/*
* Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include <unistd.h>
#include <sys/procfs.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include "symtab.h"
#include "salibelf.h"
// ----------------------------------------------------
// functions for symbol lookups
// ----------------------------------------------------
struct elf_section {
ELF_SHDR *c_shdr;
void *c_data;
};
struct elf_symbol {
char *name;
uintptr_t offset;
uintptr_t size;
};
typedef struct symtab {
char *strs;
size_t num_symbols;
struct elf_symbol *symbols;
struct hsearch_data *hash_table;
} symtab_t;
// Directory that contains global debuginfo files. In theory it
// should be possible to change this, but in a Java environment there
// is no obvious place to put a user interface to do it. Maybe this
// could be set with an environment variable.
static const char debug_file_directory[] = "/usr/lib/debug";
/* The CRC used in gnu_debuglink, retrieved from
http://sourceware.org/gdb/current/onlinedocs/gdb/Separate-Debug-Files.html#Separate-Debug-Files. */
unsigned int gnu_debuglink_crc32 (unsigned int crc,
unsigned char *buf, size_t len)
{
static const unsigned int 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
};
unsigned char *end;
crc = ~crc & 0xffffffff;
for (end = buf + len; buf < end; ++buf)
crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
return ~crc & 0xffffffff;
}
/* Open a debuginfo file and check its CRC. If it exists and the CRC
matches return its fd. */
static int
open_debug_file (const char *pathname, unsigned int crc)
{
unsigned int file_crc = 0;
unsigned char buffer[8 * 1024];
int fd = pathmap_open(pathname);
if (fd < 0)
return -1;
lseek(fd, 0, SEEK_SET);
for (;;) {
int len = read(fd, buffer, sizeof buffer);
if (len <= 0)
break;
file_crc = gnu_debuglink_crc32(file_crc, buffer, len);
}
if (crc == file_crc)
return fd;
else {
close(fd);
return -1;
}
}
/* Find an ELF section. */
static struct elf_section *find_section_by_name(char *name,
int fd,
ELF_EHDR *ehdr,
ELF_SHDR *shbuf,
struct elf_section *scn_cache)
{
ELF_SHDR* cursct = NULL;
char *strtab;
int cnt;
if (scn_cache[ehdr->e_shstrndx].c_data == NULL) {
if ((scn_cache[ehdr->e_shstrndx].c_data
= read_section_data(fd, ehdr, cursct)) == NULL) {
return NULL;
}
}
strtab = scn_cache[ehdr->e_shstrndx].c_data;
for (cursct = shbuf, cnt = 0;
cnt < ehdr->e_shnum;
cnt++, cursct++) {
if (strcmp(cursct->sh_name + strtab, name) == 0) {
scn_cache[cnt].c_data = read_section_data(fd, ehdr, cursct);
return &scn_cache[cnt];
}
}
return NULL;
}
/* Look for a ".gnu_debuglink" section. If one exists, try to open a
suitable debuginfo file. */
static int open_file_from_debug_link(const char *name,
int fd,
ELF_EHDR *ehdr,
ELF_SHDR *shbuf,
struct elf_section *scn_cache)
{
int debug_fd;
struct elf_section *debug_link = find_section_by_name(".gnu_debuglink", fd, ehdr,
shbuf, scn_cache);
if (debug_link == NULL)
return -1;
char *debug_filename = debug_link->c_data;
int offset = (strlen(debug_filename) + 4) >> 2;
static unsigned int crc;
crc = ((unsigned int*)debug_link->c_data)[offset];
char *debug_pathname = malloc(strlen(debug_filename)
+ strlen(name)
+ strlen(".debug/")
+ strlen(debug_file_directory)
+ 2);
strcpy(debug_pathname, name);
char *last_slash = strrchr(debug_pathname, '/');
if (last_slash == NULL)
return -1;
/* Look in the same directory as the object. */
strcpy(last_slash+1, debug_filename);
debug_fd = open_debug_file(debug_pathname, crc);
if (debug_fd >= 0) {
free(debug_pathname);
return debug_fd;
}
/* Look in a subdirectory named ".debug". */
strcpy(last_slash+1, ".debug/");
strcat(last_slash, debug_filename);
debug_fd = open_debug_file(debug_pathname, crc);
