From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Tri Vo <trong@android.com>
Cc: irogers@google.com, Nick Desaulniers <ndesaulniers@google.com>,
stefan@agner.ch, Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: CONFIG_FRAME_POINTER support for Clang
Date: Fri, 31 May 2019 00:13:46 +0100 [thread overview]
Message-ID: <20190530231346.ede52pjznj3pgfll@shell.armlinux.org.uk> (raw)
In-Reply-To: <CANA+-vBHL9a9fXDWxALXXuJk6r8ObZZjhrGp-p5JUnfOThEV5g@mail.gmail.com>
On Thu, May 30, 2019 at 03:56:06PM -0700, Tri Vo 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 However, APCS is obsolete and Clang doesn't support it.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
What format stack frames does Clang use? I don't use clang, never seen
any clang ARM assembly, so I've no idea on this.
> 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
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
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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
2019-05-30 23:13 ` Russell King - ARM Linux admin [this message]
2019-05-31 0:03 ` Tri Vo
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