Re: [PATCH] parisc: Add initial vDSO support

[Rolf Eike Beer <eike-kernel@sf-tec.de>]

[-- Attachment #1: Type: text/plain, Size: 1636 bytes --]

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@tausq.org/
> 
> 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.

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.

Eike

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 195 bytes --]