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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Thu, 30 Jun 2016 17:17:42 +0200
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Subject: Re: [PATCH v4] x86/power/64: Fix kernel text mapping corruption
 during image restoration
To: Borislav Petkov <bp@alien8.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Logan Gunthorpe <logang@deltatee.com>,
        Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        lkml <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Andy Lutomirski <luto@kernel.org>, Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Stephen Smalley <sds@tycho.nsa.gov>
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On Thu, Jun 30, 2016 at 5:05 PM, Borislav Petkov <bp@alien8.de> wrote:
> On Thu, Jun 30, 2016 at 03:17:20PM +0200, Rafael J. Wysocki wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> Logan Gunthorpe reports that hibernation stopped working reliably for
>> him after commit ab76f7b4ab23 (x86/mm: Set NX on gap between __ex_table
>> and rodata).
>
> ...
>
>> +static int relocate_restore_code(void)
>> +{
>> +     pgd_t *pgd;
>> +     pud_t *pud;
>> +
>> +     relocated_restore_code = get_safe_page(GFP_ATOMIC);
>> +     if (!relocated_restore_code)
>> +             return -ENOMEM;
>> +
>> +     memcpy((void *)relocated_restore_code, &core_restore_code, PAGE_SIZE);
>> +
>> +     /* Make the page containing the relocated code executable */
>> +     pgd = (pgd_t *)__va(read_cr3()) + pgd_index(relocated_restore_code);
>> +     pud = pud_offset(pgd, relocated_restore_code);
>> +     if (pud_large(*pud)) {
>> +             set_pud(pud, __pud(pud_val(*pud) & ~_PAGE_NX));
>> +     } else {
>> +             pmd_t *pmd = pmd_offset(pud, relocated_restore_code);
>> +
>> +             if (pmd_large(*pmd)) {
>> +                     set_pmd(pmd, __pmd(pmd_val(*pmd) & ~_PAGE_NX));
>> +             } else {
>> +                     pte_t *pte = pte_offset_kernel(pmd, relocated_restore_code);
>> +
>> +                     set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_NX));
>> +             }
>> +     }
>> +     flush_tlb_all();
>
> I know you want to flush TLBs but this causes the splat below on the
> resume kernel.
>
> Most likely because:
>
> resume_target_kernel() does local_irq_disable() and then
>
> swsusp_arch_resume() -> relocate_restore_code() -> flush_tlb_all()
>
> and smp_call_function_many() doesn't like it when IRQs are disabled.

Right.

Can I invoke __flush_tlb_all() from here to flush the TLB on the local
CPU?  That should be sufficient IMO.

Thanks,
Rafael