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, 9 insertions, 0 deletions

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 2fcc70bc85f3..70c74b8db875 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -182,6 +182,15 @@ extern void native_load_gs_index(unsigned);
 #define savesegment(seg, value)                         \
         asm("mov %%" #seg ",%0":"=r" (value) : : "memory")
 
+/*
+ * x86_32 user gs accessors.
+ */
+#ifdef CONFIG_X86_32
+#define get_user_gs(regs)       (u16)({unsigned long v; savesegment(gs, v); v;})
+#define set_user_gs(regs, v)    loadsegment(gs, (unsigned long)(v))
+#define task_user_gs(tsk)       ((tsk)->thread.gs)
+#endif
+
 static inline unsigned long get_limit(unsigned long segment)
 {
         unsigned long __limit;