[RFC PATCH bpf-next 0/6] bpf: Add UHMUL and SHMUL instructions

[RFC PATCH bpf-next 0/6] bpf: Add UHMUL and SHMUL instructions

[Yazhou Tang]

From: Yazhou Tang <tangyazhou518@outlook.com>

This patchset adds unsigned and signed high-half multiplication to the BPF
ISA. UHMUL returns the high 64 bits of an unsigned 64-by-64-bit product,
while SHMUL does the same for a signed product.

Both operations are BPF_ALU64 BPF_MUL variants selected by insn->off.
off == 0 remains the existing low-half multiplication, while off == 1
and off == 2 select UHMUL and SHMUL, respectively. The immediate forms
use the usual sign-extended 32-bit BPF immediate.

The patchset adds interpreter, disassembler, verifier, documentation, and
x86-64 JIT support. Unsupported JIT and hardware offload backends reject
the variants to avoid compiling them as ordinary multiplication. For
now, the verifier computes exact results for constant operands and
otherwise conservatively marks the destination unknown.

Patch 6/6 uses raw bytecode for UHMUL and SHMUL because LLVM support has
not been merged yet. Once it is available, the raw encodings can be
replaced with the uh*= and sh*= mnemonics. A draft LLVM implementation
is available at:

  https://github.com/ADSWT518/llvm-project/tree/bpf-hmul-insn

We plan to finalize and submit it as an LLVM pull request after the
kernel-side ISA changes are merged.

The instruction design is inspired by the UHMUL and SHMUL operations in
Solana sBPF. Patch 1/6 describes the encoding and immediate-semantics
differences.

Feedback on the encoding, immediate semantics, and initial verifier
model would be appreciated.

Tianci Cao (3):
  bpf: Add UHMUL and SHMUL instructions
  bpf, x86: JIT UHMUL and SHMUL on x86-64
  bpf: Add verifier support for UHMUL and SHMUL

Yazhou Tang (3):
  bpf: Reject UHMUL/SHMUL in unsupported JITs
  bpf: Refactor ALU instruction variant validation
  selftests/bpf: Add bytecode tests for UHMUL and SHMUL

 .../bpf/standardization/instruction-set.rst   |  26 +-
 arch/arc/net/bpf_jit_core.c                   |   3 +
 arch/arm/net/bpf_jit_32.c                     |   3 +
 arch/arm64/net/bpf_jit_comp.c                 |   3 +
 arch/loongarch/net/bpf_jit.c                  |   3 +
 arch/mips/net/bpf_jit_comp32.c                |   3 +
 arch/mips/net/bpf_jit_comp64.c                |   3 +
 arch/parisc/net/bpf_jit_comp32.c              |   3 +
 arch/parisc/net/bpf_jit_comp64.c              |   3 +
 arch/powerpc/net/bpf_jit_comp32.c             |   3 +
 arch/powerpc/net/bpf_jit_comp64.c             |   3 +
 arch/riscv/net/bpf_jit_comp32.c               |   3 +
 arch/riscv/net/bpf_jit_comp64.c               |   3 +
 arch/s390/net/bpf_jit_comp.c                  |   3 +
 arch/sparc/net/bpf_jit_comp_64.c              |   3 +
 arch/x86/net/bpf_jit_comp.c                   |  48 +++
 arch/x86/net/bpf_jit_comp32.c                 |   3 +
 .../net/ethernet/netronome/nfp/bpf/verifier.c |   6 +
 include/linux/filter.h                        |  39 +++
 include/uapi/linux/bpf.h                      |  10 +
 kernel/bpf/core.c                             |  45 ++-
 kernel/bpf/disasm.c                           |  18 ++
 kernel/bpf/verifier.c                         |  69 ++++-
 tools/include/uapi/linux/bpf.h                |  10 +
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../selftests/bpf/progs/verifier_hmul.c       | 284 ++++++++++++++++++
 .../bpf/progs/verifier_value_illegal_alu.c    |   9 +-
 27 files changed, 598 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_hmul.c

-- 
2.43.0

[RFC PATCH bpf-next 1/6] bpf: Add UHMUL and SHMUL instructions

[Yazhou Tang]

From: Tianci Cao <ziye@zju.edu.cn>

Define UHMUL and SHMUL as BPF_ALU64 BPF_MUL variants selected by insn->off.
UHMUL returns the high 64 bits of an unsigned 64-by-64-bit product, while
SHMUL returns the high 64 bits of a signed product. Keep off == 0 as the
existing low-half multiplication, and assign off == 1 and off == 2 to
UHMUL and SHMUL, respectively.

These operations are inspired by the UHMUL and SHMUL instructions
introduced as part of the PQR instruction class in Solana sBPF[1].

The encoding and immediate semantics differ from current sBPF.

1. Solana sBPF assigns these operations dedicated opcodes in the BPF_PQR
   class, whereas this implementation selects them through the offset
   field of BPF_MUL.

2. Solana sBPF initially sign-extended the immediate operand of UHMUL,
   but later changed unsigned PQR immediates, including UHMUL, to be
   zero-extended[2].

   Linux instead follows the existing BPF_ALU64 immediate convention.
   Both immediate forms first sign-extend the 32-bit immediate to 64 bits.
   UHMUL then interprets the resulting bit pattern as unsigned, while
   SHMUL interprets it as signed.

Add portable helpers for both operations, using mul_u64_u64_shr() and a
signed correction instead of relying on a compiler-provided 128-bit
integer type. Wire the variants into the interpreter and disassembler,
and document the encoding in the UAPI and BPF instruction set. Keep
BPF_ALU multiplication restricted to the existing low-half variant.

[1] https://github.com/solana-labs/rbpf/pull/498
[2] https://github.com/solana-labs/rbpf/pull/642

Link: https://lore.kernel.org/bpf/CAADnVQ+2O2zgdy11+vxE6dOp+3Br4zZBysHF-Hne7cP+eeucnQ@mail.gmail.com/
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Yazhou Tang <tangyazhou518@outlook.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 .../bpf/standardization/instruction-set.rst   | 26 ++++++++++-
 include/linux/filter.h                        | 39 ++++++++++++++++
 include/uapi/linux/bpf.h                      | 10 +++++
 kernel/bpf/core.c                             | 45 ++++++++++++++++++-
 kernel/bpf/disasm.c                           | 18 ++++++++
 tools/include/uapi/linux/bpf.h                | 10 +++++
 6 files changed, 145 insertions(+), 3 deletions(-)

diff --git a/Documentation/bpf/standardization/instruction-set.rst b/Documentation/bpf/standardization/instruction-set.rst
index 39c74611752b..138943d35ba7 100644
--- a/Documentation/bpf/standardization/instruction-set.rst
+++ b/Documentation/bpf/standardization/instruction-set.rst
@@ -330,6 +330,8 @@ register.
   ADD    0x0    0        dst += src
   SUB    0x1    0        dst -= src
   MUL    0x2    0        dst \*= src
+  UHMUL  0x2    1        unsigned high-half multiplication (``ALU64`` only)
+  SHMUL  0x2    2        signed high-half multiplication (``ALU64`` only)
   DIV    0x3    0        dst = (src != 0) ? (dst / src) : 0
   SDIV   0x3    1        dst = (src == 0) ? 0 : ((src == -1 && dst == LLONG_MIN) ? LLONG_MIN : (dst s/ src))
   OR     0x4    0        dst \|= src
@@ -379,13 +381,33 @@ where '(u32)' indicates that the upper 32 bits are zeroed.
 
   dst = dst ^ imm
 
-Note that most arithmetic instructions have 'offset' set to 0. Only three instructions
-(``SDIV``, ``SMOD``, ``MOVSX``) have a non-zero 'offset'.
+Note that most arithmetic instructions have 'offset' set to 0. The following
+instructions may have a non-zero 'offset':
+
+* ``SDIV`` and ``SMOD``: ``offset == 1`` selects the signed variant.
+* ``MOVSX``: ``offset`` selects the source operand width.
+* ``MUL``: ``offset`` selects the multiplication variant (see below).
 
