[PATCH v3 4/5] LoongArch: BPF: Support load-acquire and store-release instructions

[Tiezhu Yang]

Use the LoongArch common memory access instructions with the barrier dbar
to support the BPF load-acquire and store-release instructions.

With this patch, the following testcases passed on LoongArch if the macro
CAN_USE_LOAD_ACQ_STORE_REL is usable in bpf selftests:

  sudo ./test_progs -t verifier_load_acquire
  sudo ./test_progs -t verifier_store_release
  sudo ./test_progs -t verifier_precision/bpf_load_acquire
  sudo ./test_progs -t verifier_precision/bpf_store_release
  sudo ./test_progs -t compute_live_registers/atomic_load_acq_store_rel

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---
 arch/loongarch/net/bpf_jit.c | 98 +++++++++++++++++++++++++++++++++++-
 1 file changed, 97 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index c9a32f124f5e..805f95cbe798 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -344,6 +344,99 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int insn)
 #undef jmp_offset
 }
 
+static int emit_atomic_ld_st(const struct bpf_insn *insn, struct jit_ctx *ctx)
+{
+	const u8 t1 = LOONGARCH_GPR_T1;
+	const u8 src = regmap[insn->src_reg];
+	const u8 dst = regmap[insn->dst_reg];
+	const s16 off = insn->off;
+	const s32 imm = insn->imm;
+
+	switch (imm) {
+	/* dst_reg = load_acquire(src_reg + off16) */
+	case BPF_LOAD_ACQ:
+		switch (BPF_SIZE(insn->code)) {
+		case BPF_B:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, ldbu, dst, src, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, ldxbu, dst, src, t1);
+			}
+			break;
+		case BPF_H:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, ldhu, dst, src, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, ldxhu, dst, src, t1);
+			}
+			break;
+		case BPF_W:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, ldwu, dst, src, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, ldxwu, dst, src, t1);
+			}
+			break;
+		case BPF_DW:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, ldd, dst, src, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, ldxd, dst, src, t1);
+			}
+			break;
+		}
+		emit_insn(ctx, dbar, 0b10100);
+		break;
+	/* store_release(dst_reg + off16, src_reg) */
+	case BPF_STORE_REL:
+		emit_insn(ctx, dbar, 0b10010);
+		switch (BPF_SIZE(insn->code)) {
+		case BPF_B:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, stb, src, dst, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, stxb, src, dst, t1);
+			}
+			break;
+		case BPF_H:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, sth, src, dst, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, stxh, src, dst, t1);
+			}
+			break;
+		case BPF_W:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, stw, src, dst, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, stxw, src, dst, t1);
+			}
+			break;
+		case BPF_DW:
+			if (is_signed_imm12(off)) {
+				emit_insn(ctx, std, src, dst, off);
+			} else {
+				move_imm(ctx, t1, off, false);
+				emit_insn(ctx, stxd, src, dst, t1);
+			}
+			break;
+		}
+		break;
+	default:
+		pr_err_once("bpf-jit: invalid atomic load/store opcode %02x\n", imm);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int emit_atomic_rmw(const struct bpf_insn *insn, struct jit_ctx *ctx)
 {
 	const u8 t1 = LOONGARCH_GPR_T1;
@@ -1326,7 +1419,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 	case BPF_STX | BPF_ATOMIC | BPF_H:
 	case BPF_STX | BPF_ATOMIC | BPF_W:
 	case BPF_STX | BPF_ATOMIC | BPF_DW:
-		ret = emit_atomic_rmw(insn, ctx);
+		if (bpf_atomic_is_load_store(insn))
+			ret = emit_atomic_ld_st(insn, ctx);
+		else
+			ret = emit_atomic_rmw(insn, ctx);
 		if (ret)
 			return ret;
 		break;
-- 
2.42.0