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From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
	linux-arch <linux-arch@vger.kernel.org>, X86 ML <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. J. Lu" <hjl.tools@gmail.com>,
	"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>,
	"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>, Oleg Nesterov <oleg@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>,
	mike.kravetz@oracle.com
Subject: Re: [PATCH 02/10] x86/cet: Introduce WRUSS instruction
Date: Thu, 07 Jun 2018 09:51:13 -0700	[thread overview]
Message-ID: <1528390273.4636.28.camel@2b52.sc.intel.com> (raw)
In-Reply-To: <CALCETrU45Cuzvfz3c1+-+7=9KS2N33Bpp1JqBtaGxhPo8U+Fqg@mail.gmail.com>

On Thu, 2018-06-07 at 09:40 -0700, Andy Lutomirski wrote:
> On Thu, Jun 7, 2018 at 7:41 AM Yu-cheng Yu <yu-cheng.yu@intel.com> wrote:
> >
> > WRUSS is a new kernel-mode instruction but writes directly
> > to user shadow stack memory.  This is used to construct
> > a return address on the shadow stack for the signal
> > handler.
> >
> > This instruction can fault if the user shadow stack is
> > invalid shadow stack memory.  In that case, the kernel does
> > fixup.
> >
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> > ---
> >  arch/x86/include/asm/special_insns.h          | 44 +++++++++++++++++++++++++++
> >  arch/x86/lib/x86-opcode-map.txt               |  2 +-
> >  arch/x86/mm/fault.c                           | 13 +++++++-
> >  tools/objtool/arch/x86/lib/x86-opcode-map.txt |  2 +-
> >  4 files changed, 58 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
> > index 317fc59b512c..8ce532fcc171 100644
> > --- a/arch/x86/include/asm/special_insns.h
> > +++ b/arch/x86/include/asm/special_insns.h
> > @@ -237,6 +237,50 @@ static inline void clwb(volatile void *__p)
> >                 : [pax] "a" (p));
> >  }
> >
> > +#ifdef CONFIG_X86_INTEL_CET
> > +
> > +#if defined(CONFIG_IA32_EMULATION) || defined(CONFIG_X86_X32)
> > +static inline int write_user_shstk_32(unsigned long addr, unsigned int val)
> > +{
> > +       int err;
> > +
> 
> Please add a comment indicating what exact opcode this is.

I will fix it.

> 
> Peterz, isn't there some fancy better way we're supposed to handle the
> error return these days?
> 
> > +       asm volatile("1:.byte 0x66, 0x0f, 0x38, 0xf5, 0x37\n"
> > +                    "xor %[err],%[err]\n"
> > +                    "2:\n"
> > +                    ".section .fixup,\"ax\"\n"
> > +                    "3: mov $-1,%[err]; jmp 2b\n"
> > +                    ".previous\n"
> > +                    _ASM_EXTABLE(1b, 3b)
> > +               : [err] "=a" (err)
> > +               : [val] "S" (val), [addr] "D" (addr)
> > +               : "memory");
> > +       return err;
> > +}
> > +#else
> > +static inline int write_user_shstk_32(unsigned long addr, unsigned int val)
> > +{
> > +       return 0;
> 
> BUG()?  Or just omit the ifdef?  It seems unhelpful to have a stub
> function that does nothing.

I will fix it.

> 
> > +}
> > +#endif
> > +
> > +static inline int write_user_shstk_64(unsigned long addr, unsigned long val)
> > +{
> > +       int err;
> > +
> 
> Comment here too, please.

OK.

> 
> > +       asm volatile("1:.byte 0x66, 0x48, 0x0f, 0x38, 0xf5, 0x37\n"
> > +                    "xor %[err],%[err]\n"
> > +                    "2:\n"
> > +                    ".section .fixup,\"ax\"\n"
> > +                    "3: mov $-1,%[err]; jmp 2b\n"
> > +                    ".previous\n"
> > +                    _ASM_EXTABLE(1b, 3b)
> > +               : [err] "=a" (err)
> > +               : [val] "S" (val), [addr] "D" (addr)
> > +               : "memory");
> > +       return err;
> > +}
> > +#endif /* CONFIG_X86_INTEL_CET */
> > +
> >  #define nop() asm volatile ("nop")
> >
> >

  reply	other threads:[~2018-06-07 16:54 UTC|newest]

