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
Arnaldo Carvalho de Melo
parent
393be2e374
commit
b691f64360
1 changed files with 235 additions and 7 deletions
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@ -1,15 +1,71 @@
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#include "symbol.h"
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#include <elf.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <string.h>
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#include <byteswap.h>
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#include <sys/stat.h>
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int filename__read_build_id(const char *filename __used, void *bf __used,
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size_t size __used)
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static bool check_need_swap(int file_endian)
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{
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return -1;
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const int data = 1;
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u8 *check = (u8 *)&data;
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int host_endian;
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if (check[0] == 1)
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host_endian = ELFDATA2LSB;
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else
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host_endian = ELFDATA2MSB;
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return host_endian != file_endian;
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}
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int sysfs__read_build_id(const char *filename __used, void *build_id __used,
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size_t size __used)
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#define NOTE_ALIGN(sz) (((sz) + 3) & ~3)
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#define NT_GNU_BUILD_ID 3
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static int read_build_id(void *note_data, size_t note_len, void *bf,
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size_t size, bool need_swap)
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{
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struct {
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u32 n_namesz;
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u32 n_descsz;
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u32 n_type;
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} *nhdr;
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void *ptr;
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ptr = note_data;
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while (ptr < (note_data + note_len)) {
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const char *name;
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size_t namesz, descsz;
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nhdr = ptr;
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if (need_swap) {
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nhdr->n_namesz = bswap_32(nhdr->n_namesz);
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nhdr->n_descsz = bswap_32(nhdr->n_descsz);
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nhdr->n_type = bswap_32(nhdr->n_type);
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}
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namesz = NOTE_ALIGN(nhdr->n_namesz);
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descsz = NOTE_ALIGN(nhdr->n_descsz);
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ptr += sizeof(*nhdr);
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name = ptr;
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ptr += namesz;
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if (nhdr->n_type == NT_GNU_BUILD_ID &&
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nhdr->n_namesz == sizeof("GNU")) {
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if (memcmp(name, "GNU", sizeof("GNU")) == 0) {
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size_t sz = min(size, descsz);
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memcpy(bf, ptr, sz);
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memset(bf + sz, 0, size - sz);
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return 0;
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}
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}
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ptr += descsz;
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}
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return -1;
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}
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@ -19,6 +75,172 @@ int filename__read_debuglink(const char *filename __used,
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return -1;
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}
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/*
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* Just try PT_NOTE header otherwise fails
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*/
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int filename__read_build_id(const char *filename, void *bf, size_t size)
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{
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FILE *fp;
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int ret = -1;
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bool need_swap = false;
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u8 e_ident[EI_NIDENT];
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size_t buf_size;
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void *buf;
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int i;
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fp = fopen(filename, "r");
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if (fp == NULL)
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return -1;
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if (fread(e_ident, sizeof(e_ident), 1, fp) != 1)
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goto out;
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if (memcmp(e_ident, ELFMAG, SELFMAG) ||
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e_ident[EI_VERSION] != EV_CURRENT)
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goto out;
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need_swap = check_need_swap(e_ident[EI_DATA]);
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/* for simplicity */
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fseek(fp, 0, SEEK_SET);
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if (e_ident[EI_CLASS] == ELFCLASS32) {
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Elf32_Ehdr ehdr;
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Elf32_Phdr *phdr;
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if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
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goto out;
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if (need_swap) {
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ehdr.e_phoff = bswap_32(ehdr.e_phoff);
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ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
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ehdr.e_phnum = bswap_16(ehdr.e_phnum);
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}
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buf_size = ehdr.e_phentsize * ehdr.e_phnum;
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buf = malloc(buf_size);
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if (buf == NULL)
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goto out;
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fseek(fp, ehdr.e_phoff, SEEK_SET);
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if (fread(buf, buf_size, 1, fp) != 1)
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goto out_free;
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for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
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void *tmp;
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if (need_swap) {
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phdr->p_type = bswap_32(phdr->p_type);
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phdr->p_offset = bswap_32(phdr->p_offset);
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phdr->p_filesz = bswap_32(phdr->p_filesz);
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}
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if (phdr->p_type != PT_NOTE)
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continue;
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buf_size = phdr->p_filesz;
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tmp = realloc(buf, buf_size);
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if (tmp == NULL)
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goto out_free;
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buf = tmp;
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fseek(fp, phdr->p_offset, SEEK_SET);
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if (fread(buf, buf_size, 1, fp) != 1)
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goto out_free;
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ret = read_build_id(buf, buf_size, bf, size, need_swap);
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if (ret == 0)
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ret = size;
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break;
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}
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} else {
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Elf64_Ehdr ehdr;
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Elf64_Phdr *phdr;
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if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
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goto out;
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if (need_swap) {
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ehdr.e_phoff = bswap_64(ehdr.e_phoff);
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ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
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ehdr.e_phnum = bswap_16(ehdr.e_phnum);
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}
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buf_size = ehdr.e_phentsize * ehdr.e_phnum;
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buf = malloc(buf_size);
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if (buf == NULL)
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goto out;
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fseek(fp, ehdr.e_phoff, SEEK_SET);
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if (fread(buf, buf_size, 1, fp) != 1)
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goto out_free;
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for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
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void *tmp;
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if (need_swap) {
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phdr->p_type = bswap_32(phdr->p_type);
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phdr->p_offset = bswap_64(phdr->p_offset);
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phdr->p_filesz = bswap_64(phdr->p_filesz);
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}
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if (phdr->p_type != PT_NOTE)
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continue;
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buf_size = phdr->p_filesz;
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tmp = realloc(buf, buf_size);
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if (tmp == NULL)
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goto out_free;
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buf = tmp;
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fseek(fp, phdr->p_offset, SEEK_SET);
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if (fread(buf, buf_size, 1, fp) != 1)
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goto out_free;
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ret = read_build_id(buf, buf_size, bf, size, need_swap);
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if (ret == 0)
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ret = size;
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break;
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}
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}
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out_free:
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free(buf);
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out:
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fclose(fp);
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return ret;
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}
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int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
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{
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int fd;
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int ret = -1;
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struct stat stbuf;
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size_t buf_size;
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void *buf;
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fd = open(filename, O_RDONLY);
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if (fd < 0)
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return -1;
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if (fstat(fd, &stbuf) < 0)
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goto out;
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buf_size = stbuf.st_size;
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buf = malloc(buf_size);
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if (buf == NULL)
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goto out;
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if (read(fd, buf, buf_size) != (ssize_t) buf_size)
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goto out_free;
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ret = read_build_id(buf, buf_size, build_id, size, false);
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out_free:
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free(buf);
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out:
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close(fd);
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return ret;
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}
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int dso__synthesize_plt_symbols(struct dso *dso __used, char *name __used,
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struct map *map __used,
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symbol_filter_t filter __used)
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@ -26,11 +248,17 @@ int dso__synthesize_plt_symbols(struct dso *dso __used, char *name __used,
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return 0;
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}
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int dso__load_sym(struct dso *dso __used, struct map *map __used,
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const char *name __used, int fd __used,
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int dso__load_sym(struct dso *dso, struct map *map __used,
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const char *name, int fd __used,
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symbol_filter_t filter __used, int kmodule __used,
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int want_symtab __used)
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{
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unsigned char *build_id[BUILD_ID_SIZE];
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if (filename__read_build_id(name, build_id, BUILD_ID_SIZE) > 0) {
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dso__set_build_id(dso, build_id);
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return 1;
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}
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return 0;
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}
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