linux-kernel - Re: x86/stacktrace: add function for detecting reliable stack traces

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Message-ID: <20160411032948.GB12795@packer-debian-8-amd64.digitalocean.com>
Date:	Sun, 10 Apr 2016 23:29:49 -0400
From:	Jessica Yu <jeyu@...hat.com>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Jiri Kosina <jikos@...nel.org>, Miroslav Benes <mbenes@...e.cz>,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Vojtech Pavlik <vojtech@...e.com>
Subject: Re: x86/stacktrace: add function for detecting reliable stack traces

+++ Josh Poimboeuf [25/03/16 14:34 -0500]:
>For live patching and possibly other use cases, a stack trace is only
>useful if you can be assured that it's completely reliable.  Add a new
>save_stack_trace_tsk_reliable() function to achieve that.
>
>Scenarios which indicate that a stack strace may be unreliable:

s/strace/trace

>
>- interrupt stacks
>- preemption
>- corrupted stack data
>- newly forked tasks
>- running tasks
>- the user didn't provide a large enough entries array
>
>Also add a config option so arch-independent code can determine at build
>time whether the function is implemented.
>
>Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
>---
> arch/Kconfig                 |  6 ++++++
> arch/x86/Kconfig             |  1 +
> arch/x86/kernel/dumpstack.c  | 36 ++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/stacktrace.c | 32 ++++++++++++++++++++++++++++++++
> include/linux/stacktrace.h   | 20 ++++++++++++++++----
> kernel/stacktrace.c          |  4 ++--
> lib/Kconfig.debug            |  6 ++++++
> 7 files changed, 99 insertions(+), 6 deletions(-)
>
>diff --git a/arch/Kconfig b/arch/Kconfig
>index 81869a5..68b95f1 100644
>--- a/arch/Kconfig
>+++ b/arch/Kconfig
>@@ -589,6 +589,12 @@ config HAVE_STACK_VALIDATION
> 	  Architecture supports the 'objtool check' host tool command, which
> 	  performs compile-time stack metadata validation.
>
>+config HAVE_RELIABLE_STACKTRACE
>+	bool
>+	help
>+	  Architecure has a save_stack_trace_tsk_reliable() function which only

s/Architecure/Architecture