[PATCH] powerpc/ftrace: restore r2 to caller's stack on livepatch sibling call

[Christophe Leroy]

Le 24/07/2024 à 20:33, Ryan Sullivan a écrit :
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> 
> Currently, on PowerPC machines, sibling calls in livepatched functions
> cause the stack to be corrupted and are thus not supported by tools
> such as kpatch. Below is an example stack frame showing one such
> currupted stacks:
> 
> RHEL-7.6: Linux 3.10.0 ppc64le
> 

...

> 
> This is caused by the toc stub generated on a sibling call:
> 

...

> 
> This patch restores r2 value to caller's stack, on a sibling call this
> will uncorrupt the caller's stack and otherwise will be redundant.

Be carefull. On powerpc/32, r2 contains the pointer to current struct. 
When I first read the subject of the patch I was puzzled.

You should say toc instead of r2, or make it explicit in the title that 
it is for powerpc/64

Christophe