 Division, multiplication, and modulo operations for ``ALU`` are part
 of the "divmul32" conformance group, and division, multiplication, and
 modulo operations for ``ALU64`` are part of the "divmul64" conformance
 group.
+
+For ``ALU64`` multiplication, ``offset == 1`` selects unsigned
+high-half multiplication (``UHMUL``), and ``offset == 2`` selects
+signed high-half multiplication (``SHMUL``).
+
+For ``X`` mode, ``src64`` is the 64-bit value in ``src_reg``. For
+``K`` mode, ``src64`` is ``imm`` sign-extended from 32 to 64 bits.
+The operations are::
+
+  UHMUL: dst = (u64)(((u128)dst * (u128)(u64)src64) >> 64)
+  SHMUL: dst = (u64)(((s128)(s64)dst * (s128)(s64)src64) >> 64)
+
+For ``ALU`` multiplication, only ``offset == 0`` is valid. For
+``ALU64`` multiplication, offset values other than 0, 1, and 2 are
+reserved.
+
 The division and modulo operations support both unsigned and signed flavors.
 
 For unsigned operations (``DIV`` and ``MOD``), for ``ALU``,
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6e746b0a0930..49120840afb9 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -23,6 +23,7 @@
 #include <linux/sockptr.h>
 #include <linux/static_call.h>
 #include <linux/u64_stats_sync.h>
+#include <linux/math64.h>
 
 #include <net/sch_generic.h>
 
@@ -147,6 +148,44 @@ struct ctl_table_header;
 #define BPF_ALU32_IMM(OP, DST, IMM)				\
 	BPF_ALU32_IMM_OFF(OP, DST, IMM, 0)
 
+static inline u64 bpf_uhmul64(u64 a, u64 b)
+{
+	return mul_u64_u64_shr(a, b, 64);
+}
+
+static inline u64 bpf_shmul64(s64 a, s64 b)
+{
+	u64 ua = a, ub = b;
+	u64 hi = bpf_uhmul64(ua, ub);
+
+	/*
+	 * Let M = 2^64, sa = (a < 0), and sb = (b < 0). Then:
+	 *
+	 * a * b = (ua - sa * M) * (ub - sb * M)
+	 *       = ua * ub - sa * M * ub - sb * M * ua + sa * sb * M^2
+	 *
+	 * Therefore, signed_hi = unsigned_hi - sa * ub - sb * ua (mod M).
+	 */
+	if (a < 0)
+		hi -= ub;
+	if (b < 0)
+		hi -= ua;
+	return hi;
+}
+
+static inline bool bpf_is_hmul_variant(s16 off)
+{
+	return off == BPF_MUL_VARIANT_UHMUL ||
+	       off == BPF_MUL_VARIANT_SHMUL;
+}
+
+static inline bool bpf_insn_is_hmul(const struct bpf_insn *insn)
+{
+	return BPF_CLASS(insn->code) == BPF_ALU64 &&
+	       BPF_OP(insn->code) == BPF_MUL &&
+	       bpf_is_hmul_variant(insn->off);
+}
+
 /* Endianess conversion, cpu_to_{l,b}e(), {l,b}e_to_cpu() */
 
 #define BPF_ENDIAN(TYPE, DST, LEN)				\
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 732b35cc08d1..845eee536198 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -34,6 +34,16 @@
 #define BPF_FROM_LE	BPF_TO_LE
 #define BPF_FROM_BE	BPF_TO_BE
 
+/*
+ * BPF_MUL variants selected by the off field.
+ * UHMUL and SHMUL are only valid for BPF_ALU64.
+ */
+enum bpf_mul_variant {
+	BPF_MUL_VARIANT_LO    = 0,
+	BPF_MUL_VARIANT_UHMUL = 1,
+	BPF_MUL_VARIANT_SHMUL = 2,
+};
+
 /* jmp encodings */
 #define BPF_JNE		0x50	/* jump != */
 #define BPF_JLT		0xa0	/* LT is unsigned, '<' */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 5db77d7915df..05e28e8d6714 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1936,7 +1936,50 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
 	ALU(AND,  &)
 	ALU(OR,   |)
 	ALU(XOR,  ^)
-	ALU(MUL,  *)
+	/*
+	 * MUL needs explicit handlers because ALU64 insn->off selects
+	 * low-half, unsigned high-half, or signed high-half multiplication.
+	 */
+	ALU64_MUL_X:
+		switch (OFF) {
+		case BPF_MUL_VARIANT_LO:
+			DST = DST * SRC;
+			break;
+		case BPF_MUL_VARIANT_UHMUL:
+			DST = bpf_uhmul64(DST, SRC);
+			break;
+		case BPF_MUL_VARIANT_SHMUL:
+			DST = bpf_shmul64((s64)DST, (s64)SRC);
+			break;
+		default:
+			goto default_label;
+		}
+		CONT;
+	ALU_MUL_X:
+		if (OFF != BPF_MUL_VARIANT_LO)
+			goto default_label;
+		DST = (u32) DST * (u32) SRC;
+		CONT;
+	ALU64_MUL_K:
+		switch (OFF) {
+		case BPF_MUL_VARIANT_LO:
+			DST = DST * IMM;
+			break;
+		case BPF_MUL_VARIANT_UHMUL:
+			DST = bpf_uhmul64(DST, (u64)IMM);
+			break;
+		case BPF_MUL_VARIANT_SHMUL:
+			DST = bpf_shmul64((s64)DST, (s32)IMM);
+			break;
+		default:
+			goto default_label;
+		}
+		CONT;
+	ALU_MUL_K:
+		if (OFF != BPF_MUL_VARIANT_LO)
+			goto default_label;
+		DST = (u32) DST * (u32) IMM;
+		CONT;
 	SHT(LSH, <<)
 	SHT(RSH, >>)
 #undef SHT
diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c
index 50b3ca5149a0..c345b8e744b1 100644
--- a/kernel/bpf/disasm.c
+++ b/kernel/bpf/disasm.c
@@ -160,6 +160,22 @@ static bool is_sdiv_smod(const struct bpf_insn *insn)
 	       insn->off == 1;
 }
 
+/* Return the UHMUL or SHMUL operator string, or NULL for all other encodings. */
+static const char *hmul_op_string(const struct bpf_insn *insn)
+{
+	if (BPF_CLASS(insn->code) != BPF_ALU64 ||
+	    BPF_OP(insn->code) != BPF_MUL)
+		return NULL;
+	switch (insn->off) {
+	case BPF_MUL_VARIANT_UHMUL:
+		return "uh*=";
+	case BPF_MUL_VARIANT_SHMUL:
+		return "sh*=";
+	default:
+		return NULL;
+	}
+}
+
 static bool is_movsx(const struct bpf_insn *insn)
 {
 	return BPF_OP(insn->code) == BPF_MOV &&
@@ -212,6 +228,7 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 			verbose(cbs->private_data, "(%02x) %c%d %s %s%c%d",
 				insn->code, class == BPF_ALU ? 'w' : 'r',
 				insn->dst_reg,
+				hmul_op_string(insn) ?:
 				is_sdiv_smod(insn) ? bpf_alu_sign_string[BPF_OP(insn->code) >> 4]
 						   : bpf_alu_string[BPF_OP(insn->code) >> 4],
 				is_movsx(insn) ? bpf_movsx_string[(insn->off >> 3) - 1] : "",
@@ -221,6 +238,7 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs,
 			verbose(cbs->private_data, "(%02x) %c%d %s %d",
 				insn->code, class == BPF_ALU ? 'w' : 'r',
 				insn->dst_reg,
+				hmul_op_string(insn) ?:
 				is_sdiv_smod(insn) ? bpf_alu_sign_string[BPF_OP(insn->code) >> 4]
 						   : bpf_alu_string[BPF_OP(insn->code) >> 4],
 				insn->imm);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 732b35cc08d1..845eee536198 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -34,6 +34,16 @@
 #define BPF_FROM_LE	BPF_TO_LE
 #define BPF_FROM_BE	BPF_TO_BE
 
+/*
+ * BPF_MUL variants selected by the off field.
+ * UHMUL and SHMUL are only valid for BPF_ALU64.
+ */
+enum bpf_mul_variant {
+	BPF_MUL_VARIANT_LO    = 0,
+	BPF_MUL_VARIANT_UHMUL = 1,
+	BPF_MUL_VARIANT_SHMUL = 2,
+};
+
 /* jmp encodings */
 #define BPF_JNE		0x50	/* jump != */
 #define BPF_JLT		0xa0	/* LT is unsigned, '<' */
-- 
2.43.0

[RFC PATCH bpf-next 2/6] bpf, x86: JIT UHMUL and SHMUL on x86-64

[Yazhou Tang]

From: Tianci Cao <ziye@zju.edu.cn>

JIT the UHMUL and SHMUL instructions with the one-operand x86-64 mul and
imul instructions. These instructions multiply RAX by an explicit
source and return the full product in RDX:RAX, so the desired high half
is available in RDX.

