efi/libstub: Rewrite file I/O routine

The file I/O routine that is used to load initrd or dtb files from
the EFI system partition suffers from a few issues:
- it converts the u8[] command line back to a UTF-16 string, which is
  pointless since we only handle initrd or dtb arguments provided via
  the loaded image protocol anyway, which is where we got the UTF-16[]
  command line from in the first place when booting via the PE entry
  point,
- in the far majority of cases, only a single initrd= option is present,
  but it optimizes for multiple options, by going over the command line
  twice, allocating heap buffers for dynamically sized arrays, etc.
- the coding style is hard to follow, with few comments, and all logic
  including string parsing etc all combined in a single routine.

Let's fix this by rewriting most of it, based on the idea that in the
case of multiple initrds, we can just allocate a new, bigger buffer
and copy over the data before freeing the old one.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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

@@ -154,7 +154,7 @@ efi_status_t efi_entry(efi_handle_t handle, efi_system_table_t *sys_table_arg)
 	unsigned long dram_base;
 	/* addr/point and size pairs for memory management*/
 	unsigned long initrd_addr;
-	u64 initrd_size = 0;
+	unsigned long initrd_size = 0;
 	unsigned long fdt_addr = 0;  /* Original DTB */
 	unsigned long fdt_size = 0;
 	char *cmdline_ptr = NULL;
@@ -247,8 +247,7 @@ efi_status_t efi_entry(efi_handle_t handle, efi_system_table_t *sys_table_arg)
 		if (strstr(cmdline_ptr, "dtb="))
 			pr_efi("Ignoring DTB from command line.\n");
 	} else {
-		status = handle_cmdline_files(image, cmdline_ptr, "dtb=",
-					      ~0UL, &fdt_addr, &fdt_size);
+		status = efi_load_dtb(image, &fdt_addr, &fdt_size);
 
 		if (status != EFI_SUCCESS) {
 			pr_efi_err("Failed to load device tree!\n");
@@ -268,11 +267,8 @@ efi_status_t efi_entry(efi_handle_t handle, efi_system_table_t *sys_table_arg)
 	if (!fdt_addr)
 		pr_efi("Generating empty DTB\n");
 
-	status = handle_cmdline_files(image, cmdline_ptr, "initrd=",
-				      efi_get_max_initrd_addr(dram_base,
-							      image_addr),
-				      (unsigned long *)&initrd_addr,
-				      (unsigned long *)&initrd_size);
+	status = efi_load_initrd(image, &initrd_addr, &initrd_size,
+				 efi_get_max_initrd_addr(dram_base, image_addr));
 	if (status != EFI_SUCCESS)
 		pr_efi_err("Failed initrd from command line!\n");
 

drivers/firmware/efi/libstub/efistub.h

@@ -327,7 +327,7 @@ typedef struct {
 	efi_time_t		last_access_time;
 	efi_time_t		modification_time;
 	__aligned_u64		attribute;
-	efi_char16_t		filename[1];
+	efi_char16_t		filename[];
 } efi_file_info_t;
 
 typedef struct efi_file_protocol efi_file_protocol_t;
@@ -607,15 +607,18 @@ efi_status_t efi_relocate_kernel(unsigned long *image_addr,
 				 unsigned long alignment,
 				 unsigned long min_addr);
 
-efi_status_t handle_cmdline_files(efi_loaded_image_t *image,
-				  char *cmd_line, char *option_string,
-				  unsigned long max_addr,
-				  unsigned long *load_addr,
-				  unsigned long *load_size);
-
 efi_status_t efi_parse_options(char const *cmdline);
 
 efi_status_t efi_setup_gop(struct screen_info *si, efi_guid_t *proto,
 			   unsigned long size);
 
+efi_status_t efi_load_dtb(efi_loaded_image_t *image,
+			  unsigned long *load_addr,
+			  unsigned long *load_size);
+
+efi_status_t efi_load_initrd(efi_loaded_image_t *image,
+			     unsigned long *load_addr,
+			     unsigned long *load_size,
+			     unsigned long max_addr);
+
 #endif

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

@@ -421,18 +421,14 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
 	if (status != EFI_SUCCESS)
 		goto fail2;
 
-	status = handle_cmdline_files(image,
-				      (char *)(unsigned long)hdr->cmd_line_ptr,
-				      "initrd=", hdr->initrd_addr_max,
-				      &ramdisk_addr, &ramdisk_size);
+	status = efi_load_initrd(image, &ramdisk_addr, &ramdisk_size,
+				 hdr->initrd_addr_max);
 
 	if (status != EFI_SUCCESS &&
 	    hdr->xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G) {
 		efi_printk("Trying to load files to higher address\n");
-		status = handle_cmdline_files(image,
-				      (char *)(unsigned long)hdr->cmd_line_ptr,
-				      "initrd=", -1UL,
-				      &ramdisk_addr, &ramdisk_size);
+		status = efi_load_initrd(image, &ramdisk_addr, &ramdisk_size,
+					 ULONG_MAX);
 	}
 
 	if (status != EFI_SUCCESS)