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Sullivan" , Joe Lawrence Cc: live-patching@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, pmladek@suse.com, mbenes@suse.cz, jikos@kernel.org, jpoimboe@kernel.org, naveen.n.rao@linux.ibm.com, christophe.leroy@csgroup.eu, npiggin@gmail.com Subject: Re: [PATCH] powerpc/ftrace: restore r2 to caller's stack on livepatch sibling call In-Reply-To: References: <87ed6q13xk.fsf@mail.lhotse> <20240815160712.4689-1-rysulliv@redhat.com> <9ec85e72-85dd-e9bc-6531-996413014629@redhat.com> Date: Tue, 10 Sep 2024 17:21:57 +1000 Message-ID: <87bk0wrn1m.fsf@mail.lhotse> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Post: List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain "Ryan B. Sullivan" 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