x86/asm/head: Rename 'stack_start' -> 'initial_stack'

The 'stack_start' variable is similar in usage to 'initial_code' and
'initial_gs': they're all stored in head_64.S and they're all updated by
SMP and ACPI suspend before starting a CPU.

Rename it to 'initial_stack' to be consistent with the others.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
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: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/87063d773a3212051b77e17b0ee427f6582a5050.1471535549.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/realmode.h

@@ -46,6 +46,7 @@ extern unsigned char real_mode_blob_end[];
 
 extern unsigned long initial_code;
 extern unsigned long initial_gs;
+extern unsigned long initial_stack;
 
 extern unsigned char real_mode_blob[];
 extern unsigned char real_mode_relocs[];

arch/x86/include/asm/smp.h

@@ -39,9 +39,6 @@ DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid);
 DECLARE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_logical_apicid);
 #endif
 
-/* Static state in head.S used to set up a CPU */
-extern unsigned long stack_start; /* Initial stack pointer address */
-
 struct task_struct;
 
 struct smp_ops {

arch/x86/kernel/acpi/sleep.c

@@ -99,7 +99,7 @@ int x86_acpi_suspend_lowlevel(void)
 	saved_magic = 0x12345678;
 #else /* CONFIG_64BIT */
 #ifdef CONFIG_SMP
-	stack_start = (unsigned long)temp_stack + sizeof(temp_stack);
+	initial_stack = (unsigned long)temp_stack + sizeof(temp_stack);
 	early_gdt_descr.address =
 			(unsigned long)get_cpu_gdt_table(smp_processor_id());
 	initial_gs = per_cpu_offset(smp_processor_id());

arch/x86/kernel/head_32.S

@@ -94,7 +94,7 @@ RESERVE_BRK(pagetables, INIT_MAP_SIZE)
  */
 __HEAD
 ENTRY(startup_32)
-	movl pa(stack_start),%ecx
+	movl pa(initial_stack),%ecx
 	
 	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
 		us to not reload segments */
@@ -286,7 +286,7 @@ num_subarch_entries = (. - subarch_entries) / 4
  * start_secondary().
  */
 ENTRY(start_cpu0)
-	movl stack_start, %ecx
+	movl initial_stack, %ecx
 	movl %ecx, %esp
 	jmp  *(initial_code)
 ENDPROC(start_cpu0)
@@ -307,7 +307,7 @@ ENTRY(startup_32_smp)
 	movl %eax,%es
 	movl %eax,%fs
 	movl %eax,%gs
-	movl pa(stack_start),%ecx
+	movl pa(initial_stack),%ecx
 	movl %eax,%ss
 	leal -__PAGE_OFFSET(%ecx),%esp
 
@@ -703,7 +703,7 @@ ENTRY(initial_page_table)
 
 .data
 .balign 4
-ENTRY(stack_start)
+ENTRY(initial_stack)
 	.long init_thread_union+THREAD_SIZE
 
 __INITRODATA

arch/x86/kernel/head_64.S

@@ -66,7 +66,7 @@ startup_64:
 	 */
 
 	/*
-	 * Setup stack for verify_cpu(). "-8" because stack_start is defined
+	 * Setup stack for verify_cpu(). "-8" because initial_stack is defined
 	 * this way, see below. Our best guess is a NULL ptr for stack
 	 * termination heuristics and we don't want to break anything which
 	 * might depend on it (kgdb, ...).
@@ -226,7 +226,7 @@ ENTRY(secondary_startup_64)
 	movq	%rax, %cr0
 
 	/* Setup a boot time stack */
-	movq stack_start(%rip), %rsp
+	movq initial_stack(%rip), %rsp
 
 	/* zero EFLAGS after setting rsp */
 	pushq $0
@@ -310,7 +310,7 @@ ENDPROC(secondary_startup_64)
  * start_secondary().
  */
 ENTRY(start_cpu0)
-	movq stack_start(%rip),%rsp
+	movq initial_stack(%rip),%rsp
 	movq	initial_code(%rip),%rax
 	pushq	$0		# fake return address to stop unwinder
 	pushq	$__KERNEL_CS	# set correct cs
@@ -319,15 +319,14 @@ ENTRY(start_cpu0)
 ENDPROC(start_cpu0)
 #endif
 
-	/* SMP bootup changes these two */
+	/* Both SMP bootup and ACPI suspend change these variables */
 	__REFDATA
 	.balign	8
 	GLOBAL(initial_code)
 	.quad	x86_64_start_kernel
 	GLOBAL(initial_gs)
 	.quad	INIT_PER_CPU_VAR(irq_stack_union)
-
-	GLOBAL(stack_start)
+	GLOBAL(initial_stack)
 	.quad  init_thread_union+THREAD_SIZE-8
 	.word  0
 	__FINITDATA

arch/x86/kernel/smpboot.c

@@ -969,7 +969,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 
 	early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
 	initial_code = (unsigned long)start_secondary;
-	stack_start  = idle->thread.sp;
+	initial_stack  = idle->thread.sp;
 
 	/*
 	 * Enable the espfix hack for this CPU