bpf, riscv: Optimize FROM_LE using verifier_zext on RV64

This patch adds two optimizations for BPF_ALU BPF_END BPF_FROM_LE in the RV64 BPF JIT. First, it enables the verifier zero-extension optimization to avoid zero extension when imm == 32. Second, it avoids generating code for imm == 64, since it is equivalent to a no-op. Co-developed-by: Xi Wang <[email protected]> Signed-off-by: Xi Wang <[email protected]> Signed-off-by: Luke Nelson <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Reviewed-by: Björn Töpel <[email protected]> Acked-by: Björn Töpel <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
nawuyao · May 6, 2020 · 21a099a · 21a099a
1 parent 0224b2a
commit 21a099a
Showing 1 changed file with 14 additions and 6 deletions.
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
@@ -542,13 +542,21 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 
 	/* dst = BSWAP##imm(dst) */
 	case BPF_ALU | BPF_END | BPF_FROM_LE:
-	{
-		int shift = 64 - imm;
-
-		emit(rv_slli(rd, rd, shift), ctx);
-		emit(rv_srli(rd, rd, shift), ctx);
+		switch (imm) {
+		case 16:
+			emit(rv_slli(rd, rd, 48), ctx);
+			emit(rv_srli(rd, rd, 48), ctx);
+			break;
+		case 32:
+			if (!aux->verifier_zext)
+				emit_zext_32(rd, ctx);
+			break;
+		case 64:
+			/* Do nothing */
+			break;
+		}
 		break;
-	}
+
 	case BPF_ALU | BPF_END | BPF_FROM_BE:
 		emit(rv_addi(RV_REG_T2, RV_REG_ZERO, 0), ctx);