linux-kernel - [PATCH v2 04/14] lib/string: extract generic strrchr() into __generic

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Message-Id: <20260113082748.250916-5-jiangfeng@kylinos.cn>
Date: Tue, 13 Jan 2026 16:27:38 +0800
From: Feng Jiang <jiangfeng@...inos.cn>
To: pjw@...nel.org,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	kees@...nel.org,
	andy@...nel.org,
	akpm@...ux-foundation.org,
	jiangfeng@...inos.cn,
	ebiggers@...nel.org,
	martin.petersen@...cle.com,
	ardb@...nel.org,
	ajones@...tanamicro.com,
	conor.dooley@...rochip.com,
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	nathan@...nel.org
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2 04/14] lib/string: extract generic strrchr() into __generic_strrchr()

To support performance benchmarking in KUnit tests, extract the
generic C implementation of strrchr() into a standalone function
__generic_strrchr(). This allows tests to compare architecture-optimized
versions against the generic baseline without duplicating code.

Suggested-by: Andy Shevchenko <andy@...nel.org>
Signed-off-by: Feng Jiang <jiangfeng@...inos.cn>
---
 include/linux/string.h |  1 +
 lib/string.c           | 19 +++++++++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 57f8bf543891..2ede3ff0865a 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -180,6 +180,7 @@ extern char * strnchrnul(const char *, size_t, int);
 #ifndef __HAVE_ARCH_STRNCHR
 extern char * strnchr(const char *, size_t, int);
 #endif
+extern char *__generic_strrchr(const char *, int);
 #ifndef __HAVE_ARCH_STRRCHR
 extern char * strrchr(const char *,int);
 #endif
diff --git a/lib/string.c b/lib/string.c
index 8ad9b73ffe4e..4405a042eee7 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -377,6 +377,18 @@ char *strnchrnul(const char *s, size_t count, int c)
 	return (char *)s;
 }
 
+char *__generic_strrchr(const char *s, int c)
+{
+	const char *last = NULL;
+
+	do {
+		if (*s == (char)c)
+			last = s;
+	} while (*s++);
+	return (char *)last;
+}
+EXPORT_SYMBOL(__generic_strrchr);
+
 #ifndef __HAVE_ARCH_STRRCHR
 /**
  * strrchr - Find the last occurrence of a character in a string
@@ -385,12 +397,7 @@ char *strnchrnul(const char *s, size_t count, int c)
  */
 char *strrchr(const char *s, int c)
 {
-	const char *last = NULL;
-	do {
-		if (*s == (char)c)
-			last = s;
-	} while (*s++);
-	return (char *)last;
+	return __generic_strrchr(s, c);
 }
 EXPORT_SYMBOL(strrchr);
 #endif
-- 
2.25.1