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

Xu Kuohai
2023-08-15T15:21:13Z

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

Signed-off-by: Xu Kuohai <xukuohai@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