Re: [edk2-devel] [PATCH 1/1] ArmVirtPkg/FdtPL011SerialPortLib: initialize implicitly

["Laszlo Ersek" <lersek@redhat.com>]

On 9/30/23 23:23, Laszlo Ersek wrote:
> FdtPL011SerialPortLib claims that it's usable from the DXE_CORE. That's
> not correct: the DXE_CORE calls DEBUG() and ASSERT() before it calls
> ProcessLibraryConstructorList(). Via the BaseDebugLibSerialPort instance,
> those DEBUG() and ASSERT() calls result in SerialPortWrite() calls, before
> ProcessLibraryConstructorList() called either our constructor
> FdtPL011SerialPortLibInitialize(), or BaseDebugLibSerialPortConstructor().
> 
> (And even if the DXE_CORE called the latter function early enough, it
> would just invoke our SerialPortInitialize() function -- which does
> nothing.)
> 
> This means that the earliest DXE_CORE debug messages are lost.
> 
> Rename FdtPL011SerialPortLibInitialize() to SerialPortInitialize(), so
> that the same initialization occur through the constructor and the public
> SerialPortInitialize() library API.
> 
> Turn SerialPortInitialize() calls after the first one into no-ops.
> 
> Our SerialPortLib APIs already use (mSerialBaseAddress != 0) to track
> initialization. Rework those checks to actually initialize the library if
> that hasn't happened yet.
> 
> The following new lines appear in the log:
> 
>> CoreInitializeMemoryServices:
>>   BaseAddress - 0x48000000 Length - 0xF8000000 MinimalMemorySizeNeeded - 0x38C8000
>> InstallProtocolInterface: [EfiLoadedImageProtocol] 46EFC3E0
>> ProtectUefiImageCommon - 0x46EFC3E0
>>   - 0x0000000046EB2000 - 0x0000000000068000
> 
> (0x46EB2000 is the load address of the DXE Core.)
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Leif Lindholm <quic_llindhol@quicinc.com>
> Cc: Oliver Smith-Denny <osde@linux.microsoft.com>
> Cc: Oliver Steffen <osteffen@redhat.com>
> Cc: Sami Mujawar <sami.mujawar@arm.com>
> Cc: Sean Brogan <sean.brogan@microsoft.com>
> Reported-by: Oliver Smith-Denny <osde@linux.microsoft.com>
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     In my opinion this is the wrong approach to fix the bug, but the right
>     approach would require so much work all over edk2 (and outside of it)
>     that it's just not practical.

NB I'd still like this patch to be merged; "wrong approach" is too
strongly worded. I'd now refine that as "theoretically not 100% pure".
Merging this one is a compromise, but an easy one -- I had worked
several hours on the "pure approach", and it absolutely spiralled out of
control. So this is the only one practical thing to do.

