From d41fd8e839a31e6374cf37c8516311db4e4a3dbc Mon Sep 17 00:00:00 2001 From: Laszlo Ersek Date: Tue, 24 Oct 2017 17:21:25 +0200 Subject: [PATCH] OvmfPkg: restore temporary SEC/PEI RAM size to 64KB (1) In the PEI phase, the PCD database is maintained in a GUID HOB. In OVMF, we load the PCD PEIM before any other PEIMs (using APRIORI PEI), so that all other PEIMs can use dynamic PCDs. Consequently, - the PCD GUID HOB is initially allocated from the temporary SEC/PEI heap, - whenever we introduce a dynamic PCD to a PEIM built into OVMF such that the PCD is new to OVMF's whole PEI phase, the PCD GUID HOB (and its temporary heap footprint) grow. I've noticed that, if we add just one more dynamic PCD to the PEI phase, then in the X64 build, - we get very close to the half of the temporary heap (i.e., 8192 bytes), - obscure PEI phase hangs or DXE core initialization failures (ASSERTs) occur. The symptoms vary between the FD_SIZE_2MB and FD_SIZE_4MB builds of X64 OVMF. (2) I've found that commit 2bbd7e2fbd4b ("UefiCpuPkg/MtrrLib: Update algorithm to calculate optimal settings", 2017-09-27) introduced a large (16KB) stack allocation: > The patch changes existing MtrrSetMemoryAttributeInMtrrSettings() and > MtrrSetMemoryAttribute() to use the 4-page stack buffer for calculation. > ... > +#define SCRATCH_BUFFER_SIZE (4 * SIZE_4KB) > ... > @@ -2207,17 +2462,66 @@ MtrrSetMemoryAttributeInMtrrSettings ( > ... > + UINT8 Scratch[SCRATCH_BUFFER_SIZE]; (3) OVMF's temp SEC/PEI RAM size has been 32KB ever since commit 7cb6b0e06809 ("OvmfPkg: Move SEC/PEI Temporary RAM from 0x70000 to 0x810000", 2014-01-21) Of that, the upper 16KB half is stack (growing down), and the lower 16KB half is heap. Thus, OvmfPkg/PlatformPei's calls to "UefiCpuPkg/Library/MtrrLib", in QemuInitializeRam(), cause the Scratch array to overflow the entire stack (heading towards lower addresses), and corrupt the heap below the stack. It turns out that the total stack demand is about 24KB, so the overflow is able to corrupt the upper 8KB of the heap. If that part of the heap is actually used (for example because we grow the PCD GUID HOB sufficiently), mayhem ensues. (4) Right after commit 7cb6b0e06809 (see above), there would be no room left above the 32KB temp SEC/PEI RAM. However, given more recent commits 45d870815156 ("OvmfPkg/PlatformPei: rebase and resize the permanent PEI memory for S3", 2016-07-13) 6b04cca4d697 ("OvmfPkg: remove PcdS3AcpiReservedMemoryBase, PcdS3AcpiReservedMemorySize", 2016-07-12) we can now restore the temp SEC/PEI RAM size to the original (pre-7cb6b0e06809) 64KB. This will allow for a 32KB temp SEC/PEI stack, which accommodates the ~24KB demand mentioned in (3). (Prior patches in this series will let us monitor the stack usage in the future.) Cc: Ard Biesheuvel Cc: Jordan Justen Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=747 Ref: http://mid.mail-archive.com/a49cc089-12ae-a887-a4d6-4dc509233a74@redhat.com Ref: http://mid.mail-archive.com/03e369bb-77c4-0134-258f-bdae62cbc8c5@redhat.com Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek Reviewed-by: Ard Biesheuvel Reviewed-by: Jordan Justen --- OvmfPkg/OvmfPkgIa32.fdf | 2 +- OvmfPkg/OvmfPkgIa32X64.fdf | 2 +- OvmfPkg/OvmfPkgX64.fdf | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) diff --git a/OvmfPkg/OvmfPkgIa32.fdf b/OvmfPkg/OvmfPkgIa32.fdf index 7515224118..06a439f8cb 100644 --- a/OvmfPkg/OvmfPkgIa32.fdf +++ b/OvmfPkg/OvmfPkgIa32.fdf @@ -82,7 +82,7 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase|gUefiOvmfPkgTokenSpaceGuid. 0x007000|0x001000 gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize -0x010000|0x008000 +0x010000|0x010000 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize 0x020000|0x0E0000 diff --git a/OvmfPkg/OvmfPkgIa32X64.fdf b/OvmfPkg/OvmfPkgIa32X64.fdf index f1a2044fb7..ced4c5639f 100644 --- a/OvmfPkg/OvmfPkgIa32X64.fdf +++ b/OvmfPkg/OvmfPkgIa32X64.fdf @@ -82,7 +82,7 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase|gUefiOvmfPkgTokenSpaceGuid. 0x007000|0x001000 gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize -0x010000|0x008000 +0x010000|0x010000 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize 0x020000|0x0E0000 diff --git a/OvmfPkg/OvmfPkgX64.fdf b/OvmfPkg/OvmfPkgX64.fdf index 32000a3b93..62dd58f6e4 100644 --- a/OvmfPkg/OvmfPkgX64.fdf +++ b/OvmfPkg/OvmfPkgX64.fdf @@ -82,7 +82,7 @@ gUefiOvmfPkgTokenSpaceGuid.PcdOvmfLockBoxStorageBase|gUefiOvmfPkgTokenSpaceGuid. 0x007000|0x001000 gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|gUefiOvmfPkgTokenSpaceGuid.PcdGuidedExtractHandlerTableSize -0x010000|0x008000 +0x010000|0x010000 gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamBase|gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSecPeiTempRamSize 0x020000|0x0E0000