Merge branch 'riscv-bpf-add-support-for-signed-operations-and-32-bit-atomics'

Kuan-Wei Chiu says:

====================
riscv, bpf: Add support for signed operations and 32-bit atomics

Add support for missing signed operations and 32-bit atomics in the
RV32 BPF JIT compiler.

The current implementation lacks support for BPF_SDIV, BPF_SMOD, and
BPF_MOVSX, ignoring the instruction offset field and treating them as
unsigned or zero-extended. Introduce support for these operations by
checking the offset field and emitting the corresponding instructions.

Additionally, we leverage the mandatory A extension to natively support
32-bit BPF atomics (and, or, xor, xchg) by mapping them directly to
amo*.w instructions. BPF_CMPXCHG continues to fall back to the
interpreter.

As a result, test_bpf.ko now runs with 0 failures, and the total number
of successfully JIT'ed test cases increases from 843 to 902.
Tested-by: Pu Lehui <pulehui@huawei.com>
---
Changes in v4:
- Add a 'dst' param to emit_bpf_atomic().

Changes in v3:
- Pass insn directly to emit_alu_r32().
- Remove the Fixes: tag and update title.
- Consolidate size, mode, and off into insn for emit_store_r64().

Changes in v2:
- Add missing Fixes tags.
- Fix memory ordering by emitting aq=1, rl=1

Kuan-Wei Chiu (3):
  riscv, bpf: Add support for BPF_SDIV and BPF_SMOD in RV32 JIT
  riscv, bpf: Add support for BPF_MOVSX in RV32 JIT
  riscv, bpf: Add 32 bit atomic operations to RV32 JIT

 arch/riscv/net/bpf_jit_comp32.c | 111 +++++++++++++++++++++++++++-----
 1 file changed, 95 insertions(+), 16 deletions(-)
====================

Link: https://patch.msgid.link/20260714002451.4091139-1-visitorckw@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 95 insertions, 16 deletions

diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c
index 592dd86fbf81..a9e0bd5cc81d 100644
--- a/arch/riscv/net/bpf_jit_comp32.c
+++ b/arch/riscv/net/bpf_jit_comp32.c
@@ -509,12 +509,15 @@ static void emit_alu_r64(const s8 *dst, const s8 *src,
 }
 
 static void emit_alu_r32(const s8 *dst, const s8 *src,
-			 struct rv_jit_context *ctx, const u8 op)
+			 struct rv_jit_context *ctx,
+			 const struct bpf_insn *insn)
 {
 	const s8 *tmp1 = bpf2rv32[TMP_REG_1];
 	const s8 *tmp2 = bpf2rv32[TMP_REG_2];
 	const s8 *rd = bpf_get_reg32(dst, tmp1, ctx);
 	const s8 *rs = bpf_get_reg32(src, tmp2, ctx);
+	u8 op = BPF_OP(insn->code);
+	bool is_signed = insn->off == 1;
 
 	switch (op) {
 	case BPF_MOV:
@@ -539,10 +542,12 @@ static void emit_alu_r32(const s8 *dst, const s8 *src,
 		emit(rv_mul(lo(rd), lo(rd), lo(rs)), ctx);
 		break;
 	case BPF_DIV:
-		emit(rv_divu(lo(rd), lo(rd), lo(rs)), ctx);
+		emit(is_signed ? rv_div(lo(rd), lo(rd), lo(rs)) :
+				 rv_divu(lo(rd), lo(rd), lo(rs)), ctx);
 		break;
 	case BPF_MOD:
-		emit(rv_remu(lo(rd), lo(rd), lo(rs)), ctx);
+		emit(is_signed ? rv_rem(lo(rd), lo(rd), lo(rs)) :
+				 rv_remu(lo(rd), lo(rd), lo(rs)), ctx);
 		break;
 	case BPF_LSH:
 		emit(rv_sll(lo(rd), lo(rd), lo(rs)), ctx);
@@ -869,14 +874,58 @@ static int emit_load_r64(const s8 *dst, const s8 *src, s16 off,
 	return 0;
 }
 
-static int emit_store_r64(const s8 *dst, const s8 *src, s16 off,
-			  struct rv_jit_context *ctx, const u8 size,
-			  const u8 mode)
+static int emit_bpf_atomic(s8 dst, const s8 *src, const s8 *rs,
+			   struct rv_jit_context *ctx,
+			   const struct bpf_insn *insn)
+{
+	s32 imm = insn->imm;
+	bool is_fetch = (imm & BPF_FETCH) || (imm == BPF_XCHG);
+	s8 fetch_reg = is_fetch ? lo(rs) : RV_REG_ZERO;
+	int aq = is_fetch ? 1 : 0;
+	int rl = is_fetch ? 1 : 0;
+
+	switch (imm) {
+	case BPF_ADD:
+	case BPF_ADD | BPF_FETCH:
+		emit(rv_amoadd_w(fetch_reg, lo(rs), dst, aq, rl), ctx);
+		break;
+	case BPF_AND:
+	case BPF_AND | BPF_FETCH:
+		emit(rv_amoand_w(fetch_reg, lo(rs), dst, aq, rl), ctx);
+		break;
+	case BPF_OR:
+	case BPF_OR | BPF_FETCH:
+		emit(rv_amoor_w(fetch_reg, lo(rs), dst, aq, rl), ctx);
+		break;
+	case BPF_XOR:
+	case BPF_XOR | BPF_FETCH:
+		emit(rv_amoxor_w(fetch_reg, lo(rs), dst, aq, rl), ctx);
+		break;
+	case BPF_XCHG:
+		emit(rv_amoswap_w(fetch_reg, lo(rs), dst, aq, rl), ctx);
+		break;
+	default:
+		return -1;
+	}
+
+	if (is_fetch) {
+		emit(rv_addi(hi(rs), RV_REG_ZERO, 0), ctx);
+		bpf_put_reg64(src, rs, ctx);
+	}
+	return 0;
+}
+
+static int emit_store_r64(const s8 *dst, const s8 *src,
+			  struct rv_jit_context *ctx,
+			  const struct bpf_insn *insn)
 {
 	const s8 *tmp1 = bpf2rv32[TMP_REG_1];
 	const s8 *tmp2 = bpf2rv32[TMP_REG_2];
 	const s8 *rd = bpf_get_reg64(dst, tmp1, ctx);
 	const s8 *rs = bpf_get_reg64(src, tmp2, ctx);
+	u8 size = BPF_SIZE(insn->code);
+	u8 mode = BPF_MODE(insn->code);
+	s16 off = insn->off;
 
