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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: 830213786c ("powerpc/ftrace: directly call of function graph tracer by ftrace caller")
Reported-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/74edf2ff0a60e66b0d9225a137100a86a0557032.1644949750.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2022-02-15 19:31:23 +01:00 committed by Michael Ellerman
parent 34d8dac807
commit df45a55788
1 changed files with 7 additions and 0 deletions
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7
arch/powerpc/kernel/trace/ftrace.c
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@ -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;
}