Re: [FFmpeg-devel] aarch64: Implement support for elf_aux_info(3) on FreeBSD and OpenBSD

[Brad Smith <brad-at-comstyle.com@ffmpeg.org>]

On 2024-07-26 7:56 a.m., Rémi Denis-Courmont wrote:
>
> Le 26 juillet 2024 13:58:34 GMT+03:00, Brad Smith <brad-at-comstyle.com@ffmpeg.org> a écrit :
>> aarch64: Implement support for elf_aux_info(3) on FreeBSD and OpenBSD
>>
>> FreeBSD 12.0+, OpenBSD -current and what will be OpenBSD 7.6 support
>> elf_aux_info(3).
>>
>> Signed-off-by: Brad Smith <brad@comstyle.com>
>> ---
>> configure               |  2 ++
>> libavutil/aarch64/cpu.c | 23 ++++++++++++++++++++++-
>> 2 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index f6f5c29fea..e80b549582 100755
>> --- a/configure
>> +++ b/configure
>> @@ -2366,6 +2366,7 @@ SYSTEM_FUNCS="
>>      clock_gettime
>>      closesocket
>>      CommandLineToArgvW
>> +    elf_aux_info
>>      fcntl
>>      getaddrinfo
>>      getauxval
>> @@ -6565,6 +6566,7 @@ check_func_headers mach/mach_time.h mach_absolute_time
>> check_func_headers stdlib.h getenv
>> check_func_headers sys/stat.h lstat
>> check_func_headers sys/auxv.h getauxval
>> +check_func_headers sys/auxv.h elf_aux_info
>> check_func_headers sys/sysctl.h sysctlbyname
>>
>> check_func_headers windows.h GetModuleHandle
>> diff --git a/libavutil/aarch64/cpu.c b/libavutil/aarch64/cpu.c
>> index cfa9306663..05272b4db4 100644
>> --- a/libavutil/aarch64/cpu.c
>> +++ b/libavutil/aarch64/cpu.c
>> @@ -42,6 +42,27 @@ static int detect_flags(void)
>>      return flags;
>> }
>>
>> +#elif (defined(__FreeBSD__) || defined(__OpenBSD__)) && HAVE_ELF_AUX_INFO
>> +#include <stdint.h>
>> +#include <sys/auxv.h>
>> +
>> +static int detect_flags(void)
>> +{
>> +    int flags = 0;
>> +
>> +    unsigned long hwcap = 0;
>> +    elf_aux_info(AT_HWCAP, &hwcap, sizeof hwcap);
>> +    unsigned long hwcap2 = 0;
>> +    elf_aux_info(AT_HWCAP2, &hwcap2, sizeof hwcap2);
>> +
>> +    if (hwcap & HWCAP_ASIMDDP)
>> +        flags |= AV_CPU_FLAG_DOTPROD;
>> +    if (hwcap2 & HWCAP2_I8MM)
>> +        flags |= AV_CPU_FLAG_I8MM;
>> +
>> +    return flags;
>> +}
>> +
> Can't getauxval() be implemented with elf_aux_info(), or vice versa? It seems that otherwise the code should be identical to that from Linux.

QEMU has qemu_getauxval() for example as a wrapper. I will be using this 
elsewhere for arm, ppc and riscv.

I could split this up, but I am not sure where to place such a function.

>> #elif defined(__APPLE__) && HAVE_SYSCTLBYNAME
>> #include <sys/sysctl.h>
>>
>> @@ -65,7 +86,7 @@ static int detect_flags(void)
>>      return flags;
>> }
>>
>> -#elif defined(__OpenBSD__)
>> +#elif defined(__OpenBSD__) && !HAVE_ELF_AUX_INFO
>> #include <machine/armreg.h>
>> #include <machine/cpu.h>
>> #include <sys/types.h>
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