efi: x86: Handle arbitrary Unicode characters

Instead of truncating UTF-16 assuming all characters is ASCII,
properly convert it to UTF-8.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
[ Bug and style fixes. ]
Signed-off-by: Roy Franz <roy.franz@linaro.org>
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

2 files changed, 68 insertions, 22 deletions

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 4703a6c4b8e3..0331d765c2bb 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1087,8 +1087,7 @@ struct boot_params *make_boot_params(struct efi_config *c)
         hdr->type_of_loader = 0x21;
 
         /* Convert unicode cmdline to ascii */
-        cmdline_ptr = efi_convert_cmdline_to_ascii(sys_table, image,
-                                                   &options_size);
+        cmdline_ptr = efi_convert_cmdline(sys_table, image, &options_size);
         if (!cmdline_ptr)
                 goto fail;
         hdr->cmd_line_ptr = (unsigned long)cmdline_ptr;
diff --git a/drivers/firmware/efi/efi-stub-helper.c b/drivers/firmware/efi/efi-stub-helper.c
index a168dd20511f..eb6d4be9e722 100644
--- a/drivers/firmware/efi/efi-stub-helper.c
+++ b/drivers/firmware/efi/efi-stub-helper.c
@@ -536,52 +536,99 @@ static efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg,
 }
 
 /*
+ * Get the number of UTF-8 bytes corresponding to an UTF-16 character.
+ * This overestimates for surrogates, but that is okay.
+ */
+static int efi_utf8_bytes(u16 c)
+{
+        return 1 + (c >= 0x80) + (c >= 0x800);
+}
+
+/*
+ * Convert an UTF-16 string, not necessarily null terminated, to UTF-8.
+ */
+static u8 *efi_utf16_to_utf8(u8 *dst, const u16 *src, int n)
+{
+        unsigned int c;
+
+        while (n--) {
+                c = *src++;
+                if (n && c >= 0xd800 && c <= 0xdbff &&
+                    *src >= 0xdc00 && *src <= 0xdfff) {
+                        c = 0x10000 + ((c & 0x3ff) << 10) + (*src & 0x3ff);
+                        src++;
+                        n--;
+                }
+                if (c >= 0xd800 && c <= 0xdfff)
+                        c = 0xfffd; /* Unmatched surrogate */
+                if (c < 0x80) {
+                        *dst++ = c;
+                        continue;
+                }
+                if (c < 0x800) {
+                        *dst++ = 0xc0 + (c >> 6);
+                        goto t1;
+                }
+                if (c < 0x10000) {
+                        *dst++ = 0xe0 + (c >> 12);
+                        goto t2;
+                }
+                *dst++ = 0xf0 + (c >> 18);
+                *dst++ = 0x80 + ((c >> 12) & 0x3f);
+        t2:
+                *dst++ = 0x80 + ((c >> 6) & 0x3f);
+        t1:
+                *dst++ = 0x80 + (c & 0x3f);
+        }
+
+        return dst;
+}
+
+/*
  * Convert the unicode UEFI command line to ASCII to pass to kernel.
  * Size of memory allocated return in *cmd_line_len.
  * Returns NULL on error.
  */
-static char *efi_convert_cmdline_to_ascii(efi_system_table_t *sys_table_arg,
-                                      efi_loaded_image_t *image,
-                                      int *cmd_line_len)
+static char *efi_convert_cmdline(efi_system_table_t *sys_table_arg,
+                                 efi_loaded_image_t *image,
+                                 int *cmd_line_len)
 {
-        u16 *s2;
+        const u16 *s2;
         u8 *s1 = NULL;
         unsigned long cmdline_addr = 0;
-        int load_options_size = image->load_options_size / 2; /* ASCII */
-        void *options = image->load_options;
-        int options_size = 0;
+        int load_options_chars = image->load_options_size / 2; /* UTF-16 */
+        const u16 *options = image->load_options;
+        int options_bytes = 0;  /* UTF-8 bytes */
+        int options_chars = 0;  /* UTF-16 chars */
         efi_status_t status;
-        int i;
         u16 zero = 0;
 
         if (options) {
                 s2 = options;
-                while (*s2 && *s2 != '\n' && options_size < load_options_size) {
-                        s2++;
-                        options_size++;
+                while (*s2 && *s2 != '\n'
+                       && options_chars < load_options_chars) {
+                        options_bytes += efi_utf8_bytes(*s2++);
+                        options_chars++;
                 }
         }
 
-        if (options_size == 0) {
+        if (!options_chars) {
                 /* No command line options, so return empty string*/
-                options_size = 1;
                 options = &zero;
         }
 
-        options_size++;  /* NUL termination */
+        options_bytes++;        /* NUL termination */
 
-        status = efi_low_alloc(sys_table_arg, options_size, 0, &cmdline_addr);
+        status = efi_low_alloc(sys_table_arg, options_bytes, 0, &cmdline_addr);
         if (status != EFI_SUCCESS)
                 return NULL;
 
         s1 = (u8 *)cmdline_addr;
-        s2 = (u16 *)options;
-
-        for (i = 0; i < options_size - 1; i++)
-                *s1++ = *s2++;
+        s2 = (const u16 *)options;
 
+        s1 = efi_utf16_to_utf8(s1, s2, options_chars);
         *s1 = '\0';
 
-        *cmd_line_len = options_size;
+        *cmd_line_len = options_bytes;
         return (char *)cmdline_addr;
 }