 	if (mode == BPF_ATOMIC && size != BPF_W)
 		return -1;
@@ -896,9 +945,9 @@ static int emit_store_r64(const s8 *dst, const s8 *src, s16 off,
 		case BPF_MEM:
 			emit(rv_sw(RV_REG_T0, 0, lo(rs)), ctx);
 			break;
-		case BPF_ATOMIC: /* Only BPF_ADD supported */
-			emit(rv_amoadd_w(RV_REG_ZERO, lo(rs), RV_REG_T0, 0, 0),
-			     ctx);
+		case BPF_ATOMIC:
+			if (emit_bpf_atomic(RV_REG_T0, src, rs, ctx, insn))
+				return -1;
 			break;
 		}
 		break;
@@ -967,6 +1016,24 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 
 	switch (code) {
 	case BPF_ALU64 | BPF_MOV | BPF_X:
+		if (insn->off != 0) {
+			const s8 *rd = bpf_get_reg64(dst, tmp1, ctx);
+			const s8 *rs = bpf_get_reg64(src, tmp2, ctx);
+
+			if (insn->off == 8) {
+				emit(rv_slli(lo(rd), lo(rs), 24), ctx);
+				emit(rv_srai(lo(rd), lo(rd), 24), ctx);
+			} else if (insn->off == 16) {
+				emit(rv_slli(lo(rd), lo(rs), 16), ctx);
+				emit(rv_srai(lo(rd), lo(rd), 16), ctx);
+			} else {
+				emit(rv_addi(lo(rd), lo(rs), 0), ctx);
+			}
+			emit(rv_srai(hi(rd), lo(rd), 31), ctx);
+			bpf_put_reg64(dst, rd, ctx);
+			break;
+		}
+		fallthrough;
 
 	case BPF_ALU64 | BPF_ADD | BPF_X:
 	case BPF_ALU64 | BPF_ADD | BPF_K:
@@ -1017,6 +1084,20 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 			emit_zext64(dst, ctx);
 			break;
 		}
+		if (insn->off != 0) {
+			const s8 *rd = bpf_get_reg32(dst, tmp1, ctx);
+			const s8 *rs = bpf_get_reg32(src, tmp2, ctx);
+
+			if (insn->off == 8) {
+				emit(rv_slli(lo(rd), lo(rs), 24), ctx);
+				emit(rv_srai(lo(rd), lo(rd), 24), ctx);
+			} else if (insn->off == 16) {
+				emit(rv_slli(lo(rd), lo(rs), 16), ctx);
+				emit(rv_srai(lo(rd), lo(rd), 16), ctx);
+			}
+			bpf_put_reg32(dst, rd, ctx);
+			break;
+		}
 		fallthrough;
 
 	case BPF_ALU | BPF_ADD | BPF_X:
@@ -1041,7 +1122,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 			emit_imm32(tmp2, imm, ctx);
 			src = tmp2;
 		}
-		emit_alu_r32(dst, src, ctx, BPF_OP(code));
+		emit_alu_r32(dst, src, ctx, insn);
 		break;
 
 	case BPF_ALU | BPF_MOV | BPF_K:
@@ -1065,7 +1146,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 		 * src is ignored---choose tmp2 as a dummy register since it
 		 * is not on the stack.
 		 */
-		emit_alu_r32(dst, tmp2, ctx, BPF_OP(code));
+		emit_alu_r32(dst, tmp2, ctx, insn);
 		break;
 
 	case BPF_ALU | BPF_END | BPF_FROM_LE:
@@ -1266,21 +1347,19 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 			src = tmp2;
 		}
 
-		if (emit_store_r64(dst, src, off, ctx, BPF_SIZE(code),
-				   BPF_MODE(code)))
+		if (emit_store_r64(dst, src, ctx, insn))
 			return -1;
 		break;
 
 	case BPF_STX | BPF_ATOMIC | BPF_W:
-		if (insn->imm != BPF_ADD) {
+		if (insn->imm == BPF_CMPXCHG) {
 			pr_info_once(
 				"bpf-jit: not supported: atomic operation %02x ***\n",
 				insn->imm);
 			return -EFAULT;
 		}
 
-		if (emit_store_r64(dst, src, off, ctx, BPF_SIZE(code),
-				   BPF_MODE(code)))
+		if (emit_store_r64(dst, src, ctx, insn))
 			return -1;
 		break;