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authorNicolas Schichan <nschichan@freebox.fr>2015-05-06 18:31:56 +0200
committerDavid S. Miller <davem@davemloft.net>2015-05-10 19:20:32 -0400
commit19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0 (patch)
tree5a26d0599eb1e57364f82e3aa200458a1933a19a /arch/arm
parent78f5b899195019f71f7593c604d75ca61658eae3 (diff)
downloadlinux-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>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/net/bpf_jit_32.c15
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);