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 16:32:33 +0200 [thread overview]
Message-ID: <CAK8P3a03TFBi+kNccTm4WE7u9QdKfbA-Van0WpHH6VzDLtLCtw@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a0oaMS12R4tazChMHENQduO0-Wb-gw-inKjH0oz7_5s3g@mail.gmail.com>
On Wed, Aug 22, 2018 at 12:02 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> 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.
I needed a small hunk to avoid a warning:
WARNING: unmet direct dependencies detected for FRAME_POINTER
Depends on [n]: DEBUG_KERNEL [=y] && (M68K || UML || SUPERH) ||
ARCH_WANT_FRAME_POINTERS [=n]
Selected by [y]:
- LOCKDEP [=y] && DEBUG_KERNEL [=y] && LOCK_DEBUGGING_SUPPORT [=y]
&& !MIPS && !PPC && !ARM_UNWIND [=n] && !S390 && !MICROBLAZE && !ARC
&& !X86
- UNWINDER_FRAME_POINTER [=y] && <choice> && !THUMB2_KERNEL [=n] &&
!CC_IS_CLANG [=n]
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 6e27419b90c0..08f914be6248 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -57,6 +57,7 @@ choice
config UNWINDER_FRAME_POINTER
bool "Frame pointer unwinder"
depends on !THUMB2_KERNEL && !CC_IS_CLANG
+ select ARCH_WANT_FRAME_POINTERS
select FRAME_POINTER
help
This option enables the frame pointer unwinder for unwinding
next prev parent reply other threads:[~2018-08-22 14:32 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
2018-08-22 14:32 ` Arnd Bergmann [this message]
2018-08-22 14:38 ` Stefan Agner
2018-08-22 15:03 ` Arnd Bergmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAK8P3a03TFBi+kNccTm4WE7u9QdKfbA-Van0WpHH6VzDLtLCtw@mail.gmail.com \
--to=arnd@arndb.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=stefan@agner.ch \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).