[edk2-devel][Patch 1/3] MdePkg/UefiDebugLibConOut: Add destructor to CloseEvent

[Liming Gao]

Philippe:

> -----Original Message-----
> From: devel at edk2.groups.io [mailto:devel at edk2.groups.io] On Behalf Of Philippe Mathieu-Daudé
> Sent: Tuesday, July 30, 2019 1:49 AM
> To: Laszlo Ersek <lersek at redhat.com>; devel at edk2.groups.io; Xu, Wei6 <wei6.xu at intel.com>
> Cc: Kinney, Michael D <michael.d.kinney at intel.com>; Gao, Liming <liming.gao at intel.com>
> Subject: Re: [edk2-devel][Patch 1/3] MdePkg/UefiDebugLibConOut: Add destructor to CloseEvent
> 
> On 7/29/19 6:09 PM, Laszlo Ersek wrote:
> > On 07/29/19 16:38, Philippe Mathieu-Daudé wrote:
> >> Hi,
> >>
> >> On 7/26/19 5:10 AM, Xu, Wei6 wrote:
> >>> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2012
> >>>
> >>> When driver is unloaded, the ExitBootSerivesEvent must be closed at
> >>> the same time. Otherwise exception will occur when ExitBootServices.
> >>>
> >>> Cc: Michael D Kinney <michael.d.kinney at intel.com>
> >>> Cc: Liming Gao <liming.gao at intel.com>
> >>> Signed-off-by: Wei6 Xu <wei6.xu at intel.com>
> >>> ---
> >>>  .../UefiDebugLibConOut/DebugLibConstructor.c       | 23 ++++++++++++++++++++++
> >>>  .../UefiDebugLibConOut/UefiDebugLibConOut.inf      |  1 +
> >>>  2 files changed, 24 insertions(+)
> >>>
> >>> diff --git a/MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c
> b/MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c
> >>> index 8005370372..ed73f92818 100644
> >>> --- a/MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c
> >>> +++ b/MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c
> >>> @@ -73,5 +73,28 @@ DxeDebugLibConstructor(
> >>>                                  &mExitBootServicesEvent
> >>>                                  );
> >>>
> >>>    return EFI_SUCCESS;
> >>>  }
> >>> +
> >>> +/**
> >>> +  The destructor closes Exit Boot Services Event.
> >>> +
> >>> +  @param  ImageHandle   The firmware allocated handle for the EFI image.
> >>> +  @param  SystemTable   A pointer to the EFI System Table.
> >>> +
> >>> +  @retval EFI_SUCCESS   The destructor always returns EFI_SUCCESS.
> >>> +
> >>> +**/
> >>> +EFI_STATUS
> >>> +EFIAPI
> >>> +DxeDebugLibDestructor(
> >>> +  IN EFI_HANDLE                 ImageHandle,
> >>> +  IN EFI_SYSTEM_TABLE           *SystemTable
> >>> +  )
> >>> +{
> >>> +  if (mExitBootServicesEvent != NULL) {
> >>> +    SystemTable->BootServices->CloseEvent (mExitBootServicesEvent);
> >>> +  }
> >>
> >> Is it OK to let mDebugST (pointer to SystemTable) initialized?
> >
> > Yes, ignoring "mDebugST" in this function should be.
> >
> > "mDebugST" is a global variable (= an object with file scope and static
> > storage duration) defined in
> > "MdePkg/Library/UefiDebugLibConOut/DebugLibConstructor.c".
> >
> > The library instance (for which the destructor function is being added)
> > is linked into driver and application modules. The destructor function
> > is invoked whenever the driver or application is about to be unloaded
> > from memory. As part of the unloading, the ExitBootServices()
> > notification function -- which was automatically registered via the
> > constructor function when the driver or application started up -- must
> > be de-registered, otherwise the platform firmware will be left with a
> > dangling callback pointer. That's what the CloseEvent() above takes care
> > of. But it's OK to ignore "mDebugST" altogether, as the memory that
> > "mDebugST" lives inside is about to be reclaimed by the platform
> > firmware anyway.
> >
> > The library destructor is invoked:
> > - when a UEFI application exits (with success or failure), by returning
> > from its entry point function, or by calling the Exit() boot service
> >
> > - when a UEFI driver exits with failure (hence it will be unloaded
> > automatically)
> >
> > - when a UEFI driver exited with success (hence staying resident), and
> > it supports unloading, and now another agent is unloading it with the
> > UnloadImage() boot service (such as the UEFI shell with the "unload"
> > command, IIRC).
> 
> Thanks Laszlo for the explanations!
> 
> I noticed (late) this series is already pushed (commits
> e92bdcb3ecbf..28bc6992400) so it doesn't require review anymore.

Sorry, I forget to send the mail to say I have pushed these serials. 
These changes are clear to me. 
> 
> BTW Liming the author name seems incorrect: Wei6 Xu and Xu, Wei6.
> 
Seemly, the author doesn't configure his name in the consistent way. 
Author name may be Wei Xu. 

Thanks
Liming
> >>> +
> >>> +  return EFI_SUCCESS;
> >>> +}
> >>> diff --git a/MdePkg/Library/UefiDebugLibConOut/UefiDebugLibConOut.inf
> b/MdePkg/Library/UefiDebugLibConOut/UefiDebugLibConOut.inf
> >>> index 4c279a5bf2..b577d52ac6 100644
> >>> --- a/MdePkg/Library/UefiDebugLibConOut/UefiDebugLibConOut.inf
> >>> +++ b/MdePkg/Library/UefiDebugLibConOut/UefiDebugLibConOut.inf
> >>> @@ -20,10 +20,11 @@
> >>>    MODULE_TYPE                    = UEFI_DRIVER
> >>>    VERSION_STRING                 = 1.0
> >>>    LIBRARY_CLASS                  = DebugLib|DXE_CORE DXE_DRIVER DXE_RUNTIME_DRIVER UEFI_APPLICATION UEFI_DRIVER
> >>>
> >>>    CONSTRUCTOR                    = DxeDebugLibConstructor
> >>> +  DESTRUCTOR                     = DxeDebugLibDestructor
> >>>
> >>>  #
> >>>  #  VALID_ARCHITECTURES           = IA32 X64 EBC
> >>>  #
> >>>
> >>>
> >>
> >>
> >>
> >
> 
> 


-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.

View/Reply Online (#44576): https://edk2.groups.io/g/devel/message/44576
Mute This Topic: https://groups.io/mt/32605738/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub  [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-