[PATCH v2 0/8] ELF-FDPIC support for ARM

[Mickael GUENE]

Hi Nicolas,

  Thanks for explanation.

Regards
Mickael

On 08/24/2017 05:48 PM, Nicolas Pitre wrote:
> On Thu, 24 Aug 2017, Mickael GUENE wrote:
> 
>> Hi Nicolas,
>>
>>> The first one is.
>>    It also seems to me that 'Add tls support for cortex-m cpu family'
>> patch is missing. There is the one that add the get_tls syscall but
>> not this one which enable usage for cortex-m family.
> 
> The patch titled "Add tls support for cortex-m cpu family" in your
> repository does 3 things:
> 
> - It defines switch_tls to switch_tls_none. Without the patch the
>    default is switch_tls_software. But this has no purpose as on Cortex-M
>    targets there is simply no switch_tls usage at all. The switch_tls
>    macro is invoked in entry-armv.S within __switch_to whereas Cortex-M
>    uses a different implementation of __switch_to in entry-v7m.S.
> 
> - The patch also defines has_tls_reg to 0. That's the same as de default
>    without the patch.
> 
> - It also defines tls_emu to 1. That makes no sense as this is for ARMv6
>    that lack the dedicated CP15 register and is completely wrong for
>    Cortex-M. I suspect the actual reason for defining this to 1 was a
>    dubious workaround to prevent set_tls() from storing the TLS value at
>    the absolute address 0xffff0ff0. In recent kernels that particular
>    code is properly conditioned on CONFIG_KUSER_HELPERS instead.
> 
> So in the current mainline kernel this patch is useless. This is why I
> didn't consider it.
> 
> 
> Nicolas
>