Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull low-level x86 updates from Ingo Molnar:
 "In this cycle this topic tree has become one of those 'super topics'
  that accumulated a lot of changes:

   - Add CONFIG_VMAP_STACK=y support to the core kernel and enable it on
     x86 - preceded by an array of changes. v4.8 saw preparatory changes
     in this area already - this is the rest of the work. Includes the
     thread stack caching performance optimization. (Andy Lutomirski)

   - switch_to() cleanups and all around enhancements. (Brian Gerst)

   - A large number of dumpstack infrastructure enhancements and an
     unwinder abstraction. The secret long term plan is safe(r) live
     patching plus maybe another attempt at debuginfo based unwinding -
     but all these current bits are standalone enhancements in a frame
     pointer based debug environment as well. (Josh Poimboeuf)

   - More __ro_after_init and const annotations. (Kees Cook)

   - Enable KASLR for the vmemmap memory region. (Thomas Garnier)"

[ The virtually mapped stack changes are pretty fundamental, and not
  x86-specific per se, even if they are only used on x86 right now. ]

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  x86/asm: Get rid of __read_cr4_safe()
  thread_info: Use unsigned long for flags
  x86/alternatives: Add stack frame dependency to alternative_call_2()
  x86/dumpstack: Fix show_stack() task pointer regression
  x86/dumpstack: Remove dump_trace() and related callbacks
  x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder
  oprofile/x86: Convert x86_backtrace() to use the new unwinder
  x86/stacktrace: Convert save_stack_trace_*() to use the new unwinder
  perf/x86: Convert perf_callchain_kernel() to use the new unwinder
  x86/unwind: Add new unwind interface and implementations
  x86/dumpstack: Remove NULL task pointer convention
  fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y
  sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
  lib/syscall: Pin the task stack in collect_syscall()
  x86/process: Pin the target stack in get_wchan()
  x86/dumpstack: Pin the target stack when dumping it
  kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function
  sched/core: Add try_get_task_stack() and put_task_stack()
  x86/entry/64: Fix a minor comment rebase error
  iommu/amd: Don't put completion-wait semaphore on stack
  ...

1 files changed, 92 insertions, 62 deletions

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 09675712eba8..06eb322b5f9f 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -16,93 +16,121 @@
 
 #include <asm/stacktrace.h>
 
-static void *is_irq_stack(void *p, void *irq)
+void stack_type_str(enum stack_type type, const char **begin, const char **end)
 {
-	if (p < irq || p >= (irq + THREAD_SIZE))
-		return NULL;
-	return irq + THREAD_SIZE;
+	switch (type) {
+	case STACK_TYPE_IRQ:
+	case STACK_TYPE_SOFTIRQ:
+		*begin = "IRQ";
+		*end   = "EOI";
+		break;
+	default:
+		*begin = NULL;
+		*end   = NULL;
+	}
 }
 
-
-static void *is_hardirq_stack(unsigned long *stack, int cpu)
+static bool in_hardirq_stack(unsigned long *stack, struct stack_info *info)
 {
-	void *irq = per_cpu(hardirq_stack, cpu);
+	unsigned long *begin = (unsigned long *)this_cpu_read(hardirq_stack);
+	unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-	return is_irq_stack(stack, irq);
-}
+	/*
+	 * This is a software stack, so 'end' can be a valid stack pointer.
+	 * It just means the stack is empty.
+	 */
+	if (stack < begin || stack > end)
+		return false;
 
-static void *is_softirq_stack(unsigned long *stack, int cpu)
-{
-	void *irq = per_cpu(softirq_stack, cpu);
+	info->type	= STACK_TYPE_IRQ;
+	info->begin	= begin;
+	info->end	= end;
 
-	return is_irq_stack(stack, irq);
+	/*
+	 * See irq_32.c -- the next stack pointer is stored at the beginning of
+	 * the stack.
+	 */
+	info->next_sp	= (unsigned long *)*begin;
+
+	return true;
 }
 
