[PATCH bpf-next 5/6] bpf, arm32: Always zero extend for LDX with B/H/W

[Puranjay Mohan]

The JITs should not depend on the verifier for zero extending the upper
32 bits of the destination register when loading a byte, half-word, or
word.

A following patch will make the verifier stop patching zext instructions
after LDX.

Signed-off-by: Puranjay Mohan <puranja...@gmail.com>
---
 arch/arm/net/bpf_jit_32.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 6a1c9fca5260..757a99febba5 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1081,20 +1081,17 @@ static inline void emit_ldx_r(const s8 dst[], const s8 
src,
        case BPF_B:
                /* Load a Byte */
                emit(ARM_LDRB_I(rd[1], rm, off), ctx);
-               if (!ctx->prog->aux->verifier_zext)
-                       emit_a32_mov_i(rd[0], 0, ctx);
+               emit_a32_mov_i(rd[0], 0, ctx);
                break;
        case BPF_H:
                /* Load a HalfWord */
                emit(ARM_LDRH_I(rd[1], rm, off), ctx);
-               if (!ctx->prog->aux->verifier_zext)
-                       emit_a32_mov_i(rd[0], 0, ctx);
+               emit_a32_mov_i(rd[0], 0, ctx);
                break;
        case BPF_W:
                /* Load a Word */
                emit(ARM_LDR_I(rd[1], rm, off), ctx);
-               if (!ctx->prog->aux->verifier_zext)
-                       emit_a32_mov_i(rd[0], 0, ctx);
+               emit_a32_mov_i(rd[0], 0, ctx);
                break;
        case BPF_DW:
                /* Load a Double Word */
-- 
2.39.2