Re: [Qemu-devel] [PATCH] linux-user: implement HWCAP bits on MIPS

[Laurent Vivier]

Le 15/03/2018 à 11:52, James Cowgill a écrit :
> Hi,
> 
> On 14/03/18 16:13, Laurent Vivier wrote:
>> Le 14/03/2018 à 16:31, James Cowgill a écrit :
>>> Add support for the two currently defined HWCAP bits on MIPS - R6 and
>>> MSA.
>>>
>>> Buglink: https://bugs.launchpad.net/qemu/+bug/1754372
>>> Signed-off-by: James Cowgill <address@hidden>
>>> ---
>>> This was resent because I think I messed up my email config. Apologies if 
>>> you
>>> receive this twice.
>>>
>>>  linux-user/elfload.c | 24 ++++++++++++++++++++++++
>>>  1 file changed, 24 insertions(+)
>>>
>>> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
>>> index 5fc130cc20..747b0ed10b 100644
>>> --- a/linux-user/elfload.c
>>> +++ b/linux-user/elfload.c
>>> @@ -950,6 +950,30 @@ static void elf_core_copy_regs(target_elf_gregset_t 
>>> *regs, const CPUMIPSState *e
>>>  #define USE_ELF_CORE_DUMP
>>>  #define ELF_EXEC_PAGESIZE        4096
>>>  
>>> +/* See arch/mips/include/uapi/hwcap.h.  */
>>
>> in fact arch/mips/include/uapi/asm/hwcap.h
> 
> Woops.
> 
>>> +enum {
>>> +    HWCAP_MIPS_R6           = (1 << 0),
>>> +    HWCAP_MIPS_MSA          = (1 << 1),
>>> +};
>>
>> We have this for ARM only in elfload.c since:
>>
>>     afce2927aa Arm AT_HWCAP AUXV entry (Paul Brook) [2005]
>>
>> but they have been added in include/elf.h since:
>>
>>     41d9ea80ac tcg-arm: Use qemu_getauxval [Richard Henderson, 2013]
>>
>> and I think we should remove them (they are prefixed by ARM_)
>>
>> So the MIPS ones should be in include/elf.h (with the #define form).
> 
> I can do that, although I think it's a bit unusual. The HWCAP bits are
> specific to the Linux kernel and not to "the MIPS ELF format" so it
> doesn't make sense to me to put them in elf.h.

In fact, in a system, they come with the glibc <sys/auxv.h>. auxv.h
includes <elf.h> and <bits/hwcap.h>. They are both part of glibc.

They can be used with qemu_getauxval() so it's better to have them in a
header file. elfoad.c or elf.h, it's in both cases an ELF file.

Thanks,
Laurent