[PATCH bpf-next v2 0/8] bpf, riscv64: Support load-acquire and store-release instructions

[PATCH bpf-next v2 0/8] bpf, riscv64: Support load-acquire and store-release instructions

[Peilin Ye]

Hi all!

Patchset [1] introduced BPF load-acquire (BPF_LOAD_ACQ) and
store-release (BPF_STORE_REL) instructions, and added x86-64 and arm64
JIT compiler support.  As a follow-up, this v2 patchset supports
load-acquire and store-release instructions for the riscv64 JIT
compiler, and introduces some related selftests/ changes.

Specifically:

 * PATCH 1 makes insn_def_regno() handle load-acquires properly for
   bpf_jit_needs_zext() (true for riscv64) architectures
 * PATCH 2, 3 from Andrea Parri add the actual support to the riscv64
   JIT compiler
 * PATCH 4 optimizes code emission by skipping redundant zext
   instructions inserted by the verifier
 * PATCH 5, 6 and 7 are minor selftest/ improvements
 * PATCH 8 enables (non-arena) load-acquire/store-release selftests for
   riscv64

v1: https://lore.kernel.org/bpf/cover.1745970908.git.yepeilin@google.com/
Changes since v1:

 * add Acked-by:, Reviewed-by: and Tested-by: tags from Lehui and Björn
 * simplify code logic in PATCH 1 (Lehui)
 * in PATCH 3, avoid changing 'return 0;' to 'return ret;' at the end of
   bpf_jit_emit_insn() (Lehui)

Please refer to individual patches for details.  Thanks!

[1] https://lore.kernel.org/all/cover.1741049567.git.yepeilin@google.com/

Andrea Parri (2):
  bpf, riscv64: Introduce emit_load_*() and emit_store_*()
  bpf, riscv64: Support load-acquire and store-release instructions

Peilin Ye (6):
  bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()
  bpf, riscv64: Skip redundant zext instruction after load-acquire
  selftests/bpf: Use CAN_USE_LOAD_ACQ_STORE_REL when appropriate
  selftests/bpf: Avoid passing out-of-range values to __retval()
  selftests/bpf: Verify zero-extension behavior in load-acquire tests
  selftests/bpf: Enable non-arena load-acquire/store-release selftests
    for riscv64

 arch/riscv/net/bpf_jit.h                      |  15 +
 arch/riscv/net/bpf_jit_comp64.c               | 332 ++++++++++++------
 arch/riscv/net/bpf_jit_core.c                 |   3 +-
 kernel/bpf/verifier.c                         |  12 +-
 tools/testing/selftests/bpf/progs/bpf_misc.h  |   5 +-
 .../bpf/progs/verifier_load_acquire.c         |  48 ++-
 .../selftests/bpf/progs/verifier_precision.c  |   5 +-
 .../bpf/progs/verifier_store_release.c        |  39 +-
 8 files changed, 313 insertions(+), 146 deletions(-)

-- 
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[PATCH bpf-next v2 1/8] bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()

[Peilin Ye]

In preparation for supporting BPF load-acquire and store-release
instructions for architectures where bpf_jit_needs_zext() returns true
(e.g. riscv64), make insn_def_regno() handle load-acquires properly.

Acked-by: Björn Töpel <bjorn@kernel.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 kernel/bpf/verifier.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 99aa2c890e7b..28f5a7899bd6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3649,16 +3649,16 @@ static int insn_def_regno(const struct bpf_insn *insn)
 	case BPF_ST:
 		return -1;
 	case BPF_STX:
-		if ((BPF_MODE(insn->code) == BPF_ATOMIC ||
-		     BPF_MODE(insn->code) == BPF_PROBE_ATOMIC) &&
-		    (insn->imm & BPF_FETCH)) {
+		if (BPF_MODE(insn->code) == BPF_ATOMIC ||
+		    BPF_MODE(insn->code) == BPF_PROBE_ATOMIC) {
 			if (insn->imm == BPF_CMPXCHG)
 				return BPF_REG_0;
-			else
+			else if (insn->imm == BPF_LOAD_ACQ)
+				return insn->dst_reg;
+			else if (insn->imm & BPF_FETCH)
 				return insn->src_reg;
-		} else {
-			return -1;
 		}
+		return -1;
 	default:
 		return insn->dst_reg;
 	}
-- 
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[PATCH bpf-next v2 2/8] bpf, riscv64: Introduce emit_load_*() and emit_store_*()

[Peilin Ye]

From: Andrea Parri <parri.andrea@gmail.com>

We're planning to add support for the load-acquire and store-release
BPF instructions.  Define emit_load_<size>() and emit_store_<size>()
to enable/facilitate the (re)use of their code.

Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Tested-by: Peilin Ye <yepeilin@google.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
[yepeilin@google.com: cosmetic change to commit title]
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 arch/riscv/net/bpf_jit_comp64.c | 242 +++++++++++++++++++-------------
 1 file changed, 143 insertions(+), 99 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index ca60db75199d..953b6a20c69f 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -473,6 +473,140 @@ static inline void emit_kcfi(u32 hash, struct rv_jit_context *ctx)
 		emit(hash, ctx);
 }
 
