Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: fix infinite loop issue in SMM profile

["Wang, Jian J" <jian.j.wang@intel.com>]

They're following 3 pages:

   | Page before | Page triggering #PF | Page after |


because all I need to do is to make sure that there's no non-present pages during
memory operation cross pages.

Regards,
Jian


> -----Original Message-----
> From: Yao, Jiewen
> Sent: Tuesday, February 06, 2018 2:23 PM
> To: Wang, Jian J <jian.j.wang@intel.com>; edk2-devel@lists.01.org
> Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>; Dong,
> Eric <eric.dong@intel.com>
> Subject: RE: [edk2] [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: fix infinite loop
> issue in SMM profile
> 
> Hi
> May I know how "3" is calculated?
> 
> +  RestorePageNumber = 3;
> 
> Thank you
> Yao Jiewen
> 
> 
> > -----Original Message-----
> > From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Jian
> J
> > Wang
> > Sent: Tuesday, February 6, 2018 11:02 AM
> > To: edk2-devel@lists.01.org
> > Cc: Ni, Ruiyu <ruiyu.ni@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Laszlo
> > Ersek <lersek@redhat.com>; Dong, Eric <eric.dong@intel.com>
> > Subject: [edk2] [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: fix infinite loop issue
> in
> > SMM profile
> >
> > The infinite loop is caused by the memory instruction, such as
> > "rep mov", operating on memory block crossing boundary of NON-PRESENT
> > pages. Because the address triggering page fault set in CR2 will be in
> > the first page, SmmProfilePFHandler() will only change the first page
> > into PRESENT. The page following will be still in NON-PRESENT status.
> >
> > Since SmmProfilePFHandler() will setup single-step trap for the
> > instruction causing #PF, when the handler returns back to the
> > instruction and re-execute it, both #DB and #PF will be triggered
> > because the instruction wants to access both first and second page
> > but only first page is PRESENT.
> >
> > Normally #DB exception will be handled first and its handler will
> > change first page back to NON-PRESENT status. Then #PF is handled
> > and its handler will change first page to PRESENT status again and
> > setup another single-step for the instruction triggering #PF. Then
> > the whole system falls into an infinite loop and the memory operation
> > will never move on.
> >
> > This patch fix above situation by always changing 3 pages to PRESENT
> > status instead of just 1 page. Those 3 pages include the page before
> > and after the page causing #PF because memory operation instruction
> > may have direction flag (DF) set or cleared.
> >
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> > ---
> >  UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c | 22 ++++++++++++++++++----
> >  1 file changed, 18 insertions(+), 4 deletions(-)
> >
> > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c
> > b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c
> > index 9588eaf029..8cdfc82a92 100644
> > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c
> > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c
> > @@ -1302,6 +1302,8 @@ SmmProfilePFHandler (
> >  {
> >    UINT64                *PageTable;
> >    UINT64                PFAddress;
> > +  UINT64                RestoreAddress;
> > +  UINTN                 RestorePageNumber;
> >    UINTN                 CpuIndex;
> >    UINTN                 Index;
> >    UINT64                InstructionAddress;
> > @@ -1331,10 +1333,22 @@ SmmProfilePFHandler (
> >    PFAddress         = AsmReadCr2 ();
> >    CpuIndex          = GetCpuIndex ();
> >
> > -  if (PFAddress <= 0xFFFFFFFF) {
> > -    RestorePageTableBelow4G (PageTable, PFAddress, CpuIndex, ErrorCode);
> > -  } else {
> > -    RestorePageTableAbove4G (PageTable, PFAddress, CpuIndex, ErrorCode,
> > &IsValidPFAddress);
> > +  //
> > +  // Memory operation cross pages, like "rep mov" instruction, will cause
> > +  // infinite loop between this and Debug Trap handler. Since the direction
> > +  // of memory operation is unknown, the pages before and after current
> page
> > +  // should be taken into account as well.
> > +  //
> > +  RestorePageNumber = 3;
> > +  RestoreAddress = PFAddress - EFI_PAGE_SIZE;
> > +  while (RestorePageNumber > 0) {
> > +    if (RestoreAddress <= 0xFFFFFFFF) {
> > +      RestorePageTableBelow4G (PageTable, RestoreAddress, CpuIndex,
> > ErrorCode);
> > +    } else {
> > +      RestorePageTableAbove4G (PageTable, RestoreAddress, CpuIndex,
> > ErrorCode, &IsValidPFAddress);
> > +    }
> > +    RestoreAddress += EFI_PAGE_SIZE;
> > +    RestorePageNumber--;
> >    }
> >
> >    if (!IsValidPFAddress) {
> > --
> > 2.14.1.windows.1
> >
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