Re: [PATCH v2 00/23] x86_64: Improvements at compressed kernel stage

[joeyli]

Hi Evgeniy,

Thanks for your effort!

On Tue, Oct 25, 2022 at 05:12:38PM +0300, Evgeniy Baskov wrote:
> This patchset is aimed
> * to improve UEFI compatibility of compressed kernel code for x86_64
> * to setup proper memory access attributes for code and rodata sections
> * to implement W^X protection policy throughout the whole execution 
>   of compressed kernel for EFISTUB code path. 
> 
> Kernel is made to be more compatible with PE image specification [3],
> allowing it to be successfully loaded by stricter PE loader
> implementations like the one from [2]. There is at least one
> known implementation that uses that loader in production [4].
> There are also ongoing efforts to upstream these changes.
> 
> Also the patchset adds EFI_MEMORY_ATTTRIBUTE_PROTOCOL, included into
> EFI specification since version 2.10, as a better alternative to
> using DXE services for memory protection attributes manipulation,
> since it is defined by the UEFI specification itself and not UEFI PI
> specification. This protocol is not widely available so the code
> using DXE services is kept in place as a fallback in case specific
> implementation does not support the new protocol.
> One of EFI implementations that already support
> EFI_MEMORY_ATTTRIBUTE_PROTOCOL is Microsoft Project Mu [5].
>  

Because Peter Jones point out this patchset to me, so I tried it
on OVMF, and I set the EfiLoaderData in DXE memory protection policy:

Index: edk2/MdeModulePkg/MdeModulePkg.dec
===================================================================
--- edk2.orig/MdeModulePkg/MdeModulePkg.dec
+++ edk2/MdeModulePkg/MdeModulePkg.dec
@@ -1392,7 +1392,7 @@
   # e.g. 0x7BD4 can be used for all memory except Code and ACPINVS/Reserved. <BR>
   #
   # @Prompt Set DXE memory protection policy.
-  gEfiMdeModulePkgTokenSpaceGuid.PcdDxeNxMemoryProtectionPolicy|0x0000000|UINT64|0x00001048^M
+  gEfiMdeModulePkgTokenSpaceGuid.PcdDxeNxMemoryProtectionPolicy|0x0000004|UINT64|0x00001048^M
 
   ## PCI Serial Device Info. It is an array of Device, Function, and Power Management
   #  information that describes the path that contains zero or more PCI to PCI bridges


I applied this v2 patch set on top of v6.1-rc5 kernel, and boot with a shim which
set the PE NX-compatibility DLL Characteristic flag. I got a page fault exception:

Loading Linux 6.1.0-rc5-default+ ...
Loading initial ramdisk ...
!!!! X64 Exception Type - 0E(#PF - Page-Fault)  CPU Apic ID - 00000000 !!!!
ExceptionData - 0000000000000011  I:1 R:0 U:0 W:0 P:1 PK:0 SS:0 SGX:0
RIP  - 0000000076A3C390, CS  - 0000000000000038, RFLAGS - 0000000000210202
RAX  - 000000007D8CCDF8, RCX - 0000000076A3C390, RDX - 000000007DE86000
RBX  - 0000000076A3C000, RSP - 000000007FF0D2C8, RBP - 000000007DE86000
RSI  - 000000007F9EE018, RDI - 000000007DFD1C18
R8   - 0000000076A3C000, R9  - 0000000000000190, R10 - 000000007FF1D658
R11  - 0000000000000004, R12 - 0000000000000190, R13 - 000000007D8CCE00
R14  - 000000007D8C76B4, R15 - 000000007BF0CBD5
DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030
GS   - 0000000000000030, SS  - 0000000000000030
CR0  - 0000000080010033, CR2 - 0000000076A3C390, CR3 - 000000007FC01000
CR4  - 0000000000000668, CR8 - 0000000000000000
DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 000000007F9DE000 0000000000000047, LDTR - 0000000000000000
IDTR - 000000007F2E9018 0000000000000FFF,   TR - 0000000000000000
FXSAVE_STATE - 000000007FF0CF20
!!!! Find image based on IP(0x7BF0BAB5) /mnt/working/source_code-git/edk2/Build/OvmfX64/DEBUG_GCC5/X64/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableRuntimeDxe/DEBUG/VariableRuntimeDxe.dll (ImageBase=0000000000F40E7C, EntryPoint=0000000000F767B8) !!!!


My question is: Can I just set EfiLoaderData in DXE memory protection policy
in EDK2/OVMF to test this patchset? Or which platform (virtual or physical)
can we use for testing?

Thanks a lot!
Joey Lee