x86: rename stack_pointer to kernel_trap_sp

Choose a less generic name for such a special case.  Add
a comment explaining the odd use in X86_32.

Change the one user of stack_pointer.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/asm-x86/ptrace.h b/include/asm-x86/ptrace.h
index 79d5b8f..d9e04b4 100644
--- a/include/asm-x86/ptrace.h
+++ b/include/asm-x86/ptrace.h
@@ -182,7 +182,13 @@
 #endif
 }
 
-static inline unsigned long stack_pointer(struct pt_regs *regs)
+/*
+ * X86_32 CPUs don't save ss and esp if the CPU is already in kernel mode
+ * when it traps.  So regs will be the current sp.
+ *
+ * This is valid only for kernel mode traps.
+ */
+static inline unsigned long kernel_trap_sp(struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_32
 	return (unsigned long)regs;