From: Andy Lutomirski <luto@kernel.org>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>
Cc: X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-doc@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
linux-arch <linux-arch@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
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>,
"Shanbhogue, Vedvyas" <vedvyas.shanbhogue@intel.com>
Subject: Re: [RFC PATCH v4 3/9] x86/cet/ibt: Add IBT legacy code bitmap allocation function
Date: Thu, 4 Oct 2018 09:11:14 -0700 [thread overview]
Message-ID: <CALCETrUj5_kc8qr5xNJSyE4Dz18BcYCcgA1i_CvqgJzZiwG+ig@mail.gmail.com> (raw)
In-Reply-To: <20180921150553.21016-4-yu-cheng.yu@intel.com>
On Fri, Sep 21, 2018 at 8:10 AM Yu-cheng Yu <yu-cheng.yu@intel.com> 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;
> + current->thread.cet.ibt_bitmap_size = size;
> + bitmap = do_mmap_locked(0, size, PROT_READ | PROT_WRITE,
> + MAP_ANONYMOUS | MAP_PRIVATE,
> + VM_DONTDUMP);
> +
> + if (bitmap >= TASK_SIZE) {
> + current->thread.cet.ibt_bitmap_size = 0;
> + return -ENOMEM;
> + }
> +
> + current->thread.cet.ibt_bitmap_addr = bitmap;
> + }
> +
> + /*
> + * Lower bits of MSR_IA32_CET_LEG_IW_EN are for IBT
> + * settings. Clear lower bits even bitmap is already
> + * page-aligned.
> + */
> + bitmap = current->thread.cet.ibt_bitmap_addr;
> + bitmap &= PAGE_MASK;
> +
> + /*
> + * Turn on IBT legacy bitmap.
> + */
> + rdmsrl(MSR_IA32_U_CET, r);
> + r |= (MSR_IA32_CET_LEG_IW_EN | bitmap);
> + wrmsrl(MSR_IA32_U_CET, r);
> + return 0;
Why are you writing the MSRs in the case where the bitmap was already allocated?
next prev parent reply other threads:[~2018-10-04 16:11 UTC|newest]
Thread overview: 26+ 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 ` [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 ` [RFC PATCH v4 2/9] x86/cet/ibt: User-mode indirect branch tracking support Yu-cheng Yu
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
2018-10-03 19:57 ` Eugene Syromiatnikov
2018-10-05 16:13 ` Yu-cheng Yu
2018-10-05 16:28 ` Andy Lutomirski
2018-10-05 16:58 ` Yu-cheng Yu
2018-10-05 17:07 ` Andy Lutomirski
2018-10-05 17:26 ` Eugene Syromiatnikov
2018-10-10 15:56 ` Yu-cheng Yu
2018-10-04 16:11 ` Andy Lutomirski [this message]
2018-09-21 15:05 ` [RFC PATCH v4 4/9] mm/mmap: Add IBT bitmap size to address space limit check Yu-cheng Yu
2018-10-03 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 ` [RFC PATCH v4 6/9] x86/cet/ibt: Add arch_prctl functions " Yu-cheng Yu
2018-10-04 13:28 ` Eugene Syromiatnikov
2018-10-04 15:37 ` Yu-cheng Yu
2018-10-04 16:07 ` Florian Weimer
2018-10-04 16:12 ` Andy Lutomirski
2018-10-04 16:25 ` Yu-cheng Yu
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 ` [RFC PATCH v4 8/9] x86: Insert endbr32/endbr64 to vDSO Yu-cheng Yu
2018-09-21 15:05 ` [RFC PATCH v4 9/9] x86/cet: Add PTRACE interface for CET Yu-cheng Yu
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