1 files changed, 329 insertions, 0 deletions
diff --git a/tools/bpf/bpf_jit_disasm.c b/tools/bpf/bpf_jit_disasm.c
new file mode 100644
index 000000000..58c2bab4e
--- /dev/null
+++ b/tools/bpf/bpf_jit_disasm.c
@@ -0,0 +1,329 @@
+/*
+ * 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 <borkmann@redhat.com>
+ * Licensed under the GNU General Public License, version 2.0 (GPLv2)
+ */
+
+#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;
+}