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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
	X86 ML <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Brian Gerst <brgerst@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Byungchul Park <byungchul.park@lge.com>
Subject: Re: [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments
Date: Thu, 21 Jul 2016 20:41:40 -0500	[thread overview]
Message-ID: <20160722014140.nhbbhan54fhhb3k7@treble> (raw)
In-Reply-To: <CALCETrWSyR82KSm7ZwvpHyw22GdEhhrMhVD=32Q0-KraqTHFQQ@mail.gmail.com>

On Thu, Jul 21, 2016 at 02:56:52PM -0700, Andy Lutomirski wrote:
> On Thu, Jul 21, 2016 at 2:21 PM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > When calling show_stack_log_lvl() or dump_trace() with a regs argument,
> > providing a stack pointer or frame pointer is redundant.
> >
> 
> > diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
> > index 358fe1c..c533b8b 100644
> > --- a/arch/x86/kernel/dumpstack_32.c
> > +++ b/arch/x86/kernel/dumpstack_32.c
> > @@ -122,7 +122,7 @@ void show_regs(struct pt_regs *regs)
> >                 u8 *ip;
> >
> >                 pr_emerg("Stack:\n");
> > -               show_stack_log_lvl(NULL, regs, &regs->sp, 0, KERN_EMERG);
> > +               show_stack_log_lvl(NULL, regs, NULL, 0, KERN_EMERG);
> 
> This is weird -- note the &.  You're at some risk of exposing a bug in
> x86_32's kernel_stack_pointer() function, which is a mess.  (I don't
> see why it's written the way it is -- the actual return stack pointer
> given a pt_regs is quite well defined -- if regs->cs & 3 != 0, then
> it's regs->sp, else it's &regs->sp.)
> 
> That being said, this isn't a big deal, so:
> 
> Reviewed-by: Andy Lutomirski <luto@kernel.org>
> 
> If you want to make this all a bit more reliably on x86_32, you could
> fix kernel_stack_pointer().

Ok.  The whole '&regs->sp' thing threw me for a loop.  I have no idea
what kernel_stack_pointer() is trying to do.  I just assumed it was
correct.  I'll take a look at it and try to fix it in another patch.

-- 
Josh

  reply	other threads:[~2016-07-22  1:41 UTC|newest]

