linux-kernel - [PATCH v2] selftests/vDSO: Explicit unsigned char conversion for elf

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Date: Mon, 29 Apr 2024 21:07:20 +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 v2] selftests/vDSO: Explicit unsigned char conversion for elf_hash

Fixes clang compilation warnings by adding explicit unsigned conversion:

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: update commit message with correct compiler warning
---
 tools/testing/selftests/vDSO/parse_vdso.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
index 413f75620a35..7e2ea9bea394 100644
--- a/tools/testing/selftests/vDSO/parse_vdso.c
+++ b/tools/testing/selftests/vDSO/parse_vdso.c
@@ -203,8 +203,8 @@ void *vdso_sym(const char *version, const char *name)
 	if (!vdso_info.valid)
 		return 0;

-	ver_hash = elf_hash(version);
-	ELF(Word) chain = vdso_info.bucket[elf_hash(name) % vdso_info.nbucket];
+	ver_hash = elf_hash((const unsigned char *)version);
+	ELF(Word) chain = vdso_info.bucket[elf_hash((const unsigned char *)name) % vdso_info.nbucket];

 	for (; chain != STN_UNDEF; chain = vdso_info.chain[chain]) {
 		ELF(Sym) *sym = &vdso_info.symtab[chain];
--
2.44.0.769.g3c40516874-goog