linux-kernel - [PATCH v4] selftests/vDSO: change elf

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Message-ID: <20240506181951.1804451-1-edliaw@google.com>
Date: Mon,  6 May 2024 18:19:49 +0000
From: Edward Liaw <edliaw@...gle.com>
To: linux-kernel@...r.kernel.org, Shuah Khan <shuah@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Nick Desaulniers <ndesaulniers@...gle.com>, 
	Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
	Andy Lutomirski <luto@....edu>, "H. Peter Anvin" <hpa@...ux.intel.com>
Cc: linux-kselftest@...r.kernel.org, kernel-team@...roid.com, 
	Edward Liaw <edliaw@...gle.com>, llvm@...ts.linux.dev
Subject: [PATCH v4] selftests/vDSO: change elf_hash parameter to signed char

Fixes clang compilation warnings by changing elf_hash's parameter type
to char * and casting to unsigned char * inside elf_hash:

parse_vdso.c:206:22: warning: passing 'const char *' to parameter of
 type 'const unsigned char *' converts between pointers to integer types
 where one is of the unique plain 'char' type and the other is not
 [-Wpointer-sign]
        ver_hash = elf_hash(version);
                            ^~~~~~~
parse_vdso.c:59:52: note: passing argument to parameter 'name' here
static unsigned long elf_hash(const unsigned char *name)
                                                   ^
parse_vdso.c:207:46: warning: passing 'const char *' to parameter of
 type 'const unsigned char *' converts between pointers to integer types
 where one is of the unique plain 'char' type and the other is not
 [-Wpointer-sign]
        ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
                                                    ^~~~
parse_vdso.c:59:52: note: passing argument to parameter 'name' here
static unsigned long elf_hash(const unsigned char *name)

Fixes: 98eedc3a9dbf ("Document the vDSO and add a reference parser")
Signed-off-by: Edward Liaw <edliaw@...gle.com>
---
v2: updated commit message with correct compiler warning
v3: fixed checkpatch errors and indentation
https://lore.kernel.org/all/20240501180622.1676340-1-edliaw@google.com/
v4: moved the typecast into elf_hash based on libelf
https://sourceforge.net/p/elftoolchain/code/HEAD/tree/trunk/libelf/elf_hash.c#l47
---
 tools/testing/selftests/vDSO/parse_vdso.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
index 413f75620a35..33db8abd7d59 100644
--- a/tools/testing/selftests/vDSO/parse_vdso.c
+++ b/tools/testing/selftests/vDSO/parse_vdso.c
@@ -56,12 +56,15 @@ static struct vdso_info
 } vdso_info;

 /* Straight from the ELF specification. */
-static unsigned long elf_hash(const unsigned char *name)
+static unsigned long elf_hash(const char *name)
 {
 	unsigned long h = 0, g;
-	while (*name)
+	const unsigned char *s;
+
+	s = (const unsigned char *) name;
+	while (*s)
 	{
-		h = (h << 4) + *name++;
+		h = (h << 4) + *s++;
 		if (g = h & 0xf0000000)
 			h ^= g >> 24;
 		h &= ~g;
--
2.45.0.rc1.225.g2a3ae87e7f-goog