-void dump_trace(struct task_struct *task, struct pt_regs *regs,
-		unsigned long *stack, unsigned long bp,
-		const struct stacktrace_ops *ops, void *data)
+static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
 {
-	const unsigned cpu = get_cpu();
-	int graph = 0;
-	u32 *prev_esp;
+	unsigned long *begin = (unsigned long *)this_cpu_read(softirq_stack);
+	unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-	if (!task)
-		task = current;
+	/*
+	 * This is a software stack, so 'end' can be a valid stack pointer.
+	 * It just means the stack is empty.
+	 */
+	if (stack < begin || stack > end)
+		return false;
 
-	if (!stack) {
-		unsigned long dummy;
+	info->type	= STACK_TYPE_SOFTIRQ;
+	info->begin	= begin;
+	info->end	= end;
 
-		stack = &dummy;
-		if (task != current)
-			stack = (unsigned long *)task->thread.sp;
-	}
+	/*
+	 * The next stack pointer is stored at the beginning of the stack.
+	 * See irq_32.c.
+	 */
+	info->next_sp	= (unsigned long *)*begin;
 
-	if (!bp)
-		bp = stack_frame(task, regs);
+	return true;
+}
 
-	for (;;) {
-		void *end_stack;
+int get_stack_info(unsigned long *stack, struct task_struct *task,
+		   struct stack_info *info, unsigned long *visit_mask)
+{
+	if (!stack)
+		goto unknown;
 
-		end_stack = is_hardirq_stack(stack, cpu);
-		if (!end_stack)
-			end_stack = is_softirq_stack(stack, cpu);
+	task = task ? : current;
 
-		bp = ops->walk_stack(task, stack, bp, ops, data,
-				     end_stack, &graph);
+	if (in_task_stack(stack, task, info))
+		goto recursion_check;
 
-		/* Stop if not on irq stack */
-		if (!end_stack)
-			break;
+	if (task != current)
+		goto unknown;
 
-		/* The previous esp is saved on the bottom of the stack */
-		prev_esp = (u32 *)(end_stack - THREAD_SIZE);
-		stack = (unsigned long *)*prev_esp;
-		if (!stack)
-			break;
+	if (in_hardirq_stack(stack, info))
+		goto recursion_check;
 
-		if (ops->stack(data, "IRQ") < 0)
-			break;
-		touch_nmi_watchdog();
+	if (in_softirq_stack(stack, info))
+		goto recursion_check;
+
+	goto unknown;
+
+recursion_check:
+	/*
+	 * Make sure we don't iterate through any given stack more than once.
+	 * If it comes up a second time then there's something wrong going on:
+	 * just break out and report an unknown stack type.
+	 */
+	if (visit_mask) {
+		if (*visit_mask & (1UL << info->type))
+			goto unknown;
+		*visit_mask |= 1UL << info->type;
 	}
-	put_cpu();
+
+	return 0;
+
+unknown:
+	info->type = STACK_TYPE_UNKNOWN;
+	return -EINVAL;
 }
-EXPORT_SYMBOL(dump_trace);
 
-void
-show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
-		   unsigned long *sp, unsigned long bp, char *log_lvl)
+void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
+			unsigned long *sp, char *log_lvl)
 {
 	unsigned long *stack;
 	int i;
 
-	if (sp == NULL) {
-		if (regs)
-			sp = (unsigned long *)regs->sp;
-		else if (task)
-			sp = (unsigned long *)task->thread.sp;
-		else
-			sp = (unsigned long *)&sp;
-	}
+	if (!try_get_task_stack(task))
+		return;
+
+	sp = sp ? : get_stack_pointer(task, regs);
 
 	stack = sp;
 	for (i = 0; i < kstack_depth_to_print; i++) {
@@ -117,7 +145,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 		touch_nmi_watchdog();
 	}
 	pr_cont("\n");
-	show_trace_log_lvl(task, regs, sp, bp, log_lvl);
+	show_trace_log_lvl(task, regs, sp, log_lvl);
+
+	put_task_stack(task);
 }
 
 
@@ -139,7 +169,7 @@ void show_regs(struct pt_regs *regs)
 		u8 *ip;
 
 		pr_emerg("Stack:\n");
-		show_stack_log_lvl(NULL, regs, &regs->sp, 0, KERN_EMERG);
+		show_stack_log_lvl(current, regs, NULL, KERN_EMERG);
 
 		pr_emerg("Code:");