mirrors/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-12-27 15:51:30 -05:00
Code Issues Packages Projects Releases Wiki Activity
Files
master
linux/tools/perf/util/genelf.c
Namhyung Kim 25d498e636 perf jitdump: Add sym/str-tables to build-ID generation 
It was reported that python backtrace with JIT dump was broken after the
change to built-in SHA-1 implementation.  It seems python generates the
same JIT code for each function.  They will become separate DSOs but the
contents are the same.  Only difference is in the symbol name.

But this caused a problem that every JIT'ed DSOs will have the same
build-ID which makes perf confused.  And it resulted in no python
symbols (from JIT) in the output.

Looking back at the original code before the conversion, it used the
load_addr as well as the code section to distinguish each DSO.  But it'd
be better to use contents of symtab and strtab instead as it aligns with
some linker behaviors.

This patch adds a buffer to save all the contents in a single place for
SHA-1 calculation.  Probably we need to add sha1_update() or similar to
update the existing hash value with different contents and use it here.
But it's out of scope for this change and I'd like something that can be
backported to the stable trees easily.

Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Pablo Galindo <pablogsal@gmail.com>
Cc: Fangrui Song <maskray@sourceware.org>
Link: https://github.com/python/cpython/issues/139544
Fixes: e3f612c1d8 ("perf genelf: Remove libcrypto dependency and use built-in sha1()")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2025-12-02 16:06:57 -08:00

