From: "H. Peter Anvin" <hpa@zytor.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
x86 <x86@kernel.org>, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: x86-32: Early microcode loading stumbles over disabled DYNAMIC_FTRACE
Date: Fri, 30 Aug 2013 08:36:58 -0700 [thread overview]
Message-ID: <5220BC1A.3030108@zytor.com> (raw)
In-Reply-To: <5217908E.2040702@siemens.com>
On 08/23/2013 09:40 AM, Jan Kiszka wrote:
> Hi all,
>
> 32-bit kernels currently crash/reboot in early microcode loading when
> non-dynamic function tracing is enabled. Several functions in that path
> get instrumented with mcount, but its non-dynamic implementation does
> not work before paging is enabled (it accesses global variables at wrong
> addresses).
>
> Below some hunks to get it working again - at least in the absence of
> any microcode in the initrd. Marking all involved functions as __init is
> another option (as __init implies notrace). But I bet there is more
> hidden. I see e.g. a pr_warn() in find_cpio_init that should trigger the
> issue as well if we hit the error it reports (btw. printing at this
> point of the boot should not work anyway, should it?).
>
> Better ideas?
>
> Jan
>
A better idea would be for the mcount/__fentry__ function to simply
return until the function tracing stuff is actually ready.
-hpa
next prev parent reply other threads:[~2013-08-30 15:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-23 16:40 x86-32: Early microcode loading stumbles over disabled DYNAMIC_FTRACE Jan Kiszka
2013-08-23 20:17 ` Borislav Petkov
2013-08-26 8:50 ` Jan Kiszka
2013-08-30 15:36 ` H. Peter Anvin [this message]
2013-08-30 15:51 ` Steven Rostedt
2013-08-30 16:35 ` H. Peter Anvin
2013-08-30 17:03 ` Steven Rostedt
2013-08-30 17:16 ` H. Peter Anvin
2013-08-30 17:25 ` Steven Rostedt
2013-08-30 17:33 ` Jan Kiszka
2013-08-30 20:48 ` H. Peter Anvin
2013-08-31 0:17 ` Steven Rostedt
2013-08-31 5:07 ` Borislav Petkov
2013-08-31 5:23 ` Steven Rostedt
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