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| author | Nicolas Schichan <nschichan@freebox.fr> | 2015-05-06 18:31:56 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-05-10 19:20:32 -0400 |
| commit | 19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0 (patch) | |
| tree | 5a26d0599eb1e57364f82e3aa200458a1933a19a | |
| parent | 78f5b899195019f71f7593c604d75ca61658eae3 (diff) | |
| download | linux-19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0.tar.bz2 | |
ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction.
In that case, emit_udiv() will be called with rn == ARM_R0 (r_scratch)
and loading rm first into ARM_R0 will result in jit_udiv() function
being called the same dividend and divisor. Fix that by loading rn
first into ARM_R1 and then rm into ARM_R0.
Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
Cc: <stable@vger.kernel.org> # v3.13+
Fixes: aee636c4809f (bpf: do not use reciprocal divide)
Acked-by: Mircea Gherzan <mgherzan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | arch/arm/net/bpf_jit_32.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index e1268f905026..f412b53ed268 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -449,10 +449,21 @@ static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx) return; } #endif - if (rm != ARM_R0) - emit(ARM_MOV_R(ARM_R0, rm), ctx); + + /* + * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4 + * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into + * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm + * before using it as a source for ARM_R1. + * + * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is + * ARM_R5 (r_X) so there is no particular register overlap + * issues. + */ if (rn != ARM_R1) emit(ARM_MOV_R(ARM_R1, rn), ctx); + if (rm != ARM_R0) + emit(ARM_MOV_R(ARM_R0, rm), ctx); ctx->seen |= SEEN_CALL; emit_mov_i(ARM_R3, (u32)jit_udiv, ctx); |