[PATCH] i386: inline asm cleanup

i386 Inline asm cleanup.  Use cr/dr accessor functions.

Also, a potential bugfix.  Also, some CR accessors really should be volatile.
Reads from CR0 (numeric state may change in an exception handler), writes to
CR4 (flipping CR4.TSD) and reads from CR2 (page fault) prevent instruction
re-ordering.  I did not add memory clobber to CR3 / CR4 / CR0 updates, as it
was not there to begin with, and in no case should kernel memory be clobbered,
except when doing a TLB flush, which already has memory clobber.

I noticed that page invalidation does not have a memory clobber.  I can't find
a bug as a result, but there is definitely a potential for a bug here:

#define __flush_tlb_single(addr) \
	__asm__ __volatile__("invlpg %0": :"m" (*(char *) addr))

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/i386/kernel/efi.c b/arch/i386/kernel/efi.c
index 850648ae8305..921fdb15fc9b 100644
--- a/arch/i386/kernel/efi.c
+++ b/arch/i386/kernel/efi.c
@@ -79,7 +79,7 @@ static void efi_call_phys_prelog(void)
          * directory. If I have PSE, I just need to duplicate one entry in
          * page directory.
          */
-        __asm__ __volatile__("movl %%cr4, %0":"=r"(cr4));
+        cr4 = read_cr4();
 
         if (cr4 & X86_CR4_PSE) {
                 efi_bak_pg_dir_pointer[0].pgd =
@@ -115,7 +115,7 @@ static void efi_call_phys_epilog(void)
         cpu_gdt_descr[0].address =
                 (unsigned long) __va(cpu_gdt_descr[0].address);
         __asm__ __volatile__("lgdt %0":"=m"(cpu_gdt_descr));
-        __asm__ __volatile__("movl %%cr4, %0":"=r"(cr4));
+        cr4 = read_cr4();
 
         if (cr4 & X86_CR4_PSE) {
                 swapper_pg_dir[pgd_index(0)].pgd =