+static int emit_load_8(bool sign_ext, u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	int insns_start;
+
+	if (is_12b_int(off)) {
+		insns_start = ctx->ninsns;
+		if (sign_ext)
+			emit(rv_lb(rd, off, rs), ctx);
+		else
+			emit(rv_lbu(rd, off, rs), ctx);
+		return ctx->ninsns - insns_start;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
+	insns_start = ctx->ninsns;
+	if (sign_ext)
+		emit(rv_lb(rd, 0, RV_REG_T1), ctx);
+	else
+		emit(rv_lbu(rd, 0, RV_REG_T1), ctx);
+	return ctx->ninsns - insns_start;
+}
+
+static int emit_load_16(bool sign_ext, u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	int insns_start;
+
+	if (is_12b_int(off)) {
+		insns_start = ctx->ninsns;
+		if (sign_ext)
+			emit(rv_lh(rd, off, rs), ctx);
+		else
+			emit(rv_lhu(rd, off, rs), ctx);
+		return ctx->ninsns - insns_start;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
+	insns_start = ctx->ninsns;
+	if (sign_ext)
+		emit(rv_lh(rd, 0, RV_REG_T1), ctx);
+	else
+		emit(rv_lhu(rd, 0, RV_REG_T1), ctx);
+	return ctx->ninsns - insns_start;
+}
+
+static int emit_load_32(bool sign_ext, u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	int insns_start;
+
+	if (is_12b_int(off)) {
+		insns_start = ctx->ninsns;
+		if (sign_ext)
+			emit(rv_lw(rd, off, rs), ctx);
+		else
+			emit(rv_lwu(rd, off, rs), ctx);
+		return ctx->ninsns - insns_start;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
+	insns_start = ctx->ninsns;
+	if (sign_ext)
+		emit(rv_lw(rd, 0, RV_REG_T1), ctx);
+	else
+		emit(rv_lwu(rd, 0, RV_REG_T1), ctx);
+	return ctx->ninsns - insns_start;
+}
+
+static int emit_load_64(bool sign_ext, u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	int insns_start;
+
+	if (is_12b_int(off)) {
+		insns_start = ctx->ninsns;
+		emit_ld(rd, off, rs, ctx);
+		return ctx->ninsns - insns_start;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
+	insns_start = ctx->ninsns;
+	emit_ld(rd, 0, RV_REG_T1, ctx);
+	return ctx->ninsns - insns_start;
+}
+
+static void emit_store_8(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	if (is_12b_int(off)) {
+		emit(rv_sb(rd, off, rs), ctx);
+		return;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
+	emit(rv_sb(RV_REG_T1, 0, rs), ctx);
+}
+
+static void emit_store_16(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	if (is_12b_int(off)) {
+		emit(rv_sh(rd, off, rs), ctx);
+		return;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
+	emit(rv_sh(RV_REG_T1, 0, rs), ctx);
+}
+
+static void emit_store_32(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	if (is_12b_int(off)) {
+		emit_sw(rd, off, rs, ctx);
+		return;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
+	emit_sw(RV_REG_T1, 0, rs, ctx);
+}
+
+static void emit_store_64(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
+{
+	if (is_12b_int(off)) {
+		emit_sd(rd, off, rs, ctx);
+		return;
+	}
+
+	emit_imm(RV_REG_T1, off, ctx);
+	emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
+	emit_sd(RV_REG_T1, 0, rs, ctx);
+}
+
 static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
 			struct rv_jit_context *ctx)
 {
@@ -1650,8 +1784,8 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 	case BPF_LDX | BPF_PROBE_MEM32 | BPF_W:
 	case BPF_LDX | BPF_PROBE_MEM32 | BPF_DW:
 	{
-		int insn_len, insns_start;
 		bool sign_ext;
+		int insn_len;
 
 		sign_ext = BPF_MODE(insn->code) == BPF_MEMSX ||
 			   BPF_MODE(insn->code) == BPF_PROBE_MEMSX;
@@ -1663,78 +1797,16 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 
 		switch (BPF_SIZE(code)) {
 		case BPF_B:
-			if (is_12b_int(off)) {
-				insns_start = ctx->ninsns;
-				if (sign_ext)
-					emit(rv_lb(rd, off, rs), ctx);
-				else
-					emit(rv_lbu(rd, off, rs), ctx);
-				insn_len = ctx->ninsns - insns_start;
-				break;
-			}
-
-			emit_imm(RV_REG_T1, off, ctx);
-			emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
-			insns_start = ctx->ninsns;
-			if (sign_ext)
-				emit(rv_lb(rd, 0, RV_REG_T1), ctx);
-			else
-				emit(rv_lbu(rd, 0, RV_REG_T1), ctx);
-			insn_len = ctx->ninsns - insns_start;
+			insn_len = emit_load_8(sign_ext, rd, off, rs, ctx);
 			break;
 		case BPF_H:
-			if (is_12b_int(off)) {
-				insns_start = ctx->ninsns;
-				if (sign_ext)
-					emit(rv_lh(rd, off, rs), ctx);
-				else
-					emit(rv_lhu(rd, off, rs), ctx);
-				insn_len = ctx->ninsns - insns_start;
-				break;
-			}
-
-			emit_imm(RV_REG_T1, off, ctx);
-			emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
-			insns_start = ctx->ninsns;
-			if (sign_ext)
-				emit(rv_lh(rd, 0, RV_REG_T1), ctx);
-			else
-				emit(rv_lhu(rd, 0, RV_REG_T1), ctx);
-			insn_len = ctx->ninsns - insns_start;
+			insn_len = emit_load_16(sign_ext, rd, off, rs, ctx);
 			break;
 		case BPF_W:
-			if (is_12b_int(off)) {
-				insns_start = ctx->ninsns;
-				if (sign_ext)
-					emit(rv_lw(rd, off, rs), ctx);
-				else
-					emit(rv_lwu(rd, off, rs), ctx);
-				insn_len = ctx->ninsns - insns_start;
-				break;
-			}
-
-			emit_imm(RV_REG_T1, off, ctx);
-			emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
-			insns_start = ctx->ninsns;
-			if (sign_ext)
-				emit(rv_lw(rd, 0, RV_REG_T1), ctx);
-			else
-				emit(rv_lwu(rd, 0, RV_REG_T1), ctx);
-			insn_len = ctx->ninsns - insns_start;
+			insn_len = emit_load_32(sign_ext, rd, off, rs, ctx);
 			break;
 		case BPF_DW:
-			if (is_12b_int(off)) {
-				insns_start = ctx->ninsns;
-				emit_ld(rd, off, rs, ctx);
-				insn_len = ctx->ninsns - insns_start;
-				break;
-			}
-
-			emit_imm(RV_REG_T1, off, ctx);
-			emit_add(RV_REG_T1, RV_REG_T1, rs, ctx);
-			insns_start = ctx->ninsns;
-			emit_ld(rd, 0, RV_REG_T1, ctx);
-			insn_len = ctx->ninsns - insns_start;
+			insn_len = emit_load_64(sign_ext, rd, off, rs, ctx);
 			break;
 		}
 
@@ -1879,44 +1951,16 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 
 	/* STX: *(size *)(dst + off) = src */
 	case BPF_STX | BPF_MEM | BPF_B:
-		if (is_12b_int(off)) {
-			emit(rv_sb(rd, off, rs), ctx);
-			break;
-		}
-
-		emit_imm(RV_REG_T1, off, ctx);
-		emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
-		emit(rv_sb(RV_REG_T1, 0, rs), ctx);
+		emit_store_8(rd, off, rs, ctx);
 		break;
 	case BPF_STX | BPF_MEM | BPF_H:
-		if (is_12b_int(off)) {
-			emit(rv_sh(rd, off, rs), ctx);
-			break;
-		}
-
-		emit_imm(RV_REG_T1, off, ctx);
-		emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
-		emit(rv_sh(RV_REG_T1, 0, rs), ctx);
+		emit_store_16(rd, off, rs, ctx);
 		break;
 	case BPF_STX | BPF_MEM | BPF_W:
-		if (is_12b_int(off)) {
-			emit_sw(rd, off, rs, ctx);
-			break;
-		}
-
-		emit_imm(RV_REG_T1, off, ctx);
-		emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
-		emit_sw(RV_REG_T1, 0, rs, ctx);
+		emit_store_32(rd, off, rs, ctx);
 		break;
 	case BPF_STX | BPF_MEM | BPF_DW:
-		if (is_12b_int(off)) {
-			emit_sd(rd, off, rs, ctx);
-			break;
-		}
-
-		emit_imm(RV_REG_T1, off, ctx);
-		emit_add(RV_REG_T1, RV_REG_T1, rd, ctx);
-		emit_sd(RV_REG_T1, 0, rs, ctx);
+		emit_store_64(rd, off, rs, ctx);
 		break;
 	case BPF_STX | BPF_ATOMIC | BPF_W:
 	case BPF_STX | BPF_ATOMIC | BPF_DW:
-- 
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[PATCH bpf-next v2 3/8] bpf, riscv64: Support load-acquire and store-release instructions

