linux-kernel - [PATCH v3 20/60] arm64: idreg-override: avoid strlen() to check for empty strings

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Message-Id: <20230307140522.2311461-21-ardb@kernel.org>
Date:   Tue,  7 Mar 2023 15:04:42 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ryan Roberts <ryan.roberts@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH v3 20/60] arm64: idreg-override: avoid strlen() to check for empty strings

strlen() is a costly way to decide whether a string is empty, as in that
case, the first character will be NUL so we can check for that directly.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/kernel/idreg-override.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 23bbbc37ac24ba09..476dc3f0e9d90e22 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -221,7 +221,7 @@ static void __init match_options(const char *cmdline)
 
 		override = prel64_to_pointer(&reg->override_prel);
 
-		for (f = 0; strlen(reg->fields[f].name); f++) {
+		for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
 			u64 shift = reg->fields[f].shift;
 			u64 width = reg->fields[f].width ?: 4;
 			u64 mask = GENMASK_ULL(shift + width - 1, shift);
-- 
2.39.2