Commit b6518e6a authored by David Daney's avatar David Daney Committed by David S. Miller
Browse files

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: default avatarDavid Daney <david.daney@cavium.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fe6af0e1

tools/net/bpf_jit_disasm.c

+36 −4
Original line number Diff line number Diff line
@@ -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;

}

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