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ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction.

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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: aee636c480 (bpf: do not use reciprocal divide)
Acked-by: Mircea Gherzan <mgherzan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Schichan 2015-05-06 18:31:56 +02:00 committed by David S. Miller
parent 78f5b89919
commit 19fc99d0c6
1 changed files with 13 additions and 2 deletions
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15
arch/arm/net/bpf_jit_32.c
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@ -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);