linux-kernel - Re: [PATCH 4/4] x86, efi: Map runtime services 1:1

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Date:	Thu, 6 Jun 2013 17:58:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Linux EFI <linux-efi@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Jiri Kosina <jkosina@...e.cz>, X86-ML <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH 4/4] x86, efi: Map runtime services 1:1

On Thu, Jun 06, 2013 at 03:29:08PM +0200, Borislav Petkov wrote:
> On Thu, Jun 06, 2013 at 02:14:39PM +0100, Matt Fleming wrote:
> > This patch makes my TunnelMountain machine spin in handle_pte_fault()
> > when triggering one of the "firmware makes references to physical
> > addresses" code paths.
> >
> > I'll try and dig into this tomorrow to figure out what's going on.
> 
> Hmmm, looks like we have forgotten to map an EFI region and we do a #PF
> when executing the EFI code.

How about this one - I don't know whether it would flood dmesg, I guess
you'll have to try.

We could try using blockconsole to catch dmesg to an usb drive, though,
even if you don't have serial or netconsole or such. :-).

--
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 654be4ae3047..7a6129afdff1 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1021,6 +1021,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	/* Get the faulting address: */
 	address = read_cr2();
 
+	if (read_cr3() == (unsigned long)real_mode_header->trampoline_pgd)
+		pr_err("%s: #PF addr: 0x%lx\n", __func__, address);
+
 	/*
 	 * Detect and handle instructions that would cause a page fault for
 	 * both a tracked kernel page and a userspace page.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
--
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