[linux.git] / tools / bpf / bpf_jit_disasm.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Minimal BPF JIT image disassembler
 *
 * Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
 * debugging or verification purposes.
 *
 * To get the disassembly of the JIT code, do the following:
 *
 *  1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
 *  2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
 *  3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
 *
 * Copyright 2013 Daniel Borkmann <[email protected]>
 */

#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 <regex.h>
#include <fcntl.h>
#include <sys/klog.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>

#define CMD_ACTION_SIZE_BUFFER		10
#define CMD_ACTION_READ_ALL		3

static void get_exec_path(char *tpath, size_t size)
{
	char *path;
	ssize_t len;

	snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
	tpath[size - 1] = 0;

	path = strdup(tpath);
	assert(path);

	len = readlink(path, tpath, size);
	tpath[len] = 0;

	free(path);
}

static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
{
	int count, i, pc = 0;
	char tpath[PATH_MAX];
	struct disassemble_info info;
	disassembler_ftype disassemble;
	bfd *bfdf;

	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));

	init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
	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);

	do {
		printf("%4x:\t", pc);

		count = disassemble(pc, &info);

		if (opcodes) {
			printf("\n\t");
			for (i = 0; i < count; ++i)
				printf("%02x ", (uint8_t) image[pc + i]);
		}
		printf("\n");

		pc += count;
	} while(count > 0 && pc < len);

	bfd_close(bfdf);
}

static char *get_klog_buff(unsigned int *klen)
{
	int ret, len;
	char *buff;

	len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
	if (len < 0)
		return NULL;

	buff = malloc(len);
	if (!buff)
		return NULL;

	ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
	if (ret < 0) {
		free(buff);
		return NULL;
	}

	*klen = ret;
	return buff;
}

static char *get_flog_buff(const char *file, unsigned int *klen)
{
	int fd, ret, len;
	struct stat fi;
	char *buff;

	fd = open(file, O_RDONLY);
	if (fd < 0)
		return NULL;

	ret = fstat(fd, &fi);
	if (ret < 0 || !S_ISREG(fi.st_mode))
		goto out;

	len = fi.st_size + 1;
	buff = malloc(len);
	if (!buff)
		goto out;

	memset(buff, 0, len);
	ret = read(fd, buff, len - 1);
	if (ret <= 0)
		goto out_free;

	close(fd);
	*klen = ret;
	return buff;
out_free:
	free(buff);
out:
	close(fd);
	return NULL;
}

static char *get_log_buff(const char *file, unsigned int *klen)
{
	return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
}

static void put_log_buff(char *buff)
{
	free(buff);
}

static uint8_t *get_last_jit_image(char *haystack, size_t hlen,
				   unsigned int *ilen)
{
	char *ptr, *pptr, *tmp;
	off_t off = 0;
	unsigned int proglen;
	int ret, flen, pass, ulen = 0;
	regmatch_t pmatch[1];
	unsigned long base;
	regex_t regex;
	uint8_t *image;

	if (hlen == 0)
		return NULL;

	ret = regcomp(&regex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
		      "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
	assert(ret == 0);

	ptr = haystack;
	memset(pmatch, 0, sizeof(pmatch));

	while (1) {
		ret = regexec(&regex, ptr, 1, pmatch, 0);
		if (ret == 0) {
			ptr += pmatch[0].rm_eo;
			off += pmatch[0].rm_eo;
			assert(off < hlen);
		} else
			break;
	}

	ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
	ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",
		     &flen, &proglen, &pass, &base);
	if (ret != 4) {
		regfree(&regex);
		return NULL;
	}
	if (proglen > 1000000) {
		printf("proglen of %d too big, stopping\n", proglen);
		return NULL;
	}

	image = malloc(proglen);
	if (!image) {
		printf("Out of memory\n");
		return NULL;
	}
	memset(image, 0, proglen);

	tmp = ptr = haystack + off;
	while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {
		tmp = NULL;
		if (!strstr(ptr, "JIT code"))
			continue;
		pptr = ptr;
		while ((ptr = strstr(pptr, ":")))
			pptr = ptr + 1;
		ptr = pptr;
		do {
			image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
			if (ptr == pptr) {
				ulen--;
				break;
			}
			if (ulen >= proglen)
				break;
			ptr = pptr;
		} while (1);
	}

	assert(ulen == proglen);
	printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
	       proglen, pass, flen);
	printf("%lx + <x>:\n", base);