[Peilin Ye]

From: Andrea Parri <parri.andrea@gmail.com>

Support BPF load-acquire (BPF_LOAD_ACQ) and store-release
(BPF_STORE_REL) instructions in the riscv64 JIT compiler.  For example,
consider the following 64-bit load-acquire (assuming little-endian):

  db 10 00 00 00 01 00 00  r1 = load_acquire((u64 *)(r1 + 0x0))
  95 00 00 00 00 00 00 00  exit

  opcode (0xdb): BPF_ATOMIC | BPF_DW | BPF_STX
  imm (0x00000100): BPF_LOAD_ACQ

The JIT compiler will emit an LD instruction followed by a FENCE R,RW
instruction for the above, e.g.:

  ld x7,0(x6)
  fence r,rw

Similarly, consider the following 16-bit store-release:

  cb 21 00 00 10 01 00 00  store_release((u16 *)(r1 + 0x0), w2)
  95 00 00 00 00 00 00 00  exit

  opcode (0xcb): BPF_ATOMIC | BPF_H | BPF_STX
  imm (0x00000110): BPF_STORE_REL

A FENCE RW,W instruction followed by an SH instruction will be emitted,
e.g.:

  fence rw,w
  sh x2,0(x4)

8-bit and 16-bit load-acquires are zero-extending (cf., LBU, LHU).  The
verifier always rejects misaligned load-acquires/store-releases (even if
BPF_F_ANY_ALIGNMENT is set), so the emitted load and store instructions
are guaranteed to be single-copy atomic.

Introduce primitives to emit the relevant (and the most common/used in
the kernel) fences, i.e. fences with R -> RW, RW -> W and RW -> RW.

Rename emit_atomic() to emit_atomic_rmw() to make it clear that it only
handles RMW atomics, and replace its is64 parameter to allow to perform
the required checks on the opsize (BPF_SIZE(code)).

Acked-by: Björn Töpel <bjorn@kernel.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Co-developed-by: Peilin Ye <yepeilin@google.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 arch/riscv/net/bpf_jit.h        | 15 +++++++
 arch/riscv/net/bpf_jit_comp64.c | 75 ++++++++++++++++++++++++++++++---
 2 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
index 1d1c78d4cff1..e7b032dfd17f 100644
--- a/arch/riscv/net/bpf_jit.h
+++ b/arch/riscv/net/bpf_jit.h
@@ -608,6 +608,21 @@ static inline u32 rv_fence(u8 pred, u8 succ)
 	return rv_i_insn(imm11_0, 0, 0, 0, 0xf);
 }
 
+static inline void emit_fence_r_rw(struct rv_jit_context *ctx)
+{
+	emit(rv_fence(0x2, 0x3), ctx);
+}
+
+static inline void emit_fence_rw_w(struct rv_jit_context *ctx)
+{
+	emit(rv_fence(0x3, 0x1), ctx);
+}
+
+static inline void emit_fence_rw_rw(struct rv_jit_context *ctx)
+{
+	emit(rv_fence(0x3, 0x3), ctx);
+}
+
 static inline u32 rv_nop(void)
 {
 	return rv_i_insn(0, 0, 0, 0, 0x13);
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 953b6a20c69f..8767f032f2de 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -607,11 +607,65 @@ static void emit_store_64(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
 	emit_sd(RV_REG_T1, 0, rs, ctx);
 }
 
-static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
-			struct rv_jit_context *ctx)
+static int emit_atomic_ld_st(u8 rd, u8 rs, s16 off, s32 imm, u8 code, struct rv_jit_context *ctx)
+{
+	switch (imm) {
+	/* dst_reg = load_acquire(src_reg + off16) */
+	case BPF_LOAD_ACQ:
+		switch (BPF_SIZE(code)) {
+		case BPF_B:
+			emit_load_8(false, rd, off, rs, ctx);
+			break;
+		case BPF_H:
+			emit_load_16(false, rd, off, rs, ctx);
+			break;
+		case BPF_W:
+			emit_load_32(false, rd, off, rs, ctx);
+			break;
+		case BPF_DW:
+			emit_load_64(false, rd, off, rs, ctx);
+			break;
+		}
+		emit_fence_r_rw(ctx);
+		break;
+	/* store_release(dst_reg + off16, src_reg) */
+	case BPF_STORE_REL:
+		emit_fence_rw_w(ctx);
+		switch (BPF_SIZE(code)) {
+		case BPF_B:
+			emit_store_8(rd, off, rs, ctx);
+			break;
+		case BPF_H:
+			emit_store_16(rd, off, rs, ctx);
+			break;
+		case BPF_W:
+			emit_store_32(rd, off, rs, ctx);
+			break;
+		case BPF_DW:
+			emit_store_64(rd, off, rs, ctx);
+			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(u8 rd, u8 rs, s16 off, s32 imm, u8 code,
+			   struct rv_jit_context *ctx)
 {
 	u8 r0;
 	int jmp_offset;
+	bool is64;
+
+	if (BPF_SIZE(code) != BPF_W && BPF_SIZE(code) != BPF_DW) {
+		pr_err_once("bpf-jit: 1- and 2-byte RMW atomics are not supported\n");
+		return -EINVAL;
+	}
+	is64 = BPF_SIZE(code) == BPF_DW;
 
 	if (off) {
 		if (is_12b_int(off)) {
@@ -688,9 +742,14 @@ static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
 		     rv_sc_w(RV_REG_T3, rs, rd, 0, 1), ctx);
 		jmp_offset = ninsns_rvoff(-6);
 		emit(rv_bne(RV_REG_T3, 0, jmp_offset >> 1), ctx);
-		emit(rv_fence(0x3, 0x3), ctx);
+		emit_fence_rw_rw(ctx);
 		break;
+	default:
+		pr_err_once("bpf-jit: invalid atomic RMW opcode %02x\n", imm);
+		return -EINVAL;
 	}
+
+	return 0;
 }
 
