linux-kernel - Re: [PATCH] ftrace: Allow inline functions not inlined to be traced

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Date:   Fri, 9 Jun 2023 17:29:02 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Song Liu <song@...nel.org>, live-patching@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] ftrace: Allow inline functions not inlined to be traced

On Thu, 8 Jun 2023 10:50:51 +0100
Mark Rutland <mark.rutland@....com> wrote:


> Unfortunately, from a quick build-test of arm64 there are a bunch of places
> that are currently inline that need to be __always_inline for this to be safe.
> Notably we have a few low-level helpers like is_kernel_in_hyp_mode() that are
> only inlines, and those get used in the bowels of our entry code before we've
> restored some HW state (e.g. in arch_nmi_enter()).

Sounds like you also need to add noinstr ;-)

> 
> I'm happy to go audit and fixup arm64, but that will take some work.
> 
> Maybe it's worth having something like:
> 
> #ifdef ARCH_CAN_TRACE_INLINE
> #define __notrace_inline
> #else
> #define __notrace_inline	notrace
> #endif
> 
> ... so that we can opt-in where this is safe, (e.g. on x86)?

I guess I can do that.

-- Steve