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

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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>
This commit is contained in:
David Daney 2017-04-11 14:30:52 -07:00 committed by David S. Miller
parent fe6af0e122
commit b6518e6a00
1 changed files with 36 additions and 4 deletions
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40
tools/net/bpf_jit_disasm.c
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@ -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;
}