efi_loader: printing UEFI revision in helloworld.efi

We need to support multiple digits in the parts of the UEFI verision
number. E.g.

    EFI_SPECIFICATION_VERSION = (123 << 16) | 456

must be printed as

    123.45.6

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/lib/efi_loader/helloworld.c b/lib/efi_loader/helloworld.c
index 10666dc..d565f32 100644 (file)
--- a/lib/efi_loader/helloworld.c
+++ b/lib/efi_loader/helloworld.c
@@ -29,24 +29,66 @@ static struct efi_system_table *systable;
 static struct efi_boot_services *boottime;
 static struct efi_simple_text_output_protocol *con_out;
 
+/*
+ * Print an unsigned 32bit value as decimal number to an u16 string
+ *
+ * @value:     value to be printed
+ * @buf:       pointer to buffer address
+ *             on return position of terminating zero word
+ */
+static void uint2dec(u32 value, u16 **buf)
+{
+       u16 *pos = *buf;
+       int i;
+       u16 c;
+       u64 f;
+
+       /*
+        * Increment by .5 and multiply with
+        * (2 << 60) / 1,000,000,000 = 0x44B82FA0.9B5A52CC
+        * to move the first digit to bit 60-63.
+        */
+       f = 0x225C17D0;
+       f += (0x9B5A52DULL * value) >> 28;
+       f += 0x44B82FA0ULL * value;
+
+       for (i = 0; i < 10; ++i) {
+               /* Write current digit */
+               c = f >> 60;
+               if (c || pos != *buf)
+                       *pos++ = c + '0';
+               /* Eliminate current digit */
+               f &= 0xfffffffffffffff;
+               /* Get next digit */
+               f *= 0xaULL;
+       }
+       if (pos == *buf)
+               *pos++ = '0';
+       *pos = 0;
+       *buf = pos;
+}
+
 /**
  * print_uefi_revision() - print UEFI revision number
  */
 static void print_uefi_revision(void)
 {
-       u16 rev[] = u"0.0.0";
-
-       rev[0] = (systable->hdr.revision >> 16) + '0';
-       rev[4] = systable->hdr.revision & 0xffff;
-       for (; rev[4] >= 10;) {
-               rev[4] -= 10;
-               ++rev[2];
+       u16 rev[13] = {0};
+       u16 *buf = rev;
+       u16 digit;
+
+       uint2dec(systable->hdr.revision >> 16, &buf);
+       *buf++ = '.';
+       uint2dec(systable->hdr.revision & 0xffff, &buf);
+
+       /* Minor revision is only to be shown if non-zero */
+       digit = *--buf;
+       if (digit == '0') {
+               *buf = 0;
+       } else {
+               *buf++ = '.';
+               *buf = digit;
        }
-       /* Third digit is only to be shown if non-zero */
-       if (rev[4])
-               rev[4] += '0';
-       else
-               rev[3] = 0;
 
        con_out->output_string(con_out, u"Running on UEFI ");
        con_out->output_string(con_out, rev);