![Thomas Gleixner](/assets/img/avatar_default.png)
Based on 1 normalized pattern(s): licensed under the gnu general public license version 2 0 gplv2 extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 3 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Armijn Hemel <armijn@tjaldur.nl> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Enrico Weigelt <info@metux.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190602204653.630925848@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
330 lines
6.4 KiB
C
330 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Minimal BPF JIT image disassembler
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*
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* Disassembles BPF JIT compiler emitted opcodes back to asm insn's for
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* debugging or verification purposes.
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*
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* To get the disassembly of the JIT code, do the following:
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*
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* 1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
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* 2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
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* 3) Run e.g. `bpf_jit_disasm -o` to read out the last JIT code
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*
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* Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <assert.h>
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#include <unistd.h>
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#include <string.h>
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#include <bfd.h>
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#include <dis-asm.h>
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#include <regex.h>
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#include <fcntl.h>
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#include <sys/klog.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <limits.h>
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#define CMD_ACTION_SIZE_BUFFER 10
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#define CMD_ACTION_READ_ALL 3
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static void get_exec_path(char *tpath, size_t size)
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{
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char *path;
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ssize_t len;
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snprintf(tpath, size, "/proc/%d/exe", (int) getpid());
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tpath[size - 1] = 0;
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path = strdup(tpath);
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assert(path);
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len = readlink(path, tpath, size);
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tpath[len] = 0;
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free(path);
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}
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static void get_asm_insns(uint8_t *image, size_t len, int opcodes)
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{
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int count, i, pc = 0;
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char tpath[PATH_MAX];
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struct disassemble_info info;
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disassembler_ftype disassemble;
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bfd *bfdf;
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memset(tpath, 0, sizeof(tpath));
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get_exec_path(tpath, sizeof(tpath));
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bfdf = bfd_openr(tpath, NULL);
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assert(bfdf);
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assert(bfd_check_format(bfdf, bfd_object));
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init_disassemble_info(&info, stdout, (fprintf_ftype) fprintf);
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info.arch = bfd_get_arch(bfdf);
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info.mach = bfd_get_mach(bfdf);
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info.buffer = image;
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info.buffer_length = len;
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disassemble_init_for_target(&info);
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#ifdef DISASM_FOUR_ARGS_SIGNATURE
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disassemble = disassembler(info.arch,
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bfd_big_endian(bfdf),
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info.mach,
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bfdf);
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#else
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disassemble = disassembler(bfdf);
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#endif
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assert(disassemble);
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do {
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printf("%4x:\t", pc);
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count = disassemble(pc, &info);
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if (opcodes) {
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printf("\n\t");
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for (i = 0; i < count; ++i)
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printf("%02x ", (uint8_t) image[pc + i]);
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}
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printf("\n");
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pc += count;
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} while(count > 0 && pc < len);
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bfd_close(bfdf);
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}
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static char *get_klog_buff(unsigned int *klen)
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{
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int ret, len;
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char *buff;
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len = klogctl(CMD_ACTION_SIZE_BUFFER, NULL, 0);
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if (len < 0)
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return NULL;
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buff = malloc(len);
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if (!buff)
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return NULL;
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ret = klogctl(CMD_ACTION_READ_ALL, buff, len);
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if (ret < 0) {
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free(buff);
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return NULL;
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}
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*klen = ret;
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return buff;
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}
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static char *get_flog_buff(const char *file, unsigned int *klen)
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{
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int fd, ret, len;
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struct stat fi;
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char *buff;
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fd = open(file, O_RDONLY);
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if (fd < 0)
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return NULL;
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ret = fstat(fd, &fi);
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if (ret < 0 || !S_ISREG(fi.st_mode))
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goto out;
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len = fi.st_size + 1;
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buff = malloc(len);
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if (!buff)
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goto out;
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memset(buff, 0, len);
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ret = read(fd, buff, len - 1);
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if (ret <= 0)
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goto out_free;
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close(fd);
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*klen = ret;
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return buff;
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out_free:
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free(buff);
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out:
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close(fd);
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return NULL;
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}
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static char *get_log_buff(const char *file, unsigned int *klen)
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{
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return file ? get_flog_buff(file, klen) : get_klog_buff(klen);
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}
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static void put_log_buff(char *buff)
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{
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free(buff);
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}
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static uint8_t *get_last_jit_image(char *haystack, size_t hlen,
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unsigned int *ilen)
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{
