linux-kernel - [PATCH] x86/csum: Move csum_tail result parameter to a local variable.

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Message-Id: <20230530135953.3341174-1-trix@redhat.com>
Date:   Tue, 30 May 2023 09:59:53 -0400
From:   Tom Rix <trix@...hat.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, nathan@...nel.org,
        ndesaulniers@...gle.com, goldstein.w.n@...il.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] x86/csum: Move csum_tail result parameter to a local variable.

clang with W=1 reports
arch/x86/lib/csum-partial_64.c:74:20: error: variable
  'result' is uninitialized when used here [-Werror,-Wuninitialized]
                return csum_tail(result, temp64, odd);
                                 ^~~~~~
This is a false positive, but there is never an intermediate value
of result to pass into csum_trail, so move the parameter result to
a local variable.

Signed-off-by: Tom Rix <trix@...hat.com>
---
 arch/x86/lib/csum-partial_64.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
index fe5861951b15..cea25ca8b8cf 100644
--- a/arch/x86/lib/csum-partial_64.c
+++ b/arch/x86/lib/csum-partial_64.c
@@ -21,8 +21,10 @@ static inline unsigned short from32to16(unsigned a)
 	return b;
 }
 
-static inline __wsum csum_tail(unsigned int result, u64 temp64, int odd)
+static inline __wsum csum_tail(u64 temp64, int odd)
 {
+	unsigned int result;
+
 	result = add32_with_carry(temp64 >> 32, temp64 & 0xffffffff);
 	if (unlikely(odd)) {
 		result = from32to16(result);
@@ -45,7 +47,7 @@ static inline __wsum csum_tail(unsigned int result, u64 temp64, int odd)
 __wsum csum_partial(const void *buff, int len, __wsum sum)
 {
 	u64 temp64 = (__force u64)sum;
-	unsigned odd, result;
+	unsigned odd;
 
 	odd = 1 & (unsigned long) buff;
 	if (unlikely(odd)) {
@@ -71,7 +73,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 		    "adcq $0,%[res]"
 		    : [res] "+r"(temp64)
 		    : [src] "r"(buff), "m"(*(const char(*)[40])buff));
-		return csum_tail(result, temp64, odd);
+		return csum_tail(temp64, odd);
 	}
 	if (unlikely(len >= 64)) {
 		/*
@@ -141,7 +143,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum)
 		    : [res] "+r"(temp64)
 		    : [trail] "r"(trail));
 	}
-	return csum_tail(result, temp64, odd);
+	return csum_tail(temp64, odd);
 }
 EXPORT_SYMBOL(csum_partial);
 
-- 
2.27.0