On Fri, 2013-04-26 at 22:17 -0400, Xi Wang wrote:
> This patch implements the seccomp BPF_S_ANC_SECCOMP_LD_W instruction
> in x86 JIT.
>
> Signed-off-by: Xi Wang <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> Cc: Heiko Carstens <[email protected]>
> Cc: Will Drewry <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: David Laight <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Nicolas Schichan <[email protected]>
> ---
> arch/x86/net/bpf_jit_comp.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 8898680..5f1dafb 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -683,6 +683,17 @@ cond_branch: f_offset = addrs[i +
> filter[i].jf] - addrs[i];
> }
> EMIT_COND_JMP(f_op, f_offset);
> break;
> +#ifdef CONFIG_SECCOMP_FILTER
> + case BPF_S_ANC_SECCOMP_LD_W:
I would feel more comfortable if you added :
if (seen & SEEN_DATAREF) {
pr_err_once("SECCOMP_LD_W assertion failed\n"):
goto out;
}
This way, if BPF is changed in the future, but not the x86 JIT, we
can have a working kernel.
Ideally, we should add a SEEN_SKBREF to make sure rdi value can be
scratched, or you just push %rdi/pop %rdi, its only one byte
instructions.
Or completely optimize the thing and not call seccomp_bpf_load() at all.
(current would be loaded once in r9, task_pt_regs() would be loaded once
in r8)
> + func = (u8 *)seccomp_bpf_load;
> + t_offset = func - (image + addrs[i]);
> + /* seccomp filters don't use %rdi, %r8, %r9
> + * it is safe to not save these registers
> + */
> + EMIT1_off32(0xbf, K); /* mov imm32,%edi */
> + EMIT1_off32(0xe8, t_offset); /* call
> seccomp_bpf_load */
> + break;
> +#endif
> default:
> /* hmm, too complex filter, give up with jit
> compiler */
> goto out;
--
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