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 <[email protected]>
---
v2: update commit message with correct compiler warning
v3: fix checkpatch errors and indentation
---
tools/testing/selftests/vDSO/parse_vdso.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
index 413f75620a35..9e29ff0657ea 100644
--- a/tools/testing/selftests/vDSO/parse_vdso.c
+++ b/tools/testing/selftests/vDSO/parse_vdso.c
@@ -203,8 +203,9 @@ 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];
--
2.45.0.rc0.197.gbae5840b3b-goog
Hi,
On Wed, May 01, 2024 at 06:06:18PM +0000, Edward Liaw wrote:
> 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 <[email protected]>
> ---
> v2: update commit message with correct compiler warning
> v3: fix checkpatch errors and indentation
> ---
> tools/testing/selftests/vDSO/parse_vdso.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/vDSO/parse_vdso.c b/tools/testing/selftests/vDSO/parse_vdso.c
> index 413f75620a35..9e29ff0657ea 100644
> --- a/tools/testing/selftests/vDSO/parse_vdso.c
> +++ b/tools/testing/selftests/vDSO/parse_vdso.c
> @@ -203,8 +203,9 @@ void *vdso_sym(const char *version, const char *name)
Is it possible to just change the types of the parameters of vdso_sym()
or does that trigger even more warnings on the callsites of vdso_sym()?
Either way, this looks ok to me.
Acked-by: Justin Stitt <[email protected]>
> 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];
> --
> 2.45.0.rc0.197.gbae5840b3b-goog
>
Thanks
Justin
From: Justin Stitt
> Sent: 01 May 2024 20:55
..
> > static unsigned long elf_hash(const unsigned char *name)
..
> Is it possible to just change the types of the parameters of vdso_sym()
> or does that trigger even more warnings on the callsites of vdso_sym()?
Isn't the problem the definition of elf_hash()?
A '\0' terminated string really ought to be 'char *' not 'unsigned char *'.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
On Sun, May 5, 2024 at 6:21 AM David Laight <[email protected]> wrote:
>
> From: Justin Stitt
> > Sent: 01 May 2024 20:55
> ...
> > > static unsigned long elf_hash(const unsigned char *name)
> ...
> > Is it possible to just change the types of the parameters of vdso_sym()
> > or does that trigger even more warnings on the callsites of vdso_sym()?
>
> Isn't the problem the definition of elf_hash()?
> A '\0' terminated string really ought to be 'char *' not 'unsigned char *'.
Right, although note this comment just about its definition:
/* Straight from the ELF specification. */
static unsigned long elf_hash(const unsigned char *name)
{
which indeed matches [1]
[1]: https://man.freebsd.org/cgi/man.cgi?query=elf_hash&sektion=3&apropos=0&manpath=FreeBSD+7.1-RELEASE
>
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>
From: Edward Liaw
> Sent: 06 May 2024 18:34
>
> On Mon, May 6, 2024 at 10:16 AM Justin Stitt <[email protected]> wrote:
> >
> > On Sun, May 5, 2024 at 6:21 AM David Laight <[email protected]> wrote:
> > >
> > > From: Justin Stitt
> > > > Sent: 01 May 2024 20:55
> > > ...
> > > > > static unsigned long elf_hash(const unsigned char *name)
> > > ...
> > > > Is it possible to just change the types of the parameters of vdso_sym()
> > > > or does that trigger even more warnings on the callsites of vdso_sym()?
> > >
> > > Isn't the problem the definition of elf_hash()?
> > > A '\0' terminated string really ought to be 'char *' not 'unsigned char *'.
> >
> > Right, although note this comment just about its definition:
> >
> > /* Straight from the ELF specification. */
> > static unsigned long elf_hash(const unsigned char *name)
> > {
> >
> > which indeed matches [1]
> >
> > [1]: https://man.freebsd.org/cgi/man.cgi?query=elf_hash&sektion=3&apropos=0&manpath=FreeBSD+7.1-
> RELEASE
>
> How about I move the type cast into elf_hash, like libelf does
> https://sourceforge.net/p/elftoolchain/code/HEAD/tree/trunk/libelf/elf_hash.c#l47
>
> 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;
That makes a lot more sense.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
On Mon, May 6, 2024 at 12:32 PM David Laight <[email protected]> wrote:
>
>
> That makes a lot more sense.
I sent v4 https://lore.kernel.org/all/[email protected]/.
I updated the commit log to reflect the change but I'm not sure if I
did it right for the mailing list. Should I have added --in-reply-to
this thread?
Edward