Copy register or immediate sources into AUX_REG, load the destination
into RAX, and move RDX back to the BPF destination after multiplication.
Preserve RAX and RDX when they hold other live BPF registers, while
handling BPF_REG_0 and BPF_REG_3 destinations without restoring over the
result.

Leave the existing JIT handling of ordinary BPF_MUL unchanged.

Link: https://lore.kernel.org/bpf/CAADnVQ+2O2zgdy11+vxE6dOp+3Br4zZBysHF-Hne7cP+eeucnQ@mail.gmail.com/
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Yazhou Tang <tangyazhou518@outlook.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 arch/x86/net/bpf_jit_comp.c | 48 +++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 48429fae0641..233a05971cf4 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1110,6 +1110,38 @@ static void maybe_emit_1mod(u8 **pprog, u32 reg, bool is64)
 	*pprog = prog;
 }
 
+/*
+ * The one-operand x86 mul/imul forms use RAX as the implicit first
+ * operand and store the 128-bit product in RDX:RAX.
+ * The JIT uses AUX_REG as the explicit second operand.
+ */
+static void emit_hmul_aux(u8 **pprog, u32 dst_reg, bool is_signed)
+{
+	u8 *prog = *pprog;
+	bool save_rax = dst_reg != BPF_REG_0;
+	bool save_rdx = dst_reg != BPF_REG_3;
+	u8 mul_modrm_base = is_signed ? 0xE8 : 0xE0; /* imul /5 or mul /4 */
+
+	if (save_rax)
+		EMIT1(0x50); /* push rax */
+	if (save_rdx)
+		EMIT1(0x52); /* push rdx */
+
+	if (save_rax)
+		emit_mov_reg(&prog, true, BPF_REG_0, dst_reg);
+	maybe_emit_1mod(&prog, AUX_REG, true);
+	EMIT2(0xF7, add_1reg(mul_modrm_base, AUX_REG));
+	if (save_rdx)
+		emit_mov_reg(&prog, true, dst_reg, BPF_REG_3);
+
+	if (save_rdx)
+		EMIT1(0x5A); /* pop rdx */
+	if (save_rax)
+		EMIT1(0x58); /* pop rax */
+
+	*pprog = prog;
+}
+
 /* LDX: dst_reg = *(u8*)(src_reg + off) */
 static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
 {
@@ -2088,6 +2120,14 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int *
 
 		case BPF_ALU | BPF_MUL | BPF_K:
 		case BPF_ALU64 | BPF_MUL | BPF_K:
+			if (bpf_insn_is_hmul(insn)) {
+				/* imul/mul use AUX_REG as src. */
+				emit_mov_imm32(&prog, true, AUX_REG, imm32);
+				emit_hmul_aux(&prog, dst_reg,
+					      insn->off == BPF_MUL_VARIANT_SHMUL);
+				break;
+			}
+
 			maybe_emit_mod(&prog, dst_reg, dst_reg,
 				       BPF_CLASS(insn->code) == BPF_ALU64);
 
@@ -2104,6 +2144,14 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int *
 
 		case BPF_ALU | BPF_MUL | BPF_X:
 		case BPF_ALU64 | BPF_MUL | BPF_X:
+			if (bpf_insn_is_hmul(insn)) {
+				/* imul/mul use AUX_REG as src. */
+				emit_mov_reg(&prog, true, AUX_REG, src_reg);
+				emit_hmul_aux(&prog, dst_reg,
+					      insn->off == BPF_MUL_VARIANT_SHMUL);
+				break;
+			}
+
 			maybe_emit_mod(&prog, src_reg, dst_reg,
 				       BPF_CLASS(insn->code) == BPF_ALU64);
 
-- 
2.43.0

[RFC PATCH bpf-next 3/6] bpf: Reject UHMUL/SHMUL in unsupported JITs

[Yazhou Tang]

From: Yazhou Tang <tangyazhou518@outlook.com>

CPU JIT backends currently lower BPF_MUL based on the opcode without
examining insn->off. Once the verifier accepts UHMUL and SHMUL, a backend
without explicit support would therefore lower either variant as the
existing low-half multiplication and silently produce the wrong result.

Reject UHMUL and SHMUL in each affected CPU JIT without native support,
using its existing unsupported-instruction path. This makes JIT compilation
fail cleanly instead of emitting an incorrect low-half multiply, and allows
the normal interpreter fallback when available.

The NFP hardware offload compiler has the same opcode-only dispatch:
BPF_ALU64 MUL instructions are routed to mul_reg64() or mul_imm64()
without considering insn->off. Reject UHMUL and SHMUL in the NFP offload
verifier as well, before they can reach the ordinary multiplication lowering.

Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Tianci Cao <ziye@zju.edu.cn>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 arch/arc/net/bpf_jit_core.c                       | 3 +++
 arch/arm/net/bpf_jit_32.c                         | 3 +++
 arch/arm64/net/bpf_jit_comp.c                     | 3 +++
 arch/loongarch/net/bpf_jit.c                      | 3 +++
 arch/mips/net/bpf_jit_comp32.c                    | 3 +++
 arch/mips/net/bpf_jit_comp64.c                    | 3 +++
 arch/parisc/net/bpf_jit_comp32.c                  | 3 +++
 arch/parisc/net/bpf_jit_comp64.c                  | 3 +++
 arch/powerpc/net/bpf_jit_comp32.c                 | 3 +++
 arch/powerpc/net/bpf_jit_comp64.c                 | 3 +++
 arch/riscv/net/bpf_jit_comp32.c                   | 3 +++
 arch/riscv/net/bpf_jit_comp64.c                   | 3 +++
 arch/s390/net/bpf_jit_comp.c                      | 3 +++
 arch/sparc/net/bpf_jit_comp_64.c                  | 3 +++
 arch/x86/net/bpf_jit_comp32.c                     | 3 +++
 drivers/net/ethernet/netronome/nfp/bpf/verifier.c | 6 ++++++
 16 files changed, 51 insertions(+)

diff --git a/arch/arc/net/bpf_jit_core.c b/arch/arc/net/bpf_jit_core.c
index 639a2736f029..78b1819cee5a 100644
--- a/arch/arc/net/bpf_jit_core.c
+++ b/arch/arc/net/bpf_jit_core.c
@@ -734,6 +734,9 @@ static int handle_insn(struct jit_context *ctx, u32 idx)
 	u8  len = 0;
 	int ret = 0;
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (code) {
 	/* dst += src (32-bit) */
 	case BPF_ALU | BPF_ADD | BPF_X:
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 9ede81afbc50..aa466fc79d96 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -1611,6 +1611,9 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
 } while (0)
 #define check_imm24(imm) check_imm(24, imm)
 
+	if (bpf_insn_is_hmul(insn))
+		goto notyet;
+
 	switch (code) {
 	/* ALU operations */
 
