Re: [PATCH v2 net-next 3/3] ARM: net: bpf_jit_32: support BPF_S_ANC_SECCOMP_LD_Winstruction

From: Daniel Borkmann
Date: Sat Apr 27 2013 - 02:28:01 EST

On 04/27/2013 04:17 AM, Xi Wang wrote:
This patch implements the seccomp BPF_S_ANC_SECCOMP_LD_W instruction

Signed-off-by: Xi Wang <>
Cc: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Will Drewry <wad@xxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: David Laight <david.laight@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Nicolas Schichan <nschichan@xxxxxxxxxx>
arch/arm/net/bpf_jit_32.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 073b085..9bfce464 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -19,6 +19,7 @@
#include <linux/if_vlan.h>
#include <asm/cacheflush.h>
#include <asm/hwcap.h>
+#include <asm/syscall.h>

#include "bpf_jit_32.h"

@@ -845,6 +846,19 @@ b_epilogue:
off = offsetof(struct sk_buff, queue_mapping);
emit(ARM_LDRH_I(r_A, r_skb, off), ctx);
+ if (k == offsetof(struct seccomp_data, arch)) {
+ emit_mov_i(r_A, AUDIT_ARCH_ARM, ctx);
+ break;
+ }

Not an expert in ARM, but ...

Arent't you doing here a similar thing in terms of getting arch as Eric
criticized (Nicolas' implementation does not use that part btw.)? Also,
even if it would be possible here, now your 2 JIT implementations differ
in behaviour. I think this is unintended.

Besides all that, I think I also pointed you to a patch that already made
it in for ARM, not sure why you keep posting the ARM JIT implementation?

+ ctx->seen |= SEEN_CALL;
+ emit_mov_i(ARM_R3, (u32)seccomp_bpf_load, ctx);
+ emit_mov_i(ARM_R0, k, ctx);
+ emit_blx_r(ARM_R3, ctx);
+ emit(ARM_MOV_R(r_A, ARM_R0), ctx);
+ break;
return -1;

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