[fallback] Attempt to re-use existing entries when possible.

Some firmwares seem to ignore our boot entries and put their fallback
entries back on top.  Right now that results in a lot of boot entries
for our stuff, a la https://bugzilla.redhat.com/show_bug.cgi?id=995834 .

Instead of that happening, if we simply find existing entries that match
the entry we would create and move them to the top of the boot order,
the machine will continue to operate in failure mode (which we can't
avoid), but at least we won't create thousands of extra entries.

Signed-off-by: Peter Jones <pjones@redhat.com>

1 files changed, 98 insertions, 1 deletions

diff --git a/fallback.c b/fallback.c
index a12bb741..44638ec0 100644
--- a/fallback.c
+++ b/fallback.c
@@ -226,6 +226,85 @@ add_boot_option(EFI_DEVICE_PATH *hddp, EFI_DEVICE_PATH *fulldp,
 }
 
 EFI_STATUS
+find_boot_option(EFI_DEVICE_PATH *dp, CHAR16 *filename, CHAR16 *label,
+		CHAR16 *arguments, UINT16 *optnum)
+{
+	int size = sizeof(UINT32) + sizeof (UINT16) +
+		StrLen(label)*2 + 2 + DevicePathSize(dp) +
+		StrLen(arguments) * 2 + 2;
+
+	CHAR8 *data = AllocateZeroPool(size);
+	if (!data)
+		return EFI_OUT_OF_RESOURCES;
+	CHAR8 *cursor = data;
+	*(UINT32 *)cursor = LOAD_OPTION_ACTIVE;
+	cursor += sizeof (UINT32);
+	*(UINT16 *)cursor = DevicePathSize(dp);
+	cursor += sizeof (UINT16);
+	StrCpy((CHAR16 *)cursor, label);
+	cursor += StrLen(label)*2 + 2;
+	CopyMem(cursor, dp, DevicePathSize(dp));
+	cursor += DevicePathSize(dp);
+	StrCpy((CHAR16 *)cursor, arguments);
+
+	int i = 0;
+	CHAR16 varname[] = L"Boot0000";
+	CHAR16 hexmap[] = L"0123456789ABCDEF";
+	EFI_GUID global = EFI_GLOBAL_VARIABLE;
+	EFI_STATUS rc;
+
+	CHAR8 *candidate = AllocateZeroPool(size);
+	if (!candidate) {
+		FreePool(data);
+		return EFI_OUT_OF_RESOURCES;
+	}
+
+	for(i = 0; i < nbootorder && i < 0x10000; i++) {
+		varname[4] = hexmap[(bootorder[i] & 0xf000) >> 12];
+		varname[5] = hexmap[(bootorder[i] & 0x0f00) >> 8];
+		varname[6] = hexmap[(bootorder[i] & 0x00f0) >> 4];
+		varname[7] = hexmap[(bootorder[i] & 0x000f) >> 0];
+
+		UINTN candidate_size = size;
+		rc = uefi_call_wrapper(RT->GetVariable, 5, varname, &global,
+					NULL, &candidate_size, candidate);
+		if (EFI_ERROR(rc))
+			continue;
+
+		if (candidate_size != size)
+			continue;
+
+		if (CompareMem(candidate, data, size))
+			continue;
+
+		/* at this point, we have duplicate data. */
+		*optnum = i;
+		FreePool(candidate);
+		FreePool(data);
+		return EFI_SUCCESS;
+	}
+	FreePool(candidate);
+	FreePool(data);
+	return EFI_NOT_FOUND;
+}
+
+EFI_STATUS
+set_boot_order(void)
+{
+	CHAR16 *oldbootorder;
+	UINTN size;
+	EFI_GUID global = EFI_GLOBAL_VARIABLE;
+
+	oldbootorder = LibGetVariableAndSize(L"BootOrder", &global, &size);
+	if (oldbootorder) {
+		nbootorder = size / sizeof (CHAR16);
+		bootorder = oldbootorder;
+	}
+	return EFI_SUCCESS;
+
+}
+
+EFI_STATUS
 update_boot_order(void)
 {
 	CHAR16 *oldbootorder;
@@ -336,7 +415,23 @@ add_to_boot_list(EFI_FILE_HANDLE fh, CHAR16 *dirname, CHAR16 *filename, CHAR16 *
 	}
 #endif
 
-	add_boot_option(dp, full_device_path, fullpath, label, arguments);
+	UINT16 option;
+	rc = find_boot_option(dp, fullpath, label, arguments, &option);
+	if (EFI_ERROR(rc)) {
+		add_boot_option(dp, full_device_path, fullpath, label, arguments);
+	} else if (option != 0) {
+		CHAR16 *newbootorder;
+		newbootorder = AllocateZeroPool(sizeof (CHAR16) * nbootorder);
+		if (!newbootorder)
+			return EFI_OUT_OF_RESOURCES;
+
+		newbootorder[0] = bootorder[option];
+		CopyMem(newbootorder + 1, bootorder, sizeof (CHAR16) * option);
+		CopyMem(newbootorder + option + 1, bootorder + option + 1,
+			sizeof (CHAR16) * (nbootorder - option - 1));
+		FreePool(bootorder);
+		bootorder = newbootorder;
+	}
 
 err:
 	if (file)
@@ -717,6 +812,8 @@ efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
 
 	Print(L"System BootOrder not found.  Initializing defaults.\n");
 
+	set_boot_order();
+
 	rc = find_boot_options(this_image->DeviceHandle);
 	if (EFI_ERROR(rc)) {
 		Print(L"Error: could not find boot options: %d\n", rc);