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

["Rémi Denis-Courmont" <remi@remlab.net>]

Le 28 juillet 2024 07:37:51 GMT+03:00, Brad Smith <brad-at-comstyle.com@ffmpeg.org> a écrit :
>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.

I don't personally have a strong opinion on the details, I just don't fancy unnecessary duplication.

>
>>> #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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