Re: [PATCH] parisc: Add initial vDSO support

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Hi Rolf,

On 1/29/22 15:55, Rolf Eike Beer wrote:
> Am Samstag, 29. Januar 2022, 12:03:42 CET schrieb Helge Deller:
>> Add minimal vDSO support, which provides the signal trampoline helpers, but
>> none of the userspace syscall helpers like time functions.
>>
>> The big benefit of this vDSO implementation is, that we now don't need an
>> executeable stack any longer. PA-RISC is one of the last architectures where
>> an executeable stack was needed in oder to implement the signal trampolines
>> by putting assembly instructions on the stack which then gets executed.
>> With this implementation the kernel will utilize the assembler statements
>> in the vDSO page which is mapped into each userspace application instead
>> and just put the pointers to the signal information on the stack.
>> By dropping the need for executable stacks we now avoid running into issues
>> with various applications in Debian which nowadays want non-executable
>> stacks for security reasons. Additionally, alternative stacks are supported
>> better as well.
>>
>> This code is based on an initial implementation by Randolph Chung from 2006:
>> https://lore.kernel.org/linux-parisc/4544A34A.6080700@xxxxxxxxx/
>>
>> I did the porting and lifted the code to current code base. Dave fixed the
>> unwind code so that gdb and glibc are able to backtrace through the code. An
>> additional patch to gdb will be pushed upstream by Dave.
>
> There are a few extra newlines in the first few files which you may or may not
> want to remove.

Thanks for noticing.
I fixed them up now.

> OTOH I would split out the change to mm_context_t into it's own patch, without
> adding the vdso_base there. This would reduce the overall size of the actual
> vdso patch and eases review.

Yes, maybe I'll do that. Not sure yet.

Helge




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