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Commit 9bbd4c56 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
Browse files

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 arm64 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.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarLaura Abbott <labbott@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 2020a5ae

arch/arm64/kernel/process.c

+14 −6
Original line number Diff line number Diff line
@@ -350,27 +350,35 @@ struct task_struct *__switch_to(struct task_struct *prev, 
unsigned long get_wchan(struct task_struct *p)

{

	struct stackframe frame;

	unsigned long stack_page;

	unsigned long stack_page, ret = 0;

	int count = 0;

	if (!p || p == current || p->state == TASK_RUNNING)

		return 0;



	stack_page = (unsigned long)try_get_task_stack(p);

	if (!stack_page)

		return 0;



	frame.fp = thread_saved_fp(p);

	frame.sp = thread_saved_sp(p);

	frame.pc = thread_saved_pc(p);

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	frame.graph = p->curr_ret_stack;

#endif

	stack_page = (unsigned long)task_stack_page(p);

	do {

		if (frame.sp < stack_page ||

		    frame.sp >= stack_page + THREAD_SIZE ||

		    unwind_frame(p, &frame))

			return 0;

		if (!in_sched_functions(frame.pc))

			return frame.pc;

			goto out;

		if (!in_sched_functions(frame.pc)) {

			ret = frame.pc;

			goto out;

		}

	} while (count ++ < 16);

	return 0;



out:

	put_task_stack(p);

	return ret;

}



unsigned long arch_align_stack(unsigned long sp)

arch/arm64/kernel/stacktrace.c

+5 −0
Original line number Diff line number Diff line
@@ -181,6 +181,9 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
	struct stack_trace_data data;

	struct stackframe frame;



	if (!try_get_task_stack(tsk))

		return;



	data.trace = trace;

	data.skip = trace->skip;
@@ -202,6 +205,8 @@ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) 
	walk_stackframe(tsk, &frame, save_trace, &data);

	if (trace->nr_entries < trace->max_entries)

		trace->entries[trace->nr_entries++] = ULONG_MAX;



	put_task_stack(tsk);

}



void save_stack_trace(struct stack_trace *trace)

arch/arm64/kernel/traps.c

+5 −0
Original line number Diff line number Diff line
@@ -148,6 +148,9 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) 
	if (!tsk)

		tsk = current;



	if (!try_get_task_stack(tsk))

		return;



	/*

	 * Switching between stacks is valid when tracing current and in

	 * non-preemptible context.
@@ -213,6 +216,8 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) 
				 stack + sizeof(struct pt_regs));

		}

	}



	put_task_stack(tsk);

}



void show_stack(struct task_struct *tsk, unsigned long *sp)