sparc64: kern_addr_valid regression

BugLink: http://bugs.launchpad.net/bugs/1688505

[ Upstream commit adfae8a5 ]

I encountered this bug when using /proc/kcore to examine the kernel. Plus a
coworker inquired about debugging tools. We computed pa but did
not use it during the maximum physical address bits test. Instead we used
the identity mapped virtual address which will always fail this test.

I believe the defect came in here:
[bpicco@zareason linus.git]$ git describe --contains bb4e6e85
v3.18-rc1~87^2~4
.
Signed-off-by: Bob Picco <bob.picco@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

arch/sparc/mm/init_64.c

@@ -1493,7 +1493,7 @@ bool kern_addr_valid(unsigned long addr)
 	if ((long)addr < 0L) {
 		unsigned long pa = __pa(addr);
 
-		if ((addr >> max_phys_bits) != 0UL)
+		if ((pa >> max_phys_bits) != 0UL)
 			return false;
 
 		return pfn_valid(pa >> PAGE_SHIFT);