1/*
  2 * Based on:
  3 *
  4 * Minimal BPF JIT image disassembler
  5 *
  6 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
  7 * debugging or verification purposes.
  8 *
  9 * Copyright 2013 Daniel Borkmann <daniel@iogearbox.net>
 10 * Licensed under the GNU General Public License, version 2.0 (GPLv2)
 11 */
 12
 13#include <stdarg.h>
 14#include <stdint.h>
 15#include <stdio.h>
 16#include <stdlib.h>
 17#include <assert.h>
 18#include <unistd.h>
 19#include <string.h>
 20#include <bfd.h>
 21#include <dis-asm.h>
 22#include <sys/types.h>
 23#include <sys/stat.h>
 24#include <limits.h>
 25
 26#include "json_writer.h"
 27#include "main.h"
 28
 29static void get_exec_path(char *tpath, size_t size)
 30{
 31	ssize_t len;
 32	char *path;
 33
 34	snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
 35	tpath[size - 1] = 0;
 36
 37	path = strdup(tpath);
 38	assert(path);
 39
 40	len = readlink(path, tpath, size - 1);
 41	assert(len > 0);
 42	tpath[len] = 0;
 43
 44	free(path);
 45}
 46
 47static int oper_count;
 48static int fprintf_json(void *out, const char *fmt, ...)
 49{
 50	va_list ap;
 51	char *s;
 52
 53	va_start(ap, fmt);
 54	if (!oper_count) {
 55		int i;
 56
 57		s = va_arg(ap, char *);
 58
 59		/* Strip trailing spaces */
 60		i = strlen(s) - 1;
 61		while (s[i] == ' ')
 62			s[i--] = '\0';
 63
 64		jsonw_string_field(json_wtr, "operation", s);
 65		jsonw_name(json_wtr, "operands");
 66		jsonw_start_array(json_wtr);
 67		oper_count++;
 68	} else if (!strcmp(fmt, ",")) {
 69		   /* Skip */
 70	} else {
 71		s = va_arg(ap, char *);
 72		jsonw_string(json_wtr, s);
 73		oper_count++;
 74	}
 75	va_end(ap);
 76	return 0;
 77}
 78
 79void disasm_print_insn(unsigned char *image, ssize_t len, int opcodes,
 80		       const char *arch)
 81{
 82	disassembler_ftype disassemble;
 83	struct disassemble_info info;
 84	int count, i, pc = 0;
 85	char tpath[PATH_MAX];
 86	bfd *bfdf;
 87
 88	if (!len)
 89		return;
 90
 91	memset(tpath, 0, sizeof(tpath));
 92	get_exec_path(tpath, sizeof(tpath));
 93
 94	bfdf = bfd_openr(tpath, NULL);
 95	assert(bfdf);
 96	assert(bfd_check_format(bfdf, bfd_object));
 97
 98	if (json_output)
 99		init_disassemble_info(&info, stdout,
100				      (fprintf_ftype) fprintf_json);
101	else
102		init_disassemble_info(&info, stdout,
103				      (fprintf_ftype) fprintf);
104
105	/* Update architecture info for offload. */
106	if (arch) {
107		const bfd_arch_info_type *inf = bfd_scan_arch(arch);
108
109		if (inf) {
110			bfdf->arch_info = inf;
111		} else {
112			p_err("No libfd support for %s", arch);
113			return;
114		}
115	}
116
117	info.arch = bfd_get_arch(bfdf);
118	info.mach = bfd_get_mach(bfdf);
119	info.buffer = image;
120	info.buffer_length = len;
121
122	disassemble_init_for_target(&info);
123
124#ifdef DISASM_FOUR_ARGS_SIGNATURE
125	disassemble = disassembler(info.arch,
126				   bfd_big_endian(bfdf),
127				   info.mach,
128				   bfdf);
129#else
130	disassemble = disassembler(bfdf);
131#endif
132	assert(disassemble);
133
134	if (json_output)
135		jsonw_start_array(json_wtr);
136	do {
137		if (json_output) {
138			jsonw_start_object(json_wtr);
139			oper_count = 0;
140			jsonw_name(json_wtr, "pc");
141			jsonw_printf(json_wtr, "\"0x%x\"", pc);
142		} else {
143			printf("%4x:\t", pc);
144		}
145
146		count = disassemble(pc, &info);
147		if (json_output) {
148			/* Operand array, was started in fprintf_json. Before
149			 * that, make sure we have a _null_ value if no operand
150			 * other than operation code was present.
151			 */
152			if (oper_count == 1)
153				jsonw_null(json_wtr);
154			jsonw_end_array(json_wtr);
155		}
156
157		if (opcodes) {
158			if (json_output) {
159				jsonw_name(json_wtr, "opcodes");
160				jsonw_start_array(json_wtr);
161				for (i = 0; i < count; ++i)
162					jsonw_printf(json_wtr, "\"0x%02hhx\"",
163						     (uint8_t)image[pc + i]);
164				jsonw_end_array(json_wtr);
165			} else {
166				printf("\n\t");
167				for (i = 0; i < count; ++i)
168					printf("%02x ",
169					       (uint8_t)image[pc + i]);
170			}
171		}
172		if (json_output)
173			jsonw_end_object(json_wtr);
174		else
175			printf("\n");
176
177		pc += count;
178	} while (count > 0 && pc < len);
179	if (json_output)
180		jsonw_end_array(json_wtr);
181
182	bfd_close(bfdf);
183}