linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Changbin Du <changbin.du@gmail.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
	Changbin Du <changbin.du@gmail.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/mm: determine whether the fault address is canonical
Date: Sun, 6 Oct 2019 10:29:43 +0800	[thread overview]
Message-ID: <20191006022941.pvwldrjyhl4z5inu@mail.google.com> (raw)
In-Reply-To: <2d078dbc-73ca-0868-71f8-16e413ebdbf4@intel.com>

On Fri, Oct 04, 2019 at 08:14:25AM -0700, Dave Hansen wrote:
> On 10/4/19 7:59 AM, Andy Lutomirski wrote:
> >> @@ -123,7 +125,8 @@ __visible bool ex_handler_uaccess(const struct exception_table_entry *fixup,
> >>                                   unsigned long error_code,
> >>                                   unsigned long fault_addr)
> >>  {
> >> -       WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. Non-canonical address?");
> >> +       WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault at %s address in user access.",
> >> +                 is_canonical_addr(fault_addr) ? "canonical" : "non-canonical");
> > Unless the hardware behaves rather differently from the way I think it
> > does, fault_addr is garbage for anything other than #PF and sometimes
> > for #DF.  (And maybe the virtualization faults?)  I don't believe that
> > #GP fills in CR2.
> 
> For #GP, we do:
> 
> do_general_protection(struct pt_regs *regs, long error_code)
> {
> ...
>         if (!user_mode(regs)) {
>                 if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
>                         return;
> 
> Where the 0 is 'fault_addr'.  I'm not sure any other way that
> ex_handler_uaccess() can get called with trapnr == X86_TRAP_GP.  0 is
> canonical last I checked, which would make this patch a bit academic. :)
My fault. I thought the 'fault_addr' is filled with a valid value. So we really
don't know the answer without decoding the instruction which causes this #GP. :)

-- 
Cheers,
Changbin Du

      reply	other threads:[~2019-10-06  2:29 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 13:45 [PATCH] x86/mm: determine whether the fault address is canonical Changbin Du
2019-10-04 14:39 ` Dave Hansen
2019-10-04 15:31   ` Sean Christopherson
2019-10-07 14:32     ` Ingo Molnar
2019-10-07 14:44       ` Ingo Molnar
2019-10-07 15:13         ` Sean Christopherson
2019-10-04 14:59 ` Andy Lutomirski
2019-10-04 15:14   ` Dave Hansen
2019-10-06  2:29     ` Changbin Du [this message]

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=20191006022941.pvwldrjyhl4z5inu@mail.google.com \
    --to=changbin.du@gmail.com \
    --cc=dave.hansen@intel.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --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).