efi/libstub: Add a helper function to split 64-bit values

In several places 64-bit values need to be split up into two 32-bit
fields, in order to be backward-compatible with the old 32-bit ABIs.

Instead of open-coding this, add a helper function to set a 64-bit value
as two 32-bit fields.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200430182843.2510180-3-nivedita@alum.mit.eduSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/efistub.h

@@ -87,6 +87,13 @@ extern const efi_system_table_t *efi_system_table;
 		((handle = efi_get_handle_at((array), i)) || true);	\
 	     i++)
 
+static inline
+void efi_set_u64_split(u64 data, u32 *lo, u32 *hi)
+{
+	*lo = lower_32_bits(data);
+	*hi = upper_32_bits(data);
+}
+
 /*
  * Allocation types for calls to boottime->allocate_pages.
  */

drivers/firmware/efi/libstub/gop.c

@@ -422,7 +422,6 @@ static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
 	efi_graphics_output_protocol_t *gop;
 	efi_graphics_output_protocol_mode_t *mode;
 	efi_graphics_output_mode_info_t *info;
-	efi_physical_addr_t fb_base;
 
 	gop = find_gop(proto, size, handles);
 
@@ -442,9 +441,8 @@ static efi_status_t setup_gop(struct screen_info *si, efi_guid_t *proto,
 	si->lfb_width  = info->horizontal_resolution;
 	si->lfb_height = info->vertical_resolution;
 
-	fb_base		 = efi_table_attr(mode, frame_buffer_base);
-	si->lfb_base	 = lower_32_bits(fb_base);
-	si->ext_lfb_base = upper_32_bits(fb_base);
+	efi_set_u64_split(efi_table_attr(mode, frame_buffer_base),
+			  &si->lfb_base, &si->ext_lfb_base);
 	if (si->ext_lfb_base)
 		si->capabilities |= VIDEO_CAPABILITY_64BIT_BASE;
 

drivers/firmware/efi/libstub/x86-stub.c

@@ -408,9 +408,8 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 	if (!cmdline_ptr)
 		goto fail;
 
-	hdr->cmd_line_ptr = (unsigned long)cmdline_ptr;
-	/* Fill in upper bits of command line address, NOP on 32 bit  */
-	boot_params->ext_cmd_line_ptr = (u64)(unsigned long)cmdline_ptr >> 32;
+	efi_set_u64_split((unsigned long)cmdline_ptr,
+			  &hdr->cmd_line_ptr, &boot_params->ext_cmd_line_ptr);
 
 	hdr->ramdisk_image = 0;
 	hdr->ramdisk_size = 0;
@@ -427,10 +426,10 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 						 ULONG_MAX);
 			if (status != EFI_SUCCESS)
 				goto fail2;
-			hdr->ramdisk_image = ramdisk_addr & 0xffffffff;
-			hdr->ramdisk_size  = ramdisk_size & 0xffffffff;
-			boot_params->ext_ramdisk_image = (u64)ramdisk_addr >> 32;
-			boot_params->ext_ramdisk_size  = (u64)ramdisk_size >> 32;
+			efi_set_u64_split(ramdisk_addr, &hdr->ramdisk_image,
+					  &boot_params->ext_ramdisk_image);
+			efi_set_u64_split(ramdisk_size, &hdr->ramdisk_size,
+					  &boot_params->ext_ramdisk_size);
 		}
 	}
 
@@ -639,17 +638,14 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map,
 				   : EFI32_LOADER_SIGNATURE;
 	memcpy(&p->efi->efi_loader_signature, signature, sizeof(__u32));
 
-	p->efi->efi_systab		= (unsigned long)efi_system_table;
+	efi_set_u64_split((unsigned long)efi_system_table,
+			  &p->efi->efi_systab, &p->efi->efi_systab_hi);
 	p->efi->efi_memdesc_size	= *map->desc_size;
 	p->efi->efi_memdesc_version	= *map->desc_ver;
-	p->efi->efi_memmap		= (unsigned long)*map->map;
+	efi_set_u64_split((unsigned long)*map->map,
+			  &p->efi->efi_memmap, &p->efi->efi_memmap_hi);
 	p->efi->efi_memmap_size		= *map->map_size;
 
-#ifdef CONFIG_X86_64
-	p->efi->efi_systab_hi		= (unsigned long)efi_system_table >> 32;
-	p->efi->efi_memmap_hi		= (unsigned long)*map->map >> 32;
-#endif
-
 	return EFI_SUCCESS;
 }
 
@@ -785,10 +781,10 @@ unsigned long efi_main(efi_handle_t handle,
 
 		status = efi_load_initrd_dev_path(&addr, &size, ULONG_MAX);
 		if (status == EFI_SUCCESS) {
-			hdr->ramdisk_image		= (u32)addr;
-			hdr->ramdisk_size 		= (u32)size;
-			boot_params->ext_ramdisk_image	= (u64)addr >> 32;
-			boot_params->ext_ramdisk_size 	= (u64)size >> 32;
+			efi_set_u64_split(addr, &hdr->ramdisk_image,
+					  &boot_params->ext_ramdisk_image);
+			efi_set_u64_split(size, &hdr->ramdisk_size,
+					  &boot_params->ext_ramdisk_size);
 		} else if (status != EFI_NOT_FOUND) {
 			efi_printk("efi_load_initrd_dev_path() failed!\n");
 			goto fail;