 #define BPF_FIXUP_OFFSET_MASK   GENMASK(26, 0)
@@ -1962,10 +2021,16 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 	case BPF_STX | BPF_MEM | BPF_DW:
 		emit_store_64(rd, off, rs, ctx);
 		break;
+	case BPF_STX | BPF_ATOMIC | BPF_B:
+	case BPF_STX | BPF_ATOMIC | BPF_H:
 	case BPF_STX | BPF_ATOMIC | BPF_W:
 	case BPF_STX | BPF_ATOMIC | BPF_DW:
-		emit_atomic(rd, rs, off, imm,
-			    BPF_SIZE(code) == BPF_DW, ctx);
+		if (bpf_atomic_is_load_store(insn))
+			ret = emit_atomic_ld_st(rd, rs, off, imm, code, ctx);
+		else
+			ret = emit_atomic_rmw(rd, rs, off, imm, code, ctx);
+		if (ret)
+			return ret;
 		break;
 
 	case BPF_STX | BPF_PROBE_MEM32 | BPF_B:
-- 
2.49.0.967.g6a0df3ecc3-goog


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[PATCH bpf-next v2 4/8] bpf, riscv64: Skip redundant zext instruction after load-acquire

[Peilin Ye]

Currently, the verifier inserts a zext instruction right after every 8-,
16- or 32-bit load-acquire, which is already zero-extending.  Skip such
redundant zext instructions.

While we are here, update that already-obsolete comment about "skip the
next instruction" in build_body().  Also change emit_atomic_rmw()'s
parameters to keep it consistent with emit_atomic_ld_st().

Note that checking 'insn[1]' relies on 'insn' not being the last
instruction, which should have been guaranteed by the verifier; we
already use 'insn[1]' elsewhere in the file for similar purposes.
Additionally, we don't check if 'insn[1]' is actually a zext for our
load-acquire's dst_reg, or some other registers - in other words, here
we are relying on the verifier to always insert a redundant zext right
after a 8/16/32-bit load-acquire, for its dst_reg.

Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 arch/riscv/net/bpf_jit_comp64.c | 23 ++++++++++++++++++-----
 arch/riscv/net/bpf_jit_core.c   |  3 +--
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 8767f032f2de..10e01ff06312 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -607,8 +607,13 @@ static void emit_store_64(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
 	emit_sd(RV_REG_T1, 0, rs, ctx);
 }
 
-static int emit_atomic_ld_st(u8 rd, u8 rs, s16 off, s32 imm, u8 code, struct rv_jit_context *ctx)
+static int emit_atomic_ld_st(u8 rd, u8 rs, const struct bpf_insn *insn,
+			     struct rv_jit_context *ctx)
 {
+	u8 code = insn->code;
+	s32 imm = insn->imm;
+	s16 off = insn->off;
+
 	switch (imm) {
 	/* dst_reg = load_acquire(src_reg + off16) */
 	case BPF_LOAD_ACQ:
@@ -627,6 +632,12 @@ static int emit_atomic_ld_st(u8 rd, u8 rs, s16 off, s32 imm, u8 code, struct rv_
 			break;
 		}
 		emit_fence_r_rw(ctx);
+
+		/* If our next insn is a redundant zext, return 1 to tell
+		 * build_body() to skip it.
+		 */
+		if (BPF_SIZE(code) != BPF_DW && insn_is_zext(&insn[1]))
+			return 1;
 		break;
 	/* store_release(dst_reg + off16, src_reg) */
 	case BPF_STORE_REL:
@@ -654,10 +665,12 @@ static int emit_atomic_ld_st(u8 rd, u8 rs, s16 off, s32 imm, u8 code, struct rv_
 	return 0;
 }
 
-static int emit_atomic_rmw(u8 rd, u8 rs, s16 off, s32 imm, u8 code,
+static int emit_atomic_rmw(u8 rd, u8 rs, const struct bpf_insn *insn,
 			   struct rv_jit_context *ctx)
 {
-	u8 r0;
+	u8 r0, code = insn->code;
+	s16 off = insn->off;
+	s32 imm = insn->imm;
 	int jmp_offset;
 	bool is64;
 
@@ -2026,9 +2039,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 	case BPF_STX | BPF_ATOMIC | BPF_W:
 	case BPF_STX | BPF_ATOMIC | BPF_DW:
 		if (bpf_atomic_is_load_store(insn))
-			ret = emit_atomic_ld_st(rd, rs, off, imm, code, ctx);
+			ret = emit_atomic_ld_st(rd, rs, insn, ctx);
 		else
-			ret = emit_atomic_rmw(rd, rs, off, imm, code, ctx);
+			ret = emit_atomic_rmw(rd, rs, insn, ctx);
 		if (ret)
 			return ret;
 		break;
diff --git a/arch/riscv/net/bpf_jit_core.c b/arch/riscv/net/bpf_jit_core.c
index f8cd2f70a7fb..f6ca5cfa6b2f 100644
--- a/arch/riscv/net/bpf_jit_core.c
+++ b/arch/riscv/net/bpf_jit_core.c
@@ -26,9 +26,8 @@ static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
 		int ret;
 
 		ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
-		/* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */
 		if (ret > 0)
-			i++;
+			i++; /* skip the next instruction */
 		if (offset)
 			offset[i] = ctx->ninsns;
 		if (ret < 0)
-- 
2.49.0.967.g6a0df3ecc3-goog


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[PATCH bpf-next v2 5/8] selftests/bpf: Use CAN_USE_LOAD_ACQ_STORE_REL when appropriate

[Peilin Ye]

Instead of open-coding the conditions, use
'#ifdef CAN_USE_LOAD_ACQ_STORE_REL' to guard the following tests:

  verifier_precision/bpf_load_acquire
  verifier_precision/bpf_store_release
  verifier_store_release/*

Note that, for the first two tests in verifier_precision.c, switching to
'#ifdef CAN_USE_LOAD_ACQ_STORE_REL' means also checking if
'__clang_major__ >= 18', which has already been guaranteed by the outer
'#if' check.

Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 tools/testing/selftests/bpf/progs/verifier_precision.c     | 5 ++---
 tools/testing/selftests/bpf/progs/verifier_store_release.c | 7 +++----
 2 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/verifier_precision.c b/tools/testing/selftests/bpf/progs/verifier_precision.c
index 6662d4b39969..2dd0d15c2678 100644
--- a/tools/testing/selftests/bpf/progs/verifier_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_precision.c
@@ -91,8 +91,7 @@ __naked int bpf_end_bswap(void)
 		::: __clobber_all);
 }
 
-#if defined(ENABLE_ATOMICS_TESTS) && \
-	(defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86))
+#ifdef CAN_USE_LOAD_ACQ_STORE_REL
 
 SEC("?raw_tp")
 __success __log_level(2)
@@ -138,7 +137,7 @@ __naked int bpf_store_release(void)
 	: __clobber_all);
 }
 
-#endif /* load-acquire, store-release */
+#endif /* CAN_USE_LOAD_ACQ_STORE_REL */
 #endif /* v4 instruction */
 
 SEC("?raw_tp")
diff --git a/tools/testing/selftests/bpf/progs/verifier_store_release.c b/tools/testing/selftests/bpf/progs/verifier_store_release.c
index c0442d5bb049..7e456e2861b4 100644
--- a/tools/testing/selftests/bpf/progs/verifier_store_release.c
+++ b/tools/testing/selftests/bpf/progs/verifier_store_release.c
@@ -6,8 +6,7 @@
 #include "../../../include/linux/filter.h"
 #include "bpf_misc.h"
 
-#if __clang_major__ >= 18 && defined(ENABLE_ATOMICS_TESTS) && \
-	(defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86))
+#ifdef CAN_USE_LOAD_ACQ_STORE_REL
 
 SEC("socket")
 __description("store-release, 8-bit")
@@ -271,7 +270,7 @@ __naked void store_release_with_invalid_reg(void)
 	: __clobber_all);
 }
 
-#else
+#else /* CAN_USE_LOAD_ACQ_STORE_REL */
 
 SEC("socket")
 __description("Clang version < 18, ENABLE_ATOMICS_TESTS not defined, and/or JIT doesn't support store-release, use a dummy test")
@@ -281,6 +280,6 @@ int dummy_test(void)
 	return 0;
 }
 
-#endif
+#endif /* CAN_USE_LOAD_ACQ_STORE_REL */
 
 char _license[] SEC("license") = "GPL";
-- 
2.49.0.967.g6a0df3ecc3-goog


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[PATCH bpf-next v2 6/8] selftests/bpf: Avoid passing out-of-range values to __retval()

[Peilin Ye]

Currently, we pass 0x1234567890abcdef to __retval() for the following
two tests:

  verifier_load_acquire/load_acquire_64
  verifier_store_release/store_release_64

However, the upper 32 bits of that value are being ignored, since
__retval() expects an int.  Actually, the tests would still pass even if
I change '__retval(0x1234567890abcdef)' to e.g. '__retval(0x90abcdef)'.

Restructure the tests a bit to test the entire 64-bit values properly.
Do the same to their 8-, 16- and 32-bit variants as well to keep the
style consistent.

Fixes: ff3afe5da998 ("selftests/bpf: Add selftests for load-acquire and store-release instructions")
Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 .../bpf/progs/verifier_load_acquire.c         | 40 +++++++++++++------
 .../bpf/progs/verifier_store_release.c        | 32 +++++++++++----
 2 files changed, 52 insertions(+), 20 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/verifier_load_acquire.c b/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
index 77698d5a19e4..a696ab84bfd6 100644
--- a/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
+++ b/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
@@ -10,65 +10,81 @@
 
 SEC("socket")
 __description("load-acquire, 8-bit")
-__success __success_unpriv __retval(0x12)
+__success __success_unpriv __retval(0)
 __naked void load_acquire_8(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x12;"
 	"*(u8 *)(r10 - 1) = w1;"
-	".8byte %[load_acquire_insn];" // w0 = load_acquire((u8 *)(r10 - 1));
+	".8byte %[load_acquire_insn];" // w2 = load_acquire((u8 *)(r10 - 1));
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(load_acquire_insn,
-		     BPF_ATOMIC_OP(BPF_B, BPF_LOAD_ACQ, BPF_REG_0, BPF_REG_10, -1))
+		     BPF_ATOMIC_OP(BPF_B, BPF_LOAD_ACQ, BPF_REG_2, BPF_REG_10, -1))
 	: __clobber_all);
 }
 
 SEC("socket")
 __description("load-acquire, 16-bit")
-__success __success_unpriv __retval(0x1234)
+__success __success_unpriv __retval(0)
 __naked void load_acquire_16(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x1234;"
 	"*(u16 *)(r10 - 2) = w1;"
-	".8byte %[load_acquire_insn];" // w0 = load_acquire((u16 *)(r10 - 2));
+	".8byte %[load_acquire_insn];" // w2 = load_acquire((u16 *)(r10 - 2));
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(load_acquire_insn,
-		     BPF_ATOMIC_OP(BPF_H, BPF_LOAD_ACQ, BPF_REG_0, BPF_REG_10, -2))
+		     BPF_ATOMIC_OP(BPF_H, BPF_LOAD_ACQ, BPF_REG_2, BPF_REG_10, -2))
 	: __clobber_all);
 }
 
 SEC("socket")
 __description("load-acquire, 32-bit")
-__success __success_unpriv __retval(0x12345678)
+__success __success_unpriv __retval(0)
 __naked void load_acquire_32(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x12345678;"
 	"*(u32 *)(r10 - 4) = w1;"
-	".8byte %[load_acquire_insn];" // w0 = load_acquire((u32 *)(r10 - 4));
+	".8byte %[load_acquire_insn];" // w2 = load_acquire((u32 *)(r10 - 4));
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(load_acquire_insn,
-		     BPF_ATOMIC_OP(BPF_W, BPF_LOAD_ACQ, BPF_REG_0, BPF_REG_10, -4))
+		     BPF_ATOMIC_OP(BPF_W, BPF_LOAD_ACQ, BPF_REG_2, BPF_REG_10, -4))
 	: __clobber_all);
 }
 
 SEC("socket")
 __description("load-acquire, 64-bit")
-__success __success_unpriv __retval(0x1234567890abcdef)
+__success __success_unpriv __retval(0)
 __naked void load_acquire_64(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"r1 = 0x1234567890abcdef ll;"
 	"*(u64 *)(r10 - 8) = r1;"
-	".8byte %[load_acquire_insn];" // r0 = load_acquire((u64 *)(r10 - 8));
+	".8byte %[load_acquire_insn];" // r2 = load_acquire((u64 *)(r10 - 8));
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(load_acquire_insn,
-		     BPF_ATOMIC_OP(BPF_DW, BPF_LOAD_ACQ, BPF_REG_0, BPF_REG_10, -8))
+		     BPF_ATOMIC_OP(BPF_DW, BPF_LOAD_ACQ, BPF_REG_2, BPF_REG_10, -8))
 	: __clobber_all);
 }
 
diff --git a/tools/testing/selftests/bpf/progs/verifier_store_release.c b/tools/testing/selftests/bpf/progs/verifier_store_release.c
index 7e456e2861b4..72f1eb006074 100644
--- a/tools/testing/selftests/bpf/progs/verifier_store_release.c
+++ b/tools/testing/selftests/bpf/progs/verifier_store_release.c
@@ -10,13 +10,17 @@
 