if (debug_fd >= 0) {
free(debug_pathname);
return debug_fd;
}
/* Look in /usr/lib/debug + the full pathname. */
strcpy(debug_pathname, debug_file_directory);
strcat(debug_pathname, name);
last_slash = strrchr(debug_pathname, '/');
strcpy(last_slash+1, debug_filename);
debug_fd = open_debug_file(debug_pathname, crc);
if (debug_fd >= 0) {
free(debug_pathname);
return debug_fd;
}
free(debug_pathname);
return -1;
}
static struct symtab* build_symtab_internal(int fd, const char *filename, bool try_debuginfo);
/* Look for a ".gnu_debuglink" section. If one exists, try to open a
suitable debuginfo file and read a symbol table from it. */
static struct symtab *build_symtab_from_debug_link(const char *name,
int fd,
ELF_EHDR *ehdr,
ELF_SHDR *shbuf,
struct elf_section *scn_cache)
{
fd = open_file_from_debug_link(name, fd, ehdr, shbuf, scn_cache);
if (fd >= 0) {
struct symtab *symtab = build_symtab_internal(fd, NULL, /* try_debuginfo */ false);
close(fd);
return symtab;
}
return NULL;
}
// Given a build_id, find the associated debuginfo file
static char *
build_id_to_debug_filename (size_t size, unsigned char *data)
{
char *filename, *s;
filename = malloc(strlen (debug_file_directory) + (sizeof "/.build-id/" - 1) + 1
+ 2 * size + (sizeof ".debug" - 1) + 1);
s = filename + sprintf (filename, "%s/.build-id/", debug_file_directory);
if (size > 0)
{
size--;
s += sprintf (s, "%02x", *data++);
}
if (size > 0)
*s++ = '/';
while (size-- > 0)
s += sprintf (s, "%02x", *data++);
strcpy (s, ".debug");
return filename;
}
// Read a build ID note. Try to open any associated debuginfo file
// and return its symtab
static struct symtab* build_symtab_from_build_id(Elf64_Nhdr *note)
{
int fd;
struct symtab *symtab = NULL;
unsigned char *bytes
= (unsigned char*)(note+1) + note->n_namesz;
unsigned char *filename
= (build_id_to_debug_filename (note->n_descsz, bytes));
fd = pathmap_open(filename);
if (fd >= 0) {
symtab = build_symtab_internal(fd, NULL, /* try_debuginfo */ false);
close(fd);
}
free(filename);
return symtab;
}
// read symbol table from given fd. If try_debuginfo) is true, also
// try to open an associated debuginfo file
static struct symtab* build_symtab_internal(int fd, const char *filename, bool try_debuginfo) {
ELF_EHDR ehdr;
char *names = NULL;
struct symtab* symtab = NULL;
// Reading of elf header
struct elf_section *scn_cache = NULL;
int cnt = 0;
ELF_SHDR* shbuf = NULL;
ELF_SHDR* cursct = NULL;
ELF_PHDR* phbuf = NULL;
ELF_PHDR* phdr = NULL;
int sym_section = SHT_DYNSYM;
uintptr_t baseaddr = (uintptr_t)-1;
lseek(fd, (off_t)0L, SEEK_SET);
if (! read_elf_header(fd, &ehdr)) {
// not an elf
return NULL;
}
// read ELF header
if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {
goto quit;
}
baseaddr = find_base_address(fd, &ehdr);
scn_cache = (struct elf_section *)
calloc(ehdr.e_shnum * sizeof(struct elf_section), 1);
if (scn_cache == NULL) {
goto quit;
}
for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {
scn_cache[cnt].c_shdr = cursct;
if (cursct->sh_type == SHT_SYMTAB || cursct->sh_type == SHT_STRTAB
|| cursct->sh_type == SHT_NOTE || cursct->sh_type == SHT_DYNSYM) {
if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {
goto quit;
}
}
if (cursct->sh_type == SHT_SYMTAB) {
// Full symbol table available so use that
sym_section = cursct->sh_type;
}
cursct++;
}
for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {
ELF_SHDR *shdr = scn_cache[cnt].c_shdr;
if (shdr->sh_type == sym_section) {
ELF_SYM *syms;
int j, n, rslt;
size_t size;
// FIXME: there could be multiple data buffers associated with the
// same ELF section. Here we can handle only one buffer. See man page
// for elf_getdata on Solaris.
