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ftrace, orc, x86: Handle ftrace dynamically allocated trampolines

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The function tracer can create a dynamically allocated trampoline that is
called by the function mcount or fentry hook that is used to call the
function callback that is registered. The problem is that the orc undwinder
will bail if it encounters one of these trampolines. This breaks the stack
trace of function callbacks, which include the stack tracer and setting the
stack trace for individual functions.

Since these dynamic trampolines are basically copies of the static ftrace
trampolines defined in ftrace_*.S, we do not need to create new orc entries
for the dynamic trampolines. Finding the return address on the stack will be
identical as the functions that were copied to create the dynamic
trampolines. When encountering a ftrace dynamic trampoline, we can just use
the orc entry of the ftrace static function that was copied for that
trampoline.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-01-22 22:32:51 -05:00
parent e2ac83d74a
commit 6be7fa3c74
3 changed files with 66 additions and 13 deletions
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2
include/linux/ftrace.h
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@ -332,6 +332,8 @@ extern int ftrace_text_reserved(const void *start, const void *end);
extern int ftrace_nr_registered_ops(void);
struct ftrace_ops *ftrace_ops_trampoline(unsigned long addr);
bool is_ftrace_trampoline(unsigned long addr);
/*