474 lines
10 KiB
C
Raw Permalink Blame History

// SPDX-License-Identifier: GPL-2.0-only
/*
* genelf.c
* Copyright (C) 2014, Google, Inc
*
* Contributed by:
* Stephane Eranian <eranian@gmail.com>
*/
#include <sys/types.h>
#include <stddef.h>
#include <libelf.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <err.h>
#ifdef HAVE_LIBDW_SUPPORT
#include <dwarf.h>
#endif
#include "genelf.h"
#include "sha1.h"
#include "../util/jitdump.h"
#include <linux/compiler.h>
#ifndef NT_GNU_BUILD_ID
#define NT_GNU_BUILD_ID 3
#endif
typedef struct {
unsigned int namesz; /* Size of entry's owner string */
unsigned int descsz; /* Size of the note descriptor */
unsigned int type; /* Interpretation of the descriptor */
char name[0]; /* Start of the name+desc data */
} Elf_Note;
static char shd_string_table[] = {
0,
'.', 't', 'e', 'x', 't', 0, /* 1 */
'.', 's', 'h', 's', 't', 'r', 't', 'a', 'b', 0, /* 7 */
'.', 's', 'y', 'm', 't', 'a', 'b', 0, /* 17 */
'.', 's', 't', 'r', 't', 'a', 'b', 0, /* 25 */
'.', 'n', 'o', 't', 'e', '.', 'g', 'n', 'u', '.', 'b', 'u', 'i', 'l', 'd', '-', 'i', 'd', 0, /* 33 */
'.', 'd', 'e', 'b', 'u', 'g', '_', 'l', 'i', 'n', 'e', 0, /* 52 */
'.', 'd', 'e', 'b', 'u', 'g', '_', 'i', 'n', 'f', 'o', 0, /* 64 */
'.', 'd', 'e', 'b', 'u', 'g', '_', 'a', 'b', 'b', 'r', 'e', 'v', 0, /* 76 */
'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', '_', 'h', 'd', 'r', 0, /* 90 */
'.', 'e', 'h', '_', 'f', 'r', 'a', 'm', 'e', 0, /* 104 */
};
static struct buildid_note {
Elf_Note desc; /* descsz: size of build-id, must be multiple of 4 */
char name[4]; /* GNU\0 */
u8 build_id[SHA1_DIGEST_SIZE];
} bnote;
static Elf_Sym symtab[]={
/* symbol 0 MUST be the undefined symbol */
{ .st_name = 0, /* index in sym_string table */
.st_info = ELF_ST_TYPE(STT_NOTYPE),
.st_shndx = 0, /* for now */
.st_value = 0x0,
.st_other = ELF_ST_VIS(STV_DEFAULT),
.st_size = 0,
},
{ .st_name = 1, /* index in sym_string table */
.st_info = ELF_ST_BIND(STB_LOCAL) | ELF_ST_TYPE(STT_FUNC),
.st_shndx = 1,
.st_value = 0, /* for now */
.st_other = ELF_ST_VIS(STV_DEFAULT),
.st_size = 0, /* for now */
}
};
static int
jit_add_eh_frame_info(Elf *e, void* unwinding, uint64_t unwinding_header_size,
uint64_t unwinding_size, uint64_t base_offset)
{
Elf_Data *d;
Elf_Scn *scn;
Elf_Shdr *shdr;
uint64_t unwinding_table_size = unwinding_size - unwinding_header_size;
/*
* setup eh_frame section
*/
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
return -1;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
return -1;
}
d->d_align = 8;
d->d_off = 0LL;
d->d_buf = unwinding;
d->d_type = ELF_T_BYTE;
d->d_size = unwinding_table_size;
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
return -1;
}
shdr->sh_name = 104;
shdr->sh_type = SHT_PROGBITS;
shdr->sh_addr = base_offset;
shdr->sh_flags = SHF_ALLOC;
shdr->sh_entsize = 0;
/*
* setup eh_frame_hdr section
*/
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
return -1;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
return -1;
}
d->d_align = 4;
d->d_off = 0LL;
d->d_buf = unwinding + unwinding_table_size;
d->d_type = ELF_T_BYTE;
d->d_size = unwinding_header_size;
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
return -1;
}
shdr->sh_name = 90;
shdr->sh_type = SHT_PROGBITS;
shdr->sh_addr = base_offset + unwinding_table_size;
shdr->sh_flags = SHF_ALLOC;
shdr->sh_entsize = 0;
return 0;
}
/*
* fd: file descriptor open for writing for the output file
* load_addr: code load address (could be zero, just used for buildid)
* sym: function name (for native code - used as the symbol)
* code: the native code
* csize: the code size in bytes
*/
int
jit_write_elf(int fd, uint64_t load_addr __maybe_unused, const char *sym,
const void *code, int csize,
void *debug __maybe_unused, int nr_debug_entries __maybe_unused,
void *unwinding, uint64_t unwinding_header_size, uint64_t unwinding_size)
{
Elf *e;
Elf_Data *d;
Elf_Scn *scn;
Elf_Ehdr *ehdr;
Elf_Phdr *phdr;
Elf_Shdr *shdr;
uint64_t eh_frame_base_offset;
char *strsym = NULL;
void *build_id_data = NULL, *tmp;
int build_id_data_len;
int symlen;
int retval = -1;
if (elf_version(EV_CURRENT) == EV_NONE) {
warnx("ELF initialization failed");
return -1;
}
e = elf_begin(fd, ELF_C_WRITE, NULL);
if (!e) {
warnx("elf_begin failed");
goto error;
}
/*
* setup ELF header
*/
ehdr = elf_newehdr(e);
if (!ehdr) {
warnx("cannot get ehdr");
goto error;
}
ehdr->e_ident[EI_DATA] = GEN_ELF_ENDIAN;
ehdr->e_ident[EI_CLASS] = GEN_ELF_CLASS;
ehdr->e_machine = GEN_ELF_ARCH;
ehdr->e_type = ET_DYN;
ehdr->e_entry = GEN_ELF_TEXT_OFFSET;
ehdr->e_version = EV_CURRENT;
ehdr->e_shstrndx= unwinding ? 4 : 2; /* shdr index for section name */
/*
* setup program header
*/
phdr = elf_newphdr(e, 1);
