perf symbols: Implement poor man's ELF parser

Implement a minimal elf parser for getting build-id.  It assumes that
required elf.h header is provided by libc header on the system and the
parser only looks for PT_NOTE program header to check build-id.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344228082-15569-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Namhyung Kim 2012-08-06 13:41:22 +09:00 committed by Arnaldo Carvalho de Melo
parent 393be2e374
commit b691f64360

View file

@ -1,15 +1,71 @@
#include "symbol.h"
#include <elf.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <byteswap.h>
#include <sys/stat.h>
int filename__read_build_id(const char *filename __used, void *bf __used,
size_t size __used)
static bool check_need_swap(int file_endian)
{
return -1;
const int data = 1;
u8 *check = (u8 *)&data;
int host_endian;
if (check[0] == 1)
host_endian = ELFDATA2LSB;
else
host_endian = ELFDATA2MSB;
return host_endian != file_endian;
}
int sysfs__read_build_id(const char *filename __used, void *build_id __used,
size_t size __used)
#define NOTE_ALIGN(sz) (((sz) + 3) & ~3)
#define NT_GNU_BUILD_ID 3
static int read_build_id(void *note_data, size_t note_len, void *bf,
size_t size, bool need_swap)
{
struct {
u32 n_namesz;
u32 n_descsz;
u32 n_type;
} *nhdr;
void *ptr;
ptr = note_data;
while (ptr < (note_data + note_len)) {
const char *name;
size_t namesz, descsz;
nhdr = ptr;
if (need_swap) {
nhdr->n_namesz = bswap_32(nhdr->n_namesz);
nhdr->n_descsz = bswap_32(nhdr->n_descsz);
nhdr->n_type = bswap_32(nhdr->n_type);
}
namesz = NOTE_ALIGN(nhdr->n_namesz);
descsz = NOTE_ALIGN(nhdr->n_descsz);
ptr += sizeof(*nhdr);
name = ptr;
ptr += namesz;
if (nhdr->n_type == NT_GNU_BUILD_ID &&
nhdr->n_namesz == sizeof("GNU")) {
if (memcmp(name, "GNU", sizeof("GNU")) == 0) {
size_t sz = min(size, descsz);
memcpy(bf, ptr, sz);
memset(bf + sz, 0, size - sz);
return 0;
}
}
ptr += descsz;
}
return -1;
}
@ -19,6 +75,172 @@ int filename__read_debuglink(const char *filename __used,
return -1;
}
/*
* Just try PT_NOTE header otherwise fails
*/
int filename__read_build_id(const char *filename, void *bf, size_t size)
{
FILE *fp;
int ret = -1;
bool need_swap = false;
u8 e_ident[EI_NIDENT];
size_t buf_size;
void *buf;
int i;
fp = fopen(filename, "r");
if (fp == NULL)
return -1;
if (fread(e_ident, sizeof(e_ident), 1, fp) != 1)
goto out;
if (memcmp(e_ident, ELFMAG, SELFMAG) ||
e_ident[EI_VERSION] != EV_CURRENT)
goto out;
need_swap = check_need_swap(e_ident[EI_DATA]);
/* for simplicity */
fseek(fp, 0, SEEK_SET);
if (e_ident[EI_CLASS] == ELFCLASS32) {
Elf32_Ehdr ehdr;
Elf32_Phdr *phdr;
if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
goto out;
if (need_swap) {
ehdr.e_phoff = bswap_32(ehdr.e_phoff);
ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
ehdr.e_phnum = bswap_16(ehdr.e_phnum);
}
buf_size = ehdr.e_phentsize * ehdr.e_phnum;
buf = malloc(buf_size);
if (buf == NULL)
goto out;
fseek(fp, ehdr.e_phoff, SEEK_SET);
if (fread(buf, buf_size, 1, fp) != 1)
goto out_free;
for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
void *tmp;
if (need_swap) {
phdr->p_type = bswap_32(phdr->p_type);
phdr->p_offset = bswap_32(phdr->p_offset);
phdr->p_filesz = bswap_32(phdr->p_filesz);
}
if (phdr->p_type != PT_NOTE)
continue;
buf_size = phdr->p_filesz;
tmp = realloc(buf, buf_size);
if (tmp == NULL)
goto out_free;
buf = tmp;
fseek(fp, phdr->p_offset, SEEK_SET);
if (fread(buf, buf_size, 1, fp) != 1)
goto out_free;
ret = read_build_id(buf, buf_size, bf, size, need_swap);
if (ret == 0)
ret = size;
break;
}
} else {
Elf64_Ehdr ehdr;
Elf64_Phdr *phdr;
if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
goto out;
if (need_swap) {
ehdr.e_phoff = bswap_64(ehdr.e_phoff);
ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
ehdr.e_phnum = bswap_16(ehdr.e_phnum);
}
buf_size = ehdr.e_phentsize * ehdr.e_phnum;
buf = malloc(buf_size);
if (buf == NULL)
goto out;
fseek(fp, ehdr.e_phoff, SEEK_SET);
if (fread(buf, buf_size, 1, fp) != 1)
goto out_free;
for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
void *tmp;
if (need_swap) {
phdr->p_type = bswap_32(phdr->p_type);
phdr->p_offset = bswap_64(phdr->p_offset);
phdr->p_filesz = bswap_64(phdr->p_filesz);
}
if (phdr->p_type != PT_NOTE)
continue;
buf_size = phdr->p_filesz;
tmp = realloc(buf, buf_size);
if (tmp == NULL)
goto out_free;
buf = tmp;
fseek(fp, phdr->p_offset, SEEK_SET);
if (fread(buf, buf_size, 1, fp) != 1)
goto out_free;
ret = read_build_id(buf, buf_size, bf, size, need_swap);
if (ret == 0)
ret = size;
break;
}
}
out_free:
free(buf);
out:
fclose(fp);
return ret;
}
int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
{
int fd;
int ret = -1;
struct stat stbuf;
size_t buf_size;
void *buf;
fd = open(filename, O_RDONLY);
if (fd < 0)
return -1;
if (fstat(fd, &stbuf) < 0)
goto out;
buf_size = stbuf.st_size;
buf = malloc(buf_size);
if (buf == NULL)
goto out;
if (read(fd, buf, buf_size) != (ssize_t) buf_size)
goto out_free;
ret = read_build_id(buf, buf_size, build_id, size, false);
out_free:
free(buf);
out:
close(fd);
return ret;
}
int dso__synthesize_plt_symbols(struct dso *dso __used, char *name __used,
struct map *map __used,
symbol_filter_t filter __used)
@ -26,11 +248,17 @@ int dso__synthesize_plt_symbols(struct dso *dso __used, char *name __used,
return 0;
}
int dso__load_sym(struct dso *dso __used, struct map *map __used,
const char *name __used, int fd __used,
int dso__load_sym(struct dso *dso, struct map *map __used,
const char *name, int fd __used,
symbol_filter_t filter __used, int kmodule __used,
int want_symtab __used)
{
unsigned char *build_id[BUILD_ID_SIZE];
if (filename__read_build_id(name, build_id, BUILD_ID_SIZE) > 0) {
dso__set_build_id(dso, build_id);
return 1;
}
return 0;
}