linux/tools/perf/util/genelf.c
Stefano Sanfilippo 086f9f3d78 perf jit: Generate .eh_frame/.eh_frame_hdr in DSO
When the jit_buf_desc contains unwinding information, it is emitted as
eh_frame unwinding sections in the DSOs generated by perf inject.

The unwinding information is required to unwind of JITed code which do
not maintain the frame pointer register during function calls.  It can
be emitted by V8 / Chromium when the --perf_prof_unwinding_info is
passed to V8.

The eh_frame and eh_frame_hdr sections are emitted immediately after the
.text.

The .eh_frame is aligned at a 8-byte boundary, and .eh_frame_hdr at a
4-byte one. Since size of the .eh_frame is required to be a multiple of
the word size, which means there will never be additional padding
between it and the .eh_frame_hdr on machines where the word size is 4 or
8 bytes.

However, additional padding might be inserted between .text and
.eh_frame to reach the correct alignment, which will always be 8 bytes,
also on 32bit machines. The reasoning behind this choice is that 4 extra
bytes of padding worst case are not a large cost for the advantage of
removing word-size dependent offset calculations when emitting the
jitdump.

Signed-off-by: Stefano Sanfilippo <ssanfilippo@chromium.org>
Signed-off-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Stephane Eranian <eranian@google.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1476356383-30100-8-git-send-email-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2016-10-24 11:07:40 -03:00

555 lines
11 KiB
C

/*
* genelf.c
* Copyright (C) 2014, Google, Inc
*
* Contributed by:
* Stephane Eranian <eranian@gmail.com>
*
* Released under the GPL v2. (and only v2, not any later version)
*/
#include <sys/types.h>
#include <stdio.h>
#include <getopt.h>
#include <stddef.h>
#include <libelf.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <limits.h>
#include <fcntl.h>
#include <err.h>
#ifdef HAVE_DWARF_SUPPORT
#include <dwarf.h>
#endif
#include "perf.h"
#include "genelf.h"
#include "../util/jitdump.h"
#ifndef NT_GNU_BUILD_ID
#define NT_GNU_BUILD_ID 3
#endif
#define JVMTI
#define BUILD_ID_URANDOM /* different uuid for each run */
#ifdef HAVE_LIBCRYPTO
#define BUILD_ID_MD5
#undef BUILD_ID_SHA /* does not seem to work well when linked with Java */
#undef BUILD_ID_URANDOM /* different uuid for each run */
#ifdef BUILD_ID_SHA
#include <openssl/sha.h>
#endif
#ifdef BUILD_ID_MD5
#include <openssl/md5.h>
#endif
#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;
struct options {
char *output;
int fd;
};
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 */
char build_id[20];
} 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 */
}
};
#ifdef BUILD_ID_URANDOM
static void
gen_build_id(struct buildid_note *note,
unsigned long load_addr __maybe_unused,
const void *code __maybe_unused,
size_t csize __maybe_unused)
{
int fd;
size_t sz = sizeof(note->build_id);
ssize_t sret;
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1)
err(1, "cannot access /dev/urandom for builid");
sret = read(fd, note->build_id, sz);
close(fd);
if (sret != (ssize_t)sz)
memset(note->build_id, 0, sz);
}
#endif
#ifdef BUILD_ID_SHA
static void
gen_build_id(struct buildid_note *note,
unsigned long load_addr __maybe_unused,
const void *code,
size_t csize)
{
if (sizeof(note->build_id) < SHA_DIGEST_LENGTH)
errx(1, "build_id too small for SHA1");
SHA1(code, csize, (unsigned char *)note->build_id);
}
#endif
#ifdef BUILD_ID_MD5
static void
gen_build_id(struct buildid_note *note, unsigned long load_addr, const void *code, size_t csize)
{
MD5_CTX context;
if (sizeof(note->build_id) < 16)
errx(1, "build_id too small for MD5");
MD5_Init(&context);
MD5_Update(&context, &load_addr, sizeof(load_addr));
MD5_Update(&context, code, csize);
MD5_Final((unsigned char *)note->build_id, &context);
}
#endif
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, 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_Shdr *shdr;
uint64_t eh_frame_base_offset;
char *strsym = NULL;
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 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;
/*
* 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;
}
/*
* 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 */
/*
* 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;
/*
* 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
*/
gen_build_id(&bnote, load_addr, code, csize);
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_DWARF_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);
return retval;
}
#ifndef JVMTI
static unsigned char x86_code[] = {
0xBB, 0x2A, 0x00, 0x00, 0x00, /* movl $42, %ebx */
0xB8, 0x01, 0x00, 0x00, 0x00, /* movl $1, %eax */
0xCD, 0x80 /* int $0x80 */
};
static struct options options;
int main(int argc, char **argv)
{
int c, fd, ret;
while ((c = getopt(argc, argv, "o:h")) != -1) {
switch (c) {
case 'o':
options.output = optarg;
break;
case 'h':
printf("Usage: genelf -o output_file [-h]\n");
return 0;
default:
errx(1, "unknown option");
}
}
fd = open(options.output, O_CREAT|O_TRUNC|O_RDWR, 0666);
if (fd == -1)
err(1, "cannot create file %s", options.output);
ret = jit_write_elf(fd, "main", x86_code, sizeof(x86_code));
close(fd);
if (ret != 0)
unlink(options.output);
return ret;
}
#endif