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Date:   Thu, 14 Jul 2022 11:50:06 -0700
From:   Josh Poimboeuf <jpoimboe@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Kees Cook <keescook@chromium.org>,
        kernel test robot <oliver.sang@intel.com>, x86@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] x86: Allow for exclusions in checking RETHUNK
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References: <20220713213133.455599-1-keescook@chromium.org>
 <20220713235556.umnau6nd7u6bz72m@treble>
 <Ys/DNIyc+4ju7Qmb@worktop.programming.kicks-ass.net>
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On Thu, Jul 14, 2022 at 09:18:12AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 13, 2022 at 04:55:56PM -0700, Josh Poimboeuf wrote:
> > Here's the ANNOTATE_UNSAFE_RET idea.
> 
> Right, I suppose that strictly speaking the compiler can do whatever and
> there's no actual guarantee the annotation hits the RET instruction, in
> practise it should work, esp. since noinstr.

Hm, KASAN is introducing a weird function, resulting in a naked return
warning since we have RETHUNK_CFLAGS removed on that file.

0000000000000000 <_sub_I_00099_0>:
   0:	e8 00 00 00 00       	call   5 <_sub_I_00099_0+0x5>	1: R_X86_64_PLT32	__tsan_init-0x4
   5:	c3                   	ret    


Looks like the "KASAN_SANITIZE_rodata.o := n" isn't working somehow?

-- 
Josh