Commit b691f643 authored by Namhyung Kim's avatar Namhyung Kim Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarNamhyung 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 393be2e3

tools/perf/util/symbol-minimal.c

+235 −7
Original line number Diff line number Diff line 
#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;

}

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