 SEC("socket")
 __description("store-release, 8-bit")
-__success __success_unpriv __retval(0x12)
+__success __success_unpriv __retval(0)
 __naked void store_release_8(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x12;"
 	".8byte %[store_release_insn];" // store_release((u8 *)(r10 - 1), w1);
-	"w0 = *(u8 *)(r10 - 1);"
+	"w2 = *(u8 *)(r10 - 1);"
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(store_release_insn,
@@ -26,13 +30,17 @@ __naked void store_release_8(void)
 
 SEC("socket")
 __description("store-release, 16-bit")
-__success __success_unpriv __retval(0x1234)
+__success __success_unpriv __retval(0)
 __naked void store_release_16(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x1234;"
 	".8byte %[store_release_insn];" // store_release((u16 *)(r10 - 2), w1);
-	"w0 = *(u16 *)(r10 - 2);"
+	"w2 = *(u16 *)(r10 - 2);"
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(store_release_insn,
@@ -42,13 +50,17 @@ __naked void store_release_16(void)
 
 SEC("socket")
 __description("store-release, 32-bit")
-__success __success_unpriv __retval(0x12345678)
+__success __success_unpriv __retval(0)
 __naked void store_release_32(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"w1 = 0x12345678;"
 	".8byte %[store_release_insn];" // store_release((u32 *)(r10 - 4), w1);
-	"w0 = *(u32 *)(r10 - 4);"
+	"w2 = *(u32 *)(r10 - 4);"
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(store_release_insn,
@@ -58,13 +70,17 @@ __naked void store_release_32(void)
 
 SEC("socket")
 __description("store-release, 64-bit")
-__success __success_unpriv __retval(0x1234567890abcdef)
+__success __success_unpriv __retval(0)
 __naked void store_release_64(void)
 {
 	asm volatile (
+	"r0 = 0;"
 	"r1 = 0x1234567890abcdef ll;"
 	".8byte %[store_release_insn];" // store_release((u64 *)(r10 - 8), r1);
-	"r0 = *(u64 *)(r10 - 8);"
+	"r2 = *(u64 *)(r10 - 8);"
+	"if r2 == r1 goto 1f;"
+	"r0 = 1;"
+"1:"
 	"exit;"
 	:
 	: __imm_insn(store_release_insn,
-- 
2.49.0.967.g6a0df3ecc3-goog


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[PATCH bpf-next v2 7/8] selftests/bpf: Verify zero-extension behavior in load-acquire tests

[Peilin Ye]

Verify that 8-, 16- and 32-bit load-acquires are zero-extending by using
immediate values with their highest bit set.  Do the same for the 64-bit
variant to keep the style consistent.

Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 tools/testing/selftests/bpf/progs/verifier_load_acquire.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/verifier_load_acquire.c b/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
index a696ab84bfd6..74f4f19c10b8 100644
--- a/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
+++ b/tools/testing/selftests/bpf/progs/verifier_load_acquire.c
@@ -15,7 +15,7 @@ __naked void load_acquire_8(void)
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x12;"
+	"w1 = 0xfe;"
 	"*(u8 *)(r10 - 1) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u8 *)(r10 - 1));
 	"if r2 == r1 goto 1f;"
@@ -35,7 +35,7 @@ __naked void load_acquire_16(void)
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x1234;"
+	"w1 = 0xfedc;"
 	"*(u16 *)(r10 - 2) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u16 *)(r10 - 2));
 	"if r2 == r1 goto 1f;"
@@ -55,7 +55,7 @@ __naked void load_acquire_32(void)
 {
 	asm volatile (
 	"r0 = 0;"
-	"w1 = 0x12345678;"
+	"w1 = 0xfedcba09;"
 	"*(u32 *)(r10 - 4) = w1;"
 	".8byte %[load_acquire_insn];" // w2 = load_acquire((u32 *)(r10 - 4));
 	"if r2 == r1 goto 1f;"
@@ -75,7 +75,7 @@ __naked void load_acquire_64(void)
 {
 	asm volatile (
 	"r0 = 0;"
-	"r1 = 0x1234567890abcdef ll;"
+	"r1 = 0xfedcba0987654321 ll;"
 	"*(u64 *)(r10 - 8) = r1;"
 	".8byte %[load_acquire_insn];" // r2 = load_acquire((u64 *)(r10 - 8));
 	"if r2 == r1 goto 1f;"
-- 
2.49.0.967.g6a0df3ecc3-goog


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[PATCH bpf-next v2 8/8] selftests/bpf: Enable non-arena load-acquire/store-release selftests for riscv64

[Peilin Ye]

For riscv64, enable all BPF_{LOAD_ACQ,STORE_REL} selftests except the
arena_atomics/* ones (not guarded behind CAN_USE_LOAD_ACQ_STORE_REL),
since arena access is not yet supported.

Acked-by: Björn Töpel <bjorn@kernel.org>
Reviewed-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
Signed-off-by: Peilin Ye <yepeilin@google.com>
---
 tools/testing/selftests/bpf/progs/bpf_misc.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index 863df7c0fdd0..6e208e24ba3b 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -225,8 +225,9 @@
 #define CAN_USE_BPF_ST
 #endif
 
-#if __clang_major__ >= 18 && defined(ENABLE_ATOMICS_TESTS) && \
-	(defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86))
+#if __clang_major__ >= 18 && defined(ENABLE_ATOMICS_TESTS) &&		\
+	(defined(__TARGET_ARCH_arm64) || defined(__TARGET_ARCH_x86) ||	\
+	 (defined(__TARGET_ARCH_riscv) && __riscv_xlen == 64))
 #define CAN_USE_LOAD_ACQ_STORE_REL
 #endif
 
-- 
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Re: [PATCH bpf-next v2 0/8] bpf, riscv64: Support load-acquire and store-release instructions

[Peilin Ye]

