OvmfPkg/Sec/Ia32: seed the temporary RAM with PcdInitValueInTempStack

This allows the PEI core to report the maximum temporary SEC/PEI stack
usage on the DEBUG_INFO level, in the PeiCheckAndSwitchStack() function
[MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c]:

* Normal boot:

> Temp Stack : BaseAddress=0x814000 Length=0x4000
> Temp Heap  : BaseAddress=0x810000 Length=0x4000
> Total temporary memory:    32768 bytes.
>   temporary memory stack ever used:       3664 bytes. <----
>   temporary memory heap used for HobList: 5904 bytes.
>   temporary memory heap occupied by memory pages: 0 bytes.

* S3 resume (with PEI decompression / SMM):

> Temp Stack : BaseAddress=0x814000 Length=0x4000
> Temp Heap  : BaseAddress=0x810000 Length=0x4000
> Total temporary memory:    32768 bytes.
>   temporary memory stack ever used:       3428 bytes. <----
>   temporary memory heap used for HobList: 4816 bytes.
>   temporary memory heap occupied by memory pages: 0 bytes.

I unit-tested this change by transitorily adding an infinite loop right
after the "rep stosd", and dumping the guest's temp SEC/PEI RAM (32KB
currently) while the guest was stuck in the loop. The dump includes one
dword from before and after the temp SEC/PEI RAM:

> $ virsh qemu-monitor-command GUEST_NAME --hmp 'xp /8194wx 0x80FFFC'
>
> 000000000080fffc: 0x00000000 0x5aa55aa5 0x5aa55aa5 0x5aa55aa5
> 000000000081000c: 0x5aa55aa5 0x5aa55aa5 0x5aa55aa5 0x5aa55aa5
> ...
> 0000000000817fec: 0x5aa55aa5 0x5aa55aa5 0x5aa55aa5 0x5aa55aa5
> 0000000000817ffc: 0x5aa55aa5 0x00000000

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=747
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

2 files changed, 19 insertions, 0 deletions

diff --git a/OvmfPkg/Sec/Ia32/SecEntry.nasm b/OvmfPkg/Sec/Ia32/SecEntry.nasm
index 7fee1c2b2e..03501969eb 100644
--- a/OvmfPkg/Sec/Ia32/SecEntry.nasm
+++ b/OvmfPkg/Sec/Ia32/SecEntry.nasm
@@ -29,6 +29,11 @@ extern ASM_PFX(SecCoreStartupWithStack)
 ; @param[in]  EAX   Initial value of the EAX register (BIST: Built-in Self Test)

 ; @param[in]  DI    'BP': boot-strap processor, or 'AP': application processor

 ; @param[in]  EBP   Pointer to the start of the Boot Firmware Volume

+; @param[in]  DS    Selector allowing flat access to all addresses

+; @param[in]  ES    Selector allowing flat access to all addresses

+; @param[in]  FS    Selector allowing flat access to all addresses

+; @param[in]  GS    Selector allowing flat access to all addresses

+; @param[in]  SS    Selector allowing flat access to all addresses

 ;

 ; @return     None  This routine does not return

 ;

@@ -36,6 +41,19 @@ global ASM_PFX(_ModuleEntryPoint)
 ASM_PFX(_ModuleEntryPoint):

 

     ;

+    ; Fill the temporary RAM with the initial stack value.

+    ; The loop below will seed the heap as well, but that's harmless.

+    ;

+    mov     eax, FixedPcdGet32 (PcdInitValueInTempStack)      ; dword to store

+    mov     edi, FixedPcdGet32 (PcdOvmfSecPeiTempRamBase)     ; base address,

+                                                              ;   relative to

+                                                              ;   ES

+    mov     ecx, FixedPcdGet32 (PcdOvmfSecPeiTempRamSize) / 4 ; dword count

+    cld                                                       ; store from base

+                                                              ;   up

+    rep stosd

+

+    ;

     ; Load temporary RAM stack based on PCDs

     ;

     %define SEC_TOP_OF_STACK (FixedPcdGet32 (PcdOvmfSecPeiTempRamBase) + \

diff --git a/OvmfPkg/Sec/SecMain.inf b/OvmfPkg/Sec/SecMain.inf
index 711b595309..6051cb3c6c 100644
--- a/OvmfPkg/Sec/SecMain.inf
+++ b/OvmfPkg/Sec/SecMain.inf
@@ -71,6 +71,7 @@
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress

   gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize

   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd

+  gEfiMdeModulePkgTokenSpaceGuid.PcdInitValueInTempStack

 

 [FeaturePcd]

   gUefiOvmfPkgTokenSpaceGuid.PcdSmmSmramRequire