From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Ian Rogers <irogers@google.com>
Cc: Tri Vo <trong@android.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Stefan Agner <stefan@agner.ch>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Matthias Kaehlcke <mka@chromium.org>,
Manoj Gupta <manojgupta@google.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: CONFIG_FRAME_POINTER support for Clang
Date: Fri, 31 May 2019 00:14:18 +0100 [thread overview]
Message-ID: <20190530231418.nuwn2kfatcn6cxlc@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAP-5=fUQQAEcZQ4KXAa8pLQFnD0nrN42faYGY2NPAziguTnwKg@mail.gmail.com>
On Thu, May 30, 2019 at 04:12:05PM -0700, Ian Rogers wrote:
> Would it be practical to use __builtin_return_address for the caller's PC?
That works for arguments of zero, but guaranteed for non-zero arguments.
>
> Thanks,
> Ian
>
> On Thu, May 30, 2019 at 3:58 PM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > + Some more lists/people
> >
> > On Thu, May 30, 2019 at 3:56 PM Tri Vo <trong@android.com> wrote:
> > >
> > > Hello Russell,
> > >
> > > I'm trying to implement support for CONFIG_FRAME_POINTER when building Linux
> > > with Clang compiler.
> > >
> > > Currently, CONFIG_FRAME_POINTER relies on function prologue that is emitted by
> > > GCC using -mapcs flag. However, APCS is obsolete and Clang doesn't support it.
> > >
> > > So in order to accommodate Clang-emitted frame layout, I'm thinking of
> > > providing Clang-specific implementation of code that relies on frame pointer,
> > > most notably in these files:
> > > lib/backtrace.S
> > > arch/arm/kernel/stacktrace.c
> > > arch/arm/net/bpf_jit_32.c
> > >
> > > This will likely involve putting "#ifdef CC_IS_CLANG" statements in the source
> > > code. Is that OK?
> > >
> > > Another caveat is that Clang implementation of backtracing won't be able to
> > > dump saved registers or dump precise pc value of the caller, because IIUC that
> > > information is derived from APCS's fixed prologue.
> > >
> > > What do you think about this approach?
> > >
> > > Thanks,
> > > Tri
> >
> >
> >
> > --
> > Thanks,
> > ~Nick Desaulniers
>
--
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next prev parent reply other threads:[~2019-05-30 23:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 22:56 CONFIG_FRAME_POINTER support for Clang Tri Vo
2019-05-30 22:58 ` Nick Desaulniers
2019-05-30 23:12 ` Ian Rogers
2019-05-30 23:14 ` Russell King - ARM Linux admin [this message]
2019-05-30 23:13 ` Russell King - ARM Linux admin
2019-05-31 0:03 ` Tri Vo
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