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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49fdf157cdfsm56052875e9.0.2026.09.24.01.22.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Sep 2026 01:22:40 -0700 (PDT) Date: Thu, 24 Sep 2026 09:22:39 +0100 From: David Laight To: Johan Almbladh Cc: tsbogend@alpha.franken.de, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, paulburton@kernel.org, main.kalliope@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, philmd@oss.qualcomm.com Subject: Re: [PATCH bpf 1/2] bpf, mips: Fix immediate JMP JEQ/JNE on MIPS32 Message-ID: <20260924092239.0743b082@pumpkin> In-Reply-To: <20260923105158.3514342-1-johan.almbladh@anyfinetworks.com> References: <20260923105158.3514342-1-johan.almbladh@anyfinetworks.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 23 Sep 2026 12:51:57 +0200 Johan Almbladh wrote: > An addu instruction was emitted instead of addiu, causing the immediate > value 1 to be interpreted as register $at. This made the comparison > result invalid when the immediate operand was negative. Note that $at > is mapped to BPF_REG_AX, which is used for constant blinding. ^^ building?? David > > Fix the instruction to use the immediate form. > > Found with test_bpf on MIPS32r1 emulated by QEMU. > > Fixes: eb63cfcd2ee8 ("mips, bpf: Add eBPF JIT for 32-bit MIPS") > Signed-off-by: Johan Almbladh > --- > arch/mips/net/bpf_jit_comp32.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/mips/net/bpf_jit_comp32.c b/arch/mips/net/bpf_jit_comp32.c > index 40a878b672f5..15a2a153dc87 100644 > --- a/arch/mips/net/bpf_jit_comp32.c > +++ b/arch/mips/net/bpf_jit_comp32.c > @@ -1111,7 +1111,7 @@ static void emit_jmp_i64(struct jit_context *ctx, > emit(ctx, xor, tmp, lo(dst), tmp); > } > if (imm < 0) { /* Compare sign extension */ > - emit(ctx, addu, MIPS_R_T9, hi(dst), 1); > + emit(ctx, addiu, MIPS_R_T9, hi(dst), 1); > emit(ctx, or, tmp, tmp, MIPS_R_T9); > } else { /* Compare zero extension */ > emit(ctx, or, tmp, tmp, hi(dst));