uninline check_signature()

This is a rather bizarre thing to have inlined in io.h.  Stick it in lib/
instead.

While we're there, despaghetti it a bit, and fix its off-by-one behaviour when
passed a zero length.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/check_signature.c b/lib/check_signature.c
new file mode 100644
index 000000000000..fd6af199247b
--- /dev/null
+++ b/lib/check_signature.c
@@ -0,0 +1,26 @@
+#include <linux/io.h>
+#include <linux/module.h>
+
+/**
+ *      check_signature         -       find BIOS signatures
+ *      @io_addr: mmio address to check
+ *      @signature:  signature block
+ *      @length: length of signature
+ *
+ *      Perform a signature comparison with the mmio address io_addr. This
+ *      address should have been obtained by ioremap.
+ *      Returns 1 on a match.
+ */
+
+int check_signature(const volatile void __iomem *io_addr,
+                        const unsigned char *signature, int length)
+{
+        while (length--) {
+                if (readb(io_addr) != *signature)
+                        return 0;
+                io_addr++;
+                signature++;
+        }
+        return 1;
+}
+EXPORT_SYMBOL(check_signature);