From: Nathan Chancellor <nathan@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Cristian Marussi <cristian.marussi@arm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Linus Walleij <linus.walleij@linaro.org>,
Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH v3 08/13] ARM: ftrace: enable the graph tracer with the EABI unwinder
Date: Thu, 3 Feb 2022 09:09:01 -0700 [thread overview]
Message-ID: <Yfv+HbjgHRpKe27O@dev-arch.archlinux-ax161> (raw)
In-Reply-To: <CAK8P3a0j1Y9pEDVGG0aQx3iKs8zUjpaz2YmbJnfuA5vPOnbaaA@mail.gmail.com>
On Thu, Feb 03, 2022 at 10:16:57AM +0100, Arnd Bergmann wrote:
> On Thu, Feb 3, 2022 at 9:21 AM Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > Enable the function graph tracer in combination with the EABI unwinder,
> > so that Thumb2 builds or Clang ARM builds can make use of it.
> >
> > This involves using the unwinder to locate the return address of an
> > instrumented function on the stack, so that it can be overridden and
> > made to refer to the ftrace handling routines that need to be called at
> > function return.
> >
> > Given that for these builds, it is not guaranteed that the value of the
> > link register is stored on the stack, fall back to the stack slot that
> > will be used by the ftrace exit code to restore LR in the instrumented
> > function's execution context.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
>
> > diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
> > index 07055a503022..cc7523f44be4 100644
> > --- a/arch/arm/Kconfig.debug
> > +++ b/arch/arm/Kconfig.debug
> > @@ -65,7 +65,7 @@ config UNWINDER_FRAME_POINTER
> >
> > config UNWINDER_ARM
> > bool "ARM EABI stack unwinder"
> > - depends on AEABI && !FUNCTION_GRAPH_TRACER
> > + depends on AEABI
> > # https://github.com/ClangBuiltLinux/linux/issues/732
> > depends on !LD_IS_LLD || LLD_VERSION >= 110000
> > select ARM_UNWIND
>
> What are the remaining tradeoffs between the two unwinders
> on EABI kernels? Since we require llvm-11 as the minimum
> toolchain now, we can probably drop the LLD_VERSION
> check here as well, so UNWINDER_ARM should finally work
> for any EABI kernel.
For what it's worth, that check was eliminated in the same series as
bumping the minimum version: e1ab4182ca11 ("Revert "ARM: 9070/1: Make
UNWINDER_ARM depend on ld.bfd or ld.lld 11.0.0+"")
Cheers,
Nathan
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next prev parent reply other threads:[~2022-02-03 16:10 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 8:21 [PATCH v3 00/13] ARM: ftrace fixes and cleanups Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 01/13] ARM: ftrace: ensure that ADR takes the Thumb bit into account Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 02/13] ARM: ftrace: use ADD not POP to counter PUSH at entry Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 03/13] ARM: ftrace: use trampolines to keep .init.text in branching range Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 04/13] ARM: ftrace: avoid redundant loads or clobbering IP Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 05/13] ARM: ftrace: avoid unnecessary literal loads Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 06/13] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST Ard Biesheuvel
2022-02-03 8:21 ` [PATCH v3 07/13] ARM: unwind: track location of LR value in stack frame Ard Biesheuvel
2022-02-07 18:14 ` Nick Desaulniers
2022-02-03 8:21 ` [PATCH v3 08/13] ARM: ftrace: enable the graph tracer with the EABI unwinder Ard Biesheuvel
2022-02-03 9:16 ` Arnd Bergmann
2022-02-03 9:41 ` Ard Biesheuvel
2022-02-03 16:09 ` Nathan Chancellor [this message]
2022-02-03 16:11 ` Ard Biesheuvel
2022-02-03 8:22 ` [PATCH v3 09/13] ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds Ard Biesheuvel
2022-02-03 8:22 ` [PATCH v3 10/13] drivers/firmware/scmi: disable ftrace for Clang " Ard Biesheuvel
2022-02-07 18:28 ` Sudeep Holla
2022-02-08 21:18 ` Ard Biesheuvel
2022-02-11 9:56 ` Sudeep Holla
2022-02-03 8:22 ` [PATCH v3 11/13] ARM: cacheflush: avoid clobbering the frame pointer Ard Biesheuvel
2022-02-07 19:12 ` Nick Desaulniers
2022-02-08 10:08 ` Ard Biesheuvel
2022-02-08 22:34 ` Nick Desaulniers
2022-02-08 22:39 ` Nick Desaulniers
2022-02-03 8:22 ` [PATCH v3 12/13] ARM: mach-bcm: disable ftrace in SMC invocation routines Ard Biesheuvel
2022-02-03 20:39 ` Nick Desaulniers
2022-02-03 8:22 ` [PATCH v3 13/13] Revert "ARM: 9144/1: forbid ftrace with clang and thumb2_kernel" Ard Biesheuvel
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