linux-kernel - Re: x86-32: Early microcode loading stumbles over disabled DYNAMIC

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: <20130830130331.1e260e85@gandalf.local.home>
Date:	Fri, 30 Aug 2013 13:03:31 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	x86 <x86@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: x86-32: Early microcode loading stumbles over disabled
 DYNAMIC_FTRACE

On Fri, 30 Aug 2013 09:35:18 -0700
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 08/30/2013 08:51 AM, Steven Rostedt wrote:
> > 
> > It does when dynamic tracing is enabled. But this issue is with static
> > tracing, there's no code modification, thus all functions call
> > mcount/__fentry__ and we need to look at a variable to determine if we
> > should trace or not.
> > 
> 
> And of course global variables are a no-no without special handling in
> pre-paging mode.  Sigh.
> 
> You *could* bail out of the calling address is < PAGE_OFFSET.
> 

We could do that too, as static tracing already gives us high overhead,
I'm not sure how much more overhead another check like this even
matters.

Who uses static tracing? I only use it to test that it still works ;-)

-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/