[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20241017093515.GU16066@noisy.programming.kicks-ass.net>
Date: Thu, 17 Oct 2024 11:35:15 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Mike Rapoport <rppt@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Andreas Larsson <andreas@...sler.com>,
Andy Lutomirski <luto@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Brian Cain <bcain@...cinc.com>,
Catalin Marinas <catalin.marinas@....com>,
Christoph Hellwig <hch@...radead.org>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Dinh Nguyen <dinguyen@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Guo Ren <guoren@...nel.org>, Helge Deller <deller@....de>,
Huacai Chen <chenhuacai@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Johannes Berg <johannes@...solutions.net>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
Kent Overstreet <kent.overstreet@...ux.dev>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Mark Rutland <mark.rutland@....com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Matt Turner <mattst88@...il.com>, Max Filippov <jcmvbkbc@...il.com>,
Michael Ellerman <mpe@...erman.id.au>,
Michal Simek <monstr@...str.eu>, Oleg Nesterov <oleg@...hat.com>,
Palmer Dabbelt <palmer@...belt.com>,
Richard Weinberger <richard@....at>,
Russell King <linux@...linux.org.uk>, Song Liu <song@...nel.org>,
Stafford Horne <shorne@...il.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Uladzislau Rezki <urezki@...il.com>,
Vineet Gupta <vgupta@...nel.org>, Will Deacon <will@...nel.org>,
bpf@...r.kernel.org, linux-alpha@...r.kernel.org,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
linux-mips@...r.kernel.org, linux-mm@...ck.org,
linux-modules@...r.kernel.org, linux-openrisc@...r.kernel.org,
linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-sh@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
linux-trace-kernel@...r.kernel.org, linux-um@...ts.infradead.org,
linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v6 6/8] x86/module: prepare module loading for ROX
allocations of text
On Wed, Oct 16, 2024 at 05:01:28PM -0400, Steven Rostedt wrote:
> On Wed, 16 Oct 2024 15:24:22 +0300
> Mike Rapoport <rppt@...nel.org> wrote:
>
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index 8da0e66ca22d..b498897b213c 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -118,10 +118,13 @@ ftrace_modify_code_direct(unsigned long ip, const char *old_code,
> > return ret;
> >
> > /* replace the text with the new text */
> > - if (ftrace_poke_late)
> > + if (ftrace_poke_late) {
> > text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
> > - else
> > - text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
> > + } else {
> > + mutex_lock(&text_mutex);
> > + text_poke((void *)ip, new_code, MCOUNT_INSN_SIZE);
> > + mutex_unlock(&text_mutex);
> > + }
> > return 0;
> > }
>
> So this slows down the boot by over 30ms. That may not sound like much, but
> we care very much about boot times. This code is serialized with boot and
> runs whenever ftrace is configured in the kernel. The way I measured this,
> was that I added:
>
> If this is only needed for module load, can we at least still use the
> text_poke_early() at boot up?
Right, so I don't understand why this is needed at all.
ftrace_module_init() runs before complete_formation() which normally
switches to ROX, as such ftrace should be able to continue to do direct
modifications here.
Which reminds me, at some point I did patches adding a
MODULE_STATE_UNFORMED callback in order for static_call / jump_label to
be able to avoid the expensive patching on module load as well (arguably
ftrace should be using that too, instead of a custom callback).
Powered by blists - more mailing lists