]> git.baikalelectronics.ru Git - kernel.git/commit
x86: bpf_jit: fix compilation of large bpf programs
authorAlexei Starovoitov <ast@plumgrid.com>
Fri, 22 May 2015 22:42:55 +0000 (15:42 -0700)
committerDavid S. Miller <davem@davemloft.net>
Mon, 25 May 2015 04:18:35 +0000 (00:18 -0400)
commiteb29e186b34f6534aec2976324d4fb9714078223
tree44c20470cf4a971a646330bfd5d55cfc985efe36
parent3681799e5d7f9af98af0f32d6f944292f2bc9036
x86: bpf_jit: fix compilation of large bpf programs

x86 has variable length encoding. x86 JIT compiler is trying
to pick the shortest encoding for given bpf instruction.
While doing so the jump targets are changing, so JIT is doing
multiple passes over the program. Typical program needs 3 passes.
Some very short programs converge with 2 passes. Large programs
may need 4 or 5. But specially crafted bpf programs may hit the
pass limit and if the program converges on the last iteration
the JIT compiler will be producing an image full of 'int 3' insns.
Fix this corner case by doing final iteration over bpf program.

Fixes: ebcb62a514ad ("net: filter: Just In Time compiler for x86-64")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Tested-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
arch/x86/net/bpf_jit_comp.c