tools: bpf_jit_disasm: Add option to dump JIT image to a file.

When debugging the JIT on an embedded platform or cross build
environment, libbfd may not be available, making it impossible to run
bpf_jit_disasm natively.

Add an option to emit a binary image of the JIT code to a file.  This
file can then be disassembled off line.  Typical usage in this case
might be (pasting mips64 dmesg output to cat command):

   $ cat > jit.raw
   $ bpf_jit_disasm -f jit.raw -O jit.bin
   $ mips64-linux-gnu-objdump -D -b binary -m mips:isa64r2 -EB jit.bin

Signed-off-by: David Daney <david.daney@cavium.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/net/bpf_jit_disasm.c b/tools/net/bpf_jit_disasm.c
index 544b05a53b7057bbe9092e31f600065d47e3b24e..ad572e6cdbd0f47cfa947f18451a253977ff6c64 100644 (file)
--- a/tools/net/bpf_jit_disasm.c
+++ b/tools/net/bpf_jit_disasm.c
@@ -229,6 +229,7 @@ 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");
 }
@@ -238,12 +239,19 @@ int main(int argc, char **argv)
        unsigned int len, klen, opt, opcodes = 0;
        static uint8_t image[32768];
        char *kbuff, *file = NULL;
+       char *ofile = NULL;
+       int ofd;
+       ssize_t nr;
+       uint8_t *pos;
 
-       while ((opt = getopt(argc, argv, "of:")) != -1) {
+       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;
@@ -263,11 +271,35 @@ int main(int argc, char **argv)
        }
 
        len = get_last_jit_image(kbuff, klen, image, sizeof(image));
-       if (len > 0)
-               get_asm_insns(image, len, opcodes);
-       else
+       if (len <= 0) {
                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);
        return 0;
 }