Re: [PATCH v1] elf: Replace `strcpy` call with `memcpy` [BZ #29454]

[Yann Droneaud <ydroneaud@opteya.com>]

Hi,


Le 08/08/2022 à 05:26, Noah Goldstein via Libc-alpha a écrit :
> GCC normally does this optimization for us in
> strlen_pass::handle_builtin_strcpy but only for optimized
> build. To avoid needing to include strcpy.S in the rtld build to
> support the debug build, just do the optimization by hand.

It does fixes this build issue I had when using -Og (using gcc 11.2, on amd64):

     gcc   -nostdlib -nostartfiles -shared -o .../build/elf/ld.so.new        \
           -Wl,-z,relro -Wl,-z,defs     \
           -Wl,-z,pack-relative-relocs \
           .../build/elf/librtld.os -Wl,--version-script=.../build/ld.map        \
           -Wl,-soname=ld-linux-x86-64.so.2
     /usr/bin/ld: .../build/elf/librtld.os: in function `_dl_load_cache_lookup':
     .../elf/dl-cache.c:513: undefined reference to `strcpy'
     collect2: error: ld returned 1 exit status
     make[2]: *** [Makefile:1347: .../build/elf/ld.so] Error 1
     make[2]: Leaving directory '.../elf'
     make[1]: *** [Makefile:484: elf/subdir_lib] Error 2
     make[1]: Leaving directory '...'
     make: *** [Makefile:9: all] Error 2

Thanks.

> ---
>   elf/dl-cache.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/elf/dl-cache.c b/elf/dl-cache.c
> index 8bbf110d02..b97c17b3a9 100644
> --- a/elf/dl-cache.c
> +++ b/elf/dl-cache.c
> @@ -509,8 +509,9 @@ _dl_load_cache_lookup (const char *name)
>        we are accessing. Therefore we must make the copy of the
>        mapping data without using malloc.  */
>     char *temp;
> -  temp = alloca (strlen (best) + 1);
> -  strcpy (temp, best);
> +  size_t best_len = strlen (best) + 1;
> +  temp = alloca (best_len);
> +  memcpy (temp, best, best_len);
>     return __strdup (temp);
>   }
>   


Regards.

-- 

Yann Droneaud

OPTEYA