	regfree(&regex);
	*ilen = ulen;
	return image;
}

static void usage(void)
{
	printf("Usage: bpf_jit_disasm [...]\n");
	printf("       -o          Also display related opcodes (default: off).\n");
	printf("       -O <file>   Write binary image of code to file, don't disassemble to stdout.\n");
	printf("       -f <file>   Read last image dump from file or stdin (default: klog).\n");
	printf("       -h          Display this help.\n");
}

int main(int argc, char **argv)
{
	unsigned int len, klen, opt, opcodes = 0;
	char *kbuff, *file = NULL;
	char *ofile = NULL;
	int ofd;
	ssize_t nr;
	uint8_t *pos;
	uint8_t *image = NULL;

	while ((opt = getopt(argc, argv, "of:O:")) != -1) {
		switch (opt) {
		case 'o':
			opcodes = 1;
			break;
		case 'O':
			ofile = optarg;
			break;
		case 'f':
			file = optarg;
			break;
		default:
			usage();
			return -1;
		}
	}

	bfd_init();

	kbuff = get_log_buff(file, &klen);
	if (!kbuff) {
		fprintf(stderr, "Could not retrieve log buffer!\n");
		return -1;
	}

	image = get_last_jit_image(kbuff, klen, &len);
	if (!image) {
		fprintf(stderr, "No JIT image found!\n");
		goto done;
	}
	if (!ofile) {
		get_asm_insns(image, len, opcodes);
		goto done;
	}

	ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
	if (ofd < 0) {
		fprintf(stderr, "Could not open file %s for writing: ", ofile);
		perror(NULL);
		goto done;
	}
	pos = image;
	do {
		nr = write(ofd, pos, len);
		if (nr < 0) {
			fprintf(stderr, "Could not write data to %s: ", ofile);
			perror(NULL);
			goto done;
		}
		len -= nr;
		pos += nr;
	} while (len);
	close(ofd);

