diff options
Diffstat (limited to 'tools/bpf/bpf_jit_disasm.c')
| -rw-r--r-- | tools/bpf/bpf_jit_disasm.c | 329 |
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..c8ae95804 --- /dev/null +++ b/tools/bpf/bpf_jit_disasm.c @@ -0,0 +1,329 @@ +// 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 <borkmann@redhat.com> + */ + +#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(®ex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ " + "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED); + assert(ret == 0); + + ptr = haystack; + memset(pmatch, 0, sizeof(pmatch)); + + while (1) { + ret = regexec(®ex, 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(®ex); + 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(®ex); + *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; +} |