Thread overview: 98+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 14:37 [PATCH 00/10] Control Flow Enforcement - Part (3) Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 01/10] x86/cet: User-mode shadow stack support Yu-cheng Yu
2018-06-07 16:37   ` Andy Lutomirski
2018-06-07 17:46     ` Yu-cheng Yu
2018-06-07 17:55       ` Dave Hansen
2018-06-07 18:23       ` Andy Lutomirski
2018-06-12 11:56   ` Balbir Singh
2018-06-12 15:03     ` Yu-cheng Yu
2018-06-07 14:37 ` [PATCH 02/10] x86/cet: Introduce WRUSS instruction Yu-cheng Yu
2018-06-07 16:40   ` Andy Lutomirski
2018-06-07 16:51     ` Yu-cheng Yu [this message]
2018-06-07 18:41     ` Peter Zijlstra
2018-06-07 20:31       ` Yu-cheng Yu
2018-06-11  8:17     ` Peter Zijlstra
2018-06-11 15:02       ` Yu-cheng Yu
2018-06-14  1:30   ` Balbir Singh
2018-06-14 14:43     ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 03/10] x86/cet: Signal handling for shadow stack Yu-cheng Yu
2018-06-07 18:30   ` Andy Lutomirski
2018-06-07 18:58     ` Florian Weimer
2018-06-07 19:51       ` Yu-cheng Yu
2018-06-07 20:07     ` Cyrill Gorcunov
2018-06-07 20:57       ` Andy Lutomirski
2018-06-08 12:07         ` Cyrill Gorcunov
2018-06-07 20:12     ` Yu-cheng Yu
2018-06-07 20:17       ` Dave Hansen
2018-06-07 14:38 ` [PATCH 04/10] x86/cet: Handle thread " Yu-cheng Yu
2018-06-07 18:21   ` Andy Lutomirski
2018-06-07 19:47     ` Florian Weimer
2018-06-07 20:53       ` Andy Lutomirski
2018-06-08 14:53         ` Florian Weimer
2018-06-08 15:01           ` Andy Lutomirski
2018-06-08 15:50             ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 05/10] x86/cet: ELF header parsing of Control Flow Enforcement Yu-cheng Yu
2018-06-07 18:38   ` Andy Lutomirski
2018-06-07 20:40     ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 06/10] x86/cet: Add arch_prctl functions for shadow stack Yu-cheng Yu
2018-06-07 18:48   ` Andy Lutomirski
2018-06-07 20:30     ` Yu-cheng Yu
2018-06-07 21:01       ` Andy Lutomirski
2018-06-07 22:02         ` H.J. Lu
2018-06-07 23:01           ` Andy Lutomirski
2018-06-08  4:09             ` H.J. Lu
2018-06-08  4:38               ` Andy Lutomirski
2018-06-08 12:24                 ` H.J. Lu
2018-06-08 14:57                   ` Andy Lutomirski
2018-06-08 15:52                     ` Cyrill Gorcunov
2018-06-08  4:22           ` H.J. Lu
2018-06-08  4:35             ` Andy Lutomirski
2018-06-08 12:17               ` H.J. Lu
2018-06-12 10:03           ` Thomas Gleixner
2018-06-12 11:43             ` H.J. Lu
2018-06-12 16:01               ` Andy Lutomirski
2018-06-12 16:05                 ` H.J. Lu
2018-06-12 16:34                   ` Andy Lutomirski
2018-06-12 16:51                     ` H.J. Lu
2018-06-12 18:59                       ` Thomas Gleixner
2018-06-12 19:34                         ` H.J. Lu
2018-06-18 22:03                           ` Andy Lutomirski
2018-06-19  0:52                             ` Kees Cook
2018-06-19  6:40                               ` Florian Weimer
2018-06-19 14:50                               ` Andy Lutomirski
2018-06-19 16:44                                 ` Kees Cook
2018-06-19 16:59                                   ` Yu-cheng Yu
2018-06-19 17:07                                     ` Kees Cook
2018-06-19 17:20                                       ` Andy Lutomirski
2018-06-19 20:12                                         ` Kees Cook
2018-06-19 20:47                                           ` Andy Lutomirski
2018-06-19 22:38                                             ` Yu-cheng Yu
2018-06-20  0:50                                               ` Andy Lutomirski
2018-06-21 23:07                                                 ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 07/10] mm: Prevent mprotect from changing " Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 08/10] mm: Prevent mremap of " Yu-cheng Yu
2018-06-07 18:48   ` Andy Lutomirski
2018-06-07 20:18     ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 09/10] mm: Prevent madvise from changing " Yu-cheng Yu
2018-06-07 20:54   ` Andy Lutomirski
2018-06-07 21:09   ` Nadav Amit
2018-06-07 21:18     ` Yu-cheng Yu
2018-06-07 14:38 ` [PATCH 10/10] mm: Prevent munmap and remap_file_pages of " Yu-cheng Yu
2018-06-07 18:50   ` Andy Lutomirski
2018-06-07 20:15     ` Yu-cheng Yu
2018-06-12 10:56 ` [PATCH 00/10] Control Flow Enforcement - Part (3) Balbir Singh
2018-06-12 15:03   ` Yu-cheng Yu
2018-06-12 16:00     ` Andy Lutomirski
2018-06-12 16:21       ` Yu-cheng Yu
2018-06-12 16:31         ` Andy Lutomirski
2018-06-12 17:24           ` Yu-cheng Yu
2018-06-12 20:15             ` Yu-cheng Yu
2018-06-14  1:07     ` Balbir Singh
2018-06-14 14:56       ` Yu-cheng Yu
2018-06-17  3:16         ` Balbir Singh
2018-06-18 21:44           ` Andy Lutomirski
2018-06-19  8:52             ` Balbir Singh
2018-06-26  2:46 ` Jann Horn
2018-06-26 14:56   ` Yu-cheng Yu
2018-06-26  5:26 ` Andy Lutomirski
2018-06-26 14:56   ` Yu-cheng Yu

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