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, 16 insertions, 25 deletions

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 7fc78b019815..8562387c75a7 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -50,27 +50,23 @@
 # define FIX_EFLAGS     __FIX_EFLAGS
 #endif
 
-#define COPY(x)                 {               \
-        get_user_ex(regs->x, &sc->x);           \
-}
+#define COPY(x)                 do {                    \
+        get_user_ex(regs->x, &sc->x);                   \
+} while (0)
 
-#define COPY_SEG(seg)           {                       \
-                unsigned short tmp;                     \
-                get_user_ex(tmp, &sc->seg);             \
-                regs->seg = tmp;                        \
-}
+#define GET_SEG(seg)            ({                      \
+        unsigned short tmp;                             \
+        get_user_ex(tmp, &sc->seg);                     \
+        tmp;                                            \
+})
 
-#define COPY_SEG_CPL3(seg)      {                       \
-                unsigned short tmp;                     \
-                get_user_ex(tmp, &sc->seg);             \
-                regs->seg = tmp | 3;                    \
-}
+#define COPY_SEG(seg)           do {                    \
+        regs->seg = GET_SEG(seg);                       \
+} while (0)
 
-#define GET_SEG(seg)            {                       \
-                unsigned short tmp;                     \
-                get_user_ex(tmp, &sc->seg);             \
-                loadsegment(seg, tmp);                  \
-}
+#define COPY_SEG_CPL3(seg)      do {                    \
+        regs->seg = GET_SEG(seg) | 3;                   \
+} while (0)
 
 static int
 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
@@ -86,7 +82,7 @@ restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
         get_user_try {
 
 #ifdef CONFIG_X86_32
-                GET_SEG(gs);
+                set_user_gs(regs, GET_SEG(gs));
                 COPY_SEG(fs);
                 COPY_SEG(es);
                 COPY_SEG(ds);
@@ -138,12 +134,7 @@ setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
         put_user_try {
 
 #ifdef CONFIG_X86_32
-                {
-                        unsigned int tmp;
-
-                        savesegment(gs, tmp);
-                        put_user_ex(tmp, (unsigned int __user *)&sc->gs);
-                }
+                put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);