[PATCH] powerpc: Don't clobber fr0/vs0 during fp|altivec register save

[Linux regression tracking (Thorsten Leemhuis)]

On 19.11.23 00:45, Timothy Pearson wrote:
> During floating point and vector save to thread data fr0/vs0 are clobbered
> by the FPSCR/VSCR store routine.  This leads to userspace register corruption
> and application data corruption / crash under the following rare condition:
> [...]
> Tested-by: Timothy Pearson <tpearson at raptorengineering.com>

Many thx for this, good to see you finally found the problem.

FWIW, you might want to add a

 Closes:
https://lore.kernel.org/all/480932026.45576726.1699374859845.JavaMail.zimbra@raptorengineeringinc.com/

here. Yes, I care about those tags because of regression tracking. But
it only relies on Link:/Closes: tags because they were meant to be used
in the first place to link to backstories and details of a change[1].

And you and Jens did such good debugging in that thread, which is why
it's IMHO really worth linking here in case anyone ever needs to look
into the backstory later.

> Signed-off-by: Timothy Pearson <tpearson at raptorengineering.com>
> [..]

Thx again for all your work you put into this.

Ciao, Thorsten

[1] see Documentation/process/submitting-patches.rst
(http://docs.kernel.org/process/submitting-patches.html) and
Documentation/process/5.Posting.rst
(https://docs.kernel.org/process/5.Posting.html)

See also these mails from Linus:
https://lore.kernel.org/all/CAHk-=wjMmSZzMJ3Xnskdg4+GGz=5p5p+GSYyFBTh0f-DgvdBWg@mail.gmail.com/
https://lore.kernel.org/all/CAHk-=wgs38ZrfPvy=nOwVkVzjpM3VFU1zobP37Fwd_h9iAD5JQ@mail.gmail.com/
https://lore.kernel.org/all/CAHk-=wjxzafG-=J8oT30s7upn4RhBs6TX-uVFZ5rME+L5_DoJA@mail.gmail.com/