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>

diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
index 416ecf3bccf5ec6fef2065b66c57a9b7b11bc28d..bd8720b6780c4f3aae68fc2d1ead38c71addfd19 100644 (file)
--- a/tools/perf/util/symbol-minimal.c
+++ b/tools/perf/util/symbol-minimal.c
@@ -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;
 }