From: Arnd Bergmann <arnd@arndb.de>
To: Stefan Agner <stefan@agner.ch>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: use choice for kernel unwinders
Date: Wed, 22 Aug 2018 12:02:19 +0200 [thread overview]
Message-ID: <CAK8P3a0oaMS12R4tazChMHENQduO0-Wb-gw-inKjH0oz7_5s3g@mail.gmail.com> (raw)
In-Reply-To: <20180821222416.7771-1-stefan@agner.ch>
On Wed, Aug 22, 2018 at 12:24 AM Stefan Agner <stefan@agner.ch> wrote:
>
> While in theory multiple unwinders could be compiled in, it does
> not make sense in practise. Use a choice to make the unwinder
> selection mutually exclusive and mandatory.
>
> Already before this commit it has not been possible to deselect
> FRAME_POINTER. Remove the obsolete comment.
>
> Furthermore, to produce a meaningful backtrace with FRAME_POINTER
> enabled the kernel needs a specific function prologue:
> mov ip, sp
> stmfd sp!, {fp, ip, lr, pc}
> sub fp, ip, #4
>
> To get to the required prologue gcc uses apcs and no-sched-prolog.
> This compiler options are not available on clang, and clang is not
> able to generate the required prologue. Make the FRAME_POINTER
> config symbol depending on !clang.
>
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
Looks ok to me. I've added it to my randconfig test environment, you
will hear from me within a day if I run into build regressions.
We may still want to clean up these three lines:
lib/Kconfig.debug: select FRAME_POINTER if !MIPS && !PPC &&
!ARM_UNWIND && !S390 && !MICROBLAZE && !ARC && !X86
lib/Kconfig.debug: select FRAME_POINTER if !MIPS && !PPC && !S390 &&
!MICROBLAZE && !ARM_UNWIND && !ARC && !X86
lib/Kconfig.debug: select FRAME_POINTER if !MIPS && !PPC && !S390 &&
!MICROBLAZE && !ARM_UNWIND && !ARC && !X86
in which ARM is the odd case that currently depends on an architecture
specific rather than the architecture itself.
We could introduce a 'config ARCH_HAS_UNWINDER' symbol that gets
selected by mips, ppc, s390, microblaze, arm and x86 unconditionally,
and then simplify the 'select' statements here.
Arnd
next prev parent reply other threads:[~2018-08-22 10:02 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-21 22:24 [PATCH] ARM: use choice for kernel unwinders Stefan Agner
2018-08-22 10:02 ` Arnd Bergmann [this message]
2018-08-22 14:32 ` Arnd Bergmann
2018-08-22 14:38 ` Stefan Agner
2018-08-22 15:03 ` Arnd Bergmann
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