From: Carlos Llamas <cmllamas@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Sami Tolvanen" <samitolvanen@google.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will@kernel.org>,
"Josh Poimboeuf" <jpoimboe@kernel.org>,
"Jason Baron" <jbaron@akamai.com>,
"Alice Ryhl" <aliceryhl@google.com>,
"Steven Rostedt" <rostedt@goodmis.org>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Arnaldo Carvalho de Melo" <acme@kernel.org>,
"Namhyung Kim" <namhyung@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
"Jiri Olsa" <jolsa@kernel.org>, "Ian Rogers" <irogers@google.com>,
"Adrian Hunter" <adrian.hunter@intel.com>,
"James Clark" <james.clark@linaro.org>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Vincent Guittot" <vincent.guittot@linaro.org>,
"Dietmar Eggemann" <dietmar.eggemann@arm.com>,
"Ben Segall" <bsegall@google.com>, "Mel Gorman" <mgorman@suse.de>,
"Valentin Schneider" <vschneid@redhat.com>,
"Kees Cook" <kees@kernel.org>,
"Linus Walleij" <linusw@kernel.org>,
"Borislav Petkov (AMD)" <bp@alien8.de>,
"Nathan Chancellor" <nathan@kernel.org>,
"Thomas Gleixner" <tglx@kernel.org>,
"Mathieu Desnoyers" <mathieu.desnoyers@efficios.com>,
"Shaopeng Tan" <tan.shaopeng@jp.fujitsu.com>,
"Jens Remus" <jremus@linux.ibm.com>,
"Juergen Gross" <jgross@suse.com>,
"Conor Dooley" <conor.dooley@microchip.com>,
"David Kaplan" <david.kaplan@amd.com>,
"Lukas Bulwahn" <lukas.bulwahn@redhat.com>,
"Jinjie Ruan" <ruanjinjie@huawei.com>,
"James Morse" <james.morse@arm.com>,
"Thomas Huth" <thuth@redhat.com>,
"Sean Christopherson" <seanjc@google.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
kernel-team@android.com, linux-kernel@vger.kernel.org,
"Will McVicker" <willmcvicker@google.com>,
"Thomas Weißschuh" <thomas.weissschuh@linutronix.de>,
"moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)"
<linux-arm-kernel@lists.infradead.org>,
"open list:PERFORMANCE EVENTS SUBSYSTEM"
<linux-perf-users@vger.kernel.org>
Subject: Re: [PATCH] static_call: use CFI-compliant return0 stubs
Date: Thu, 12 Mar 2026 00:16:01 +0000 [thread overview]
Message-ID: <abIFwSF1RqhC96C2@google.com> (raw)
In-Reply-To: <20260311231406.GZ606826@noisy.programming.kicks-ass.net>
On Thu, Mar 12, 2026 at 12:14:06AM +0100, Peter Zijlstra wrote:
> On Wed, Mar 11, 2026 at 10:57:40PM +0000, Carlos Llamas wrote:
> > Architectures with !HAVE_STATIC_CALL (such as arm64) rely on the generic
> > static_call implementation via indirect calls. In particular, users of
> > DEFINE_STATIC_CALL_RET0, default to the generic __static_call_return0
> > stub to optimize the unset path.
> >
> > However, __static_call_return0 has a fixed signature of "long (*)(void)"
> > which may not match the expected prototype at callsites. This triggers
> > CFI failures when CONFIG_CFI is enabled. A trivial linux-perf command
> > does it:
>
> *sigh*...
>
> And ARM64 can't really do the inline thing because its immediate range
> is too small and it all turns into a mess constructing the address in a
> register and doing an indirect call anyway, right?
>
Right, the range for the jump is very limited. I _think_ tracepoints
have managed to implement the trampoline work-around:
arch/arm64/kernel/ftrace.c
So it looks do-able I think but a much complex route.
--
Carlos Llamas
next prev parent reply other threads:[~2026-03-12 0:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260309223156.GA73501@google.com>
2026-03-11 22:57 ` [PATCH] static_call: use CFI-compliant return0 stubs Carlos Llamas
2026-03-11 23:14 ` Peter Zijlstra
2026-03-12 0:16 ` Carlos Llamas [this message]
2026-03-12 7:40 ` Ard Biesheuvel
2026-03-12 8:07 ` Peter Zijlstra
2026-03-12 17:18 ` Carlos Llamas
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