linux-kernel - [PATCH] riscv: fix multi-letter extension compare

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Message-Id: <20221006070257.11632-1-nikita.shubin@maquefel.me>
Date:   Thu,  6 Oct 2022 10:02:56 +0300
From:   Nikita Shubin <nikita.shubin@...uefel.me>
To:     Atish Patra <atishp@...osinc.com>
Cc:     Nikita Shubin <nikita.shubin@...uefel.me>, linux@...ro.com,
        Nikita Shubin <n.shubin@...ro.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Heiko Stuebner <heiko@...ech.de>, Guo Ren <guoren@...nel.org>,
        Tsukasa OI <research_trasio@....a4lg.com>,
        Jisheng Zhang <jszhang@...nel.org>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Yury Norov <yury.norov@...il.com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] riscv: fix multi-letter extension compare

From: Nikita Shubin <n.shubin@...ro.com>

Increment ext pointer to match letters after 'z' character, so it points
to actual extension name.

Fixes: 4905ec2fb7e6 ("RISC-V: Add sscofpmf extension support")
Signed-off-by: Nikita Shubin <n.shubin@...ro.com>
---
Hello Atish,

Sorry to blame you, but i double checked this and i don't see a way 
how extensions from device tree could be successfully matched with 
encoded ones without incrementing the ext pointer or prepending 
the encoded extensions with 'z' letter.

I have no idea how this could slip through review - am i missing something ?
---
 arch/riscv/kernel/cpufeature.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 3b5583db9d80..031546052dc0 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -199,6 +199,7 @@ void __init riscv_fill_hwcap(void)
 				this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
 				set_bit(*ext - 'a', this_isa);
 			} else {
+				ext++;
 				SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
 				SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
 				SET_ISA_EXT_MAP("zicbom", RISCV_ISA_EXT_ZICBOM);
-- 
2.35.1