From: Jann Horn <jannh@google.com>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: kernel list <linux-kernel@vger.kernel.org>,
sean.j.christopherson@intel.com,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
"the arch/x86 maintainers" <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [RFC][PATCH 7/8] x86/mm/vsyscall: consider vsyscall page part of user address space
Date: Sat, 8 Sep 2018 03:16:09 +0200 [thread overview]
Message-ID: <CAG48ez2e8yJJjHeKRTbu46=5mbssZo84iMinBx6B5BgziDJiVQ@mail.gmail.com> (raw)
In-Reply-To: <20180907194902.63F36CFE@viggo.jf.intel.com>
On Sat, Sep 8, 2018 at 2:28 AM Dave Hansen <dave.hansen@linux.intel.com> wrote:
> The vsyscall page is weird. It is in what is traditionally part of the
> kernel address space. But, it has user permissions and we handle faults
> on it like we would on a user page: interrupts on.
>
> Right now, we handle vsyscall emulation in the "bad_area" code, which
> is used for both user-address-space and kernel-address-space faults. Move
> the handling to the user-address-space code *only* and ensure we get there
> by "excluding" the vsyscall page from the kernel address space via a check
> in fault_in_kernel_space().
[...]
> static int fault_in_kernel_space(unsigned long address)
> {
> + /*
> + * The vsyscall page is at an address above TASK_SIZE_MAX,
> + * but is not considered part of the kernel address space.
> + */
> + if (is_vsyscall_vaddr(address))
> + return false;
I think something should check for "#ifdef CONFIG_X86_64"? 32-bit
doesn't have a vsyscall page, right? And this code probably shouldn't
veer off into the userspace-area fault handling code for addresses in
the range 0xff600000-0xff600fff... what is in that region on 32-bit?
Modules or something like that?
Maybe change is_vsyscall_vaddr() so that it always returns false on
32-bit, or put both the definition of is_vsyscall_vaddr() and this
code behind #ifdef guards.
And, in a separate patch, maybe also #ifdef-guard the definition of
VSYSCALL_ADDR in vsyscall.h? Nothing good is going to result from
making a garbage VSYSCALL_ADDR available to 32-bit code.
> +#ifdef CONFIG_X86_64
> + /*
> + * Instruction fetch faults in the vsyscall page might need
> + * emulation. The vsyscall page is at a high address
> + * (>PAGE_OFFSET), but is considered to be part of the user
> + * address space.
> + *
> + * The vsyscall page does not have a "real" VMA, so do this
> + * emulation before we go searching for VMAse
"VMAse"? Is that a typo?
next prev parent reply other threads:[~2018-09-08 1:17 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 19:48 [RFC][PATCH 0/8] x86/mm: page fault handling cleanups Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 1/8] x86/mm: clarify hardware vs. software "error_code" Dave Hansen
2018-09-07 22:48 ` Andy Lutomirski
2018-09-10 20:07 ` Dave Hansen
2018-09-10 21:17 ` Andy Lutomirski
2018-09-07 19:48 ` [RFC][PATCH 2/8] x86/mm: break out kernel address space handling Dave Hansen
2018-09-07 21:06 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen
2018-09-07 22:21 ` Andy Lutomirski
2018-09-07 22:37 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 3/8] x86/mm: break out user " Dave Hansen
2018-09-08 9:38 ` Peter Zijlstra
2018-09-10 20:20 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 4/8] x86/mm: add clarifying comments for user addr space Dave Hansen
2018-09-07 19:49 ` [RFC][PATCH 5/8] x86/mm: fix exception table comments Dave Hansen
2018-09-07 21:04 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen
2018-09-10 20:43 ` Sean Christopherson
2018-09-08 0:37 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 6/8] x86/mm: add vsyscall address helper Dave Hansen
2018-09-08 0:46 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 7/8] x86/mm/vsyscall: consider vsyscall page part of user address space Dave Hansen
2018-09-07 22:58 ` Andy Lutomirski
2018-09-08 1:16 ` Jann Horn [this message]
2018-09-07 19:49 ` [RFC][PATCH 8/8] x86/mm: remove spurious fault pkey check Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAG48ez2e8yJJjHeKRTbu46=5mbssZo84iMinBx6B5BgziDJiVQ@mail.gmail.com' \
--to=jannh@google.com \
--cc=dave.hansen@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=peterz@infradead.org \
--cc=sean.j.christopherson@intel.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).