Thanks
Laszlo

> 
>  ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.inf |  2 +-
>  ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c   | 84 ++++++++++++--------
>  2 files changed, 52 insertions(+), 34 deletions(-)
> 
> diff --git a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.inf b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.inf
> index 2b9a34aa30d1..c417514e3ed5 100644
> --- a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.inf
> +++ b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.inf
> @@ -15,7 +15,7 @@ [Defines]
>    MODULE_TYPE                    = BASE
>    VERSION_STRING                 = 1.0
>    LIBRARY_CLASS                  = SerialPortLib|DXE_CORE DXE_DRIVER UEFI_DRIVER DXE_RUNTIME_DRIVER UEFI_APPLICATION
> -  CONSTRUCTOR                    = FdtPL011SerialPortLibInitialize
> +  CONSTRUCTOR                    = SerialPortInitialize
>  
>  [Sources.common]
>    FdtPL011SerialPortLib.c
> diff --git a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> index 614ea5a860b9..9d71f369570f 100644
> --- a/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> +++ b/ArmVirtPkg/Library/FdtPL011SerialPortLib/FdtPL011SerialPortLib.c
> @@ -23,49 +23,57 @@
>  #include <Library/HobLib.h>
>  #include <Guid/EarlyPL011BaseAddress.h>
>  
> -STATIC UINTN  mSerialBaseAddress;
> -
> -RETURN_STATUS
> -EFIAPI
> -SerialPortInitialize (
> -  VOID
> -  )
> -{
> -  return RETURN_SUCCESS;
> -}
> +STATIC UINTN          mSerialBaseAddress;
> +STATIC RETURN_STATUS  mPermanentStatus = RETURN_SUCCESS;
>  
>  /**
> -
>    Program hardware of Serial port
>  
> -  @return    RETURN_NOT_FOUND if no PL011 base address could be found
> -             Otherwise, result of PL011UartInitializePort () is returned
> +  @retval RETURN_SUCCESS    If the serial port was initialized successfully by
> +                            this call, or an earlier call, to
> +                            SerialPortInitialize().
>  
> +  @retval RETURN_NOT_FOUND  If no PL011 base address could be found.
> +
> +  @return                   Error codes forwarded from
> +                            PL011UartInitializePort().
>  **/
>  RETURN_STATUS
>  EFIAPI
> -FdtPL011SerialPortLibInitialize (
> +SerialPortInitialize (
>    VOID
>    )
>  {
>    VOID                *Hob;
> +  RETURN_STATUS       Status;
>    CONST UINT64        *UartBase;
> +  UINTN               SerialBaseAddress;
>    UINT64              BaudRate;
>    UINT32              ReceiveFifoDepth;
>    EFI_PARITY_TYPE     Parity;
>    UINT8               DataBits;
>    EFI_STOP_BITS_TYPE  StopBits;
>  
> +  if (mSerialBaseAddress != 0) {
> +    return RETURN_SUCCESS;
> +  }
> +
> +  if (RETURN_ERROR (mPermanentStatus)) {
> +    return mPermanentStatus;
> +  }
> +
>    Hob = GetFirstGuidHob (&gEarlyPL011BaseAddressGuid);
>    if ((Hob == NULL) || (GET_GUID_HOB_DATA_SIZE (Hob) != sizeof *UartBase)) {
> -    return RETURN_NOT_FOUND;
> +    Status = RETURN_NOT_FOUND;
> +    goto Failed;
>    }
>  
>    UartBase = GET_GUID_HOB_DATA (Hob);
>  
> -  mSerialBaseAddress = (UINTN)*UartBase;
> -  if (mSerialBaseAddress == 0) {
> -    return RETURN_NOT_FOUND;
> +  SerialBaseAddress = (UINTN)*UartBase;
> +  if (SerialBaseAddress == 0) {
> +    Status = RETURN_NOT_FOUND;
> +    goto Failed;
>    }
>  
>    BaudRate         = (UINTN)PcdGet64 (PcdUartDefaultBaudRate);
> @@ -74,15 +82,25 @@ FdtPL011SerialPortLibInitialize (
>    DataBits         = PcdGet8 (PcdUartDefaultDataBits);
>    StopBits         = (EFI_STOP_BITS_TYPE)PcdGet8 (PcdUartDefaultStopBits);
>  
> -  return PL011UartInitializePort (
> -           mSerialBaseAddress,
> -           FixedPcdGet32 (PL011UartClkInHz),
> -           &BaudRate,
> -           &ReceiveFifoDepth,
> -           &Parity,
> -           &DataBits,
> -           &StopBits
> -           );
> +  Status = PL011UartInitializePort (
> +             SerialBaseAddress,
> +             FixedPcdGet32 (PL011UartClkInHz),
> +             &BaudRate,
> +             &ReceiveFifoDepth,
> +             &Parity,
> +             &DataBits,
> +             &StopBits
> +             );
> +  if (RETURN_ERROR (Status)) {
> +    goto Failed;
> +  }
> +
> +  mSerialBaseAddress = SerialBaseAddress;
> +  return RETURN_SUCCESS;
> +
> +Failed:
> +  mPermanentStatus = Status;
> +  return Status;
>  }
>  
>  /**
> @@ -102,7 +120,7 @@ SerialPortWrite (
>    IN UINTN  NumberOfBytes
>    )
>  {
> -  if (mSerialBaseAddress != 0) {
> +  if (!RETURN_ERROR (SerialPortInitialize ())) {
>      return PL011UartWrite (mSerialBaseAddress, Buffer, NumberOfBytes);
>    }
>  
> @@ -126,7 +144,7 @@ SerialPortRead (
>    IN  UINTN  NumberOfBytes
>    )
>  {
> -  if (mSerialBaseAddress != 0) {
> +  if (!RETURN_ERROR (SerialPortInitialize ())) {
>      return PL011UartRead (mSerialBaseAddress, Buffer, NumberOfBytes);
>    }
>  
> @@ -146,7 +164,7 @@ SerialPortPoll (
>    VOID
>    )
>  {
> -  if (mSerialBaseAddress != 0) {
> +  if (!RETURN_ERROR (SerialPortInitialize ())) {
>      return PL011UartPoll (mSerialBaseAddress);
>    }
>  
> @@ -199,7 +217,7 @@ SerialPortSetAttributes (
>  {
>    RETURN_STATUS  Status;
>  
> -  if (mSerialBaseAddress == 0) {
> +  if (RETURN_ERROR (SerialPortInitialize ())) {
>      Status = RETURN_UNSUPPORTED;
>    } else {
>      Status = PL011UartInitializePort (
> @@ -234,7 +252,7 @@ SerialPortSetControl (
>  {
>    RETURN_STATUS  Status;
>  
> -  if (mSerialBaseAddress == 0) {
> +  if (RETURN_ERROR (SerialPortInitialize ())) {
>      Status = RETURN_UNSUPPORTED;
>    } else {
>      Status = PL011UartSetControl (mSerialBaseAddress, Control);
> @@ -261,7 +279,7 @@ SerialPortGetControl (
>  {
>    RETURN_STATUS  Status;
>  
> -  if (mSerialBaseAddress == 0) {
> +  if (RETURN_ERROR (SerialPortInitialize ())) {
>      Status = RETURN_UNSUPPORTED;
>    } else {
>      Status = PL011UartGetControl (mSerialBaseAddress, Control);
> 
> 
> 
> 
> 



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