Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit cfeeed27 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

x86/dumpstack: Allow preemption in show_stack_log_lvl() and dump_trace() 



show_stack_log_lvl() and dump_trace() are already preemption safe:

- If they're running in irq or exception context, preemption is already
  disabled and the percpu stack pointers can be trusted.

- If they're running with preemption enabled, they must be running on
  the task stack anyway, so it doesn't matter if they're comparing the
  stack pointer against a percpu stack pointer from this CPU or another
  one: either way it won't match.

Signed-off-by: default avatarJosh 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/a0ca0b1044eca97d4f0ec7c1619cf80b3b65560d.1473371307.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 85063fac

arch/x86/kernel/dumpstack_32.c

+6 −8
Original line number Diff line number Diff line
@@ -24,16 +24,16 @@ static void *is_irq_stack(void *p, void *irq) 
}





static void *is_hardirq_stack(unsigned long *stack, int cpu)

static void *is_hardirq_stack(unsigned long *stack)

{

	void *irq = per_cpu(hardirq_stack, cpu);

	void *irq = this_cpu_read(hardirq_stack);



	return is_irq_stack(stack, irq);

}



static void *is_softirq_stack(unsigned long *stack, int cpu)

static void *is_softirq_stack(unsigned long *stack)

{

	void *irq = per_cpu(softirq_stack, cpu);

	void *irq = this_cpu_read(softirq_stack);



	return is_irq_stack(stack, irq);

}
@@ -42,7 +42,6 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
		unsigned long *stack, unsigned long bp,

		const struct stacktrace_ops *ops, void *data)

{

	const unsigned cpu = get_cpu();

	int graph = 0;

	u32 *prev_esp;
@@ -53,9 +52,9 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
	for (;;) {

		void *end_stack;



		end_stack = is_hardirq_stack(stack, cpu);

		end_stack = is_hardirq_stack(stack);

		if (!end_stack)

			end_stack = is_softirq_stack(stack, cpu);

			end_stack = is_softirq_stack(stack);



		bp = ops->walk_stack(task, stack, bp, ops, data,

				     end_stack, &graph);
@@ -74,7 +73,6 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
			break;

		touch_nmi_watchdog();

	}

	put_cpu();

}

EXPORT_SYMBOL(dump_trace);

arch/x86/kernel/dumpstack_64.c

+9 −17
Original line number Diff line number Diff line
@@ -31,8 +31,8 @@ static char x86_stack_ids[][8] = { 
#endif

};



static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,

					 unsigned *usedp, char **idp)

static unsigned long *in_exception_stack(unsigned long stack, unsigned *usedp,

					 char **idp)

{

	unsigned k;
@@ -41,7 +41,7 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack, 
	 * 'stack' is in one of them:

	 */

	for (k = 0; k < N_EXCEPTION_STACKS; k++) {

		unsigned long end = per_cpu(orig_ist, cpu).ist[k];

		unsigned long end = raw_cpu_ptr(&orig_ist)->ist[k];

		/*

		 * Is 'stack' above this exception frame's end?

		 * If yes then skip to the next frame.
@@ -111,7 +111,7 @@ enum stack_type { 
};



static enum stack_type

analyze_stack(int cpu, struct task_struct *task, unsigned long *stack,

analyze_stack(struct task_struct *task, unsigned long *stack,

	      unsigned long **stack_end, unsigned long *irq_stack,

	      unsigned *used, char **id)

{
@@ -121,8 +121,7 @@ analyze_stack(int cpu, struct task_struct *task, unsigned long *stack, 
	if ((unsigned long)task_stack_page(task) == addr)

		return STACK_IS_NORMAL;



	*stack_end = in_exception_stack(cpu, (unsigned long)stack,

					used, id);

	*stack_end = in_exception_stack((unsigned long)stack, used, id);

	if (*stack_end)

		return STACK_IS_EXCEPTION;
@@ -149,8 +148,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
		unsigned long *stack, unsigned long bp,

		const struct stacktrace_ops *ops, void *data)

{

	const unsigned cpu = get_cpu();

	unsigned long *irq_stack = (unsigned long *)per_cpu(irq_stack_ptr, cpu);

	unsigned long *irq_stack = (unsigned long *)this_cpu_read(irq_stack_ptr);

	unsigned used = 0;

	int graph = 0;

	int done = 0;
@@ -169,8 +167,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
		enum stack_type stype;

		char *id;



		stype = analyze_stack(cpu, task, stack, &stack_end,

				      irq_stack, &used, &id);

		stype = analyze_stack(task, stack, &stack_end, irq_stack, &used,

				      &id);



		/* Default finish unless specified to continue */

		done = 1;
@@ -225,7 +223,6 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs, 
	 * This handles the process stack:

	 */

	bp = ops->walk_stack(task, stack, bp, ops, data, NULL, &graph);

	put_cpu();

}

EXPORT_SYMBOL(dump_trace);
@@ -236,13 +233,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, 
	unsigned long *irq_stack_end;

	unsigned long *irq_stack;

	unsigned long *stack;

	int cpu;

	int i;



	preempt_disable();

	cpu = smp_processor_id();



	irq_stack_end = (unsigned long *)(per_cpu(irq_stack_ptr, cpu));

	irq_stack_end = (unsigned long *)this_cpu_read(irq_stack_ptr);

	irq_stack     = irq_stack_end - (IRQ_STACK_SIZE / sizeof(long));



	sp = sp ? : get_stack_pointer(task, regs);
@@ -274,7 +267,6 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, 
		stack++;

		touch_nmi_watchdog();

	}

	preempt_enable();



	pr_cont("\n");

	show_trace_log_lvl(task, regs, sp, bp, log_lvl);