linux-kernel - re: LoongArch: Add BPF JIT support

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Message-ID: <bcf97046-e336-712a-ac68-7fd194f2953e@gmail.com>
Date:   Mon, 24 Jul 2023 13:27:26 +0100
From:   "Colin King (gmail)" <colin.i.king@...il.com>
To:     Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc:     Youling Tang <tangyouling@...ngson.cn>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        loongarch@...ts.linux.dev,
        "bpf@...r.kernel.org >> bpf" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: LoongArch: Add BPF JIT support

Hi,

Static analysis with clang scan build on arch/loongarch/net/bpf_jit.h 
has detected a potential issue with the following commit:

commit 5dc615520c4dfb358245680f1904bad61116648e
Author: Tiezhu Yang <yangtiezhu@...ngson.cn>
Date:   Wed Oct 12 16:36:20 2022 +0800

     LoongArch: Add BPF JIT support

This issue is as follows:

arch/loongarch/net/bpf_jit.h:153:23: warning: Logical disjunction always 
evaluates to true: imm_51_31 != 0 || imm_51_31 != 0x1fffff. 
[incorrectLogicOperator]
    if (imm_51_31 != 0 || imm_51_31 != 0x1fffff) {


The statement seems to be always true. I suspect it should it be instead:

    if (imm_51_31 != 0 && imm_51_31 != 0x1fffff) {

regards,

Colin