linux/tools/bpf/bpftool/jit_disasm.c
Jiri Olsa aa52bcbe0e tools: bpftool: Fix json dump crash on powerpc
Michael reported crash with by bpf program in json mode on powerpc:

  # bpftool prog -p dump jited id 14
  [{
        "name": "0xd00000000a9aa760",
        "insns": [{
                "pc": "0x0",
                "operation": "nop",
                "operands": [null
                ]
            },{
                "pc": "0x4",
                "operation": "nop",
                "operands": [null
                ]
            },{
                "pc": "0x8",
                "operation": "mflr",
  Segmentation fault (core dumped)

The code is assuming char pointers in format, which is not always
true at least for powerpc. Fixing this by dumping the whole string
into buffer based on its format.

Please note that libopcodes code does not check return values from
fprintf callback, but as per Jakub suggestion returning -1 on allocation
failure so we do the best effort to propagate the error.

Fixes: 107f041212 ("tools: bpftool: add JSON output for `bpftool prog dump jited *` command")
Reported-by: Michael Petlan <mpetlan@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2019-07-05 23:50:38 +02:00

208 lines
4.3 KiB
C

// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/*
* Based on:
*
* Minimal BPF JIT image disassembler
*
* Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
* debugging or verification purposes.
*
* Copyright 2013 Daniel Borkmann <daniel@iogearbox.net>
* Licensed under the GNU General Public License, version 2.0 (GPLv2)
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <bfd.h>
#include <dis-asm.h>
#include <sys/stat.h>
#include <limits.h>
#include <libbpf.h>
#include "json_writer.h"
#include "main.h"
static void get_exec_path(char *tpath, size_t size)
{
const char *path = "/proc/self/exe";
ssize_t len;
len = readlink(path, tpath, size - 1);
assert(len > 0);
tpath[len] = 0;
}
static int oper_count;
static int fprintf_json(void *out, const char *fmt, ...)
{
va_list ap;
char *s;
va_start(ap, fmt);
if (vasprintf(&s, fmt, ap) < 0)
return -1;
va_end(ap);
if (!oper_count) {
int i;
/* Strip trailing spaces */
i = strlen(s) - 1;
while (s[i] == ' ')
s[i--] = '\0';
jsonw_string_field(json_wtr, "operation", s);
jsonw_name(json_wtr, "operands");
jsonw_start_array(json_wtr);
oper_count++;
} else if (!strcmp(fmt, ",")) {
/* Skip */
} else {
jsonw_string(json_wtr, s);
oper_count++;
}
free(s);
return 0;
}
void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
const char *arch, const char *disassembler_options,
const struct btf *btf,
const struct bpf_prog_linfo *prog_linfo,
__u64 func_ksym, unsigned int func_idx,
bool linum)
{
const struct bpf_line_info *linfo = NULL;
disassembler_ftype disassemble;
struct disassemble_info info;
unsigned int nr_skip = 0;
int count, i, pc = 0;
char tpath[PATH_MAX];
bfd *bfdf;
if (!len)
return;
memset(tpath, 0, sizeof(tpath));
get_exec_path(tpath, sizeof(tpath));
bfdf = bfd_openr(tpath, NULL);
assert(bfdf);
assert(bfd_check_format(bfdf, bfd_object));
if (json_output)
init_disassemble_info(&info, stdout,
(fprintf_ftype) fprintf_json);
else
init_disassemble_info(&info, stdout,
(fprintf_ftype) fprintf);
/* Update architecture info for offload. */
if (arch) {
const bfd_arch_info_type *inf = bfd_scan_arch(arch);
if (inf) {
bfdf->arch_info = inf;
} else {
p_err("No libbfd support for %s", arch);
return;
}
}
info.arch = bfd_get_arch(bfdf);
info.mach = bfd_get_mach(bfdf);
if (disassembler_options)
info.disassembler_options = disassembler_options;
info.buffer = image;
info.buffer_length = len;
disassemble_init_for_target(&info);
#ifdef DISASM_FOUR_ARGS_SIGNATURE
disassemble = disassembler(info.arch,
bfd_big_endian(bfdf),
info.mach,
bfdf);
#else
disassemble = disassembler(bfdf);
#endif
assert(disassemble);
if (json_output)
jsonw_start_array(json_wtr);
do {
if (prog_linfo) {
linfo = bpf_prog_linfo__lfind_addr_func(prog_linfo,
func_ksym + pc,
func_idx,
nr_skip);
if (linfo)
nr_skip++;
}
if (json_output) {
jsonw_start_object(json_wtr);
oper_count = 0;
if (linfo)
btf_dump_linfo_json(btf, linfo, linum);
jsonw_name(json_wtr, "pc");
jsonw_printf(json_wtr, "\"0x%x\"", pc);
} else {
if (linfo)
btf_dump_linfo_plain(btf, linfo, "; ",
linum);
printf("%4x:\t", pc);
}
count = disassemble(pc, &info);
if (json_output) {
/* Operand array, was started in fprintf_json. Before
* that, make sure we have a _null_ value if no operand
* other than operation code was present.
*/
if (oper_count == 1)
jsonw_null(json_wtr);
jsonw_end_array(json_wtr);
}
if (opcodes) {
if (json_output) {
jsonw_name(json_wtr, "opcodes");
jsonw_start_array(json_wtr);
for (i = 0; i < count; ++i)
jsonw_printf(json_wtr, "\"0x%02hhx\"",
(uint8_t)image[pc + i]);
jsonw_end_array(json_wtr);
} else {
printf("\n\t");
for (i = 0; i < count; ++i)
printf("%02x ",
(uint8_t)image[pc + i]);
}
}
if (json_output)
jsonw_end_object(json_wtr);
else
printf("\n");
pc += count;
} while (count > 0 && pc < len);
if (json_output)
jsonw_end_array(json_wtr);
bfd_close(bfdf);
}
int disasm_init(void)
{
bfd_init();
return 0;
}