[PATCH 10/17] x86: make __VIRTUAL_MASK safe to use on 32 bit

Dave Hansen
2015-03-26T18:33:42Z

From: Dave Hansen <dave.hansen@linux.intel.com>

We are going to do some calculations in a moment that are based on the
size of the virtual address space. __VIRTUAL_MASK is currently unsafe
to use on 32-bit since it overflows an unsigned long with its shift.

The current version will emit a warning if used at all on 32-bit
kernels.

Add a version which is safe on 32-bit and consequently does not spit
out a warning.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

b/arch/x86/include/asm/page_types.h | 8 ++++++++
1 file changed, 8 insertions(+)

diff -puN arch/x86/include/asm/page_types.h~x86-make-__VIRTUAL_MASK-safe-to-use-on-32-bit arch/x86/include/asm/page_types.h
--- a/arch/x86/include/asm/page_types.h~x86-make-__VIRTUAL_MASK-safe-to-use-on-32-bit 2015-03-26 11:27:32.079437469 -0700
+++ b/arch/x86/include/asm/page_types.h 2015-03-26 11:27:32.082437604 -0700
@@ -10,7 +10,15 @@
#define PAGE_MASK (~(PAGE_SIZE-1))

#define __PHYSICAL_MASK ((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1))
+#ifdef CONFIG_X86_64
+/*
+ * This version doesn't work on 32-bit because __VIRTUAL_MASK_SHIFT=32
+ * overflows the unsigned long we're trying to shift.
+ */
#define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1)
+#else
+#define __VIRTUAL_MASK (~0UL)
+#endif

/* Cast PAGE_MASK to a signed type so that it is sign-extended if
virtual addresses are 32-bits but physical addresses are larger
_