x86/asm/entry/64: Rename 'old_rsp' to 'rsp_scratch'

Make clear that the usage of PER_CPU(old_rsp) is purely temporary,
by renaming it to 'rsp_scratch'.

Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/entry_64.S

@@ -237,16 +237,16 @@ ENTRY(system_call)
 GLOBAL(system_call_after_swapgs)
 
 	/*
-	 * We use 'old_rsp' as a scratch register, hence this block must execute
+	 * We use 'rsp_scratch' as a scratch register, hence this block must execute
 	 * atomically in the face of possible interrupt-driven task preemption,
-	 * so we can enable interrupts only after we're done with using old_rsp:
+	 * so we can enable interrupts only after we're done with using rsp_scratch:
 	 */
-	movq	%rsp,PER_CPU_VAR(old_rsp)
+	movq	%rsp,PER_CPU_VAR(rsp_scratch)
 	/* kernel_stack is set so that 5 slots (iret frame) are preallocated */
 	movq	PER_CPU_VAR(kernel_stack),%rsp
 	ALLOC_PT_GPREGS_ON_STACK 8		/* +8: space for orig_ax */
 	movq	%rcx,RIP(%rsp)
-	movq	PER_CPU_VAR(old_rsp),%rcx
+	movq	PER_CPU_VAR(rsp_scratch),%rcx
 	movq	%r11,EFLAGS(%rsp)
 	movq	%rcx,RSP(%rsp)
 	/*
@@ -657,7 +657,7 @@ common_interrupt:
 	ASM_CLAC
 	addq $-0x80,(%rsp)		/* Adjust vector to [-256,-1] range */
 	interrupt do_IRQ
-	/* 0(%rsp): old_rsp */
+	/* 0(%rsp): rsp_scratch */
 ret_from_intr:
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF

arch/x86/kernel/process_64.c

@@ -52,7 +52,7 @@
 
 asmlinkage extern void ret_from_fork(void);
 
-__visible DEFINE_PER_CPU(unsigned long, old_rsp);
+__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
 
 /* Prints also some state that isn't saved in the pt_regs */
 void __show_regs(struct pt_regs *regs, int all)

arch/x86/xen/xen-asm_64.S

@@ -68,11 +68,11 @@ ENTRY(xen_sysret64)
 	 * We're already on the usermode stack at this point, but
 	 * still with the kernel gs, so we can easily switch back
 	 */
-	movq %rsp, PER_CPU_VAR(old_rsp)
+	movq %rsp, PER_CPU_VAR(rsp_scratch)
 	movq PER_CPU_VAR(kernel_stack), %rsp
 
 	pushq $__USER_DS
-	pushq PER_CPU_VAR(old_rsp)
+	pushq PER_CPU_VAR(rsp_scratch)
 	pushq %r11
 	pushq $__USER_CS
 	pushq %rcx
@@ -87,11 +87,11 @@ ENTRY(xen_sysret32)
 	 * We're already on the usermode stack at this point, but
 	 * still with the kernel gs, so we can easily switch back
 	 */
-	movq %rsp, PER_CPU_VAR(old_rsp)
+	movq %rsp, PER_CPU_VAR(rsp_scratch)
 	movq PER_CPU_VAR(kernel_stack), %rsp
 
 	pushq $__USER32_DS
-	pushq PER_CPU_VAR(old_rsp)
+	pushq PER_CPU_VAR(rsp_scratch)
 	pushq %r11
 	pushq $__USER32_CS
 	pushq %rcx