Commit 88dc8b36 authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

selftests/bpf: Add read_build_id function 



Adding read_build_id function that parses out build id from
specified binary.

It will replace extract_build_id and also be used in following
changes.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230331093157.1749137-3-jolsa@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 328bafc9

tools/testing/selftests/bpf/trace_helpers.c

+82 −0
Original line number Diff line number Diff line
@@ -11,6 +11,9 @@ 
#include <linux/perf_event.h>

#include <sys/mman.h>

#include "trace_helpers.h"

#include <linux/limits.h>

#include <libelf.h>

#include <gelf.h>



#define TRACEFS_PIPE	"/sys/kernel/tracing/trace_pipe"

#define DEBUGFS_PIPE	"/sys/kernel/debug/tracing/trace_pipe"
@@ -234,3 +237,82 @@ ssize_t get_rel_offset(uintptr_t addr) 
	fclose(f);

	return -EINVAL;

}



static int

parse_build_id_buf(const void *note_start, Elf32_Word note_size, char *build_id)

{

	Elf32_Word note_offs = 0;



	while (note_offs + sizeof(Elf32_Nhdr) < note_size) {

		Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);



		if (nhdr->n_type == 3 && nhdr->n_namesz == sizeof("GNU") &&

		    !strcmp((char *)(nhdr + 1), "GNU") && nhdr->n_descsz > 0 &&

		    nhdr->n_descsz <= BPF_BUILD_ID_SIZE) {

			memcpy(build_id, note_start + note_offs +

			       ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr), nhdr->n_descsz);

			memset(build_id + nhdr->n_descsz, 0, BPF_BUILD_ID_SIZE - nhdr->n_descsz);

			return (int) nhdr->n_descsz;

		}



		note_offs = note_offs + sizeof(Elf32_Nhdr) +

			   ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);

	}



	return -ENOENT;

}



/* Reads binary from *path* file and returns it in the *build_id* buffer

 * with *size* which is expected to be at least BPF_BUILD_ID_SIZE bytes.

 * Returns size of build id on success. On error the error value is

 * returned.

 */

int read_build_id(const char *path, char *build_id, size_t size)

{

	int fd, err = -EINVAL;

	Elf *elf = NULL;

	GElf_Ehdr ehdr;

	size_t max, i;



	if (size < BPF_BUILD_ID_SIZE)

		return -EINVAL;



	fd = open(path, O_RDONLY | O_CLOEXEC);

	if (fd < 0)

		return -errno;



	(void)elf_version(EV_CURRENT);



	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);

	if (!elf)

		goto out;

	if (elf_kind(elf) != ELF_K_ELF)

		goto out;

	if (!gelf_getehdr(elf, &ehdr))

		goto out;



	for (i = 0; i < ehdr.e_phnum; i++) {

		GElf_Phdr mem, *phdr;

		char *data;



		phdr = gelf_getphdr(elf, i, &mem);

		if (!phdr)

			goto out;

		if (phdr->p_type != PT_NOTE)

			continue;

		data = elf_rawfile(elf, &max);

		if (!data)

			goto out;

		if (phdr->p_offset + phdr->p_memsz > max)

			goto out;

		err = parse_build_id_buf(data + phdr->p_offset, phdr->p_memsz, build_id);

		if (err > 0)

			break;

	}



out:

	if (elf)

		elf_end(elf);

	close(fd);

	return err;

}

tools/testing/selftests/bpf/trace_helpers.h

+5 −0
Original line number Diff line number Diff line
@@ -4,6 +4,9 @@ 


#include <bpf/libbpf.h>



#define __ALIGN_MASK(x, mask)	(((x)+(mask))&~(mask))

#define ALIGN(x, a)		__ALIGN_MASK(x, (typeof(x))(a)-1)



struct ksym {

	long addr;

	char *name;
@@ -23,4 +26,6 @@ void read_trace_pipe(void); 
ssize_t get_uprobe_offset(const void *addr);

ssize_t get_rel_offset(uintptr_t addr);



int read_build_id(const char *path, char *build_id, size_t size);



#endif