done:
	put_log_buff(kbuff);
	free(image);
	return 0;
}
Commit	Line	Data
a7d7a392	1	// SPDX-License-Identifier: GPL-2.0-only
e306e2c1 DB	2	/*
	3	* Minimal BPF JIT image disassembler
	4	*
	5	* Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
	6	* debugging or verification purposes.
	7	*
	8	* To get the disassembly of the JIT code, do the following:
	9	*
	10	* 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
	11	* 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
	12	* 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
	13	*
	14	* Copyright 2013 Daniel Borkmann <[email protected]>
e306e2c1 DB	15	*/
	16
	17	#include <stdint.h>
	18	#include <stdio.h>
	19	#include <stdlib.h>
	20	#include <assert.h>
	21	#include <unistd.h>
	22	#include <string.h>
	23	#include <bfd.h>
	24	#include <dis-asm.h>
a6ed3836 DB	25	#include <regex.h>
a6ed3836 DB	26	#include <fcntl.h>
e306e2c1 DB	27	#include <sys/klog.h>
e306e2c1 DB	28	#include <sys/types.h>
a6ed3836	29	#include <sys/stat.h>
cdc89c91	30	#include <limits.h>
a6ed3836 DB	31
	32	#define CMD_ACTION_SIZE_BUFFER 10
	33	#define CMD_ACTION_READ_ALL 3
e306e2c1 DB	34
	35	static void get_exec_path(char *tpath, size_t size)
	36	{
	37	char *path;
	38	ssize_t len;
	39
	40	snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
	41	tpath[size - 1] = 0;
	42
	43	path = strdup(tpath);
	44	assert(path);
	45
	46	len = readlink(path, tpath, size);
	47	tpath[len] = 0;
	48
	49	free(path);
	50	}
	51
ed4afd45	52	static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
e306e2c1 DB	53	{
e306e2c1 DB	54	int count, i, pc = 0;
cdc89c91	55	char tpath[PATH_MAX];
e306e2c1 DB	56	struct disassemble_info info;
	57	disassembler_ftype disassemble;
	58	bfd *bfdf;
	59
	60	memset(tpath, 0, sizeof(tpath));
	61	get_exec_path(tpath, sizeof(tpath));
	62
	63	bfdf = bfd_openr(tpath, NULL);
	64	assert(bfdf);
	65	assert(bfd_check_format(bfdf, bfd_object));
	66
	67	init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
	68	info.arch = bfd_get_arch(bfdf);
	69	info.mach = bfd_get_mach(bfdf);
	70	info.buffer = image;
	71	info.buffer_length = len;
	72
	73	disassemble_init_for_target(&info);
	74
fb982666 RG	75	#ifdef DISASM_FOUR_ARGS_SIGNATURE
	76	disassemble = disassembler(info.arch,
	77	bfd_big_endian(bfdf),
	78	info.mach,
	79	bfdf);
	80	#else
e306e2c1	81	disassemble = disassembler(bfdf);
fb982666	82	#endif
e306e2c1 DB	83	assert(disassemble);
	84
	85	do {
	86	printf("%4x:\t", pc);
	87
	88	count = disassemble(pc, &info);
	89
	90	if (opcodes) {
	91	printf("\n\t");
	92	for (i = 0; i < count; ++i)
	93	printf("%02x ", (uint8_t) image[pc + i]);
	94	}
	95	printf("\n");
	96
	97	pc += count;
	98	} while(count > 0 && pc < len);
	99
	100	bfd_close(bfdf);
	101	}
	102
a6ed3836	103	static char get_klog_buff(unsigned int klen)
e306e2c1	104	{
a6ed3836 DB	105	int ret, len;
	106	char *buff;
	107
	108	len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
25a54342 CIK	109	if (len < 0)
	110	return NULL;
	111
a6ed3836 DB	112	buff = malloc(len);
	113	if (!buff)
	114	return NULL;
	115
	116	ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
	117	if (ret < 0) {
	118	free(buff);
	119	return NULL;
	120	}
e306e2c1	121
e306e2c1	122	*klen = ret;
a6ed3836 DB	123	return buff;
a6ed3836 DB	124	}
e306e2c1	125
a6ed3836 DB	126	static char get_flog_buff(const char file, unsigned int *klen)
	127	{
	128	int fd, ret, len;
	129	struct stat fi;
	130	char *buff;
	131
	132	fd = open(file, O_RDONLY);
	133	if (fd < 0)
	134	return NULL;
	135
	136	ret = fstat(fd, &fi);
	137	if (ret < 0 \|\| !S_ISREG(fi.st_mode))
	138	goto out;
	139
	140	len = fi.st_size + 1;
	141	buff = malloc(len);
	142	if (!buff)
	143	goto out;
	144
	145	memset(buff, 0, len);
	146	ret = read(fd, buff, len - 1);
	147	if (ret <= 0)
	148	goto out_free;
	149
	150	close(fd);
	151	*klen = ret;
e306e2c1	152	return buff;
a6ed3836 DB	153	out_free:
	154	free(buff);
	155	out:
	156	close(fd);
	157	return NULL;
	158	}
	159
	160	static char get_log_buff(const char file, unsigned int *klen)
	161	{
	162	return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
e306e2c1 DB	163	}
e306e2c1 DB	164
a6ed3836	165	static void put_log_buff(char *buff)
e306e2c1 DB	166	{
	167	free(buff);
	168	}
	169
e274da1a DD	170	static uint8_t get_last_jit_image(char haystack, size_t hlen,
e274da1a DD	171	unsigned int *ilen)
e306e2c1 DB	172	{
	173	char ptr, pptr, *tmp;