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 3aa3ea0bc30b..dc60a931c364 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -1325,6 +1325,9 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn
 	int ret;
 	bool sign_extend;
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	if (bpf_insn_is_indirect_target(env, ctx->prog, i))
 		emit_bti(A64_BTI_J, ctx);
 
diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
index 29c281bef28e..f0a433dc0ccd 100644
--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -730,6 +730,9 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext
 	const s32 imm = insn->imm;
 	const bool is32 = BPF_CLASS(insn->code) == BPF_ALU || BPF_CLASS(insn->code) == BPF_JMP32;
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (code) {
 	/* dst = src */
 	case BPF_ALU | BPF_MOV | BPF_X:
diff --git a/arch/mips/net/bpf_jit_comp32.c b/arch/mips/net/bpf_jit_comp32.c
index 40a878b672f5..1afe15162af2 100644
--- a/arch/mips/net/bpf_jit_comp32.c
+++ b/arch/mips/net/bpf_jit_comp32.c
@@ -1472,6 +1472,9 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 	s32 val, rel;
 	u8 alu, jmp;
 
+	if (bpf_insn_is_hmul(insn))
+		goto notyet;
+
 	switch (code) {
 	/* ALU operations */
 	/* dst = imm */
diff --git a/arch/mips/net/bpf_jit_comp64.c b/arch/mips/net/bpf_jit_comp64.c
index fa7e9aa37f49..a9765ea25282 100644
--- a/arch/mips/net/bpf_jit_comp64.c
+++ b/arch/mips/net/bpf_jit_comp64.c
@@ -643,6 +643,9 @@ int build_insn(const struct bpf_insn *insn, struct jit_context *ctx)
 	s32 val, rel;
 	u8 alu, jmp;
 
+	if (bpf_insn_is_hmul(insn))
+		goto notyet;
+
 	switch (code) {
 	/* ALU operations */
 	/* dst = imm */
diff --git a/arch/parisc/net/bpf_jit_comp32.c b/arch/parisc/net/bpf_jit_comp32.c
index 5ff0cf925fe9..6bf72d04855b 100644
--- a/arch/parisc/net/bpf_jit_comp32.c
+++ b/arch/parisc/net/bpf_jit_comp32.c
@@ -1133,6 +1133,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct hppa_jit_context *ctx,
 		BPF_CLASS(code), code, (code & BPF_ALU64) ? 1:0, BPF_SIZE(code),
 		BPF_OP(code), insn->src_reg, insn->dst_reg);
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (code) {
 	/* dst = src */
 	case BPF_ALU64 | BPF_MOV | BPF_X:
diff --git a/arch/parisc/net/bpf_jit_comp64.c b/arch/parisc/net/bpf_jit_comp64.c
index 54b0d5e25e02..36b6078a146f 100644
--- a/arch/parisc/net/bpf_jit_comp64.c
+++ b/arch/parisc/net/bpf_jit_comp64.c
@@ -603,6 +603,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct hppa_jit_context *ctx,
 
 	init_regs(&rd, &rs, insn, ctx);
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (code) {
 	/* dst = src */
 	case BPF_ALU | BPF_MOV | BPF_X:
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index bfdc50740da8..b578b19017b2 100644
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -349,6 +349,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 		u32 true_cond;
 		u32 tmp_idx;
 
+		if (bpf_insn_is_hmul(insn))
+			return -EOPNOTSUPP;
+
 		if (i && (BPF_CLASS(code) == BPF_ALU64 || BPF_CLASS(code) == BPF_ALU) &&
 		    (BPF_CLASS(prevcode) == BPF_ALU64 || BPF_CLASS(prevcode) == BPF_ALU) &&
 		    BPF_OP(prevcode) == BPF_MOV && BPF_SRC(prevcode) == BPF_X &&
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index fc9db691e820..4ef0f3cffe84 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -992,6 +992,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 		u32 tmp_idx;
 		u32 jmp_off;
 
+		if (bpf_insn_is_hmul(insn))
+			return -EOPNOTSUPP;
+
 		/*
 		 * addrs[] maps a BPF bytecode address into a real offset from
 		 * the start of the body code.
diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c
index a9e0bd5cc81d..64bc6779d25c 100644
--- a/arch/riscv/net/bpf_jit_comp32.c
+++ b/arch/riscv/net/bpf_jit_comp32.c
@@ -1014,6 +1014,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 	const s8 *tmp1 = bpf2rv32[TMP_REG_1];
 	const s8 *tmp2 = bpf2rv32[TMP_REG_2];
 
+	if (bpf_insn_is_hmul(insn))
+		goto notsupported;
+
 	switch (code) {
 	case BPF_ALU64 | BPF_MOV | BPF_X:
 		if (insn->off != 0) {
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index e7378be171a9..2fc263b4adfe 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -1373,6 +1373,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 
 	init_regs(&rd, &rs, insn, ctx);
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (code) {
 	/* dst = src */
 	case BPF_ALU | BPF_MOV | BPF_X:
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index c46872b071ce..402af90c9281 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -969,6 +969,9 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
 
 	bpf_jit_probe_init(&probe);
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	switch (insn->code) {
 	/*
 	 * BPF_MOV
diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c
index 2fa0e9375127..1154ddc515b0 100644
--- a/arch/sparc/net/bpf_jit_comp_64.c
+++ b/arch/sparc/net/bpf_jit_comp_64.c
@@ -901,6 +901,9 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
 	const s16 off = insn->off;
 	const s32 imm = insn->imm;
 
+	if (bpf_insn_is_hmul(insn))
+		return -EOPNOTSUPP;
+
 	if (insn->src_reg == BPF_REG_FP)
 		ctx->saw_frame_pointer = true;
 
diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c
index 852baf2e4db4..11ed65130d1e 100644
--- a/arch/x86/net/bpf_jit_comp32.c
+++ b/arch/x86/net/bpf_jit_comp32.c
@@ -1683,6 +1683,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 		int ilen;
 		u8 *func;
 
+		if (bpf_insn_is_hmul(insn))
+			goto notyet;
+
 		switch (code) {
 		/* ALU operations */
 		/* dst = src */
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index 1caa87da72b5..effce27f3b88 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -3,6 +3,7 @@
 
 #include <linux/bpf.h>
 #include <linux/bpf_verifier.h>
+#include <linux/filter.h>
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
 #include <linux/pkt_cls.h>
@@ -561,6 +562,11 @@ nfp_bpf_check_alu(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
 	const struct bpf_reg_state *dreg =
 		cur_regs(env) + meta->insn.dst_reg;
 
+	if (bpf_insn_is_hmul(&meta->insn)) {
+		pr_vlog(env, "UHMUL/SHMUL are not supported\n");
+		return -EOPNOTSUPP;
+	}
+
 	meta->umin_src = min(meta->umin_src, reg_umin(sreg));
 	meta->umax_src = max(meta->umax_src, reg_umax(sreg));
 	meta->umin_dst = min(meta->umin_dst, reg_umin(dreg));
-- 
2.43.0

[RFC PATCH bpf-next 4/6] bpf: Refactor ALU instruction variant validation

[Yazhou Tang]

From: Yazhou Tang <tangyazhou518@outlook.com>

check_alu_fields() currently validates insn->off together with the
source-specific reserved fields. This duplicates the DIV and MOD
variant rules between register and immediate forms and makes the valid
instruction variants difficult to identify.

Move the opcode-specific insn->off validation into is_valid_alu_variant().
The helper permits off == 1 for DIV and MOD and requires off == 0 for all
other ALU operations. Validate the variant once, then separately check the
reserved immediate field for register sources and src_reg for immediate sources.

This is a pure refactoring and does not change which instruction encodings
the verifier accepts.

Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Tianci Cao <ziye@zju.edu.cn>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 kernel/bpf/verifier.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8f585ceb2cd5..92ab55ba349d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19108,6 +19108,18 @@ static int fd_array_get_map_idx(struct bpf_verifier_env *env, u32 idx)
 	return -EPROTO;
 }
 
+static bool is_valid_alu_variant(const struct bpf_insn *insn)
+{
+	switch (BPF_OP(insn->code)) {
+	case BPF_DIV:
+	case BPF_MOD:
+		/* off == 1 selects SDIV/SMOD. */
+		return insn->off == 0 || insn->off == 1;
+	default:
+		return insn->off == 0;
+	}
+}
+
 static int check_alu_fields(struct bpf_verifier_env *env, struct bpf_insn *insn)
 {
 	u8 class = BPF_CLASS(insn->code);
@@ -19163,15 +19175,9 @@ static int check_alu_fields(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	case BPF_MUL:
 	case BPF_DIV:
 	case BPF_MOD:
-		if (BPF_SRC(insn->code) == BPF_X) {
-			if (insn->imm != 0 || (insn->off != 0 && insn->off != 1) ||
-			    (insn->off == 1 && opcode != BPF_MOD && opcode != BPF_DIV)) {
-				verbose(env, "BPF_ALU uses reserved fields\n");
-				return -EINVAL;
-			}
-		} else if (insn->src_reg != BPF_REG_0 ||
-			   (insn->off != 0 && insn->off != 1) ||
-			   (insn->off == 1 && opcode != BPF_MOD && opcode != BPF_DIV)) {
+		if (!is_valid_alu_variant(insn) ||
+		    (BPF_SRC(insn->code) == BPF_X && insn->imm != 0) ||
+		    (BPF_SRC(insn->code) == BPF_K && insn->src_reg != BPF_REG_0)) {
 			verbose(env, "BPF_ALU uses reserved fields\n");
 			return -EINVAL;
 		}
-- 
2.43.0

[RFC PATCH bpf-next 5/6] bpf: Add verifier support for UHMUL and SHMUL

[Yazhou Tang]

From: Tianci Cao <ziye@zju.edu.cn>

Extend ALU variant validation to accept off == 1 and off == 2 as UHMUL and
SHMUL, respectively, for BPF_ALU64 MUL instructions. Both offsets remain
reserved for BPF_ALU MUL, since the high-half variants are only defined
for 64-bit operations. All other MUL offsets remain invalid.

For scalar tracking, compute the exact high-half result when both operands
are constants. Mark the destination unknown when either operand is variable
until range analysis for these variants is added. Keep the existing scalar
analysis for ordinary low-half MUL unchanged.

Reject UHMUL and SHMUL when either operand is PTR_TO_ARENA. Arena
arithmetic can be rewritten from BPF_ALU64 to BPF_ALU to enforce its 32-bit
pointer representation, but such a rewrite cannot preserve the semantics of
variants that are only defined for BPF_ALU64.

Link: https://lore.kernel.org/bpf/CAADnVQ+2O2zgdy11+vxE6dOp+3Br4zZBysHF-Hne7cP+eeucnQ@mail.gmail.com/
Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Yazhou Tang <tangyazhou518@outlook.com>
Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 kernel/bpf/verifier.c | 45 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 92ab55ba349d..82a45550d2ee 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -15056,6 +15056,24 @@ static void scalar_min_max_mul(struct bpf_reg_state *dst_reg,
 					cnum64_from_srange(smin, smax));
 }
 
+static void scalar_min_max_uhmul(struct bpf_reg_state *dst_reg,
+				 struct bpf_reg_state *src_reg)
+{
+	u64 dst = reg_const_value(dst_reg, false);
+	u64 src = reg_const_value(src_reg, false);
+
+	___mark_reg_known(dst_reg, bpf_uhmul64(dst, src));
+}
+
+static void scalar_min_max_shmul(struct bpf_reg_state *dst_reg,
+				 struct bpf_reg_state *src_reg)
+{
+	s64 dst = reg_const_value(dst_reg, false);
+	s64 src = reg_const_value(src_reg, false);
+
+	___mark_reg_known(dst_reg, bpf_shmul64(dst, src));
+}
+
 static void scalar32_min_max_udiv(struct bpf_reg_state *dst_reg,
 				  struct bpf_reg_state *src_reg)
 {
@@ -15752,6 +15770,25 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 		dst_reg->var_off = tnum_neg(env->fake_reg[0].var_off);
 		break;
 	case BPF_MUL:
+		/*
+		 * Range analysis for UHMUL/SHMUL is not implemented yet.
+		 * Compute an exact result only when both operands are constants.
+		 * Ordinary low-half MUL continues to use the analysis below.
+		 */
+		if (bpf_insn_is_hmul(insn) &&
+		    (!is_reg_const(dst_reg, false) ||
+		     !is_reg_const(&src_reg, false))) {
+			__mark_reg_unknown(env, dst_reg);
+			break;
+		}
+		if (!alu32 && insn->off == BPF_MUL_VARIANT_UHMUL) {
+			scalar_min_max_uhmul(dst_reg, &src_reg);
+			break;
+		}
+		if (!alu32 && insn->off == BPF_MUL_VARIANT_SHMUL) {
+			scalar_min_max_shmul(dst_reg, &src_reg);
+			break;
+		}
 		dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off);
 		scalar32_min_max_mul(dst_reg, &src_reg);
 		scalar_min_max_mul(dst_reg, &src_reg);
@@ -15877,6 +15914,11 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 	if (dst_reg->type == PTR_TO_ARENA || (src_reg && src_reg->type == PTR_TO_ARENA)) {
 		struct bpf_insn_aux_data *aux = cur_aux(env);
 
+		if (bpf_insn_is_hmul(insn)) {
+			verbose(env, "UHMUL/SHMUL with arena pointers are not supported\n");
+			return -EOPNOTSUPP;
+		}
+
 		if (dst_reg->type != PTR_TO_ARENA)
 			*dst_reg = *src_reg;
 
@@ -19111,6 +19153,9 @@ static int fd_array_get_map_idx(struct bpf_verifier_env *env, u32 idx)
 static bool is_valid_alu_variant(const struct bpf_insn *insn)
 {
 	switch (BPF_OP(insn->code)) {
+	case BPF_MUL:
+		return insn->off == BPF_MUL_VARIANT_LO ||
+		       bpf_insn_is_hmul(insn);
 	case BPF_DIV:
 	case BPF_MOD:
 		/* off == 1 selects SDIV/SMOD. */
-- 
2.43.0

[RFC PATCH bpf-next 6/6] selftests/bpf: Add bytecode tests for UHMUL and SHMUL

[Yazhou Tang]

From: Yazhou Tang <tangyazhou518@outlook.com>

Add test_progs coverage for UHMUL and SHMUL with the following changes:

1. Add arithmetic execution tests in verifier_hmul.c and register the new
   test suite with the verifier test runner:
   - Gate the execution cases on __TARGET_ARCH_x86, matching the initial
     JIT support, and provide a dummy program for other targets.
   - Inject only UHMUL and SHMUL as raw .8byte values built with
     BPF_RAW_INSN(), while keeping the surrounding instructions in the
     existing assembly syntax. This avoids requiring assembler support
     for the new mnemonics.
   - Exercise register and immediate sources, signed and unsigned boundary
     values, negative immediate sign extension, and R0, R1, and R3
     destinations. The R3 case covers the x86 JIT path where BPF R3 aliases
     the implicit RDX result register. Run these cases in both privileged
     and unprivileged modes.
   - BPF_PROG_TEST_RUN exposes only the low 32 bits of R0 as its return
     value, so a direct __retval() check cannot validate the upper 32 bits.
     Build a 64-bit mismatch mask as actual ^ expected, then fold it to
     32 bits as (u32)mismatch | (u32)(mismatch >> 32) and return the folded
     value through R0. The return value is zero if and only if the complete
     64-bit result matches the expected value.

2. Add arena pointer rejection tests in verifier_hmul.c. Use an arena
   pointer as the destination of UHMUL and as the source of SHMUL, and
   verify that the verifier rejects both programs.

3. Extend the illegal instruction encoding tests in verifier_value_illegal_alu.c.
   Check reserved MUL offsets and UHMUL and SHMUL encodings in the BPF_ALU
   class, reusing the existing DEFINE_BAD_OFFSET_TEST() macro.

