Commit 9a7c348b authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

ftrace: Add return address pointer to ftrace_ret_stack 



Storing this value will help prevent unwinders from getting out of sync
with the function graph tracer ret_stack.  Now instead of needing a
stateful iterator, they can compare the return address pointer to find
the right ret_stack entry.

Note that an array of 50 ftrace_ret_stack structs is allocated for every
task.  So when an arch implements this, it will add either 200 or 400
bytes of memory usage per task (depending on whether it's a 32-bit or
64-bit platform).

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a95cfcc39e8f26b89a430c56926af0bb217bc0a1.1471607358.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent daa460a8

Documentation/trace/ftrace-design.txt

+11 −0
Original line number Diff line number Diff line
@@ -203,6 +203,17 @@ along to ftrace_push_return_trace() instead of a stub value of 0. 


Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.



HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

--------------------------------



An arch may pass in a pointer to the return address on the stack.  This

prevents potential stack unwinding issues where the unwinder gets out of

sync with ret_stack and the wrong addresses are reported by

ftrace_graph_ret_addr().



Adding support for it is easy: just define the macro in asm/ftrace.h and

pass the return address pointer as the 'retp' argument to

ftrace_push_return_trace().



HAVE_FTRACE_NMI_ENTER

---------------------

arch/arm/kernel/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -218,7 +218,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
	}



	err = ftrace_push_return_trace(old, self_addr, &trace.depth,

				       frame_pointer);

				       frame_pointer, NULL);

	if (err == -EBUSY) {

		*parent = old;

		return;

arch/arm64/kernel/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -138,7 +138,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
		return;



	err = ftrace_push_return_trace(old, self_addr, &trace.depth,

				       frame_pointer);

				       frame_pointer, NULL);

	if (err == -EBUSY)

		return;

	else

arch/blackfin/kernel/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -107,7 +107,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 
		return;



	if (ftrace_push_return_trace(*parent, self_addr, &trace.depth,

	                             frame_pointer) == -EBUSY)

				     frame_pointer, NULL) == -EBUSY)

		return;



	trace.func = self_addr;

arch/microblaze/kernel/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) 
		return;

	}



	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);

	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0, NULL);

	if (err == -EBUSY) {

		*parent = old;

		return;

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