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From: Dave Hansen <dave.hansen@intel.com>
To: Andy Lutomirski <luto@kernel.org>, Changbin Du <changbin.du@gmail.com>
Cc: 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: Fri, 4 Oct 2019 08:14:25 -0700	[thread overview]
Message-ID: <2d078dbc-73ca-0868-71f8-16e413ebdbf4@intel.com> (raw)
In-Reply-To: <CALCETrWEhNCWDz7OVpbYJceJ5eShsWWhuyuAQQSzAdKncUo7zA@mail.gmail.com>

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. :)

  reply	other threads:[~2019-10-04 15:14 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 [this message]
2019-10-06  2:29     ` Changbin Du

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