Commit Graph

6 Commits

Author SHA1 Message Date
Andrzej Hajda 4de61ba234 tools: bpf_jit_disasm: make get_last_jit_image return unsigned
The function returns always non-negative values.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-28 22:18:01 -07:00
Daniel Borkmann a6ed38361b bpf_jit_disasm: also support reading jit dump from file
This patch adds support to read the dmesg BPF JIT dump also from a
file instead of the klog buffer. I found this quite useful when going
through some 'before/after patch' logs. It also fixes a regex leak
found by valgrind when no image dump was found.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-31 15:13:14 -07:00
Daniel Borkmann 082739aa45 tools: bpf_jit_disasm: fix segfault on disabled debugging log output
With recent debugging, I noticed that bpf_jit_disasm segfaults when
there's no debugging output from the JIT compiler to the kernel log.

Reason is that when regexec(3) doesn't match on anything, start/end
offsets are not being filled out and contain some uninitialized garbage
from stack. Thus, we need zero out offsets first.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-05-27 00:24:10 -04:00
Alexei Starovoitov 9bb1a208fd tools: bpf_jit_disasm: increase image buffer size
JITed seccomp filters can be quite large if they check a lot of syscalls
Simply increase buffer size

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-16 16:44:08 -04:00
Alexei Starovoitov ed4afd451f tools: bpf_jit_disasm: ignore image address for disasm
seccomp filters use kernel JIT image addresses, so bpf_jit_enable=2 prints
[ 20.146438] flen=3 proglen=82 pass=0 image=0000000000000000
[ 20.146442] JIT code: 00000000: 55 48 89 e5 48 81 ec 28 02 00 00 ...

ignore image address, so that seccomp filters can be disassembled

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-16 16:44:08 -04:00
Daniel Borkmann e306e2c13b filter: add minimal BPF JIT image disassembler
This is a minimal stand-alone user space helper, that allows for debugging or
verification of emitted BPF JIT images. This is in particular useful for
emitted opcode debugging, since minor bugs in the JIT compiler can be fatal.
The disassembler is architecture generic and uses libopcodes and libbfd.

How to get to the disassembly, example:

  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 disassemble the most recent JIT code output

`bpf_jit_disasm -o` will display the related opcodes to a particular instruction
as well. Example for x86_64:

$ ./bpf_jit_disasm
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
   1:	mov    %rsp,%rbp
   4:	sub    $0x60,%rsp
   8:	mov    %rbx,-0x8(%rbp)
   c:	mov    0x68(%rdi),%r9d
  10:	sub    0x6c(%rdi),%r9d
  14:	mov    0xe0(%rdi),%r8
  1b:	mov    $0xc,%esi
  20:	callq  0xffffffffe0d01b71
  25:	cmp    $0x86dd,%eax
  2a:	jne    0x000000000000003d
  2c:	mov    $0x14,%esi
  31:	callq  0xffffffffe0d01b8d
  36:	cmp    $0x6,%eax
[...]
  5c:	leaveq
  5d:	retq

$ ./bpf_jit_disasm -o
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
	55
   1:	mov    %rsp,%rbp
	48 89 e5
   4:	sub    $0x60,%rsp
	48 83 ec 60
   8:	mov    %rbx,-0x8(%rbp)
	48 89 5d f8
   c:	mov    0x68(%rdi),%r9d
	44 8b 4f 68
  10:	sub    0x6c(%rdi),%r9d
	44 2b 4f 6c
[...]
  5c:	leaveq
	c9
  5d:	retq
	c3

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-03-21 11:35:41 -04:00