Commit df45a557 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/ftrace: Add recursion protection in prepare_ftrace_return() 



The function_graph_enter() does not provide any recursion protection.

Add a protection in prepare_ftrace_return() in case
function_graph_enter() calls something that gets
function graph traced.

Fixes: 83021378 ("powerpc/ftrace: directly call of function graph tracer by ftrace caller")
Reported-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/74edf2ff0a60e66b0d9225a137100a86a0557032.1644949750.git.christophe.leroy@csgroup.eu
parent 34d8dac8

arch/powerpc/kernel/trace/ftrace.c

+7 −0
Original line number Diff line number Diff line
@@ -944,6 +944,7 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip, 
						unsigned long sp)

{

	unsigned long return_hooker;

	int bit;



	if (unlikely(ftrace_graph_is_dead()))

		goto out;
@@ -951,10 +952,16 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip, 
	if (unlikely(atomic_read(&current->tracing_graph_pause)))

		goto out;



	bit = ftrace_test_recursion_trylock(ip, parent);

	if (bit < 0)

		goto out;



	return_hooker = ppc_function_entry(return_to_handler);



	if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))

		parent = return_hooker;



	ftrace_test_recursion_unlock(bit);

out:

	return parent;

}