diff --git a/configure.ac b/configure.ac
index 4ad7584..0182b42 100644
--- a/configure.ac
+++ b/configure.ac
@@ -829,7 +848,7 @@ CFLAGS="$TARGET_CFLAGS -Wl,--defsym,abort=main"
 fi
 
 # Check for libgcc symbols
-AC_CHECK_FUNCS(__bswapsi2 __bswapdi2 __ashldi3 __ashrdi3 __lshrdi3 __ucmpdi2 _restgpr_14_x __ctzdi2 __ctzsi2)
+AC_CHECK_FUNCS(__bswapsi2 __bswapdi2 __ashldi3 __ashrdi3 __lshrdi3 __ucmpdi2 _restgpr_14_x)
 
 if test "x$TARGET_APPLE_CC" = x1 ; then
 CFLAGS="$TARGET_CFLAGS -nostdlib"
diff --git a/grub-core/kern/misc.c b/grub-core/kern/misc.c
index 194e770..0b3bd6d 100644
--- a/grub-core/kern/misc.c
+++ b/grub-core/kern/misc.c
@@ -615,6 +615,74 @@ __umodsi3 (grub_uint32_t a, grub_uint32_t b)
 }
 
 
+unsigned
+__ctzdi2 (grub_uint64_t x)
+{
+  unsigned ret = 0;
+  if (!(x & 0xffffffff))
+    {
+      x >>= 32;
+      ret += 32;
+    }
+  if (!(x & 0xffff))
+    {
+      x >>= 16;
+      ret += 16;
+    }
+  if (!(x & 0xff))
+    {
+      x >>= 8;
+      ret += 8;
+    }
+  if (!(x & 0xf))
+    {
+      x >>= 4;
+      ret += 4;
+    }
+  if (!(x & 0x3))
+    {
+      x >>= 2;
+      ret += 2;
+    }
+  if (!(x & 0x1))
+    {
+      x >>= 2;
+      ret++;
+    }
+  return ret;
+}
+unsigned
+__ctzsi2 (grub_uint32_t x)
+{
+  unsigned ret = 0;
+  if (!(x & 0xffff))
+    {
+      x >>= 16;
+      ret += 16;
+    }
+  if (!(x & 0xff))
+    {
+      x >>= 8;
+      ret += 8;
+    }
+  if (!(x & 0xf))
+    {
+      x >>= 4;
+      ret += 4;
+    }
+  if (!(x & 0x3))
+    {
+      x >>= 2;
+      ret += 2;
+    }
+  if (!(x & 0x1))
+    {
+      x >>= 2;
+      ret++;
+    }
+  return ret;
+}
+
 #endif
 
 #ifdef __arm__
diff --git a/include/grub/misc.h b/include/grub/misc.h
index a46e086..192f503 100644
--- a/include/grub/misc.h
+++ b/include/grub/misc.h
@@ -463,6 +463,11 @@ EXPORT_FUNC (__udivsi3) (grub_uint32_t a, grub_uint32_t b);
 grub_uint32_t
 EXPORT_FUNC (__umodsi3) (grub_uint32_t a, grub_uint32_t b);
 
+unsigned
+EXPORT_FUNC (__ctzdi2) (grub_uint64_t x);
+unsigned
+EXPORT_FUNC (__ctzsi2) (grub_uint32_t x);
+
 #endif
 
 #ifdef __arm__