Re: OpenProtocol() giving me EFI_INVALID_PARAMETER

["Ethin Probst" <harlydavidsen@gmail.com>]

I mean, possible... The code I'm using to initialize the handle buffer is this:

```C
EFI_STATUS EFIAPI UefiMain(IN EFI_HANDLE imageHandle, IN EFI_SYSTEM_TABLE* st) {
  Print(L"Attempting to find USB IO protocol\n");
  UINTN numHandles = 0;
  UINTN i = 0;
  UINT32 UsbStatus = 0;
  EFI_HANDLE* handles = NULL;
  EFI_USB_IO_PROTOCOL* UsbIo = NULL;
  EFI_STATUS status = st->BootServices->LocateHandleBuffer(ByProtocol,
&gEfiUsbIoProtocolGuid, NULL, &numHandles, &handles);
  if (EFI_ERROR(status)) {
    Print(L"Cannot find any handles for USB devices, reason: %r\n", status);
    return EFI_ABORTED;
  }
  Print(L"Found %d USB devices; enumerating\n", numHandles);
  for (; i < numHandles; ++i) {
    Print(L"Trying to open handle %d (%x)... ", i, handles[i]);
    status = st->BootServices->OpenProtocol(handles[i],
&gEfiUsbIoProtocolGuid, (void**)&UsbIo, imageHandle, NULL,
EFI_OPEN_PROTOCOL_EXCLUSIVE);
    if (EFI_ERROR(status)) {
      Print(L"%r, skipping\n", status);
      continue;
    }
    // ...
```
I've done my best to follow SEI secure C coding standards, like
initializing all variables, regardless of type -- e.g. initializing
pointers to 0/NULL. But I will definitely try that idea.

On 7/17/21, Andrew Fish <afish@apple.com> wrote:
>
>
>> On Jul 17, 2021, at 9:41 AM, Ethin Probst <harlydavidsen@gmail.com>
>> wrote:
>>
>> Hey all,
>>
>> So my UsbAudio.efi app has hit a bit of a roadblock. This code:
>>
>> ```C
>>    status = st->BootServices->OpenProtocol(handles[i],
>> &gEfiUsbIoProtocolGuid, (void**)&UsbIo, imageHandle, NULL,
>> EFI_OPEN_PROTOCOL_EXCLUSIVE);
>>    if (EFI_ERROR(status)) {
>>      Print(L"%r, skipping\n", status);
>>      continue;
>>    }
>> ```
>
> How are you constructing handle[]? Could it have gotten stale? You could
> print out the value of handle[I] on the failure.
>
> The contents of a handle are not defined, but the current implementation is
> a pointer to an IHANDLE internal data structure in the DXE Core. If you are
> at the UEFI Shell and you `dh -v <handleNum> it will show the <handleNum>
> and the value.
>
> Shell> dh -v 98
> 98: 6d5CF18
> ….
>
> I think you can `dh -p UsbIo’ to get the list of the UsbIo handles.
>
> So you can poke around and see what is happening on that handle.
>
> I guess the handle[] array could be getting corrupted? So you could check
> for that?
>
> Thanks,
>
> Andrew Fish
>
>> Is giving me EFI_INVALID_PARAMETER and I don’t know why. I don't think
>> I'm violating any of its constraints, according to the specification,
>> and I haven't touched this code since it was written. It also happens
>> irregularly: sometimes it happens on the USB audio streaming device,
>> or if I have a device plugged in it might happen on that device, you
>> get the idea. But it doesn't consistently fail. Does anybody have any
>> idea what's going on?
>>
>> --
>> Signed,
>> Ethin D. Probst
>
>


-- 
Signed,
Ethin D. Probst