Hi Lehui,

On Wed, May 07, 2025 at 03:42:29AM +0000, Peilin Ye wrote:
> v1: https://lore.kernel.org/bpf/cover.1745970908.git.yepeilin@google.com/
> Changes since v1:
> 
>  * add Acked-by:, Reviewed-by: and Tested-by: tags from Lehui and Björn
>  * simplify code logic in PATCH 1 (Lehui)
>  * in PATCH 3, avoid changing 'return 0;' to 'return ret;' at the end of
>    bpf_jit_emit_insn() (Lehui)
> 
> Please refer to individual patches for details.  Thanks!
> 
> [1] https://lore.kernel.org/all/cover.1741049567.git.yepeilin@google.com/
> 
> Andrea Parri (2):
>   bpf, riscv64: Introduce emit_load_*() and emit_store_*()
>   bpf, riscv64: Support load-acquire and store-release instructions
> 
> Peilin Ye (6):
>   bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()
>   bpf, riscv64: Skip redundant zext instruction after load-acquire
>   selftests/bpf: Use CAN_USE_LOAD_ACQ_STORE_REL when appropriate
>   selftests/bpf: Avoid passing out-of-range values to __retval()
>   selftests/bpf: Verify zero-extension behavior in load-acquire tests
>   selftests/bpf: Enable non-arena load-acquire/store-release selftests
>     for riscv64
> 
>  arch/riscv/net/bpf_jit.h                      |  15 +
>  arch/riscv/net/bpf_jit_comp64.c               | 332 ++++++++++++------
>  arch/riscv/net/bpf_jit_core.c                 |   3 +-
>  kernel/bpf/verifier.c                         |  12 +-
>  tools/testing/selftests/bpf/progs/bpf_misc.h  |   5 +-
>  .../bpf/progs/verifier_load_acquire.c         |  48 ++-
>  .../selftests/bpf/progs/verifier_precision.c  |   5 +-
>  .../bpf/progs/verifier_store_release.c        |  39 +-
>  8 files changed, 313 insertions(+), 146 deletions(-)

Please take another look at v2 PATCH 1/8 and 3/8, thanks!

Peilin Ye


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Re: [PATCH bpf-next v2 1/8] bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()

[Pu Lehui]

On 2025/5/7 11:42, Peilin Ye wrote:
> In preparation for supporting BPF load-acquire and store-release
> instructions for architectures where bpf_jit_needs_zext() returns true
> (e.g. riscv64), make insn_def_regno() handle load-acquires properly.
> 
> Acked-by: Björn Töpel <bjorn@kernel.org>
> Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
> Signed-off-by: Peilin Ye <yepeilin@google.com>
> ---
>   kernel/bpf/verifier.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 99aa2c890e7b..28f5a7899bd6 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -3649,16 +3649,16 @@ static int insn_def_regno(const struct bpf_insn *insn)
>   	case BPF_ST:
>   		return -1;
>   	case BPF_STX:
> -		if ((BPF_MODE(insn->code) == BPF_ATOMIC ||
> -		     BPF_MODE(insn->code) == BPF_PROBE_ATOMIC) &&
> -		    (insn->imm & BPF_FETCH)) {
> +		if (BPF_MODE(insn->code) == BPF_ATOMIC ||
> +		    BPF_MODE(insn->code) == BPF_PROBE_ATOMIC) {
>   			if (insn->imm == BPF_CMPXCHG)
>   				return BPF_REG_0;
> -			else
> +			else if (insn->imm == BPF_LOAD_ACQ)
> +				return insn->dst_reg;
> +			else if (insn->imm & BPF_FETCH)
>   				return insn->src_reg;
> -		} else {
> -			return -1;
>   		}
> +		return -1;
>   	default:
>   		return insn->dst_reg;
>   	}

lgtm, thanks
Reviewed-by: Pu Lehui <pulehui@huawei.com>

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Re: [PATCH bpf-next v2 3/8] bpf, riscv64: Support load-acquire and store-release instructions

[Pu Lehui]