phdr[0].p_type = PT_LOAD;
phdr[0].p_offset = GEN_ELF_TEXT_OFFSET;
phdr[0].p_vaddr = GEN_ELF_TEXT_OFFSET;
phdr[0].p_paddr = GEN_ELF_TEXT_OFFSET;
phdr[0].p_filesz = csize;
phdr[0].p_memsz = csize;
phdr[0].p_flags = PF_X | PF_R;
phdr[0].p_align = 8;
/*
* setup text section
*/
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
goto error;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
goto error;
}
d->d_align = 16;
d->d_off = 0LL;
d->d_buf = (void *)code;
d->d_type = ELF_T_BYTE;
d->d_size = csize;
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
goto error;
}
shdr->sh_name = 1;
shdr->sh_type = SHT_PROGBITS;
shdr->sh_addr = GEN_ELF_TEXT_OFFSET;
shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
shdr->sh_entsize = 0;
build_id_data = malloc(csize);
if (build_id_data == NULL) {
warnx("cannot allocate build-id data");
goto error;
}
memcpy(build_id_data, code, csize);
build_id_data_len = csize;
/*
* Setup .eh_frame_hdr and .eh_frame
*/
if (unwinding) {
eh_frame_base_offset = ALIGN_8(GEN_ELF_TEXT_OFFSET + csize);
retval = jit_add_eh_frame_info(e, unwinding,
unwinding_header_size, unwinding_size,
eh_frame_base_offset);
if (retval)
goto error;
retval = -1;
}
/*
* setup section headers string table
*/
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
goto error;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
goto error;
}
d->d_align = 1;
d->d_off = 0LL;
d->d_buf = shd_string_table;
d->d_type = ELF_T_BYTE;
d->d_size = sizeof(shd_string_table);
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
goto error;
}
shdr->sh_name = 7; /* offset of '.shstrtab' in shd_string_table */
shdr->sh_type = SHT_STRTAB;
shdr->sh_flags = 0;
shdr->sh_entsize = 0;
/*
* setup symtab section
*/
symtab[1].st_size = csize;
symtab[1].st_value = GEN_ELF_TEXT_OFFSET;
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
goto error;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
goto error;
}
d->d_align = 8;
d->d_off = 0LL;
d->d_buf = symtab;
d->d_type = ELF_T_SYM;
d->d_size = sizeof(symtab);
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
goto error;
}
shdr->sh_name = 17; /* offset of '.symtab' in shd_string_table */
shdr->sh_type = SHT_SYMTAB;
shdr->sh_flags = 0;
shdr->sh_entsize = sizeof(Elf_Sym);
shdr->sh_link = unwinding ? 6 : 4; /* index of .strtab section */
tmp = realloc(build_id_data, build_id_data_len + sizeof(symtab));
if (tmp == NULL) {
warnx("cannot allocate build-id data");
goto error;
}
memcpy(tmp + build_id_data_len, symtab, sizeof(symtab));
build_id_data = tmp;
build_id_data_len += sizeof(symtab);
/*
* setup symbols string table
* 2 = 1 for 0 in 1st entry, 1 for the 0 at end of symbol for 2nd entry
*/
symlen = 2 + strlen(sym);
strsym = calloc(1, symlen);
if (!strsym) {
warnx("cannot allocate strsym");
goto error;
}
strcpy(strsym + 1, sym);
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
goto error;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
goto error;
}
d->d_align = 1;
d->d_off = 0LL;
d->d_buf = strsym;
d->d_type = ELF_T_BYTE;
d->d_size = symlen;
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
goto error;
}
shdr->sh_name = 25; /* offset in shd_string_table */
shdr->sh_type = SHT_STRTAB;
shdr->sh_flags = 0;
shdr->sh_entsize = 0;
tmp = realloc(build_id_data, build_id_data_len + symlen);
if (tmp == NULL) {
warnx("cannot allocate build-id data");
goto error;
}
memcpy(tmp + build_id_data_len, strsym, symlen);
build_id_data = tmp;
build_id_data_len += symlen;
/*
* setup build-id section
*/
scn = elf_newscn(e);
if (!scn) {
warnx("cannot create section");
goto error;
}
d = elf_newdata(scn);
if (!d) {
warnx("cannot get new data");
goto error;
}
/*
* build-id generation
*/
sha1(build_id_data, build_id_data_len, bnote.build_id);
bnote.desc.namesz = sizeof(bnote.name); /* must include 0 termination */
bnote.desc.descsz = sizeof(bnote.build_id);
bnote.desc.type = NT_GNU_BUILD_ID;
strcpy(bnote.name, "GNU");
d->d_align = 4;
d->d_off = 0LL;
d->d_buf = &bnote;
d->d_type = ELF_T_BYTE;
d->d_size = sizeof(bnote);
d->d_version = EV_CURRENT;
shdr = elf_getshdr(scn);
if (!shdr) {
warnx("cannot get section header");
goto error;
}
shdr->sh_name = 33; /* offset in shd_string_table */
shdr->sh_type = SHT_NOTE;
shdr->sh_addr = 0x0;
shdr->sh_flags = SHF_ALLOC;
shdr->sh_size = sizeof(bnote);
shdr->sh_entsize = 0;
#ifdef HAVE_LIBDW_SUPPORT
if (debug && nr_debug_entries) {
retval = jit_add_debug_info(e, load_addr, debug, nr_debug_entries);
if (retval)
goto error;
} else
#endif
{
if (elf_update(e, ELF_C_WRITE) < 0) {
warnx("elf_update 4 failed");
goto error;
}
}
retval = 0;
error:
(void)elf_end(e);
free(strsym);
free(build_id_data);
return retval;
}
Reference in New Issue View Git Blame Copy Permalink