x86: add %gs accessors for x86_32

Impact: cleanup

On x86_32, %gs is handled lazily.  It's not saved and restored on
kernel entry/exit but only when necessary which usually is during task
switch but there are few other places.  Currently, it's done by
calling savesegment() and loadsegment() explicitly.  Define
get_user_gs(), set_user_gs() and task_user_gs() and use them instead.

While at it, clean up register access macros in signal.c.

This cleans up code a bit and will help future changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 4 deletions

diff --git a/arch/x86/math-emu/get_address.c b/arch/x86/math-emu/get_address.c
index 420b3b6e3915..6ef5e99380f9 100644
--- a/arch/x86/math-emu/get_address.c
+++ b/arch/x86/math-emu/get_address.c
@@ -150,11 +150,9 @@ static long pm_address(u_char FPU_modrm, u_char segment,
 #endif /* PARANOID */
 
         switch (segment) {
-                /* gs isn't used by the kernel, so it still has its
-                   user-space value. */
         case PREFIX_GS_ - 1:
-                /* N.B. - movl %seg, mem is a 2 byte write regardless of prefix */
-                savesegment(gs, addr->selector);
+                /* user gs handling can be lazy, use special accessors */
+                addr->selector = get_user_gs(FPU_info->regs);
                 break;
         default:
                 addr->selector = PM_REG_(segment);