linux-kernel - [PATCH v2 3/5] MIPS: BPF: Use unsigned access for unsigned SKB fields.

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Date:   Tue, 14 Mar 2017 14:21:42 -0700
From:   David Daney <david.daney@...ium.com>
To:     linux-mips@...ux-mips.org, ralf@...ux-mips.org,
        James Hogan <james.hogan@...tec.com>,
        Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "Steven J. Hill" <steven.hill@...ium.com>,
        David Daney <david.daney@...ium.com>
Subject: [PATCH v2 3/5] MIPS: BPF: Use unsigned access for unsigned SKB fields.

The SKB vlan_tci and queue_mapping fields are unsigned, don't sign
extend these in the BPF JIT.  In the vlan_tci case, the value gets
masked so the change is not needed for correctness, but do it anyway
for agreement with the types defined in struct sk_buff.

Signed-off-by: David Daney <david.daney@...ium.com>
---
 arch/mips/net/bpf_jit.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 880e329..a68cd36 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -1156,7 +1156,7 @@ static int build_body(struct jit_ctx *ctx)
 			BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
 						  vlan_tci) != 2);
 			off = offsetof(struct sk_buff, vlan_tci);
-			emit_half_load(r_s0, r_skb, off, ctx);
+			emit_half_load_unsigned(r_s0, r_skb, off, ctx);
 			if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
 				emit_andi(r_A, r_s0, (u16)~VLAN_TAG_PRESENT, ctx);
 			} else {
@@ -1183,7 +1183,7 @@ static int build_body(struct jit_ctx *ctx)
 			BUILD_BUG_ON(offsetof(struct sk_buff,
 					      queue_mapping) > 0xff);
 			off = offsetof(struct sk_buff, queue_mapping);
-			emit_half_load(r_A, r_skb, off, ctx);
+			emit_half_load_unsigned(r_A, r_skb, off, ctx);
 			break;
 		default:
 			pr_debug("%s: Unhandled opcode: 0x%02x\n", __FILE__,
-- 
2.9.3