Signed-off-by: Yazhou Tang <tangyazhou518@outlook.com>
Co-developed-by: Tianci Cao <ziye@zju.edu.cn>
Signed-off-by: Tianci Cao <ziye@zju.edu.cn>
Co-developed-by: Shenghao Yuan <shenghaoyuan0928@163.com>
Signed-off-by: Shenghao Yuan <shenghaoyuan0928@163.com>
---
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../selftests/bpf/progs/verifier_hmul.c       | 284 ++++++++++++++++++
 .../bpf/progs/verifier_value_illegal_alu.c    |   9 +-
 3 files changed, 294 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_hmul.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index f7f94ccebce2..bb352ad0d36f 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -50,6 +50,7 @@
 #include "verifier_helper_packet_access.skel.h"
 #include "verifier_helper_restricted.skel.h"
 #include "verifier_helper_value_access.skel.h"
+#include "verifier_hmul.skel.h"
 #include "verifier_int_ptr.skel.h"
 #include "verifier_iterating_callbacks.skel.h"
 #include "verifier_jeq_infer_not_null.skel.h"
@@ -214,6 +215,7 @@ void test_verifier_helper_access_var_len(void) { RUN(verifier_helper_access_var_
 void test_verifier_helper_packet_access(void) { RUN(verifier_helper_packet_access); }
 void test_verifier_helper_restricted(void)    { RUN(verifier_helper_restricted); }
 void test_verifier_helper_value_access(void)  { RUN(verifier_helper_value_access); }
+void test_verifier_hmul(void)                 { RUN(verifier_hmul); }
 void test_verifier_int_ptr(void)              { RUN(verifier_int_ptr); }
 void test_verifier_iterating_callbacks(void)  { RUN(verifier_iterating_callbacks); }
 void test_verifier_jeq_infer_not_null(void)   { RUN(verifier_jeq_infer_not_null); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_hmul.c b/tools/testing/selftests/bpf/progs/verifier_hmul.c
new file mode 100644
index 000000000000..b29565b30913
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_hmul.c
@@ -0,0 +1,284 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Tianci Cao */
+
+#include <linux/bpf.h>
+#include <limits.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "../../../include/linux/filter.h"
+
+#define BPF_UHMUL64_REG(DST, SRC) \
+	BPF_RAW_INSN(BPF_ALU64 | BPF_MUL | BPF_X, DST, SRC, \
+		     BPF_MUL_VARIANT_UHMUL, 0)
+
+#define BPF_UHMUL64_IMM(DST, IMM) \
+	BPF_RAW_INSN(BPF_ALU64 | BPF_MUL | BPF_K, DST, 0, \
+		     BPF_MUL_VARIANT_UHMUL, IMM)
+
+#define BPF_SHMUL64_REG(DST, SRC) \
+	BPF_RAW_INSN(BPF_ALU64 | BPF_MUL | BPF_X, DST, SRC, \
+		     BPF_MUL_VARIANT_SHMUL, 0)
+
+#define BPF_SHMUL64_IMM(DST, IMM) \
+	BPF_RAW_INSN(BPF_ALU64 | BPF_MUL | BPF_K, DST, 0, \
+		     BPF_MUL_VARIANT_SHMUL, IMM)
+
+/*
+ * Inject UHMUL/SHMUL as raw instructions so these tests do not require
+ * assembler support for the new mnemonics. All surrounding instructions use
+ * existing BPF assembly syntax supported by the baseline selftests toolchain.
+ */
+
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARENA);
+	__uint(map_flags, BPF_F_MMAPABLE);
+	__uint(max_entries, 1);
+} arena SEC(".maps");
+
+SEC("syscall")
+__description("UHMUL64 with arena pointer dst")
+__failure __msg("UHMUL/SHMUL with arena pointers are not supported")
+__naked void uhmul64_arena_ptr(void)
+{
+	asm volatile (
+	"r1 = %[arena] ll;"
+	"r0 = 1;"
+	"r0 = addr_space_cast(r0, 0x0, 0x1);"
+	".8byte %[hmul];"
+	"exit;"
+	:
+	: __imm_addr(arena),
+	  __imm_insn(hmul, BPF_UHMUL64_IMM(BPF_REG_0, 2))
+	: __clobber_all);
+}
+
+SEC("syscall")
+__description("SHMUL64 with arena pointer src")
+__failure __msg("UHMUL/SHMUL with arena pointers are not supported")
+__naked void shmul64_arena_ptr(void)
+{
+	asm volatile (
+	"r1 = %[arena] ll;"
+	"r1 = 1;"
+	"r1 = addr_space_cast(r1, 0x0, 0x1);"
+	"r0 = 2;"
+	".8byte %[hmul];"
+	"exit;"
+	:
+	: __imm_addr(arena),
+	  __imm_insn(hmul, BPF_SHMUL64_REG(BPF_REG_0, BPF_REG_1))
+	: __clobber_all);
+}
+
+#endif
+
+#if defined(__TARGET_ARCH_x86)
+
+/*
+ * BPF_PROG_TEST_RUN reports a 32-bit retval. Fold both halves of
+ * (actual ^ expected) into w0 so retval == 0 checks the full 64-bit result.
+ */
+
+SEC("socket")
+__description("UHMUL64, U64_MAX * U64_MAX, register source")
+__success __success_unpriv __retval(0)
+__naked void uhmul64_max_reg(void)
+{
+	asm volatile (
+	"r0 = -1;"
+	"r1 = -1;"
+	".8byte %[hmul];"
+	"r2 = -2;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_insn(hmul, BPF_UHMUL64_REG(BPF_REG_0, BPF_REG_1))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("UHMUL64, (1ULL << 63) * 2, register source")
+__success __success_unpriv __retval(0)
+__naked void uhmul64_pow2_reg(void)
+{
+	asm volatile (
+	"r0 = 2;"
+	"r1 = %[llong_min] ll;"
+	".8byte %[hmul];"
+	"r0 = r1;"
+	"r2 = 1;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_insn(hmul, BPF_UHMUL64_REG(BPF_REG_1, BPF_REG_0))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("UHMUL64, (1ULL << 63) * 2, R3 destination")
+__success __success_unpriv __retval(0)
+__naked void uhmul64_r3_dst(void)
+{
+	asm volatile (
+	"r3 = %[llong_min] ll;"
+	"r0 = 2;"
+	".8byte %[hmul];"
+	"r2 = 1;"
+	"r3 ^= r2;"
+	"r2 = r3;"
+	"r2 >>= 32;"
+	"w3 |= w2;"
+	"r0 = r3;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_insn(hmul, BPF_UHMUL64_REG(BPF_REG_3, BPF_REG_0))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("UHMUL64, (1ULL << 63) * 2, immediate source")
+__success __success_unpriv __retval(0)
+__naked void uhmul64_pow2_imm(void)
+{
+	asm volatile (
+	"r0 = %[llong_min] ll;"
+	".8byte %[hmul];"
+	"r2 = 1;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_insn(hmul, BPF_UHMUL64_IMM(BPF_REG_0, 2))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("UHMUL64, (1ULL << 63) * -2, immediate source")
+__success __success_unpriv __retval(0)
+__naked void uhmul64_neg_imm(void)
+{
+	asm volatile (
+	"r0 = %[llong_min] ll;"
+	".8byte %[hmul];"
+	"r2 = %[llong_max] ll;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_const(llong_max, LLONG_MAX),
+	  __imm_insn(hmul, BPF_UHMUL64_IMM(BPF_REG_0, -2))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SHMUL64, INT64_MAX * INT64_MAX, register source")
+__success __success_unpriv __retval(0)
+__naked void shmul64_max_reg(void)
+{
+	asm volatile (
+	"r0 = %[llong_max] ll;"
+	"r1 = %[llong_max] ll;"
+	".8byte %[hmul];"
+	"r2 = %[expected] ll;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(expected, 0x3fffffffffffffffULL),
+	  __imm_const(llong_max, LLONG_MAX),
+	  __imm_insn(hmul, BPF_SHMUL64_REG(BPF_REG_0, BPF_REG_1))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SHMUL64, INT64_MIN * -2, register source")
+__success __success_unpriv __retval(0)
+__naked void shmul64_min_neg2_reg(void)
+{
+	asm volatile (
+	"r0 = %[llong_min] ll;"
+	"r1 = -2;"
+	".8byte %[hmul];"
+	"r2 = 1;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_insn(hmul, BPF_SHMUL64_REG(BPF_REG_0, BPF_REG_1))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SHMUL64, 1 * -2, immediate source")
+__success __success_unpriv __retval(0)
+__naked void shmul64_neg_imm(void)
+{
+	asm volatile (
+	"r0 = 1;"
+	".8byte %[hmul];"
+	"r2 = -1;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_insn(hmul, BPF_SHMUL64_IMM(BPF_REG_0, -2))
+	: __clobber_all);
+}
+
+SEC("socket")
+__description("SHMUL64, INT64_MIN * 2, immediate source")
+__success __success_unpriv __retval(0)
+__naked void shmul64_min_imm(void)
+{
+	asm volatile (
+	"r0 = %[llong_min] ll;"
+	".8byte %[hmul];"
+	"r2 = -1;"
+	"r0 ^= r2;"
+	"r2 = r0;"
+	"r2 >>= 32;"
+	"w0 |= w2;"
+	"exit;"
+	:
+	: __imm_const(llong_min, LLONG_MIN),
+	  __imm_insn(hmul, BPF_SHMUL64_IMM(BPF_REG_0, 2))
+	: __clobber_all);
+}
+
+#else
+
+SEC("socket")
+__description("UHMUL/SHMUL are not supported by this JIT, use a dummy test")
+__skip("UHMUL/SHMUL are not supported by this jit")
+__success
+int dummy_test(void)
+{
+	return 0;
+}
+
+#endif
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
index 4d8273c258d5..d7fb6b71b206 100644
--- a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
+++ b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
@@ -202,7 +202,8 @@ __naked void flow_keys_illegal_variable_offset_alu(void)
 
