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function_graph: Reverse the order of pushing the ret_stack and the callback

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The function graph profiler uses the ret_stack to store the "subtime" and
reuse it by nested functions and also on the return. But the current logic
has the profiler callback called before the ret_stack is updated, and it is
just modifying the ret_stack that will later be allocated (it's just lucky
that the "subtime" is not touched when it is allocated).

This could also cause a crash if we are at the end of the ret_stack when
this happens.

By reversing the order of the allocating the ret_stack and then calling the
callbacks attached to a function being traced, the ret_stack entry is no
longer used before it is allocated.

Cc: stable@kernel.org
Fixes: 03274a3ffb ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-11-20 12:40:25 -05:00
parent 552701dd0f
commit 7c6ea35ef5
1 changed files with 6 additions and 4 deletions
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10
kernel/trace/trace_functions_graph.c
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@ -188,15 +188,17 @@ int function_graph_enter(unsigned long ret, unsigned long func,
trace.func = func;
trace.depth = ++current->curr_ret_depth;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
goto out;
if (ftrace_push_return_trace(ret, func,
frame_pointer, retp))
goto out;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
goto out_ret;
return 0;
out_ret:
current->curr_ret_stack--;
out:
current->curr_ret_depth--;
return -EBUSY;