netdev - Re: [PATCH 00/33] Compile-time stack metadata validation

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Date:	Fri, 22 Jan 2016 13:14:47 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Chris J Arges <chris.j.arges@...onical.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	David Vrabel <david.vrabel@...rix.com>,
	Borislav Petkov <bp@...e.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Chris Wright <chrisw@...s-sol.org>,
	Alok Kataria <akataria@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Alexei Starovoitov <ast@...nel.org>, netdev@...r.kernel.org,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
	Wim Van Sebroeck <wim@...ana.be>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-watchdog@...r.kernel.org, Waiman Long <Waiman.Long@....com>
Subject: Re: [PATCH 00/33] Compile-time stack metadata validation

On Fri, Jan 22, 2016 at 11:43:48AM -0600, Chris J Arges wrote:
> On Thu, Jan 21, 2016 at 04:49:04PM -0600, Josh Poimboeuf wrote:
> > This is v16 of the compile-time stack metadata validation patch set,
> > along with proposed fixes for most of the warnings it found.  It's based
> > on the tip/master branch.
> >
> Josh,
> 
> Looks good, with my config [1] I do still get a few warnings building
> linux/linux-next.
> 
> Here are the warnings:
> $ grep ^stacktool build.log | grep -v staging

Thanks for reporting these!

> stacktool: arch/x86/kvm/vmx.o: vmx_handle_external_intr()+0x67: call without frame pointer save/setup

This can be fixed by setting the stack pointer as an output operand for
the inline asm call in vmx_handle_external_intr().

Feel free to submit a patch, or I'll get around to it eventually.

> stacktool: fs/reiserfs/namei.o: set_de_name_and_namelen()+0x9e: return without frame pointer restore
> stacktool: fs/reiserfs/namei.o: set_de_name_and_namelen()+0x89: duplicate frame pointer save
> stacktool: fs/reiserfs/namei.o: set_de_name_and_namelen()+0x8a: duplicate frame pointer setup
> stacktool: fs/reiserfs/namei.o: set_de_name_and_namelen()+0x9e: frame pointer state mismatch
> stacktool: fs/reiserfs/namei.o: set_de_name_and_namelen()+0x0: frame pointer state mismatch

These are false positives.  Stacktool is confused by the use of a
"noreturn" function which it doesn't know about (__reiserfs_panic).

Unfortunately the only solution I currently have for dealing with global
noreturn functions is to just hard-code a list of them.  So the short
term fix would be to add "__reiserfs_panic" to the global_noreturns list
in tools/stacktool/builtin-check.c.

I'm still trying to figure out a better way to deal with this type of
issue, as it's a pain to have to keep a hard-coded list of noreturn
functions.  Unfortunately that info isn't available in the ELF.

> stacktool: fs/reiserfs/ibalance.o: .text: unexpected end of section
> stacktool: fs/reiserfs/tail_conversion.o: .text: unexpected end of section

For some reason I'm not able to recreate these warnings...  Can you
share one of the .o files?

-- 
Josh