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/*
* 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/types.h>
#include <sys/stat.h>
#include <limits.h>
#include "json_writer.h"
#include "main.h"
static void get_exec_path(char *tpath, size_t size)
{
ssize_t len;
char *path;
snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
tpath[size - 1] = 0;
path = strdup(tpath);
assert(path);
len = readlink(path, tpath, size - 1);
assert(len > 0);
tpath[len] = 0;
free(path);
}
static int oper_count;
static int fprintf_json(void *out, const char *fmt, ...)
{
va_list ap;
char *s;
int err;
va_start(ap, fmt);
err = vasprintf(&s, fmt, ap);
va_end(ap);
if (err < 0)
return -1;
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)
{
disassembler_ftype disassemble;
struct disassemble_info info;
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 libfd support for %s", arch);
return;
}
}
info.arch = bfd_get_arch(bfdf);
info.mach = bfd_get_mach(bfdf);
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 (json_output) {
jsonw_start_object(json_wtr);
oper_count = 0;
jsonw_name(json_wtr, "pc");
jsonw_printf(json_wtr, "\"0x%x\"", pc);
} else {
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);
}
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