Thread overview: 91+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-21 21:21 [PATCH 00/19] x86/dumpstack: rewrite x86 stack dump code Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 01/19] x86/dumpstack: remove show_trace() Josh Poimboeuf
2016-07-21 21:49   ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 02/19] x86/dumpstack: add get_stack_pointer() and get_frame_pointer() Josh Poimboeuf
2016-07-21 21:53   ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 03/19] x86/dumpstack: remove unnecessary stack pointer arguments Josh Poimboeuf
2016-07-21 21:56   ` Andy Lutomirski
2016-07-22  1:41     ` Josh Poimboeuf [this message]
2016-07-22  2:29       ` Andy Lutomirski
2016-07-22  3:08       ` Brian Gerst
2016-07-21 21:21 ` [PATCH 04/19] x86/dumpstack: make printk_stack_address() more generally useful Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 05/19] x86/dumpstack: fix function graph tracing stack dump reliability issues Josh Poimboeuf
2016-07-29 22:55   ` Steven Rostedt
2016-07-30  0:50     ` Josh Poimboeuf
2016-07-30  2:20       ` Steven Rostedt
2016-07-30 13:51         ` Josh Poimboeuf
2016-08-01 14:28           ` Steven Rostedt
2016-08-01 15:36             ` Josh Poimboeuf
2016-08-02 21:00               ` Josh Poimboeuf
2016-08-02 21:16                 ` Steven Rostedt
2016-08-02 22:13                   ` Josh Poimboeuf
2016-08-02 23:16                     ` Steven Rostedt
2016-08-03  1:56                       ` Josh Poimboeuf
2016-08-03  2:30                         ` Steven Rostedt
2016-08-03  2:50                           ` Josh Poimboeuf
2016-08-03  2:59                             ` Steven Rostedt
2016-08-03  3:12                               ` Josh Poimboeuf
2016-08-03  3:18                                 ` Steven Rostedt
2016-08-03  3:21                                   ` Steven Rostedt
2016-08-03  3:31                                     ` Josh Poimboeuf
2016-08-03  3:45                                       ` Steven Rostedt
2016-08-03 14:13                                         ` Josh Poimboeuf
2016-08-03  3:30                                   ` Josh Poimboeuf
2016-08-01 15:59     ` Josh Poimboeuf
2016-08-01 16:05       ` Steven Rostedt
2016-08-01 16:19         ` Josh Poimboeuf
2016-08-01 16:24     ` Josh Poimboeuf
2016-08-01 16:56       ` Steven Rostedt
2016-07-21 21:21 ` [PATCH 06/19] x86/dumpstack: remove extra brackets around "EOE" Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 07/19] x86/dumpstack: add IRQ_USABLE_STACK_SIZE define Josh Poimboeuf
2016-07-21 22:01   ` Andy Lutomirski
2016-07-22  1:48     ` Josh Poimboeuf
2016-07-22  8:24       ` Ingo Molnar
2016-07-21 21:21 ` [PATCH 08/19] x86/dumpstack: don't disable preemption in show_stack_log_lvl() and dump_trace() Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 09/19] x86/dumpstack: simplify in_exception_stack() Josh Poimboeuf
2016-07-21 22:05   ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 10/19] x86/dumpstack: add get_stack_info() interface Josh Poimboeuf
2016-07-22 23:26   ` Andy Lutomirski
2016-07-22 23:52     ` Andy Lutomirski
2016-07-23 13:09       ` Josh Poimboeuf
2016-07-22 23:54     ` Josh Poimboeuf
2016-07-23  0:15       ` Andy Lutomirski
2016-07-23 14:04         ` Josh Poimboeuf
2016-07-26  0:09           ` Andy Lutomirski
2016-07-26 16:26             ` Josh Poimboeuf
2016-07-26 17:51               ` Steven Rostedt
2016-07-26 18:56                 ` Josh Poimboeuf
2016-07-26 20:59               ` Andy Lutomirski
2016-07-26 22:24                 ` Josh Poimboeuf
2016-07-26 22:31                   ` Steven Rostedt
2016-07-26 22:37                   ` Andy Lutomirski
2016-07-26 16:47             ` Josh Poimboeuf
2016-07-26 17:49               ` Brian Gerst
2016-07-26 18:59                 ` Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 11/19] x86/dumptrace: add new unwind interface and implementations Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 12/19] perf/x86: convert perf_callchain_kernel() to the new unwinder Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 13/19] x86/stacktrace: convert save_stack_trace_*() " Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 14/19] oprofile/x86: convert x86_backtrace() " Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 15/19] x86/dumpstack: convert show_trace_log_lvl() " Josh Poimboeuf
2016-07-21 21:49   ` Byungchul Park
2016-07-22  1:38     ` Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 16/19] x86/dumpstack: remove dump_trace() Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 17/19] x86/entry/dumpstack: encode pt_regs pointer in frame pointer Josh Poimboeuf
2016-07-21 22:27   ` Andy Lutomirski
2016-07-21 21:21 ` [PATCH 18/19] x86/dumpstack: print stack identifier on its own line Josh Poimboeuf
2016-07-21 21:21 ` [PATCH 19/19] x86/dumpstack: print any pt_regs found on the stack Josh Poimboeuf
2016-07-21 22:32   ` Andy Lutomirski
2016-07-22  3:30     ` Josh Poimboeuf
2016-07-22  5:13       ` Andy Lutomirski
2016-07-22 15:57         ` Josh Poimboeuf
2016-07-22 21:46           ` Andy Lutomirski
2016-07-22 22:20             ` Josh Poimboeuf
2016-07-22 23:18               ` Andy Lutomirski
2016-07-22 23:30                 ` Josh Poimboeuf
2016-07-22 23:39                   ` Andy Lutomirski
2016-07-23  0:00                     ` Josh Poimboeuf
2016-07-23  0:22 ` [PATCH 00/19] x86/dumpstack: rewrite x86 stack dump code Linus Torvalds
2016-07-23  0:31   ` Andy Lutomirski
2016-07-23  5:35     ` Josh Poimboeuf
2016-07-23  5:39       ` Linus Torvalds
2016-07-23 12:53         ` Josh Poimboeuf

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