efi/libstub: Use a helper to iterate over a EFI handle array

Iterating over a EFI handle array is a bit finicky, since we have
to take mixed mode into account, where handles are only 32-bit
while the native efi_handle_t type is 64-bit.

So introduce a helper, and replace the various occurrences of
this pattern.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-8-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/boot/compressed/eboot.c

@@ -135,6 +135,7 @@ static void setup_efi_pci(struct boot_params *params)
 	unsigned long size = 0;
 	unsigned long nr_pci;
 	struct setup_data *data;
+	efi_handle_t h;
 	int i;
 
 	status = efi_call_early(locate_handle,
@@ -164,14 +165,11 @@ static void setup_efi_pci(struct boot_params *params)
 	while (data && data->next)
 		data = (struct setup_data *)(unsigned long)data->next;
 
-	nr_pci = size / (efi_is_64bit() ? sizeof(u64) : sizeof(u32));
-	for (i = 0; i < nr_pci; i++) {
+	for_each_efi_handle(h, pci_handle, size, i) {
 		efi_pci_io_protocol_t *pci = NULL;
 		struct pci_setup_rom *rom;
 
-		status = efi_call_early(handle_protocol,
-					efi_is_64bit() ? ((u64 *)pci_handle)[i]
-						       : ((u32 *)pci_handle)[i],
+		status = efi_call_early(handle_protocol, h,
 					&pci_proto, (void **)&pci);
 		if (status != EFI_SUCCESS || !pci)
 			continue;
@@ -266,6 +264,7 @@ setup_uga(struct screen_info *si, efi_guid_t *uga_proto, unsigned long size)
 	void **uga_handle = NULL;
 	efi_uga_draw_protocol_t *uga = NULL, *first_uga;
 	unsigned long nr_ugas;
+	efi_handle_t handle;
 	int i;
 
 	status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
@@ -283,13 +282,10 @@ setup_uga(struct screen_info *si, efi_guid_t *uga_proto, unsigned long size)
 	width = 0;
 
 	first_uga = NULL;
-	nr_ugas = size / (efi_is_64bit() ? sizeof(u64) : sizeof(u32));
-	for (i = 0; i < nr_ugas; i++) {
+	for_each_efi_handle(handle, uga_handle, size, i) {
 		efi_guid_t pciio_proto = EFI_PCI_IO_PROTOCOL_GUID;
 		u32 w, h, depth, refresh;
 		void *pciio;
-		unsigned long handle = efi_is_64bit() ? ((u64 *)uga_handle)[i]
-						      : ((u32 *)uga_handle)[i];
 
 		status = efi_call_early(handle_protocol, handle,
 					uga_proto, (void **)&uga);

drivers/firmware/efi/libstub/gop.c

@@ -91,7 +91,6 @@ setup_gop(efi_system_table_t *sys_table_arg, struct screen_info *si,
 	  efi_guid_t *proto, unsigned long size, void **handles)
 {
 	efi_graphics_output_protocol_t *gop, *first_gop;
-	unsigned long nr_gops;
 	u16 width, height;
 	u32 pixels_per_scan_line;
 	u32 ext_lfb_base;
@@ -99,22 +98,18 @@ setup_gop(efi_system_table_t *sys_table_arg, struct screen_info *si,
 	efi_pixel_bitmask_t pixel_info;
 	int pixel_format;
 	efi_status_t status;
+	efi_handle_t h;
 	int i;
-	bool is64 = efi_is_64bit();
 
 	first_gop = NULL;
 	gop = NULL;
 
-	nr_gops = size / (is64 ? sizeof(u64) : sizeof(u32));
-	for (i = 0; i < nr_gops; i++) {
+	for_each_efi_handle(h, handles, size, i) {
 		efi_graphics_output_protocol_mode_t *mode;
 		efi_graphics_output_mode_info_t *info = NULL;
 		efi_guid_t conout_proto = EFI_CONSOLE_OUT_DEVICE_GUID;
 		bool conout_found = false;
 		void *dummy = NULL;
-		efi_handle_t h = (efi_handle_t)(unsigned long)
-				 (is64 ? ((u64 *)handles)[i]
-				       : ((u32 *)handles)[i]);
 		efi_physical_addr_t current_fb_base;
 
 		status = efi_call_early(handle_protocol, h,

include/linux/efi.h

@@ -48,6 +48,19 @@ typedef u16 efi_char16_t;		/* UNICODE character */
 typedef u64 efi_physical_addr_t;
 typedef void *efi_handle_t;
 
+#define efi_get_handle_at(array, idx)					\
+	(efi_is_64bit() ? (efi_handle_t)(unsigned long)((u64 *)(array))[idx] \
+		: (efi_handle_t)(unsigned long)((u32 *)(array))[idx])
+
+#define efi_get_handle_num(size)					\
+	((size) / (efi_is_64bit() ? sizeof(u64) : sizeof(u32)))
+
+#define for_each_efi_handle(handle, array, size, i)			\
+	for (i = 0;							\
+	     i < efi_get_handle_num(size) &&				\
+		((handle = efi_get_handle_at((array), i)) || true);	\
+	     i++)
+
 /*
  * The UEFI spec and EDK2 reference implementation both define EFI_GUID as
  * struct { u32 a; u16; b; u16 c; u8 d[8]; }; and so the implied alignment