems kind of pointless to me--why would it have the right
name but not the right build ID?--so skipping the check. */
return ret;
}
/* Try to open a file whose name is PREFIX (length PREFIX_LEN)
concatenated with PREFIX2 (length PREFIX2_LEN) concatenated with
DEBUGLINK_NAME. Returns an open file descriptor, or -1. */
static int
elf_try_debugfile (struct backtrace_state *state, const char *prefix,
size_t prefix_len, const char *prefix2, size_t prefix2_len,
const char *debuglink_name,
const char *ref_filename,
backtrace_error_callback error_callback, void *data)
{
size_t debuglink_len;
size_t try_len;
char *try;
int does_not_exist;
int ret;
debuglink_len = strlen (debuglink_name);
try_len = prefix_len + prefix2_len + debuglink_len + 1;
try = backtrace_alloc (state, try_len, error_callback, data);
if (try == NULL)
return -1;
memcpy (try, prefix, prefix_len);
memcpy (try + prefix_len, prefix2, prefix2_len);
memcpy (try + prefix_len + prefix2_len, debuglink_name, debuglink_len);
try[prefix_len + prefix2_len + debuglink_len] = '\0';
if(ref_filename && *ref_filename && !strcmp(try, ref_filename))
return -1; // loop detected
ret = backtrace_open (try, error_callback, data, &does_not_exist);
backtrace_free (state, try, try_len, error_callback, data);
return ret;
}
/* Find a separate debug info file, using the debuglink section data
to find it. Returns an open file descriptor, or -1. */
static int
elf_find_debugfile_by_debuglink (struct backtrace_state *state,
const char *filename,
const char *debuglink_name,
backtrace_error_callback error_callback,
void *data)
{
int ret;
char *alc;
size_t alc_len;
const char *slash;
int ddescriptor;
const char *prefix;
size_t prefix_len;
/* Resolve symlinks in FILENAME. Since FILENAME is fairly likely to
be /proc/self/exe, symlinks are common. We don't try to resolve
the whole path name, just the base name. */
ret = -1;
alc = NULL;
alc_len = 0;
while (elf_is_symlink (filename))
{
char *new_buf;
size_t new_len;
new_buf = elf_readlink (state, filename, error_callback, data, &new_len);
if (new_buf == NULL)
break;
if (new_buf[0] == '/')
filename = new_buf;
else
{