Commit 018cce33 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: prep stack walkers for THREAD_INFO_IN_TASK 



[text copied from commit 9bbd4c56
("arm64: prep stack walkers for THREAD_INFO_IN_TASK")]

When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed
before a task is destroyed. To account for this, the stacks are
refcounted, and when manipulating the stack of another task, it is
necessary to get/put the stack to ensure it isn't freed and/or re-used
while we do so.

This patch reworks the powerpc stack walking code to account for this.
When CONFIG_THREAD_INFO_IN_TASK is not selected these perform no
refcounting, and this should only be a structural change that does not
affect behaviour.

Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
[mpe: Move try_get_task_stack() below tsk == NULL check in show_stack()]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 05486089

arch/powerpc/kernel/process.c

+23 −3
Original line number Diff line number Diff line
@@ -2027,7 +2027,7 @@ int validate_sp(unsigned long sp, struct task_struct *p, 


EXPORT_SYMBOL(validate_sp);



unsigned long get_wchan(struct task_struct *p)

static unsigned long __get_wchan(struct task_struct *p)

{

	unsigned long ip, sp;

	int count = 0;
@@ -2053,6 +2053,20 @@ unsigned long get_wchan(struct task_struct *p) 
	return 0;

}



unsigned long get_wchan(struct task_struct *p)

{

	unsigned long ret;



	if (!try_get_task_stack(p))

		return 0;



	ret = __get_wchan(p);



	put_task_stack(p);



	return ret;

}



static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;



void show_stack(struct task_struct *tsk, unsigned long *stack)
@@ -2067,9 +2081,13 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) 
	int curr_frame = 0;

#endif



	sp = (unsigned long) stack;

	if (tsk == NULL)

		tsk = current;



	if (!try_get_task_stack(tsk))

		return;



	sp = (unsigned long) stack;

	if (sp == 0) {

		if (tsk == current)

			sp = current_stack_pointer();
@@ -2081,7 +2099,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) 
	printk("Call Trace:\n");

	do {

		if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))

			return;

			break;



		stack = (unsigned long *) sp;

		newsp = stack[0];
@@ -2121,6 +2139,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack) 


		sp = newsp;

	} while (count++ < kstack_depth_to_print);



	put_task_stack(tsk);

}



#ifdef CONFIG_PPC64

arch/powerpc/kernel/stacktrace.c

+26 −3
Original line number Diff line number Diff line
@@ -67,12 +67,17 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
{

	unsigned long sp;



	if (!try_get_task_stack(tsk))

		return;



	if (tsk == current)

		sp = current_stack_pointer();

	else

		sp = tsk->thread.ksp;



	save_context_stack(trace, sp, tsk, 0);



	put_task_stack(tsk);

}

EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
@@ -90,8 +95,7 @@ EXPORT_SYMBOL_GPL(save_stack_trace_regs); 
 *

 * If the task is not 'current', the caller *must* ensure the task is inactive.

 */

int

save_stack_trace_tsk_reliable(struct task_struct *tsk,

static int __save_stack_trace_tsk_reliable(struct task_struct *tsk,

					   struct stack_trace *trace)

{

	unsigned long sp;
@@ -197,6 +201,25 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk, 
	}

	return 0;

}



int save_stack_trace_tsk_reliable(struct task_struct *tsk,

				  struct stack_trace *trace)

{

	int ret;



	/*

	 * If the task doesn't have a stack (e.g., a zombie), the stack is

	 * "reliably" empty.

	 */

	if (!try_get_task_stack(tsk))

		return 0;



	ret = __save_stack_trace_tsk_reliable(tsk, trace);



	put_task_stack(tsk);



	return ret;

}

EXPORT_SYMBOL_GPL(save_stack_trace_tsk_reliable);

#endif /* CONFIG_HAVE_RELIABLE_STACKTRACE */

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