	174	off_t off = 0;
b223e3b4 DC	175	unsigned int proglen;
b223e3b4 DC	176	int ret, flen, pass, ulen = 0;
e306e2c1	177	regmatch_t pmatch[1];
ed4afd45	178	unsigned long base;
e306e2c1	179	regex_t regex;
e274da1a	180	uint8_t *image;
e306e2c1 DB	181
e306e2c1 DB	182	if (hlen == 0)
e274da1a	183	return NULL;
e306e2c1 DB	184
	185	ret = regcomp(&regex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
	186	"pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
	187	assert(ret == 0);
	188
	189	ptr = haystack;
082739aa DB	190	memset(pmatch, 0, sizeof(pmatch));
082739aa DB	191
e306e2c1 DB	192	while (1) {
	193	ret = regexec(&regex, ptr, 1, pmatch, 0);
	194	if (ret == 0) {
	195	ptr += pmatch[0].rm_eo;
	196	off += pmatch[0].rm_eo;
	197	assert(off < hlen);
	198	} else
	199	break;
	200	}
	201
	202	ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
b223e3b4	203	ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",
ed4afd45	204	&flen, &proglen, &pass, &base);
a6ed3836 DB	205	if (ret != 4) {
a6ed3836 DB	206	regfree(&regex);
e274da1a DD	207	return NULL;
	208	}
	209	if (proglen > 1000000) {
	210	printf("proglen of %d too big, stopping\n", proglen);
	211	return NULL;
a6ed3836	212	}
e306e2c1	213
e274da1a DD	214	image = malloc(proglen);
	215	if (!image) {
	216	printf("Out of memory\n");
	217	return NULL;
	218	}
	219	memset(image, 0, proglen);
	220
e306e2c1	221	tmp = ptr = haystack + off;
e274da1a	222	while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {
e306e2c1 DB	223	tmp = NULL;
	224	if (!strstr(ptr, "JIT code"))
	225	continue;
	226	pptr = ptr;
	227	while ((ptr = strstr(pptr, ":")))
	228	pptr = ptr + 1;
	229	ptr = pptr;
	230	do {
	231	image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
e274da1a	232	if (ptr == pptr) {
e306e2c1 DB	233	ulen--;
	234	break;
	235	}
e274da1a DD	236	if (ulen >= proglen)
e274da1a DD	237	break;
e306e2c1 DB	238	ptr = pptr;
	239	} while (1);
	240	}
	241
	242	assert(ulen == proglen);
b223e3b4	243	printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
e306e2c1	244	proglen, pass, flen);
ed4afd45	245	printf("%lx + <x>:\n", base);
e306e2c1 DB	246
e306e2c1 DB	247	regfree(&regex);
e274da1a DD	248	*ilen = ulen;
e274da1a DD	249	return image;
e306e2c1 DB	250	}
e306e2c1 DB	251
a6ed3836 DB	252	static void usage(void)
	253	{
	254	printf("Usage: bpf_jit_disasm [...]\n");
	255	printf(" -o Also display related opcodes (default: off).\n");
b6518e6a	256	printf(" -O <file> Write binary image of code to file, don't disassemble to stdout.\n");
a6ed3836 DB	257	printf(" -f <file> Read last image dump from file or stdin (default: klog).\n");
	258	printf(" -h Display this help.\n");
	259	}
	260
e306e2c1 DB	261	int main(int argc, char **argv)
e306e2c1 DB	262	{
a6ed3836	263	unsigned int len, klen, opt, opcodes = 0;
a6ed3836	264	char kbuff, file = NULL;
b6518e6a DD	265	char *ofile = NULL;
	266	int ofd;
	267	ssize_t nr;
	268	uint8_t *pos;
e274da1a	269	uint8_t *image = NULL;
e306e2c1	270
b6518e6a	271	while ((opt = getopt(argc, argv, "of:O:")) != -1) {
a6ed3836 DB	272	switch (opt) {
a6ed3836 DB	273	case 'o':
e306e2c1	274	opcodes = 1;
a6ed3836	275	break;
b6518e6a DD	276	case 'O':
	277	ofile = optarg;
	278	break;
a6ed3836 DB	279	case 'f':
	280	file = optarg;
	281	break;
	282	default:
	283	usage();
	284	return -1;
e306e2c1 DB	285	}
	286	}
	287
	288	bfd_init();
e306e2c1	289
a6ed3836 DB	290	kbuff = get_log_buff(file, &klen);
	291	if (!kbuff) {
	292	fprintf(stderr, "Could not retrieve log buffer!\n");
	293	return -1;
	294	}
e306e2c1	295
e274da1a DD	296	image = get_last_jit_image(kbuff, klen, &len);
e274da1a DD	297	if (!image) {
a6ed3836	298	fprintf(stderr, "No JIT image found!\n");
b6518e6a DD	299	goto done;
	300	}
	301	if (!ofile) {
	302	get_asm_insns(image, len, opcodes);
	303	goto done;
	304	}
	305
	306	ofd = open(ofile, O_WRONLY \| O_CREAT \| O_TRUNC, DEFFILEMODE);
	307	if (ofd < 0) {
	308	fprintf(stderr, "Could not open file %s for writing: ", ofile);
	309	perror(NULL);
	310	goto done;
	311	}
	312	pos = image;
	313	do {
	314	nr = write(ofd, pos, len);
	315	if (nr < 0) {
	316	fprintf(stderr, "Could not write data to %s: ", ofile);
	317	perror(NULL);
	318	goto done;
	319	}
	320	len -= nr;
	321	pos += nr;
	322	} while (len);
	323	close(ofd);
e306e2c1	324
b6518e6a	325	done:
a6ed3836	326	put_log_buff(kbuff);
e274da1a	327	free(image);
e306e2c1 DB	328	return 0;
e306e2c1 DB	329	}