Reviewed-by: Eric Dong <eric.d...@intel.com>
> -----Original Message----- > From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of > Jian J Wang > Sent: Friday, March 1, 2019 8:58 AM > To: edk2-devel@lists.01.org > Cc: Ni, Ray <ray...@intel.com>; Laszlo Ersek <ler...@redhat.com>; Dong, > Eric <eric.d...@intel.com>; Zeng, Star <star.z...@intel.com> > Subject: [edk2] [PATCH 2] UefiCpuPkg: restore strict page attributes via #DB > in nonstop mode only > > > v2: Per Laszlo's comments, repack origianl two patches into one with > > title changed and relevant commits added > > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1576 > > The root cause of this issue is that non-stop mode of Heap Guard and NULL > Detection set TF bit (single-step) in EFLAG unconditionally in the common > handler in CpuExceptionLib. > > If PcdCpuSmmStaticPageTable is FALSE, the SMM will only create page table > for memory below 4G. If SMM tries to access memory beyond 4G, a page > fault exception will be triggered and the memory to access will be added to > page table so that SMM code can continue the access. > > Because of above issue, the TF bit is set after the page fault is handled and > then fall into another DEBUG exception. Since non-stop mode of Heap Guard > and NULL Detection are not enabled, no special DEBUG exception handler is > registered. The default handler just prints exception context and go into > dead loop. > > Actually EFLAGS can be changed in any standard exception handler. > There's no need to do single-step setup in assembly code. So the fix is to > move the logic to C code part of page fault exception handler so that we can > fully validate the configuration and prevent TF bit from being set > unexpectedly. > > Fixes: dcc026217fdc363f55c217039fc43d344f69fed6 > 16b918bbaf51211a32ae04d9d8a5ba6ccca25a6a > Test: > - Pass special test of accessing memory beyond 4G in SMM mode > - Boot to OS with Qemu emulator platform (Fedora27, Ubuntu18.04, > Windows7, Windows10) > > Cc: Eric Dong <eric.d...@intel.com> > Cc: Laszlo Ersek <ler...@redhat.com> > Cc: Ruiyu Ni <ruiyu...@intel.com> > Cc: Star Zeng <star.z...@intel.com> > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Jian J Wang <jian.j.w...@intel.com> > Acked-by: Laszlo Ersek <ler...@redhat.com> > --- > UefiCpuPkg/CpuDxe/CpuPageTable.c | 11 ++++++++++- > .../Ia32/ExceptionHandlerAsm.nasm | 7 ------- > .../X64/ExceptionHandlerAsm.nasm | 4 ---- > 3 files changed, 10 insertions(+), 12 deletions(-) > > diff --git a/UefiCpuPkg/CpuDxe/CpuPageTable.c > b/UefiCpuPkg/CpuDxe/CpuPageTable.c > index 4bee8c7772..812537417d 100644 > --- a/UefiCpuPkg/CpuDxe/CpuPageTable.c > +++ b/UefiCpuPkg/CpuDxe/CpuPageTable.c > @@ -1300,7 +1300,16 @@ PageFaultExceptionHandler ( > // Display ExceptionType, CPU information and Image information > // > DumpCpuContext (ExceptionType, SystemContext); > - if (!NonStopMode) { > + if (NonStopMode) { > + // > + // Set TF in EFLAGS > + // > + if (mPagingContext.MachineType == IMAGE_FILE_MACHINE_I386) { > + SystemContext.SystemContextIa32->Eflags |= (UINT32)BIT8; > + } else { > + SystemContext.SystemContextX64->Rflags |= (UINT64)BIT8; > + } > + } else { > CpuDeadLoop (); > } > } > diff --git > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionHandlerAsm. > nasm > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionHandlerAsm. > nasm > index 6fcf5fb23f..45d6474091 100644 > --- > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionHandlerAsm. > nasm > +++ > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionHandlerAsm > +++ .nasm > @@ -383,13 +383,6 @@ ErrorCodeAndVectorOnStack: > pop dword [ebp - 4] > mov esp, ebp > pop ebp > - > -; Enable TF bit after page fault handler runs > - cmp dword [esp], 14 ; #PF? > - jne .5 > - bts dword [esp + 16], 8 ; EFLAGS > - > -.5: > add esp, 8 > cmp dword [esp - 16], 0 ; check > EXCEPTION_HANDLER_CONTEXT.OldIdtHandler > jz DoReturn > diff --git > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > index f842af2336..7b97810d10 100644 > --- > a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n > asm > +++ > b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm. > +++ nasm > @@ -336,10 +336,6 @@ HasErrorCode: > pop r15 > > mov rsp, rbp > - cmp qword [rbp + 8], 14 ; #PF? > - jne .1 > - bts qword [rsp + 40], 8 ; RFLAGS.TF > -.1: > pop rbp > add rsp, 16 > cmp qword [rsp - 32], 0 ; check > EXCEPTION_HANDLER_CONTEXT.OldIdtHandler > -- > 2.17.1.windows.2 > > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
