Prevent the UEFI watchdog timer from resetting the platform during MD…

…5 processing

* UEFI firmwares implement a watchdog timer, set to 5 minutes, that considers a bootloader
  is stalled if it hasn't reported to the watchdog during that time, as described in:
  https://uefi.org/specs/UEFI/2.9_A/07_Services_Boot_Services.html#efi-boot-services-setwatchdogtimer
* Because our processing can take much longer than 5 minutes, make sure we manifest ourselves
  to the watchdog for every 128 MB of data we process.
* Also update the MD5 buffer size to 64 MB and add a missing File->Close() call in parser.c

src/boot.c

@@ -177,6 +177,8 @@ STATIC EFI_STATUS ExitProcess(
 			// not be found, in which case continue boot right away.
 			if (Status != EFI_NOT_FOUND) {
 				SetText(TEXT_YELLOW);
+				// Give the user 1 hour to answer the question
+				gBS->SetWatchdogTimer(3600, 0x11D5, 0, NULL);
 				PrintCentered(L"Continue with boot? [y/N]", Console.Rows - 2);
 				gST->ConIn->Reset(gST->ConIn, FALSE);
 				while (gST->ConIn->ReadKeyStroke(gST->ConIn, &Key) == EFI_NOT_READY);
@@ -187,6 +189,8 @@ STATIC EFI_STATUS ExitProcess(
 			}
 			RunCountDown = FALSE;
 		}
+		// Reset the watchdog to the default 5 minutes timeout and system code
+		gBS->SetWatchdogTimer(300, 0, 0, NULL);
 		Status = gBS->LoadImage(FALSE, MainImageHandle, DevicePath, NULL, 0, &ImageHandle);
 		SafeFree(DevicePath);
 		if (Status == EFI_SUCCESS) {

src/boot.h

@@ -96,10 +96,10 @@ extern UINTN                AlertYPos;
 #define MD5_BLOCKSIZE       64
 
 /* Buffer size used for MD5 hashing */
-#define MD5_BUFFERSIZE      4096
+#define MD5_BUFFERSIZE      65536
 
-/* How many buffers we process between checks for user cancel */
-#define MD5_CHECK_CANCEL    64
+/* Number of MD5 buffers to process for each MB of data */
+#define MD5_PROCESSED_1MB   ((1024 * 1024) / MD5_BUFFERSIZE)
 
 /* Size of the hexascii representation of a hash */
 #define HASH_HEXASCII_SIZE  (MD5_HASHSIZE * 2)
@@ -266,6 +266,8 @@ NO_RETURN STATIC __inline VOID ShutDown()
 /* Freeze the system with current screen output, then shut it down after one hour */
 NO_RETURN STATIC __inline VOID Halt()
 {
+	// Disable the watchdog timer, since we don't want an early reset
+	gBS->SetWatchdogTimer(0, 0, 0, NULL);
 	Sleep((UINTN)3600 * 1000 * 1000);
 	gRT->ResetSystem(EfiResetShutdown, EFI_SUCCESS, 0, NULL);
 	while (1);

src/hash.c

@@ -281,10 +281,11 @@ EFI_STATUS HashFile(
 )
 {
 	STATIC UINTN BlocksProcessed = 0;
+	STATIC UINTN LastWatchDogReset = 0;
 	EFI_STATUS Status = EFI_INVALID_PARAMETER;
 	EFI_FILE_HANDLE File = NULL;
 	EFI_FILE_INFO* Info = NULL;
-	HASH_CONTEXT Context = { {0} };
+	HASH_CONTEXT Context = { 0 };
 	UINTN Size, ReadSize;
 	UINT64 ReadBytes;
 	UINT8 Buffer[MD5_BUFFERSIZE];
@@ -328,9 +329,15 @@ EFI_STATUS HashFile(
 		if (Progress != NULL && Progress->Type == PROGRESS_TYPE_BYTE)
 			Progress->Current += ReadSize;
 		Md5Write(&Context, Buffer, ReadSize);
-		// Check for user cancel and report progress every few blocks
-		if (BlocksProcessed++ % MD5_CHECK_CANCEL == 0) {
+		// Check for user cancel and report progress for each MB of data
+		if (BlocksProcessed++ % MD5_PROCESSED_1MB == 0) {
 			UpdateProgress(Progress);
+			// We need to set the watchdog timer regularly or else the UEFI firmware
+			// considers the bootloader stalled and resets the system. Do it for every
+			// 128 MB processed, as, with a default watchdog period of 5 mins, even
+			// very slow systems should be fine...
+			if (LastWatchDogReset++ % 128 == 0)
+				gBS->SetWatchdogTimer(300, 0x11D5, 0, NULL);
 			if (gST->BootServices->CheckEvent(gST->ConIn->WaitForKey) != EFI_NOT_READY) {
 				Status = EFI_ABORTED;
 				goto out;

src/parse.c

@@ -43,7 +43,7 @@ EFI_STATUS Parse(
 )
 {
 	EFI_STATUS Status;
-	EFI_FILE_HANDLE File;
+	EFI_FILE_HANDLE File = NULL;
 	EFI_FILE_INFO* Info = NULL;
 	UINT8* HashFile = NULL;
 	HASH_ENTRY* HashList = NULL;
@@ -268,6 +268,8 @@ EFI_STATUS Parse(
 
 out:
 	SafeFree(Info);
+	if (File != NULL)
+		File->Close(File);
 	if (EFI_ERROR(Status)) {
 		SafeFree(HashFile);
 		SafeFree(HashList);