On 5/28/24 2:16 AM, John Hubbard wrote: > When building with clang, via: > > make LLVM=1 -C tools/testing/selftests > > ...there are several warnings, and an error. This fixes all of those and > allows these tests to run and pass. > > 1. Fix linker error (undefined reference to memcpy) by providing a local > version of memcpy. > > 2. clang complains about using this form: > > if (g = h & 0xf0000000) > > ...so factor out the assignment into a separate step. > > 3. The code is passing a signed const char* to elf_hash(), which expects > a const unsigned char *. There are several callers, so fix this at > the source by allowing the function to accept a signed argument, and > then converting to unsigned operations, once inside the function. > > 4. clang doesn't have __attribute__((externally_visible)) and generates > a warning to that effect. Fortunately, gcc 12 and gcc 13 do not seem > to require that attribute in order to build, run and pass tests here, > so remove it. Just checked with GCC 5.1, it builds fine without any errors.
> > [1] > https://lore.kernel.org/all/20240329-selftests-libmk-llvm-rfc-v1-1-2f9ed7d1c...@valentinobst.de/ > > Signed-off-by: John Hubbard <[email protected]> LGTM Reviewed-by: Muhammad Usama Anjum <[email protected]> Tested-by: Muhammad Usama Anjum <[email protected]> > --- > > Changes since the first version: > > 1) Rebased onto Linux 6.10-rc1 > > thanks, > John Hubbard > > tools/testing/selftests/vDSO/parse_vdso.c | 16 +++++++++++----- > .../selftests/vDSO/vdso_standalone_test_x86.c | 18 ++++++++++++++++-- > 2 files changed, 27 insertions(+), 7 deletions(-) > > diff --git a/tools/testing/selftests/vDSO/parse_vdso.c > b/tools/testing/selftests/vDSO/parse_vdso.c > index 413f75620a35..4ae417372e9e 100644 > --- a/tools/testing/selftests/vDSO/parse_vdso.c > +++ b/tools/testing/selftests/vDSO/parse_vdso.c > @@ -55,14 +55,20 @@ static struct vdso_info > ELF(Verdef) *verdef; > } vdso_info; > > -/* Straight from the ELF specification. */ > -static unsigned long elf_hash(const unsigned char *name) > +/* > + * Straight from the ELF specification...and then tweaked slightly, in order > to > + * avoid a few clang warnings. > + */ > +static unsigned long elf_hash(const char *name) > { > unsigned long h = 0, g; > - while (*name) > + const unsigned char *uch_name = (const unsigned char *)name; > + > + while (*uch_name) > { > - h = (h << 4) + *name++; > - if (g = h & 0xf0000000) > + h = (h << 4) + *uch_name++; > + g = h & 0xf0000000; > + if (g) > h ^= g >> 24; > h &= ~g; > } > diff --git a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c > b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c > index 8a44ff973ee1..27f6fdf11969 100644 > --- a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c > +++ b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c > @@ -18,7 +18,7 @@ > > #include "parse_vdso.h" > > -/* We need a libc functions... */ > +/* We need some libc functions... */ > int strcmp(const char *a, const char *b) > { > /* This implementation is buggy: it never returns -1. */ > @@ -34,6 +34,20 @@ int strcmp(const char *a, const char *b) > return 0; > } > > +/* > + * The clang build needs this, although gcc does not. > + * Stolen from lib/string.c. > + */ > +void *memcpy(void *dest, const void *src, size_t count) > +{ > + char *tmp = dest; > + const char *s = src; > + > + while (count--) > + *tmp++ = *s++; > + return dest; > +} > + > /* ...and two syscalls. This is x86-specific. */ > static inline long x86_syscall3(long nr, long a0, long a1, long a2) > { > @@ -70,7 +84,7 @@ void to_base10(char *lastdig, time_t n) > } > } > > -__attribute__((externally_visible)) void c_main(void **stack) > +void c_main(void **stack) > { > /* Parse the stack */ > long argc = (long)*stack; > > base-commit: 2bfcfd584ff5ccc8bb7acde19b42570414bf880b -- BR, Muhammad Usama Anjum
