[PATCH bpf-next 3/7] bpf, arm64: Support sign-extension mov instructions

[Xu Kuohai]

From: Xu Kuohai <xukuohai at huawei.com>

Add jit support for BPF sign-extension mov instructions with
arm64 SXTB/SXTH/SXTW instructions.

Signed-off-by: Xu Kuohai <xukuohai at huawei.com>
---
 arch/arm64/net/bpf_jit.h      |  5 +++++
 arch/arm64/net/bpf_jit_comp.c | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h
index 086ffbad0eb5..949810a0c48c 100644
--- a/arch/arm64/net/bpf_jit.h
+++ b/arch/arm64/net/bpf_jit.h
@@ -192,6 +192,11 @@
 #define A64_UXTH(sf, Rd, Rn) A64_UBFM(sf, Rd, Rn, 0, 15)
 #define A64_UXTW(sf, Rd, Rn) A64_UBFM(sf, Rd, Rn, 0, 31)
 
+/* Sign extend */
+#define A64_SXTB(sf, Rd, Rn) A64_SBFM(sf, Rd, Rn, 0, 7)
+#define A64_SXTH(sf, Rd, Rn) A64_SBFM(sf, Rd, Rn, 0, 15)
+#define A64_SXTW(sf, Rd, Rn) A64_SBFM(sf, Rd, Rn, 0, 31)
+
 /* Move wide (immediate) */
 #define A64_MOVEW(sf, Rd, imm16, shift, type) \
 	aarch64_insn_gen_movewide(Rd, imm16, shift, \
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 22f1b0d5fb3c..9b796e74ef42 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -786,7 +786,20 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
 	/* dst = src */
 	case BPF_ALU | BPF_MOV | BPF_X:
 	case BPF_ALU64 | BPF_MOV | BPF_X:
-		emit(A64_MOV(is64, dst, src), ctx);
+		switch (insn->off) {
+		case 0:
+			emit(A64_MOV(is64, dst, src), ctx);
+			break;
+		case 8:
+			emit(A64_SXTB(is64, dst, src), ctx);
+			break;
+		case 16:
+			emit(A64_SXTH(is64, dst, src), ctx);
+			break;
+		case 32:
+			emit(A64_SXTW(is64, dst, src), ctx);
+			break;
+		}
 		break;
 	/* dst = dst OP src */
 	case BPF_ALU | BPF_ADD | BPF_X:
-- 
2.30.2