// guarantee(symtab == NULL, "multiple symtab");
symtab = (struct symtab*)calloc(1, sizeof(struct symtab));
if (symtab == NULL) {
goto quit;
}
// the symbol table
syms = (ELF_SYM *)scn_cache[cnt].c_data;
// number of symbols
n = shdr->sh_size / shdr->sh_entsize;
// create hash table, we use hcreate_r, hsearch_r and hdestroy_r to
// manipulate the hash table.
symtab->hash_table = (struct hsearch_data*) calloc(1, sizeof(struct hsearch_data));
rslt = hcreate_r(n, symtab->hash_table);
// guarantee(rslt, "unexpected failure: hcreate_r");
// shdr->sh_link points to the section that contains the actual strings
// for symbol names. the st_name field in ELF_SYM is just the
// string table index. we make a copy of the string table so the
// strings will not be destroyed by elf_end.
size = scn_cache[shdr->sh_link].c_shdr->sh_size;
symtab->strs = (char *)malloc(size);
memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);
// allocate memory for storing symbol offset and size;
symtab->num_symbols = n;
symtab->symbols = (struct elf_symbol *)calloc(n , sizeof(struct elf_symbol));
// copy symbols info our symtab and enter them info the hash table
for (j = 0; j < n; j++, syms++) {
ENTRY item, *ret;
char *sym_name = symtab->strs + syms->st_name;
// skip non-object and non-function symbols
int st_type = ELF_ST_TYPE(syms->st_info);
if ( st_type != STT_FUNC && st_type != STT_OBJECT)
continue;
// skip empty strings and undefined symbols
if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;
symtab->symbols[j].name = sym_name;
symtab->symbols[j].offset = syms->st_value - baseaddr;
symtab->symbols[j].size = syms->st_size;
item.key = sym_name;
item.data = (void *)&(symtab->symbols[j]);
hsearch_r(item, ENTER, &ret, symtab->hash_table);
}
}
}
// Look for a separate debuginfo file.
if (try_debuginfo) {
// We prefer a debug symtab to an object's own symtab, so look in
// the debuginfo file. We stash a copy of the old symtab in case
// there is no debuginfo.
struct symtab* prev_symtab = symtab;
symtab = NULL;
#ifdef NT_GNU_BUILD_ID
// First we look for a Build ID
for (cursct = shbuf, cnt = 0;
symtab == NULL && cnt < ehdr.e_shnum;
cnt++) {
if (cursct->sh_type == SHT_NOTE) {
Elf64_Nhdr *note = (Elf64_Nhdr *)scn_cache[cnt].c_data;
if (note->n_type == NT_GNU_BUILD_ID) {
symtab = build_symtab_from_build_id(note);
}
}
cursct++;
}
#endif
// Then, if that doesn't work, the debug link
if (symtab == NULL) {
symtab = build_symtab_from_debug_link(filename, fd, &ehdr, shbuf,
scn_cache);
}
// If we still haven't found a symtab, use the object's own symtab.
if (symtab != NULL) {
if (prev_symtab != NULL)
destroy_symtab(prev_symtab);
} else {
symtab = prev_symtab;
}
}
quit:
if (shbuf) free(shbuf);
if (phbuf) free(phbuf);
if (scn_cache) {
for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {
if (scn_cache[cnt].c_data != NULL) {
free(scn_cache[cnt].c_data);
}
}
free(scn_cache);
}
return symtab;
}
struct symtab* build_symtab(int fd, const char *filename) {
return build_symtab_internal(fd, filename, /* try_debuginfo */ true);
}
void destroy_symtab(struct symtab* symtab) {
if (!symtab) return;
if (symtab->strs) free(symtab->strs);
if (symtab->symbols) free(symtab->symbols);
if (symtab->hash_table) {
hdestroy_r(symtab->hash_table);
free(symtab->hash_table);
}
free(symtab);
}
uintptr_t search_symbol(struct symtab* symtab, uintptr_t base,
const char *sym_name, int *sym_size) {
ENTRY item;
ENTRY* ret = NULL;
// library does not have symbol table
if (!symtab || !symtab->hash_table)
return (uintptr_t)NULL;
item.key = (char*) strdup(sym_name);
hsearch_r(item, FIND, &ret, symtab->hash_table);
if (ret) {
struct elf_symbol * sym = (struct elf_symbol *)(ret->data);
uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);
if (sym_size) *sym_size = sym->size;
free(item.key);
return rslt;
}
quit:
free(item.key);
return (uintptr_t) NULL;
}
const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,
uintptr_t* poffset) {
int n = 0;
if (!symtab) return NULL;
for (; n < symtab->num_symbols; n++) {
struct elf_symbol* sym = &(symtab->symbols[n]);
if (sym->name != NULL &&
offset >= sym->offset && offset < sym->offset + sym->size) {
if (poffset) *poffset = (offset - sym->offset);
return sym->name;
}
}
return NULL;
}