On 4/14/23 15:23, Tom Lendacky wrote:
I've been trying to debug a problem I'm seeing when I moved to the GCC 12
compiler. Under SEV it results in the guest crashing.
False alarm, I was on the wrong branch that does not have ff36b2550f94
("OvmfPkg/Sec: fix stack switch")... disregard.
Thanks,
Tom
I narrowed the issue down to the call to TemporaryRamMigration() in
PeiCheckAndSwitchStack() of MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c.
I get this output on GCC11:
Old Stack size 32768, New stack size 131072
Stack Hob: BaseAddress=0x3BF76000 Length=0x20000
Heap Offset = 0x3B786000 Stack Offset = 0x3B776000
*** DEBUG: PeiCheckAndSwitchStack:851 - SecCoreData=3BF95D20
TemporaryRamMigration(0x810000, 0x3BF8E000, 0x10000)
*** DEBUG: PeiCheckAndSwitchStack:871 - SecCoreData=3BF95D20
and everything is good.
However, I get this output on GCC12:
Old Stack size 32768, New stack size 131072
Stack Hob: BaseAddress=0x3BF76000 Length=0x20000
Heap Offset = 0x3B786000 Stack Offset = 0x3B776000
*** DEBUG: PeiCheckAndSwitchStack:851 - SecCoreData=3BF95D20
TemporaryRamMigration(0x810000, 0x3BF8E000, 0x10000)
*** DEBUG: PeiCheckAndSwitchStack:871 - SecCoreData=7770BD20
MMIO using encrypted memory: 7770BD48
!!!! X64 Exception Type - 0D(#GP - General Protection) CPU Apic ID -
00000000 !!!!
and terminate because SecCoreData has been corrupted and points to an
address in an MMIO range (this is an SEV-ES/SEV-SNP example).
As near as I can tell from looking at the object code, on GCC12 it looks
like the SecCoreData value is stored in the RBP register, which appears to
be getting corrupted when calling TemporaryRamMigration().
Does anyone have any thoughts on this?
Thanks,
Tom
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