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Commit a1d863ac authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Vasily Gorbik
Browse files

s390/unwind: fix mixing regs and sp 



unwind_for_each_frame stops after the first frame if regs->gprs[15] <=
sp.

The reason is that in case regs are specified, the first frame should be
regs->psw.addr and the second frame should be sp->gprs[8]. However,
currently the second frame is regs->gprs[15], which confuses
outside_of_stack().

Fix by introducing a flag to distinguish this special case from
unwinding the interrupt handler, for which the current behavior is
appropriate.

Fixes: 78c98f90 ("s390/unwind: introduce stack unwind API")
Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Cc: stable@vger.kernel.org # v5.2+
Reviewed-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent b8e51a6a

arch/s390/include/asm/unwind.h

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ struct unwind_state { 
	struct task_struct *task;

	struct pt_regs *regs;

	unsigned long sp, ip;

	bool reuse_sp;

	int graph_idx;

	bool reliable;

	bool error;

arch/s390/kernel/unwind_bc.c

+13 −5
Original line number Diff line number Diff line
@@ -46,11 +46,16 @@ bool unwind_next_frame(struct unwind_state *state) 


	regs = state->regs;

	if (unlikely(regs)) {

		if (state->reuse_sp) {

			sp = state->sp;

			state->reuse_sp = false;

		} else {

			sp = READ_ONCE_NOCHECK(regs->gprs[15]);

			if (unlikely(outside_of_stack(state, sp))) {

				if (!update_stack_info(state, sp))

					goto out_err;

			}

		}

		sf = (struct stack_frame *) sp;

		ip = READ_ONCE_NOCHECK(sf->gprs[8]);

		reliable = false;
@@ -107,9 +112,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, 
{

	struct stack_info *info = &state->stack_info;

	unsigned long *mask = &state->stack_mask;

	bool reliable, reuse_sp;

	struct stack_frame *sf;

	unsigned long ip;

	bool reliable;



	memset(state, 0, sizeof(*state));

	state->task = task;
@@ -134,10 +139,12 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, 
	if (regs) {

		ip = READ_ONCE_NOCHECK(regs->psw.addr);

		reliable = true;

		reuse_sp = true;

	} else {

		sf = (struct stack_frame *) sp;

		ip = READ_ONCE_NOCHECK(sf->gprs[8]);

		reliable = false;

		reuse_sp = false;

	}



#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -151,5 +158,6 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, 
	state->sp = sp;

	state->ip = ip;

	state->reliable = reliable;

	state->reuse_sp = reuse_sp;

}

EXPORT_SYMBOL_GPL(__unwind_start);