Re: [edk2-devel] [PATCH v2 2/4] MdeModulePkg/SMM: Disallow unregister SMI handler in other SMI handler

["Zhiguang Liu" <zhiguang.liu@intel.com>]

Thanks Laszlo. Both are good comments. I will follow in next version

Thanks
Zhiguang

> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Wednesday, February 28, 2024 4:45 PM
> To: devel@edk2.groups.io; Liu, Zhiguang <zhiguang.liu@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>; Wu, Jiaxin
> <jiaxin.wu@intel.com>; Ni, Ray <ray.ni@intel.com>
> Subject: Re: [edk2-devel] [PATCH v2 2/4] MdeModulePkg/SMM: Disallow
> unregister SMI handler in other SMI handler
> 
> On 2/28/24 03:27, Zhiguang Liu wrote:
> > In last patch, we add code support to unregister SMI handler inside
> > itself. However, the code doesn't support unregister SMI handler
> > insider other SMI handler. While this is not a must-have usage.
> > So add check to disallow unregister SMI handler in other SMI handler.
> >
> > Cc: Liming Gao <gaoliming@byosoft.com.cn>
> > Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
> > ---
> >  MdeModulePkg/Core/PiSmmCore/Smi.c | 32
> > +++++++++++++++++++++++--------
> >  1 file changed, 24 insertions(+), 8 deletions(-)
> >
> > diff --git a/MdeModulePkg/Core/PiSmmCore/Smi.c
> > b/MdeModulePkg/Core/PiSmmCore/Smi.c
> > index 3489c130fd..1bfbc635fc 100644
> > --- a/MdeModulePkg/Core/PiSmmCore/Smi.c
> > +++ b/MdeModulePkg/Core/PiSmmCore/Smi.c
> > @@ -8,7 +8,8 @@
> >
> >  #include "PiSmmCore.h"
> >
> > -LIST_ENTRY  mSmiEntryList = INITIALIZE_LIST_HEAD_VARIABLE
> > (mSmiEntryList);
> > +SMI_HANDLER  *gCurrentSmiHandler = NULL;
> > +LIST_ENTRY   mSmiEntryList       = INITIALIZE_LIST_HEAD_VARIABLE
> (mSmiEntryList);
> >
> >  SMI_ENTRY  mRootSmiEntry = {
> >    SMI_ENTRY_SIGNATURE,
> > @@ -142,13 +143,18 @@ SmiManage (
> >      // Link points to may be freed if unregister SMI handler.
> >      //
> >      Link = Link->ForwardLink;
> > -
> > -    Status = SmiHandler->Handler (
> > -                           (EFI_HANDLE)SmiHandler,
> > -                           Context,
> > -                           CommBuffer,
> > -                           CommBufferSize
> > -                           );
> > +    //
> > +    // Assign gCurrentSmiHandle before calling the SMI handler and
> > +    // set to NULL when it returns.
> > +    //
> > +    gCurrentSmiHandler = SmiHandler;
> > +    Status             = SmiHandler->Handler (
> > +                                       (EFI_HANDLE)SmiHandler,
> > +                                       Context,
> > +                                       CommBuffer,
> > +                                       CommBufferSize
> > +                                       );
> > +    gCurrentSmiHandler = NULL;
> >
> >      switch (Status) {
> >        case EFI_INTERRUPT_PENDING:
> > @@ -328,6 +334,16 @@ SmiHandlerUnRegister (
> >      return EFI_INVALID_PARAMETER;
> >    }
> >
> > +  //
> > +  // Check if unregister SMI handler inside a SMI Handler  //  if
> > + (gCurrentSmiHandler != NULL) {
> > +    //
> > +    // Only allow to unregister SMI Handler inside itself.
> > +    //
> > +    ASSERT (gCurrentSmiHandler == SmiHandler);  }
> > +
> >    SmiEntry = SmiHandler->SmiEntry;
> >
> >    RemoveEntryList (&SmiHandler->Link);
> 
> (1) Why not:
> 
>   if ((gCurrentSmiHandler != NULL) && (gCurrentSmiHandler != SmiHandler)) {
>     return EFI_INVALID_PARAMETER;
>   }
> 
> ?
> 
> (2) Why do we call the new global variable "gCurrentSmiHandler" rather than
> "mCurrentSmiHandler"?
> 
> Thanks
> Laszlo



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