From: Yu-cheng Yu <yu-cheng.yu@intel.com>
To: Eugene Syromiatnikov <esyr@redhat.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@amacapital.net>,
Balbir Singh <bsingharora@gmail.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.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>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Subject: Re: [RFC PATCH v4 3/9] x86/cet/ibt: Add IBT legacy code bitmap allocation function
Date: Fri, 05 Oct 2018 09:13:40 -0700 [thread overview]
Message-ID: <fc2f98ab46240c0498bdf4d7458b4373c1f02bf8.camel@intel.com> (raw)
Message-ID: <20181005161340.C9vbRIhTB3yoKvleUI7j4sVbS0xQpC99dS8E5ASNzAk@z> (raw)
In-Reply-To: <20181003195702.GF32759@asgard.redhat.com>
On Wed, 2018-10-03 at 21:57 +0200, Eugene Syromiatnikov wrote:
> On Fri, Sep 21, 2018 at 08:05:47AM -0700, Yu-cheng Yu wrote:
> > Indirect branch tracking provides an optional legacy code bitmap
> > that indicates locations of non-IBT compatible code. When set,
> > each bit in the bitmap represents a page in the linear address is
> > legacy code.
> >
> > We allocate the bitmap only when the application requests it.
> > Most applications do not need the bitmap.
> >
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> > ---
> > arch/x86/kernel/cet.c | 45 +++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 45 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
> > index 6adfe795d692..a65d9745af08 100644
> > --- a/arch/x86/kernel/cet.c
> > +++ b/arch/x86/kernel/cet.c
> > @@ -314,3 +314,48 @@ void cet_disable_ibt(void)
> > wrmsrl(MSR_IA32_U_CET, r);
> > current->thread.cet.ibt_enabled = 0;
> > }
> > +
> > +int cet_setup_ibt_bitmap(void)
> > +{
> > + u64 r;
> > + unsigned long bitmap;
> > + unsigned long size;
> > +
> > + if (!cpu_feature_enabled(X86_FEATURE_IBT))
> > + return -EOPNOTSUPP;
> > +
> > + if (!current->thread.cet.ibt_bitmap_addr) {
> > + /*
> > + * Calculate size and put in thread header.
> > + * may_expand_vm() needs this information.
> > + */
> > + size = TASK_SIZE / PAGE_SIZE / BITS_PER_BYTE;
>
> TASK_SIZE_MAX is likely needed here, as an application can easily switch
> between long an 32-bit protected mode. And then the case of a CPU that
> doesn't support 5LPT.
If we had calculated bitmap size from TASK_SIZE_MAX, all 32-bit apps would have
failed the allocation for bitmap size > TASK_SIZE. Please see values below,
which is printed from the current code.
Yu-cheng
x64:
TASK_SIZE_MAX = 0000 7fff ffff f000
TASK_SIZE = 0000 7fff ffff f000
bitmap size = 0000 0000 ffff ffff
x32:
TASK_SIZE_MAX = 0000 7fff ffff f000
TASK_SIZE = 0000 0000 ffff e000
bitmap size = 0000 0000 0001 ffff
next prev parent reply other threads:[~2018-10-05 23:18 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 15:05 [RFC PATCH v4 0/9] Control Flow Enforcement: Branch Tracking, PTRACE Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 1/9] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 2/9] x86/cet/ibt: User-mode indirect branch tracking support Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-10-03 18:58 ` Eugene Syromiatnikov
2018-10-03 18:58 ` Eugene Syromiatnikov
2018-09-21 15:05 ` [RFC PATCH v4 3/9] x86/cet/ibt: Add IBT legacy code bitmap allocation function Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-10-03 19:57 ` Eugene Syromiatnikov
2018-10-03 19:57 ` Eugene Syromiatnikov
2018-10-05 16:13 ` Yu-cheng Yu [this message]
2018-10-05 16:13 ` Yu-cheng Yu
2018-10-05 16:28 ` Andy Lutomirski
2018-10-05 16:28 ` Andy Lutomirski
2018-10-05 16:58 ` Yu-cheng Yu
2018-10-05 16:58 ` Yu-cheng Yu
2018-10-05 17:07 ` Andy Lutomirski
2018-10-05 17:07 ` Andy Lutomirski
2018-10-05 17:26 ` Eugene Syromiatnikov
2018-10-05 17:26 ` Eugene Syromiatnikov
2018-10-10 15:56 ` Yu-cheng Yu
2018-10-10 15:56 ` Yu-cheng Yu
2018-10-04 16:11 ` Andy Lutomirski
2018-10-04 16:11 ` Andy Lutomirski
2018-09-21 15:05 ` [RFC PATCH v4 4/9] mm/mmap: Add IBT bitmap size to address space limit check Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-10-03 20:21 ` Eugene Syromiatnikov
2018-10-03 20:21 ` Eugene Syromiatnikov
2018-09-21 15:05 ` [RFC PATCH v4 5/9] x86/cet/ibt: ELF header parsing for IBT Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 6/9] x86/cet/ibt: Add arch_prctl functions " Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-10-04 13:28 ` Eugene Syromiatnikov
2018-10-04 13:28 ` Eugene Syromiatnikov
2018-10-04 15:37 ` Yu-cheng Yu
2018-10-04 15:37 ` Yu-cheng Yu
2018-10-04 16:07 ` Florian Weimer
2018-10-04 16:07 ` Florian Weimer
2018-10-04 16:12 ` Andy Lutomirski
2018-10-04 16:12 ` Andy Lutomirski
2018-10-04 16:25 ` Yu-cheng Yu
2018-10-04 16:25 ` Yu-cheng Yu
2018-10-04 16:08 ` Andy Lutomirski
2018-10-04 16:08 ` Andy Lutomirski
2018-09-21 15:05 ` [RFC PATCH v4 7/9] x86/cet/ibt: Add ENDBR to op-code-map Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 8/9] x86: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 9/9] x86/cet: Add PTRACE interface for CET Yu-cheng Yu
2018-09-21 15:05 ` Yu-cheng Yu
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