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char *ptr, *pptr, *tmp;
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off_t off = 0;
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unsigned int proglen;
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int ret, flen, pass, ulen = 0;
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regmatch_t pmatch[1];
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unsigned long base;
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regex_t regex;
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uint8_t *image;
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if (hlen == 0)
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return NULL;
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ret = regcomp(®ex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
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"pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
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assert(ret == 0);
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ptr = haystack;
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memset(pmatch, 0, sizeof(pmatch));
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while (1) {
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ret = regexec(®ex, ptr, 1, pmatch, 0);
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if (ret == 0) {
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ptr += pmatch[0].rm_eo;
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off += pmatch[0].rm_eo;
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assert(off < hlen);
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} else
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break;
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}
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ptr = haystack + off - (pmatch[0].rm_eo - pmatch[0].rm_so);
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ret = sscanf(ptr, "flen=%d proglen=%u pass=%d image=%lx",
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&flen, &proglen, &pass, &base);
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if (ret != 4) {
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regfree(®ex);
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return NULL;
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}
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if (proglen > 1000000) {
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printf("proglen of %d too big, stopping\n", proglen);
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return NULL;
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}
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image = malloc(proglen);
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if (!image) {
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printf("Out of memory\n");
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return NULL;
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}
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memset(image, 0, proglen);
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tmp = ptr = haystack + off;
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while ((ptr = strtok(tmp, "\n")) != NULL && ulen < proglen) {
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tmp = NULL;
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if (!strstr(ptr, "JIT code"))
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continue;
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pptr = ptr;
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while ((ptr = strstr(pptr, ":")))
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pptr = ptr + 1;
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ptr = pptr;
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do {
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image[ulen++] = (uint8_t) strtoul(pptr, &pptr, 16);
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if (ptr == pptr) {
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ulen--;
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break;
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}
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if (ulen >= proglen)
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break;
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ptr = pptr;
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} while (1);
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}
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assert(ulen == proglen);
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printf("%u bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
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proglen, pass, flen);
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printf("%lx + <x>:\n", base);
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regfree(®ex);
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*ilen = ulen;
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return image;
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}
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static void usage(void)
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{
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printf("Usage: bpf_jit_disasm [...]\n");
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printf(" -o Also display related opcodes (default: off).\n");
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printf(" -O <file> Write binary image of code to file, don't disassemble to stdout.\n");
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printf(" -f <file> Read last image dump from file or stdin (default: klog).\n");
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printf(" -h Display this help.\n");
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}
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int main(int argc, char **argv)
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{
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unsigned int len, klen, opt, opcodes = 0;
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char *kbuff, *file = NULL;
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char *ofile = NULL;
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int ofd;
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ssize_t nr;
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uint8_t *pos;
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uint8_t *image = NULL;
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while ((opt = getopt(argc, argv, "of:O:")) != -1) {
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switch (opt) {
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case 'o':
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opcodes = 1;
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break;
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case 'O':
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ofile = optarg;
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break;
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case 'f':
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file = optarg;
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break;
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default:
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usage();
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return -1;
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}
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}
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bfd_init();
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kbuff = get_log_buff(file, &klen);
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if (!kbuff) {
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fprintf(stderr, "Could not retrieve log buffer!\n");
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return -1;
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}
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image = get_last_jit_image(kbuff, klen, &len);
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if (!image) {
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fprintf(stderr, "No JIT image found!\n");
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goto done;
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}
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if (!ofile) {
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get_asm_insns(image, len, opcodes);
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goto done;
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}
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ofd = open(ofile, O_WRONLY | O_CREAT | O_TRUNC, DEFFILEMODE);
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if (ofd < 0) {
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fprintf(stderr, "Could not open file %s for writing: ", ofile);
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perror(NULL);
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goto done;
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}
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pos = image;
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do {
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nr = write(ofd, pos, len);
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if (nr < 0) {
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fprintf(stderr, "Could not write data to %s: ", ofile);
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perror(NULL);
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goto done;
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}
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len -= nr;
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pos += nr;
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} while (len);
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close(ofd);
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done:
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put_log_buff(kbuff);
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free(image);
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return 0;
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}
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