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[34.80.237.32]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-364a419c9a6sm2261855a91.7.2026.04.29.05.35.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 05:35:33 -0700 (PDT) From: Kuan-Wei Chiu To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, luke.r.nels@gmail.com, xi.wang@gmail.com, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, alex@ghiti.fr, jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com, marscheng@google.com, bpf@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Kuan-Wei Chiu Subject: [PATCH bpf-next 1/3] riscv, bpf: Fix support for BPF_SDIV and BPF_SMOD in RV32 JIT Date: Wed, 29 Apr 2026 12:35:11 +0000 Message-ID: <20260429123513.3477780-2-visitorckw@gmail.com> X-Mailer: git-send-email 2.54.0.545.g6539524ca2-goog In-Reply-To: <20260429123513.3477780-1-visitorckw@gmail.com> References: <20260429123513.3477780-1-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The current rv32 bpf jit compiler incorrectly treats BPF_SDIV and BPF_SMOD as unsigned operations. The BPF instruction set allows signed division and modulo by reusing the BPF_DIV and BPF_MOD opcodes with the instruction offset set to 1. Update the emit_alu_r32() function to accept an 'is_sdiv' variable and emit the correct div and rem instructions when the offset is 1. Before this patch: [ 44.161771] test_bpf: #165 ALU_SDIV_X: -6 / 2 = -3 jited:1 ret 2147483645 != -3 (0x7ffffffd != 0xfffffffd)FAIL (1 times) [ 44.167385] test_bpf: #166 ALU_SDIV_K: -6 / 2 = -3 jited:1 ret 2147483645 != -3 (0x7ffffffd != 0xfffffffd)FAIL (1 times) [ 44.171053] test_bpf: #169 ALU_SMOD_X: -7 % 2 = -1 jited:1 ret 1 != -1 (0x1 != 0xffffffff)FAIL (1 times) [ 44.172081] test_bpf: #170 ALU_SMOD_K: -7 % 2 = -1 jited:1 ret 1 != -1 (0x1 != 0xffffffff)FAIL (1 times) After this patch: [ 16.002192] test_bpf: #165 ALU_SDIV_X: -6 / 2 = -3 jited:1 95 PASS [ 16.002983] test_bpf: #166 ALU_SDIV_K: -6 / 2 = -3 jited:1 1059 PASS [ 16.017167] test_bpf: #169 ALU_SMOD_X: -7 % 2 = -1 jited:1 136 PASS [ 16.023002] test_bpf: #170 ALU_SMOD_K: -7 % 2 = -1 jited:1 109 PASS Signed-off-by: Kuan-Wei Chiu --- arch/riscv/net/bpf_jit_comp32.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c index 592dd86fbf81..7396899ea276 100644 --- a/arch/riscv/net/bpf_jit_comp32.c +++ b/arch/riscv/net/bpf_jit_comp32.c @@ -509,7 +509,7 @@ static void emit_alu_r64(const s8 *dst, const s8 *src, } static void emit_alu_r32(const s8 *dst, const s8 *src, - struct rv_jit_context *ctx, const u8 op) + struct rv_jit_context *ctx, const u8 op, bool is_sdiv) { const s8 *tmp1 = bpf2rv32[TMP_REG_1]; const s8 *tmp2 = bpf2rv32[TMP_REG_2]; @@ -539,10 +539,16 @@ static void emit_alu_r32(const s8 *dst, const s8 *src, emit(rv_mul(lo(rd), lo(rd), lo(rs)), ctx); break; case BPF_DIV: - emit(rv_divu(lo(rd), lo(rd), lo(rs)), ctx); + if (is_sdiv) + emit(rv_div(lo(rd), lo(rd), lo(rs)), ctx); + else + emit(rv_divu(lo(rd), lo(rd), lo(rs)), ctx); break; case BPF_MOD: - emit(rv_remu(lo(rd), lo(rd), lo(rs)), ctx); + if (is_sdiv) + emit(rv_rem(lo(rd), lo(rd), lo(rs)), ctx); + else + emit(rv_remu(lo(rd), lo(rd), lo(rs)), ctx); break; case BPF_LSH: emit(rv_sll(lo(rd), lo(rd), lo(rs)), ctx); @@ -959,6 +965,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, u8 code = insn->code; s16 off = insn->off; s32 imm = insn->imm; + bool is_sdiv = false; const s8 *dst = bpf2rv32[insn->dst_reg]; const s8 *src = bpf2rv32[insn->src_reg]; @@ -1041,7 +1048,9 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, emit_imm32(tmp2, imm, ctx); src = tmp2; } - emit_alu_r32(dst, src, ctx, BPF_OP(code)); + if ((BPF_OP(code) == BPF_DIV || BPF_OP(code) == BPF_MOD) && insn->off == 1) + is_sdiv = true; + emit_alu_r32(dst, src, ctx, BPF_OP(code), is_sdiv); break; case BPF_ALU | BPF_MOV | BPF_K: @@ -1065,7 +1074,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, * src is ignored---choose tmp2 as a dummy register since it * is not on the stack. */ - emit_alu_r32(dst, tmp2, ctx, BPF_OP(code)); + emit_alu_r32(dst, tmp2, ctx, BPF_OP(code), false); break; case BPF_ALU | BPF_END | BPF_FROM_LE: -- 2.54.0.545.g6539524ca2-goog