linux-kernel - Re: [PATCH] sched/x86: Add stack frame dependency to __preempt_schedule[

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56C70500.1020904@suse.cz>
Date:	Fri, 19 Feb 2016 13:05:20 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org
Subject: Re: [PATCH] sched/x86: Add stack frame dependency to
 __preempt_schedule[_notrace]

On 02/18/2016, 06:41 PM, Josh Poimboeuf wrote:
> If __preempt_schedule() or __preempt_schedule_notrace() is referenced at
> the beginning of a function, gcc can insert the asm inline "call
> ___preempt_schedule[_notrace]" instruction before setting up a stack
> frame, which breaks frame pointer convention if CONFIG_FRAME_POINTER is
> enabled and can result in bad stack traces.
> 
> Force a stack frame to be created if CONFIG_FRAME_POINTER is enabled by
> listing the stack pointer as an output operand for the inline asm
> statements.
> 
> Specifically this fixes the following stacktool warnings:
> 
>   stacktool: drivers/scsi/hpsa.o: hpsa_scsi_do_simple_cmd.constprop.106()+0x79: call without frame pointer save/setup
...
> Reported-by: Jiri Slaby <jslaby@...e.cz>

This patch and adding lbug_with_loc to global_noreturns makes all
stacktool warnings go away here.

> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> ---
>  arch/x86/include/asm/preempt.h | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
> index 01bcde8..d397deb 100644
> --- a/arch/x86/include/asm/preempt.h
> +++ b/arch/x86/include/asm/preempt.h
> @@ -94,10 +94,19 @@ static __always_inline bool should_resched(int preempt_offset)
>  
>  #ifdef CONFIG_PREEMPT
>    extern asmlinkage void ___preempt_schedule(void);
> -# define __preempt_schedule() asm ("call ___preempt_schedule")
> +# define __preempt_schedule()					\
> +({								\
> +	register void *__sp asm(_ASM_SP);			\
> +	asm volatile ("call ___preempt_schedule" : "+r"(__sp));	\
> +})
> +
>    extern asmlinkage void preempt_schedule(void);
>    extern asmlinkage void ___preempt_schedule_notrace(void);
> -# define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
> +# define __preempt_schedule_notrace()					\
> +({									\
> +	register void *__sp asm(_ASM_SP);				\
> +	asm volatile ("call ___preempt_schedule_notrace" : "+r"(__sp));	\
> +})
>    extern asmlinkage void preempt_schedule_notrace(void);
>  #endif
>  
> 

thanks,
-- 
js
suse labs