From: Michael Ellerman <mpe@ellerman.id.au>
To: Ryan Sullivan <rysulliv@redhat.com>,
live-patching@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: rysulliv@redhat.com, joe.lawrence@redhat.com, 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
Date: Thu, 15 Aug 2024 20:22:15 +1000 [thread overview]
Message-ID: <87ed6q13xk.fsf@mail.lhotse> (raw)
In-Reply-To: <20240729150246.8939-1-rysulliv@redhat.com>
Ryan Sullivan <rysulliv@redhat.com> writes:
> Hello Michael,
>
> In the case of no sibling call within the livepatch then the store is
> only "restoring" the r2 value that was already there as it is stored
> and retrieved from the livepatch stack.
But what guarantee do we have that it's the value that was already
there?
Notice that the current livepatch_handler doesn't store to the (normal)
stack at all, because it doesn't know the context it's called in.
Does kpatch do anything special to induce the sibling call? Is it doing
objcopy or anything else weird?
I tried writing a selftest (in tools/testing/selftests/livepatch) to
trigger this case but couldn't get it to work. The compiler never
generates a sibling call across modules.
cheers
next prev parent reply other threads:[~2024-08-15 10:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-24 18:33 [PATCH] powerpc/ftrace: restore r2 to caller's stack on livepatch sibling call Ryan Sullivan
2024-07-29 14:17 ` Michael Ellerman
2024-07-29 15:02 ` Ryan Sullivan
2024-08-15 10:22 ` Michael Ellerman [this message]
2024-08-15 16:07 ` Ryan Sullivan
2024-08-15 16:24 ` Joe Lawrence
2024-09-09 16:33 ` Ryan B. Sullivan
2024-09-10 7:21 ` Michael Ellerman
2024-09-10 15:02 ` Ryan B. Sullivan
2024-08-08 7:00 ` Christophe Leroy
2024-08-08 17:55 ` [PATCH v2] powerpc/ftrace: restore caller's toc on ppc64 " Ryan Sullivan
2024-08-08 21:17 ` Ryan Sullivan
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