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From: Kees Cook <keescook@chromium.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
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>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Nadav Amit <nadav.amit@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
	Peter Zijlstra <peterz@infradead.org>,
	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 3/5] selftest/x86: Fix sigreturn_64 test.
Date: Thu, 21 May 2020 15:47:15 -0700
Message-ID: <202005211545.30156BFC4@keescook> (raw)
In-Reply-To: <20200521211720.20236-4-yu-cheng.yu@intel.com>

On Thu, May 21, 2020 at 02:17:18PM -0700, Yu-cheng Yu wrote:
> When shadow stack is enabled, selftests/x86/sigreturn_64 triggers a fault
> when doing sigreturn to 32-bit context but the task's shadow stack pointer
> is above 32-bit address range.  Fix it by:
> 
> - Allocate a small shadow stack below 32-bit address,
> - Switch to the new shadow stack,
> - Run tests,
> - Switch back to the original 64-bit shadow stack.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> ---
>  tools/testing/selftests/x86/sigreturn.c | 28 +++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/tools/testing/selftests/x86/sigreturn.c b/tools/testing/selftests/x86/sigreturn.c
> index 57c4f67f16ef..5bcd74d416ff 100644
> --- a/tools/testing/selftests/x86/sigreturn.c
> +++ b/tools/testing/selftests/x86/sigreturn.c
> @@ -45,6 +45,14 @@
>  #include <stdbool.h>
>  #include <sys/ptrace.h>
>  #include <sys/user.h>
> +#include <x86intrin.h>
> +#include <asm/prctl.h>
> +#include <sys/prctl.h>
> +
> +#ifdef __x86_64__
> +int arch_prctl(int code, unsigned long *addr);
> +#define ARCH_CET_ALLOC_SHSTK 0x3004
> +#endif
>  
>  /* Pull in AR_xyz defines. */
>  typedef unsigned int u32;
> @@ -766,6 +774,20 @@ int main()
>  	int total_nerrs = 0;
>  	unsigned short my_cs, my_ss;
>  
> +#ifdef __x86_64__

I think this should also be gated by whether the compiler will know what
to do with the shadow stack instructions. (Perhaps the earlier Makefile
define can be exported and tested here.)

> +	/* Alloc a shadow stack within 32-bit address range */
> +	unsigned long arg, ssp_64, ssp_32;
> +	ssp_64 = _get_ssp();
> +
> +	if (ssp_64 != 0) {
> +		arg = 0x1001;
> +		arch_prctl(ARCH_CET_ALLOC_SHSTK, &arg);
> +		ssp_32 = arg + 0x1000 - 8;
> +		asm volatile("RSTORSSP (%0)\n":: "r" (ssp_32));
> +		asm volatile("SAVEPREVSSP");
> +	}
> +#endif

-- 
Kees Cook

  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 [this message]
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
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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