On 2025/5/7 11:43, Peilin Ye wrote:
> From: Andrea Parri <parri.andrea@gmail.com>
> 
> Support BPF load-acquire (BPF_LOAD_ACQ) and store-release
> (BPF_STORE_REL) instructions in the riscv64 JIT compiler.  For example,
> consider the following 64-bit load-acquire (assuming little-endian):
> 
>    db 10 00 00 00 01 00 00  r1 = load_acquire((u64 *)(r1 + 0x0))
>    95 00 00 00 00 00 00 00  exit
> 
>    opcode (0xdb): BPF_ATOMIC | BPF_DW | BPF_STX
>    imm (0x00000100): BPF_LOAD_ACQ
> 
> The JIT compiler will emit an LD instruction followed by a FENCE R,RW
> instruction for the above, e.g.:
> 
>    ld x7,0(x6)
>    fence r,rw
> 
> Similarly, consider the following 16-bit store-release:
> 
>    cb 21 00 00 10 01 00 00  store_release((u16 *)(r1 + 0x0), w2)
>    95 00 00 00 00 00 00 00  exit
> 
>    opcode (0xcb): BPF_ATOMIC | BPF_H | BPF_STX
>    imm (0x00000110): BPF_STORE_REL
> 
> A FENCE RW,W instruction followed by an SH instruction will be emitted,
> e.g.:
> 
>    fence rw,w
>    sh x2,0(x4)
> 
> 8-bit and 16-bit load-acquires are zero-extending (cf., LBU, LHU).  The
> verifier always rejects misaligned load-acquires/store-releases (even if
> BPF_F_ANY_ALIGNMENT is set), so the emitted load and store instructions
> are guaranteed to be single-copy atomic.
> 
> Introduce primitives to emit the relevant (and the most common/used in
> the kernel) fences, i.e. fences with R -> RW, RW -> W and RW -> RW.
> 
> Rename emit_atomic() to emit_atomic_rmw() to make it clear that it only
> handles RMW atomics, and replace its is64 parameter to allow to perform
> the required checks on the opsize (BPF_SIZE(code)).
> 
> Acked-by: Björn Töpel <bjorn@kernel.org>
> Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23
> Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
> Co-developed-by: Peilin Ye <yepeilin@google.com>
> Signed-off-by: Peilin Ye <yepeilin@google.com>
> ---
>   arch/riscv/net/bpf_jit.h        | 15 +++++++
>   arch/riscv/net/bpf_jit_comp64.c | 75 ++++++++++++++++++++++++++++++---
>   2 files changed, 85 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/riscv/net/bpf_jit.h b/arch/riscv/net/bpf_jit.h
> index 1d1c78d4cff1..e7b032dfd17f 100644
> --- a/arch/riscv/net/bpf_jit.h
> +++ b/arch/riscv/net/bpf_jit.h
> @@ -608,6 +608,21 @@ static inline u32 rv_fence(u8 pred, u8 succ)
>   	return rv_i_insn(imm11_0, 0, 0, 0, 0xf);
>   }
>   
> +static inline void emit_fence_r_rw(struct rv_jit_context *ctx)
> +{
> +	emit(rv_fence(0x2, 0x3), ctx);
> +}
> +
> +static inline void emit_fence_rw_w(struct rv_jit_context *ctx)
> +{
> +	emit(rv_fence(0x3, 0x1), ctx);
> +}
> +
> +static inline void emit_fence_rw_rw(struct rv_jit_context *ctx)
> +{
> +	emit(rv_fence(0x3, 0x3), ctx);
> +}
> +
>   static inline u32 rv_nop(void)
>   {
>   	return rv_i_insn(0, 0, 0, 0, 0x13);
> diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
> index 953b6a20c69f..8767f032f2de 100644
> --- a/arch/riscv/net/bpf_jit_comp64.c
> +++ b/arch/riscv/net/bpf_jit_comp64.c
> @@ -607,11 +607,65 @@ static void emit_store_64(u8 rd, s32 off, u8 rs, struct rv_jit_context *ctx)
>   	emit_sd(RV_REG_T1, 0, rs, ctx);
>   }
>   
> -static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
> -			struct rv_jit_context *ctx)
> +static int emit_atomic_ld_st(u8 rd, u8 rs, s16 off, s32 imm, u8 code, struct rv_jit_context *ctx)
> +{
> +	switch (imm) {
> +	/* dst_reg = load_acquire(src_reg + off16) */
> +	case BPF_LOAD_ACQ:
> +		switch (BPF_SIZE(code)) {
> +		case BPF_B:
> +			emit_load_8(false, rd, off, rs, ctx);
> +			break;
> +		case BPF_H:
> +			emit_load_16(false, rd, off, rs, ctx);
> +			break;
> +		case BPF_W:
> +			emit_load_32(false, rd, off, rs, ctx);
> +			break;
> +		case BPF_DW:
> +			emit_load_64(false, rd, off, rs, ctx);
> +			break;
> +		}
> +		emit_fence_r_rw(ctx);
> +		break;
> +	/* store_release(dst_reg + off16, src_reg) */
> +	case BPF_STORE_REL:
> +		emit_fence_rw_w(ctx);
> +		switch (BPF_SIZE(code)) {
> +		case BPF_B:
> +			emit_store_8(rd, off, rs, ctx);
> +			break;
> +		case BPF_H:
> +			emit_store_16(rd, off, rs, ctx);
> +			break;
> +		case BPF_W:
> +			emit_store_32(rd, off, rs, ctx);
> +			break;
> +		case BPF_DW:
> +			emit_store_64(rd, off, rs, ctx);
> +			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(u8 rd, u8 rs, s16 off, s32 imm, u8 code,
> +			   struct rv_jit_context *ctx)
>   {
>   	u8 r0;
>   	int jmp_offset;
> +	bool is64;
> +
> +	if (BPF_SIZE(code) != BPF_W && BPF_SIZE(code) != BPF_DW) {
> +		pr_err_once("bpf-jit: 1- and 2-byte RMW atomics are not supported\n");
> +		return -EINVAL;
> +	}
> +	is64 = BPF_SIZE(code) == BPF_DW;
>   
>   	if (off) {
>   		if (is_12b_int(off)) {
> @@ -688,9 +742,14 @@ static void emit_atomic(u8 rd, u8 rs, s16 off, s32 imm, bool is64,
>   		     rv_sc_w(RV_REG_T3, rs, rd, 0, 1), ctx);
>   		jmp_offset = ninsns_rvoff(-6);
>   		emit(rv_bne(RV_REG_T3, 0, jmp_offset >> 1), ctx);
> -		emit(rv_fence(0x3, 0x3), ctx);
> +		emit_fence_rw_rw(ctx);
>   		break;
> +	default:
> +		pr_err_once("bpf-jit: invalid atomic RMW opcode %02x\n", imm);
> +		return -EINVAL;
>   	}
> +
> +	return 0;
>   }
>   
>   #define BPF_FIXUP_OFFSET_MASK   GENMASK(26, 0)
> @@ -1962,10 +2021,16 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
>   	case BPF_STX | BPF_MEM | BPF_DW:
>   		emit_store_64(rd, off, rs, ctx);
>   		break;
> +	case BPF_STX | BPF_ATOMIC | BPF_B:
> +	case BPF_STX | BPF_ATOMIC | BPF_H:
>   	case BPF_STX | BPF_ATOMIC | BPF_W:
>   	case BPF_STX | BPF_ATOMIC | BPF_DW:
> -		emit_atomic(rd, rs, off, imm,
> -			    BPF_SIZE(code) == BPF_DW, ctx);
> +		if (bpf_atomic_is_load_store(insn))
> +			ret = emit_atomic_ld_st(rd, rs, off, imm, code, ctx);
> +		else
> +			ret = emit_atomic_rmw(rd, rs, off, imm, code, ctx);
> +		if (ret)
> +			return ret;
>   		break;
>   
>   	case BPF_STX | BPF_PROBE_MEM32 | BPF_B:


Reviewed-by: Pu Lehui <pulehui@huawei.com>

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Re: [PATCH bpf-next v2 0/8] bpf, riscv64: Support load-acquire and store-release instructions

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed,  7 May 2025 03:42:29 +0000 you wrote:
> Hi all!
> 
> Patchset [1] introduced BPF load-acquire (BPF_LOAD_ACQ) and
> store-release (BPF_STORE_REL) instructions, and added x86-64 and arm64
> JIT compiler support.  As a follow-up, this v2 patchset supports
> load-acquire and store-release instructions for the riscv64 JIT
> compiler, and introduces some related selftests/ changes.
> 
> [...]

Here is the summary with links:
  - [bpf-next,v2,1/8] bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()
    https://git.kernel.org/bpf/bpf-next/c/fce7bd8e385a
  - [bpf-next,v2,2/8] bpf, riscv64: Introduce emit_load_*() and emit_store_*()
    https://git.kernel.org/bpf/bpf-next/c/118ae46b7942
  - [bpf-next,v2,3/8] bpf, riscv64: Support load-acquire and store-release instructions
    https://git.kernel.org/bpf/bpf-next/c/8afd3170d511
  - [bpf-next,v2,4/8] bpf, riscv64: Skip redundant zext instruction after load-acquire
    https://git.kernel.org/bpf/bpf-next/c/db7a3822b5f4
  - [bpf-next,v2,5/8] selftests/bpf: Use CAN_USE_LOAD_ACQ_STORE_REL when appropriate
    https://git.kernel.org/bpf/bpf-next/c/13fdecf3456e
  - [bpf-next,v2,6/8] selftests/bpf: Avoid passing out-of-range values to __retval()
    https://git.kernel.org/bpf/bpf-next/c/6e492ffcab60
  - [bpf-next,v2,7/8] selftests/bpf: Verify zero-extension behavior in load-acquire tests
    https://git.kernel.org/bpf/bpf-next/c/0357f29de809
  - [bpf-next,v2,8/8] selftests/bpf: Enable non-arena load-acquire/store-release selftests for riscv64
    https://git.kernel.org/bpf/bpf-next/c/d3131466b4f8

You are awesome, thank you!
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