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tracing, x86: add low level support for ftrace return tracing

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Impact: add infrastructure for function-return tracing

Add low level support for ftrace return tracing.

This plug-in stores return addresses on the thread_info structure of
the current task.

The index of the current return address is initialized when the task
is the first one (init) and when a process forks (the child). It is
not needed when a task does a sys_execve because after this syscall,
it still needs to return on the kernel functions it called.

Note that the code of return_to_handler has been suggested by Steven
Rostedt as almost all of the ideas of improvements in this V3.

For purpose of security, arch/x86/kernel/process_32.c is not traced
because __switch_to() changes the current task during its execution.
That could cause inconsistency in the stored return address of this
function even if I didn't have any crash after testing with tracing on
this function enabled.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker
2008-11-11 07:03:45 +01:00
committed by Ingo Molnar
parent d844222a54
commit caf4b323b0
10 changed files with 301 additions and 9 deletions
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11
include/linux/sched.h
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@@ -2005,6 +2005,17 @@ static inline void setup_thread_stack(struct task_struct *p, struct task_struct
{
*task_thread_info(p) = *task_thread_info(org);
task_thread_info(p)->task = p;
#ifdef CONFIG_FUNCTION_RET_TRACER
/*
* When fork() creates a child process, this function is called.
* But the child task may not inherit the return adresses traced
* by the return function tracer because it will directly execute
* in userspace and will not return to kernel functions its parent
* used.
*/
task_thread_info(p)->curr_ret_stack = -1;
#endif
}
static inline unsigned long *end_of_stack(struct task_struct *p)