linux-kernel - Re: [PATCH] x86_64/efi: Mapping Boot and Runtime EFI memory regions to different starting virtual address

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Date:	Thu, 30 Jul 2015 19:18:19 +0800
From:	joeyli <jlee@...e.com>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	"Lee, Chun-Yi" <joeyli.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86_64/efi: Mapping Boot and Runtime EFI memory regions
 to different starting virtual address

On Thu, Jul 30, 2015 at 07:09:59PM +0800, joeyli wrote:
> On Thu, Jul 30, 2015 at 11:11:31AM +0100, Matt Fleming wrote:
> > On Thu, 30 Jul, at 10:03:23AM, Borislav Petkov wrote:
> > > On Thu, Jul 30, 2015 at 12:53:42AM -0700, H. Peter Anvin wrote:
> > > > This changelog is at least partially incomprehensive. It also seems
> > > > more than a bit aggressive to expect that 1 GB will be sufficient
> > > > forever.
> > > 
> > > Right, before we do anything, I'd like for us to figure out first why
> > > this is a problem all of a sudden. And why should we even keep boot
> > > code/data, if it is fair game, once runtime services get enabled.
> > > 
> > > Matt, can you please chime in first before we even talk about a
> > > solution...
> > 
> > Yeah, I do not understand the issue properly.
> > 
> > Why do we care about EfiBoot* regions after hibernate? Surely we've
> > already freed those regions in efi_free_boot_services() during boot and
> > nobody should be touching them again? If the firmware does, that's a
> > whole new bug we've never encountered before.
> > 
> > And we obviously can't allow the runtime regions to move around during
> > hibernate/resume because we've already informed the firmware where those
> > regions live during SetVirtualAddressMap() at boot.
> > 
> > I admit that I haven't looked at the hibernate code paths. Let me go do
> > that now.
> > 
> > -- 
> > Matt Fleming, Intel Open Source Technology Center
> 
> In efi_map_regions(), kernel mapping EFI_MEMORY_RUNTIME and
> EFI_BOOT_SERVICES_CODE/DATA regions to trampoline_pgd.
> 
> UEFI keeps the physical address of Runtime Code/Data were not changed in
> hibernate cycle. But the changes of Boot regions causes Runtime Code/Data
> mapping to different virtual address in trampoline_pgd.
> 
> The following is a case from Intel DQ57TM.
> 
> Boot:
> [    0.036509] efi: mem11: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b7f7e000-0x00000000b7f9e000) va=[0xfffffffefff7e000-0xfffffffefff9e000) (0MB)
> [    0.051393] efi: mem17: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b8b4f000-0x00000000b8b50000) va=[0xfffffffefff4f000-0xfffffffefff50000) (0MB)
> [    0.066271] efi: mem19: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b8c2f000-0x00000000b9135000) va=[0xfffffffeffa2f000-0xfffffffefff35000) (5MB)
> [    0.081152] efi: mem21: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b9138000-0x00000000baf7d000) va=[0xfffffffefdb38000-0xfffffffeff97d000) (30MB)
> [    0.096120] efi: mem23: [Boot Code          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb04b000-0x00000000bb385000) va=[0xfffffffefd64b000-0xfffffffefd985000) (3MB)
> [    0.111002] efi: mem24: [Runtime Code       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb385000-0x00000000bb3e5000) va=[0xfffffffefd585000-0xfffffffefd5e5000) (0MB)
> [    0.125883] efi: mem25: [Runtime Data       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb3e5000-0x00000000bb445000) va=[0xfffffffefd3e5000-0xfffffffefd445000) (0MB)
> [    0.140764] efi: mem29: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb7ff000-0x00000000bb800000) va=[0xfffffffefd1ff000-0xfffffffefd200000) (0MB)
> 
> Hibernate resumed:
> [    0.036486] efi: mem11: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b7f7e000-0x00000000b7f9e000) va=[0xfffffffefff7e000-0xfffffffefff9e000) (0MB)
> [    0.051375] efi: mem17: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b8c0d000-0x00000000b9113000) va=[0xfffffffeffa0d000-0xfffffffefff13000) (5MB)	<=== order of Boot Data changed
> [    0.066253] efi: mem20: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b9132000-0x00000000b9133000) va=[0xfffffffeff932000-0xfffffffeff933000) (0MB)
> [    0.081135] efi: mem22: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000b9138000-0x00000000baf7d000) va=[0xfffffffefd938000-0xfffffffeff77d000) (30MB)
> [    0.096103] efi: mem24: [Boot Code          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb04b000-0x00000000bb385000) va=[0xfffffffefd44b000-0xfffffffefd785000) (3MB)
> [    0.110984] efi: mem25: [Runtime Code       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb385000-0x00000000bb3e5000) va=[0xfffffffefd385000-0xfffffffefd3e5000) (0MB)	<=== va changed
> [    0.125865] efi: mem26: [Runtime Data       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb3e5000-0x00000000bb445000) va=[0xfffffffefd1e5000-0xfffffffefd245000) (0MB)
> [    0.140747] efi: mem30: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb7ff000-0x00000000bb800000) va=[0xfffffffefcfff000-0xfffffffefd000000) (0MB)
> 
> Look at the origin va of Runtime Code is 0xfffffffefd585000, but after hibernate
> result boot, the new va is 0xfffffffefd385000.
> 
> Issue machine's UEFI keeps the PA of Runtime regions unchanged, but Boot regions
> moved. That causes Runtime regions mapping to different VA.
> 
> 
> 
> Regards
> Joey Lee

In the above case, just simply accessing EFI variable through efivars to
reproduce issue:

linux-aiip:~ # hexdump -C /sys/firmware/efi/efivars/SecureBoot-8be4df61-93ca-11d2-aa0d-00e098032b8c
Killed

[  257.856185] BUG: unable to handle kernel paging request at fffffffefd244e60		<=== address is in Runtime Data region
[  257.863200] IP: [<ffffffff81457cdd>] virt_efi_get_variable+0x5d/0xa0
[  257.869586] PGD 1a0c067 PUD 13b0ae063 PMD 13b0bc063 PTE 0
[  257.875056] Oops: 0000 [#1] SMP 
[...snip]
[  258.149804] RIP  [<ffffffff81457cdd>] virt_efi_get_variable+0x5d/0xa0
[  258.156273]  RSP <ffff8800ba07fd78>
[  258.159769] CR2: fffffffefd244e60
[  258.163090] ---[ end trace 9edb589760c07d3e ]---

0xfffffffefd244e60 is covered by Runtime Data region after hibernate resumed:  

[    0.125865] efi: mem26: [Runtime Data       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb3e5000-0x00000000bb445000) va=[0xfffffffefd1e5000-0xfffffffefd245000) (0MB)
										  					     			0xfffffffefd244e60

But this va address didn't mapped to any pa in hibernating kernel (image kernel):

[    0.111002] efi: mem24: [Runtime Code       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb385000-0x00000000bb3e5000) va=[0xfffffffefd585000-0xfffffffefd5e5000) (0MB)
[    0.125883] efi: mem25: [Runtime Data       |RUN|  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb3e5000-0x00000000bb445000) va=[0xfffffffefd3e5000-0xfffffffefd445000) (0MB)
																                0xfffffffefd244e60	<=== no mapping
[    0.140764] efi: mem29: [Boot Data          |   |  |  |  |   |WB|WT|WC|UC] pa=[0x00000000bb7ff000-0x00000000bb800000) va=[0xfffffffefd1ff000-0xfffffffefd200000) (0MB)


So, when call EFI runtime services, got problem.


Regards
Joey Lee

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