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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-mm@kvack.org, linux-arch@vger.kernel.org,
	linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Andy Lutomirski <luto@kernel.org>,
	Balbir Singh <bsingharora@gmail.com>,
	Borislav Petkov <bp@alien8.de>,
	Cyrill Gorcunov <gorcunov@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Eugene Syromiatnikov <esyr@redhat.com>,
	Florian Weimer <fweimer@redhat.com>,
	"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Randy Dunlap <rdunlap@infradead.org>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Weijiang Yang <weijiang.yang@intel.com>
Subject: Re: [RFC PATCH 5/5] selftest/x86: Add CET quick test
Date: Fri, 22 May 2020 08:10:14 -0700
Message-ID: <cc3d7668eb7dd738a85f0b0935624496efae43be.camel@intel.com> (raw)
In-Reply-To: <20200522092848.GJ325280@hirez.programming.kicks-ass.net>

On Fri, 2020-05-22 at 11:28 +0200, Peter Zijlstra wrote:
> On Thu, May 21, 2020 at 02:17:20PM -0700, Yu-cheng Yu wrote:
> 
> > +#pragma GCC push_options
> > +#pragma GCC optimize ("O0")
> > +void ibt_violation(void)
> > +{
> > +#ifdef __i386__
> > +	asm volatile("lea 1f, %eax");
> > +	asm volatile("jmp *%eax");
> > +#else
> > +	asm volatile("lea 1f, %rax");
> > +	asm volatile("jmp *%rax");
> > +#endif
> > +	asm volatile("1:");
> > +	result[test_id] = -1;
> > +	test_id++;
> > +	setcontext(&ucp);
> > +}
> > +
> > +void shstk_violation(void)
> > +{
> > +#ifdef __i386__
> > +	unsigned long x = 0;
> > +
> > +	((unsigned long *)&x)[2] = (unsigned long)stack_hacked;
> > +#else
> > +	unsigned long long x = 0;
> > +
> > +	((unsigned long long *)&x)[2] = (unsigned long)stack_hacked;
> > +#endif
> > +}
> > +#pragma GCC pop_options
> 
> This is absolutely atrocious.
> 
> The #pragma like Kees already said just need to go. Also, there's
> absolutely no clue what so ever what it attempts to achieve.
> 
> The __i386__ ifdeffery is horrible crap. Splitting an asm with #ifdef
> like that is also horrible crap.
> 
> This is not how you write code.
> 
> Get asm/asm.h into userspace and then write something like:
> 
> 
> void ibt_violation(void)
> {
> 	asm volatile("lea  1f, %" _ASM_AX "\n\t"
> 		     "jmp  *%" _ASM_AX "\n\t"
> 		     "1:\n\t" ::: "a");
> 
> 	WRITE_ONCE(result[test_id], -1);
> 	WRITE_ONCE(test_id, test_id+1);
> 
> 	setcontext(&ucp);
> }
> 
> void shstk_violation(void)
> {
> 	unsigned long x = 0;
> 
> 	WRITE_ONCE(x[2], stack_hacked);
> }

Thanks!  I will change it.

Yu-cheng


  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 21:17 [RFC PATCH 0/5] Update selftests/x86 for CET Yu-cheng Yu
2020-05-21 21:17 ` [RFC PATCH 1/5] x86/cet/shstk: Modify ARCH_X86_CET_ALLOC_SHSTK for 32-bit address range Yu-cheng Yu
2020-05-21 22:43   ` Kees Cook
2020-05-21 21:17 ` [RFC PATCH 2/5] selftest/x86: Enable CET for selftests/x86 Yu-cheng Yu
2020-05-21 22:44   ` Kees Cook
2020-05-21 22:58     ` Yu-cheng Yu
2020-05-21 21:17 ` [RFC PATCH 3/5] selftest/x86: Fix sigreturn_64 test Yu-cheng Yu
2020-05-21 22:47   ` Kees Cook
2020-05-21 22:48   ` Kees Cook
2020-05-21 21:17 ` [RFC PATCH 4/5] selftest/x86: Fix sysret_rip with ENDBR Yu-cheng Yu
2020-05-21 21:34   ` Thomas Gleixner
2020-05-21 22:59     ` Yu-cheng Yu
2020-05-21 21:17 ` [RFC PATCH 5/5] selftest/x86: Add CET quick test Yu-cheng Yu
2020-05-21 23:02   ` Kees Cook
2020-05-21 23:23     ` Yu-cheng Yu
2020-05-22  9:28   ` Peter Zijlstra
2020-05-22 15:10     ` Yu-cheng Yu [this message]
2020-05-22 17:22     ` Kees Cook
2020-05-22 17:27       ` Peter Zijlstra
2020-05-22 17:36         ` Kees Cook
2020-05-22 18:07           ` Yu-cheng Yu

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