Thread (12 messages) 12 messages, 4 authors, 2024-09-10

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

From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2024-09-10 07:22:01
Also in: live-patching

"Ryan B. Sullivan" [off-list ref] writes:
Hello all,

Just wanted to ping and see if there was any further feedback or
questions regarding the patch?
Hi Ryan,

I'd really like a selftest that triggers the sibling call behaviour.

As I said upthread I tried writing one but failed. Which you later
explained is because the cross-module sibling call is not generated by
the compiler but rather by the code being objcopy'ed (or similar).

I think it should be possible to trick the compiler into letting us do a
cross-module sibling call by doing it in an inline asm block. Obviously
that's non-standard, but I think it might work well enough for a test?

We have an example of calling a function within an inline asm block in
call_do_irq().

I'll try to find time to get that done, but I can't promise when.

cheers
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