 /*
  * Offset fields of 0 and 1 are legal for BPF_{DIV,MOD} instructions.
- * Offset fields of 0 are legal for the rest of ALU instructions.
+ * Offset fields of 0, 1 and 2 are legal for BPF_ALU64 | BPF_MUL.
+ * Only offset 0 is legal for BPF_ALU | BPF_MUL.
  * Test that error is reported for illegal offsets, assuming that tests
  * for legal offsets exist.
  */
@@ -212,5 +213,11 @@ DEFINE_BAD_OFFSET_TEST(bad_offset_addx, BPF_ALU64 | BPF_ADD | BPF_X, -1, 0)
 DEFINE_BAD_OFFSET_TEST(bad_offset_divx2, BPF_ALU64 | BPF_DIV | BPF_X, 2, 0)
 DEFINE_BAD_OFFSET_TEST(bad_offset_modk2, BPF_ALU64 | BPF_MOD | BPF_K, 2, 1)
 DEFINE_BAD_OFFSET_TEST(bad_offset_addx2, BPF_ALU64 | BPF_ADD | BPF_X, 1, 0)
+DEFINE_BAD_OFFSET_TEST(bad_offset_mulx, BPF_ALU64 | BPF_MUL | BPF_X, -1, 0)
+DEFINE_BAD_OFFSET_TEST(bad_offset_mulk, BPF_ALU64 | BPF_MUL | BPF_K, 3, 0)
+DEFINE_BAD_OFFSET_TEST(bad_uhmul32_x, BPF_ALU | BPF_MUL | BPF_X,
+		       BPF_MUL_VARIANT_UHMUL, 0)
+DEFINE_BAD_OFFSET_TEST(bad_shmul32_k, BPF_ALU | BPF_MUL | BPF_K,
+		       BPF_MUL_VARIANT_SHMUL, 0)
 
 char _license[] SEC("license") = "GPL";
-- 
2.43.0

Re: [RFC PATCH bpf-next 3/6] bpf: Reject UHMUL/SHMUL in unsupported JITs

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The PowerPC JIT backends check the first instruction of the program instead of the current instruction when rejecting UHMUL/SHMUL.
--

commit 1bfedfff9f6c73dc718b4f4866c0696e836592cb
Author: Yazhou Tang <tangyazhou518@outlook.com>

bpf: Reject UHMUL/SHMUL in unsupported JITs

CPU JIT backends currently lower BPF_MUL based on the opcode without
examining insn->off. Once the verifier accepts UHMUL and SHMUL, a backend
without explicit support would therefore lower either variant as the
existing low-half multiplication and silently produce the wrong result.

> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
> index bfdc50740da8e..b578b19017b22 100644
> --- a/arch/powerpc/net/bpf_jit_comp32.c
> +++ b/arch/powerpc/net/bpf_jit_comp32.c
> @@ -349,6 +349,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
>  		u32 true_cond;
>  		u32 tmp_idx;
>  
> +		if (bpf_insn_is_hmul(insn))
> +			return -EOPNOTSUPP;
> +

[Severity: High]
Does this code check the correct instruction? In bpf_jit_build_body(),
insn points to the first instruction of the program (fp->insnsi), and
the loop uses the index i. By calling bpf_insn_is_hmul(insn) instead of
bpf_insn_is_hmul(&insn[i]), the check only ever looks at the 0-th
instruction of the program.

If an unsupported UHMUL or SHMUL instruction occurs anywhere other than the
very first instruction, it will not be rejected and will instead be compiled
silently as a standard lower-half multiplication.

>  		if (i && (BPF_CLASS(code) == BPF_ALU64 || BPF_CLASS(code) == BPF_ALU) &&
>  		    (BPF_CLASS(prevcode) == BPF_ALU64 || BPF_CLASS(prevcode) == BPF_ALU) &&
>  		    BPF_OP(prevcode) == BPF_MOV && BPF_SRC(prevcode) == BPF_X &&

[ ... ]

> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index fc9db691e8203..4ef0f3cffe848 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -992,6 +992,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
>  		u32 tmp_idx;
>  		u32 jmp_off;
>  
> +		if (bpf_insn_is_hmul(insn))
> +			return -EOPNOTSUPP;
> +

[Severity: High]
Similarly, does this code check the correct instruction for the 64-bit JIT?
It appears to check the first instruction instead of &insn[i], which will
cause the same silent incorrect compilation for unsupported UHMUL/SHMUL
instructions not located at the first position in the program.

>  		/*
>  		 * addrs[] maps a BPF bytecode address into a real offset from
>  		 * the start of the body code.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260902070534.2141812-1-tangyazhou@zju.edu.cn?part=3

Re: [RFC PATCH bpf-next 3/6] bpf: Reject UHMUL/SHMUL in unsupported JITs

[Yazhou Tang]

On 9/2/26 3:21 PM, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] The PowerPC JIT backends check the first instruction of the program instead of the current instruction when rejecting UHMUL/SHMUL.
> --
> 
> commit 1bfedfff9f6c73dc718b4f4866c0696e836592cb
> Author: Yazhou Tang <tangyazhou518@outlook.com>
> 
> bpf: Reject UHMUL/SHMUL in unsupported JITs
> 
> CPU JIT backends currently lower BPF_MUL based on the opcode without
> examining insn->off. Once the verifier accepts UHMUL and SHMUL, a backend
> without explicit support would therefore lower either variant as the
> existing low-half multiplication and silently produce the wrong result.
> 
>> diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
>> index bfdc50740da8e..b578b19017b22 100644
>> --- a/arch/powerpc/net/bpf_jit_comp32.c
>> +++ b/arch/powerpc/net/bpf_jit_comp32.c
>> @@ -349,6 +349,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
>>   		u32 true_cond;
>>   		u32 tmp_idx;
>>   
>> +		if (bpf_insn_is_hmul(insn))
>> +			return -EOPNOTSUPP;
>> +
> 
> [Severity: High]
> Does this code check the correct instruction? In bpf_jit_build_body(),
> insn points to the first instruction of the program (fp->insnsi), and
> the loop uses the index i. By calling bpf_insn_is_hmul(insn) instead of
> bpf_insn_is_hmul(&insn[i]), the check only ever looks at the 0-th
> instruction of the program.

Thanks for catching this. I overlooked that the PowerPC JIT keeps insn
pointing at fp->insnsi and uses i to select the current instruction,
whereas the other modified JITs use insn to refer to the current instruction.

Both PowerPC checks should use &insn[i]. I will fix them in the next revision.

