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From: Mark Rutland <mark.rutland@arm.com>
To: Florent Revest <revest@chromium.org>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
	bpf@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org,
	rostedt@goodmis.org, mhiramat@kernel.org, ast@kernel.org,
	daniel@iogearbox.net, andrii@kernel.org, kpsingh@kernel.org,
	jolsa@kernel.org, xukuohai@huaweicloud.com
Subject: Re: [PATCH 5/8] ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS
Date: Fri, 3 Feb 2023 10:03:38 +0000	[thread overview]
Message-ID: <Y9zb+uKqQN9gJJBI@FVFF77S0Q05N> (raw)
In-Reply-To: <CABRcYm+nwsyyKEhvz9dr8sDiOWfha-YxOkGMFSx4mH9O+HAiYg@mail.gmail.com>

On Thu, Feb 02, 2023 at 07:19:58PM +0100, Florent Revest wrote:
> On Thu, Feb 2, 2023 at 5:57 PM Mark Rutland <mark.rutland@arm.com> wrote:
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 84f717f8959e..3d2156e335d7 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -241,6 +241,12 @@ enum {
> >         FTRACE_OPS_FL_DIRECT                    = BIT(17),
> >  };
> >
> > +#ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> > +#define FTRACE_OPS_FL_SAVE_ARGS                        FTRACE_OPS_FL_SAVE_REGS
> > +#else
> > +#define FTRACE_OPS_FL_SAVE_ARGS                        0
> 
> Mh, could we (theoretically) be in a situation where an arch supports
> WITH_ARGS but it also has two ftrace_caller trampolines: one that
> saves the args and the other that saves nothing ? (For example if x86
> migrates their WITH_REGS to WITH_ARGS only)

I don't think so -- the point of WITH_ARGS is that we always have to
save/restore the args, and when WITH_ARGS is selected they're unconditionally
available (though not necessarily a full pt_regs), which is what other code
assumes when WITH_ARGS is selected.

> Wouldn't it make sense then to define FTRACE_OPS_FL_SAVE_ARGS as an
> extra bit to tell ftrace that we need the args, similarly to
> FTRACE_OPS_FL_SAVE_REGS ?
> 
> If that can't happen or if we want to leave this up for later, the
> patch lgtm and I can squash it into my patch 5 in v2. ;)

I think that can't happen, and for now the above should be fine.

Thanks,
Mark.

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  reply	other threads:[~2023-02-03 10:04 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-01 16:34 [PATCH 0/8] Add ftrace direct call for arm64 Florent Revest
2023-02-01 16:34 ` [PATCH 1/8] ftrace: Replace uses of _ftrace_direct APIs with _ftrace_direct_multi Florent Revest
2023-02-02 15:01   ` Mark Rutland
2023-02-02 17:37     ` Florent Revest
2023-02-07 15:21       ` Florent Revest
2023-02-07 15:35         ` Steven Rostedt
2023-02-07 16:19           ` Florent Revest
2023-02-01 16:34 ` [PATCH 2/8] ftrace: Remove the legacy _ftrace_direct API Florent Revest
2023-02-02 15:11   ` Mark Rutland
2023-02-01 16:34 ` [PATCH 3/8] ftrace: Rename _ftrace_direct_multi APIs to _ftrace_direct APIs Florent Revest
2023-02-02 15:17   ` Mark Rutland
2023-02-01 16:34 ` [PATCH 4/8] ftrace: Store direct called addresses in their ops Florent Revest
2023-02-02 15:29   ` Mark Rutland
2023-02-02 17:41     ` Florent Revest
2023-02-01 16:34 ` [PATCH 5/8] ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS Florent Revest
2023-02-02 15:54   ` Mark Rutland
2023-02-02 16:56     ` Mark Rutland
2023-02-02 18:19       ` Florent Revest
2023-02-03 10:03         ` Mark Rutland [this message]
2023-02-03 11:01           ` Florent Revest
2023-02-02 18:18     ` Florent Revest
2023-02-01 16:34 ` [PATCH 6/8] ftrace: Fix dead loop caused by direct call in ftrace selftest Florent Revest
2023-02-02 19:03   ` Mark Rutland
2023-02-03 12:35     ` Florent Revest
2023-02-03 15:37       ` Mark Rutland
2023-02-06 16:25         ` Florent Revest
2023-02-01 16:34 ` [PATCH 7/8] arm64: ftrace: Add direct call support Florent Revest
2023-02-03 15:34   ` Mark Rutland
2023-02-06 16:25     ` Florent Revest
2023-02-01 16:34 ` [PATCH 8/8] arm64: ftrace: Add direct called trampoline samples support Florent Revest
2023-02-02  8:36 ` [PATCH 0/8] Add ftrace direct call for arm64 Xu Kuohai
2023-02-02 10:50   ` Daniel Borkmann
2023-02-02 17:32     ` Florent Revest
2023-02-02 20:06 ` Steven Rostedt
2023-02-03  9:49   ` Mark Rutland

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