Re: [PATCH 0 of 4] x86: some more patches

Ingo Molnar
2008-01-16T15:47:36Z

* Jan Beulich <jbeulich@novell.com> wrote:

> > Yes, but if you cast to long the result will be 32bit again. Or do
> > you rely on it being always used in 64bit signed context with sign
> > extension? While that might work it would seem rather fragile to me,
> > just asking for similar future bugs.
>
> Even if conversion is to 64-bit unsigned, the value (being signed)
> will be sign-extended first (to preserve its value modulo 2**<target
> type width>).

yes. It would be nice if Andi could test my fix instead of arguing why
he thinks it's unlikely to work ;-)

(i've got the cleanup patch below as well ontop of today's x86.git which
includes the first fix, but it's an RFC as it has wider impact and might
break stuff.)

Ingo

--------------->
Subject: x86: PAGE_MASK cleanup
From: Ingo Molnar <mingo@elte.hu>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/asm-x86/page.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-x86.q/include/asm-x86/page.h
===================================================================
--- linux-x86.q.orig/include/asm-x86/page.h
+++ linux-x86.q/include/asm-x86/page.h
@@ -6,12 +6,12 @@
/* PAGE_SHIFT determines the page size */
#define PAGE_SHIFT 12
#define PAGE_SIZE (_AC(1,UL) << PAGE_SHIFT)
-#define PAGE_MASK (~(PAGE_SIZE-1))
+#define PAGE_MASK (_AT(phys_addr_t, ~(PAGE_SIZE-1)))

#ifdef __KERNEL__

#define PHYSICAL_PAGE_MASK (PAGE_MASK & __PHYSICAL_MASK)
-#define PTE_MASK (_AT(long, PHYSICAL_PAGE_MASK))
+#define PTE_MASK PHYSICAL_PAGE_MASK

#define LARGE_PAGE_SIZE (_AC(1,UL) << PMD_SHIFT)
#define LARGE_PAGE_MASK (~(LARGE_PAGE_SIZE-1))