> 
> If an unsupported UHMUL or SHMUL instruction occurs anywhere other than the
> very first instruction, it will not be rejected and will instead be compiled
> silently as a standard lower-half multiplication.
> 
>>   		if (i && (BPF_CLASS(code) == BPF_ALU64 || BPF_CLASS(code) == BPF_ALU) &&
>>   		    (BPF_CLASS(prevcode) == BPF_ALU64 || BPF_CLASS(prevcode) == BPF_ALU) &&
>>   		    BPF_OP(prevcode) == BPF_MOV && BPF_SRC(prevcode) == BPF_X &&
> 
> [ ... ]
> 
>> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
>> index fc9db691e8203..4ef0f3cffe848 100644
>> --- a/arch/powerpc/net/bpf_jit_comp64.c
>> +++ b/arch/powerpc/net/bpf_jit_comp64.c
>> @@ -992,6 +992,9 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
>>   		u32 tmp_idx;
>>   		u32 jmp_off;
>>   
>> +		if (bpf_insn_is_hmul(insn))
>> +			return -EOPNOTSUPP;
>> +
> 
> [Severity: High]
> Similarly, does this code check the correct instruction for the 64-bit JIT?
> It appears to check the first instruction instead of &insn[i], which will
> cause the same silent incorrect compilation for unsupported UHMUL/SHMUL
> instructions not located at the first position in the program.
> 
>>   		/*
>>   		 * addrs[] maps a BPF bytecode address into a real offset from
>>   		 * the start of the body code.
> 

Re: [RFC PATCH bpf-next 1/6] bpf: Add UHMUL and SHMUL instructions

[Alexei Starovoitov]

On Wed Sep 2, 2026 at 12:05 AM PDT, Yazhou Tang wrote:
> From: Tianci Cao <ziye@zju.edu.cn>
>
> Define UHMUL and SHMUL as BPF_ALU64 BPF_MUL variants selected by insn->off.
> UHMUL returns the high 64 bits of an unsigned 64-by-64-bit product, while
> SHMUL returns the high 64 bits of a signed product. Keep off == 0 as the
> existing low-half multiplication, and assign off == 1 and off == 2 to
> UHMUL and SHMUL, respectively.
>
> These operations are inspired by the UHMUL and SHMUL instructions
> introduced as part of the PQR instruction class in Solana sBPF[1].
>
> The encoding and immediate semantics differ from current sBPF.
>
> 1. Solana sBPF assigns these operations dedicated opcodes in the BPF_PQR
>    class, whereas this implementation selects them through the offset
>    field of BPF_MUL.
>
> 2. Solana sBPF initially sign-extended the immediate operand of UHMUL,
>    but later changed unsigned PQR immediates, including UHMUL, to be
>    zero-extended[2].

Why did you switch to zero-extend ?
Sounds odd to do zero extend just for these ops.

Overall the patch set look pretty good.
Please drop RFC and respin.

Re: [RFC PATCH bpf-next 3/6] bpf: Reject UHMUL/SHMUL in unsupported JITs

[Alexei Starovoitov]

On Wed Sep 2, 2026 at 12:05 AM PDT, Yazhou Tang wrote:
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 3aa3ea0bc30b..dc60a931c364 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -1325,6 +1325,9 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn
>  	int ret;
>  	bool sign_extend;
>  
> +	if (bpf_insn_is_hmul(insn))
> +		return -EOPNOTSUPP;
> +

Please add arm64 support in this patch set and may be one more like riscv.
Just x86 is not enough to see whether new insns map cleanly on other archs.

Re: [RFC PATCH bpf-next 1/6] bpf: Add UHMUL and SHMUL instructions

[Yazhou Tang]

On 9/8/26 3:51 AM, Alexei Starovoitov wrote:
> On Wed Sep 2, 2026 at 12:05 AM PDT, Yazhou Tang wrote:
>> From: Tianci Cao <ziye@zju.edu.cn>
>>
>> Define UHMUL and SHMUL as BPF_ALU64 BPF_MUL variants selected by insn->off.
>> UHMUL returns the high 64 bits of an unsigned 64-by-64-bit product, while
>> SHMUL returns the high 64 bits of a signed product. Keep off == 0 as the
>> existing low-half multiplication, and assign off == 1 and off == 2 to
>> UHMUL and SHMUL, respectively.
>>
>> These operations are inspired by the UHMUL and SHMUL instructions
>> introduced as part of the PQR instruction class in Solana sBPF[1].
>>
>> The encoding and immediate semantics differ from current sBPF.
>>
>> 1. Solana sBPF assigns these operations dedicated opcodes in the BPF_PQR
>>     class, whereas this implementation selects them through the offset
>>     field of BPF_MUL.
>>
>> 2. Solana sBPF initially sign-extended the immediate operand of UHMUL,
>>     but later changed unsigned PQR immediates, including UHMUL, to be
>>     zero-extended[2].
> 
> Why did you switch to zero-extend ?
> Sounds odd to do zero extend just for these ops.

Sorry, I wasn't clear. This patch does not zero-extend the UHMUL immediate.

Both UHMUL and SHMUL follow the existing BPF_ALU64 convention and
sign-extend the 32-bit immediate to 64 bits first. The zero-extension
I mentioned refers only to current Solana sBPF behavior. I'll clarify
this in the respin.

> 
> Overall the patch set look pretty good.
> Please drop RFC and respin.

Thanks for the review. I'll respin soon.

Re: [RFC PATCH bpf-next 3/6] bpf: Reject UHMUL/SHMUL in unsupported JITs

[Yazhou Tang]

On 9/8/26 3:53 AM, Alexei Starovoitov wrote:
> On Wed Sep 2, 2026 at 12:05 AM PDT, Yazhou Tang wrote:
>> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
>> index 3aa3ea0bc30b..dc60a931c364 100644
>> --- a/arch/arm64/net/bpf_jit_comp.c
>> +++ b/arch/arm64/net/bpf_jit_comp.c
>> @@ -1325,6 +1325,9 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn
>>   	int ret;
>>   	bool sign_extend;
>>   
>> +	if (bpf_insn_is_hmul(insn))
>> +		return -EOPNOTSUPP;
>> +
> 
> Please add arm64 support in this patch set and may be one more like riscv.
> Just x86 is not enough to see whether new insns map cleanly on other archs.
Sounds good. I'll try to add both arm64 and RISC-V support in the respin.

Re: [RFC PATCH bpf-next 1/6] bpf: Add UHMUL and SHMUL instructions

[Alexei Starovoitov]

On Tue Sep 8, 2026 at 1:30 AM PDT, Yazhou Tang wrote:
>
>
> On 9/8/26 3:51 AM, Alexei Starovoitov wrote:
>> On Wed Sep 2, 2026 at 12:05 AM PDT, Yazhou Tang wrote:
>>> From: Tianci Cao <ziye@zju.edu.cn>
>>>
>>> Define UHMUL and SHMUL as BPF_ALU64 BPF_MUL variants selected by insn->off.
>>> UHMUL returns the high 64 bits of an unsigned 64-by-64-bit product, while
>>> SHMUL returns the high 64 bits of a signed product. Keep off == 0 as the
>>> existing low-half multiplication, and assign off == 1 and off == 2 to
>>> UHMUL and SHMUL, respectively.
>>>
>>> These operations are inspired by the UHMUL and SHMUL instructions
>>> introduced as part of the PQR instruction class in Solana sBPF[1].
>>>
>>> The encoding and immediate semantics differ from current sBPF.
>>>
>>> 1. Solana sBPF assigns these operations dedicated opcodes in the BPF_PQR
>>>     class, whereas this implementation selects them through the offset
>>>     field of BPF_MUL.
>>>
>>> 2. Solana sBPF initially sign-extended the immediate operand of UHMUL,
>>>     but later changed unsigned PQR immediates, including UHMUL, to be
>>>     zero-extended[2].
>> 
>> Why did you switch to zero-extend ?
>> Sounds odd to do zero extend just for these ops.
>
> Sorry, I wasn't clear. This patch does not zero-extend the UHMUL immediate.
>
> Both UHMUL and SHMUL follow the existing BPF_ALU64 convention and
> sign-extend the 32-bit immediate to 64 bits first. The zero-extension
> I mentioned refers only to current Solana sBPF behavior. I'll clarify
> this in the respin.

My question was "why in Solana you switched to zero-extend?"