Messages in this thread | | | Date | Fri, 1 May 2015 18:37:21 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 4/4] ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction. |
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On Wed, Apr 29, 2015 at 03:37:37PM +0200, Nicolas Schichan wrote: > 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> > --- > arch/arm/net/bpf_jit_32.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c > index b5f470d..ffaf311 100644 > --- a/arch/arm/net/bpf_jit_32.c > +++ b/arch/arm/net/bpf_jit_32.c > @@ -449,10 +449,10 @@ 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); > if (rn != ARM_R1) > emit(ARM_MOV_R(ARM_R1, rn), ctx); > + if (rm != ARM_R0) > + emit(ARM_MOV_R(ARM_R0, rm), ctx);
I don't think you've thought enough about this. What if rm is ARM_R1? What if rn = ARM_R0 and rm = ARM_R1?
How about:
if (rn == ARM_R0 && rm == ARM_R1) { emit(ARM_MOV_R(ARM_R3, rn), ctx); // r3 <- r0(rn) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- r1(rm) emit(ARM_MOV_R(ARM_R1, ARM_R3), ctx); // r1 <- r3 } else if (rn == ARM_R0) { emit(ARM_MOV_R(ARM_R1, rn), ctx); // r1 <- rn if (rm != ARM_R0) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- rm } else { if (rm != ARM_R0) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- rm if (rn != ARM_R1) emit(ARM_MOV_R(ARM_R1, rn), ctx); // r1 <- rn }
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