ftrace: Allow archs to specify if they need a separate function graph trampoline (646d7043) · Commits · 戴 / test

Currently if an arch supports function graph tracing, the core code will just assign the function graph trampoline to the function graph addr that gets called. But as the old method for function graph tracing always calls the function trampoline first and that calls the function graph trampoline, some archs may have the function graph trampoline dependent on operations that were done in the function trampoline. This causes function graph tracer to break on those archs. Instead of having the default be to set the function graph ftrace_ops to the function graph trampoline, have it instead just set it to zero which will keep it from jumping to a trampoline that is not set up to be jumped directly too. Link: http://lkml.kernel.org/r/53BED155.9040607@nvidia.com Reported-by:

Tuomas Tynkkynen <ttynkkynen@nvidia.com> Tested-by:

Tuomas Tynkkynen <ttynkkynen@nvidia.com> Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -453,6 +453,16 @@ void ftrace_modify_all_code(int command);
		#endif
		#endif

		/*
		* If an arch would like functions that are only traced
		* by the function graph tracer to jump directly to its own
		* trampoline, then they can define FTRACE_GRAPH_TRAMP_ADDR
		* to be that address to jump to.
		*/
		#ifndef FTRACE_GRAPH_TRAMP_ADDR
		#define FTRACE_GRAPH_TRAMP_ADDR ((unsigned long) 0)
		#endif

		#ifdef CONFIG_FUNCTION_GRAPH_TRACER
		extern void ftrace_graph_caller(void);
		extern int ftrace_enable_ftrace_graph_caller(void);

kernel/trace/ftrace.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -5366,7 +5366,8 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,

		#ifdef CONFIG_DYNAMIC_FTRACE
		/* Optimize function graph calling (if implemented by arch) */
		global_ops.trampoline = FTRACE_GRAPH_ADDR;
		if (FTRACE_GRAPH_TRAMP_ADDR != 0)
		global_ops.trampoline = FTRACE_GRAPH_TRAMP_ADDR;
		#endif

		ret = ftrace_startup(&global_ops, FTRACE_START_FUNC_RET);
		@@ -5390,6 +5391,7 @@ void unregister_ftrace_graph(void)
		ftrace_shutdown(&global_ops, FTRACE_STOP_FUNC_RET);
		global_ops.flags &= ~FTRACE_OPS_FL_STUB;
		#ifdef CONFIG_DYNAMIC_FTRACE
		if (FTRACE_GRAPH_TRAMP_ADDR != 0)
		global_ops.trampoline = 0;
		#endif
		unregister_pm_notifier(&ftrace_suspend_notifier);

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