1 files changed, 199 insertions, 0 deletions

diff --git a/tools/net/bpf_jit_disasm.c b/tools/net/bpf_jit_disasm.c
new file mode 100644
index 000000000000..cfe0cdcda3de
--- /dev/null
+++ b/tools/net/bpf_jit_disasm.c
@@ -0,0 +1,199 @@
+/*
+ * 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 <sys/klog.h>
+#include <sys/types.h>
+#include <regex.h>
+
+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, unsigned long base,
+                          int opcodes)
+{
+        int count, i, pc = 0;
+        char tpath[256];
+        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);
+
+        disassemble = disassembler(bfdf);
+        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(int *klen)
+{
+        int ret, len = klogctl(10, NULL, 0);
+        char *buff = malloc(len);
+
+        assert(buff && klen);
+        ret = klogctl(3, buff, len);
+        assert(ret >= 0);
+        *klen = ret;
+
+        return buff;
+}
+
+static void put_klog_buff(char *buff)
+{
+        free(buff);
+}
+
+static int get_last_jit_image(char *haystack, size_t hlen,
+                              uint8_t *image, size_t ilen,
+                              unsigned long *base)
+{
+        char *ptr, *pptr, *tmp;
+        off_t off = 0;
+        int ret, flen, proglen, pass, ulen = 0;
+        regmatch_t pmatch[1];
+        regex_t regex;
+
+        if (hlen == 0)
+                return 0;
+
+        ret = regcomp(&regex, "flen=[[:alnum:]]+ proglen=[[:digit:]]+ "
+                      "pass=[[:digit:]]+ image=[[:xdigit:]]+", REG_EXTENDED);
+        assert(ret == 0);
+
+        ptr = haystack;
+        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=%d pass=%d image=%lx",
+                     &flen, &proglen, &pass, base);
+        if (ret != 4)
+                return 0;
+
+        tmp = ptr = haystack + off;
+        while ((ptr = strtok(tmp, "\n")) != NULL && ulen < ilen) {
+                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 >= ilen) {
+                                ulen--;
+                                break;
+                        }
+                        ptr = pptr;
+                } while (1);
+        }
+
+        assert(ulen == proglen);
+        printf("%d bytes emitted from JIT compiler (pass:%d, flen:%d)\n",
+               proglen, pass, flen);
+        printf("%lx + <x>:\n", *base);
+
+        regfree(&regex);
+        return ulen;
+}
+
+int main(int argc, char **argv)
+{
+        int len, klen, opcodes = 0;
+        char *kbuff;
+        unsigned long base;
+        uint8_t image[4096];
+
+        if (argc > 1) {
+                if (!strncmp("-o", argv[argc - 1], 2)) {
+                        opcodes = 1;
+                } else {
+                        printf("usage: bpf_jit_disasm [-o: show opcodes]\n");
+                        exit(0);
+                }
+        }
+
+        bfd_init();
+        memset(image, 0, sizeof(image));
+
+        kbuff = get_klog_buff(&klen);
+
+        len = get_last_jit_image(kbuff, klen, image, sizeof(image), &base);
+        if (len > 0 && base > 0)
+                get_asm_insns(image, len, base, opcodes);
+
+        put_klog_buff(kbuff);
+
+        return 0;
+}