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, 3 insertions, 3 deletions

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 1a1ae8edc40c..d58a340e1be3 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -131,7 +131,7 @@ void __show_regs(struct pt_regs *regs, int all)
         if (user_mode_vm(regs)) {
                 sp = regs->sp;
                 ss = regs->ss & 0xffff;
-                savesegment(gs, gs);
+                gs = get_user_gs(regs);
         } else {
                 sp = (unsigned long) (&regs->sp);
                 savesegment(ss, ss);
@@ -304,7 +304,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 
         p->thread.ip = (unsigned long) ret_from_fork;
 
-        savesegment(gs, p->thread.gs);
+        task_user_gs(p) = get_user_gs(regs);
 
         tsk = current;
         if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
@@ -342,7 +342,7 @@ int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 void
 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 {
-        __asm__("movl %0, %%gs" : : "r"(0));
+        set_user_gs(regs, 0);
         regs->fs                = 0;
         set_fs(USER_DS);
         regs->ds                = __USER_DS;