From daa460a88c09b26b68e8b017de589c217e901afb Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 19 Aug 2016 06:52:56 -0500 Subject: ftrace: Only allocate the ret_stack 'fp' field when needed This saves some memory when HAVE_FUNCTION_GRAPH_FP_TEST isn't defined. On x86_64 with newer versions of gcc which have -mfentry, it saves 400 bytes per task. Signed-off-by: Josh Poimboeuf Acked-by: Steven Rostedt Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Byungchul Park Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Nilay Vaish Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/5c7747d9ea7b5cb47ef0a8ce8a6cea6bf7aa94bf.1471607358.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- include/linux/ftrace.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 7d565afe35d2..4ad9ccc60e38 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -795,7 +795,9 @@ struct ftrace_ret_stack { unsigned long func; unsigned long long calltime; unsigned long long subtime; +#ifdef HAVE_FUNCTION_GRAPH_FP_TEST unsigned long fp; +#endif }; /* -- cgit v1.2.3 From 9a7c348ba6a46f6270d4fe49577649dad5664fe7 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 19 Aug 2016 06:52:57 -0500 Subject: 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: Josh Poimboeuf Acked-by: Steven Rostedt Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Byungchul Park Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Nilay Vaish Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/a95cfcc39e8f26b89a430c56926af0bb217bc0a1.1471607358.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- include/linux/ftrace.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 4ad9ccc60e38..483e02a50d37 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -798,6 +798,9 @@ struct ftrace_ret_stack { #ifdef HAVE_FUNCTION_GRAPH_FP_TEST unsigned long fp; #endif +#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR + unsigned long *retp; +#endif }; /* @@ -809,7 +812,7 @@ extern void return_to_handler(void); extern int ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth, - unsigned long frame_pointer); + unsigned long frame_pointer, unsigned long *retp); /* * Sometimes we don't want to trace a function with the function -- cgit v1.2.3 From 223918e32a87c79ac55ca4aa513ba405ba4d57cd Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 19 Aug 2016 06:52:58 -0500 Subject: ftrace: Add ftrace_graph_ret_addr() stack unwinding helpers When function graph tracing is enabled for a function, ftrace modifies the stack by replacing the original return address with the address of a hook function (return_to_handler). Stack unwinders need a way to get the original return address. Add an arch-independent helper function for that named ftrace_graph_ret_addr(). This adds two variations of the function: one depends on HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, and the other relies on an index state variable. The former is recommended because, in some cases, the latter can cause problems when the unwinder skips stack frames. It can get out of sync with the ret_stack index and wrong addresses can be reported for the stack trace. Once all arches have been ported to use HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, we can get rid of the distinction. Signed-off-by: Josh Poimboeuf Acked-by: Steven Rostedt Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Byungchul Park Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Nilay Vaish Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/36bd90f762fc5e5af3929e3797a68a64906421cf.1471607358.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar --- include/linux/ftrace.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 483e02a50d37..6f93ac46e7f0 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -814,6 +814,9 @@ extern int ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth, unsigned long frame_pointer, unsigned long *retp); +unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx, + unsigned long ret, unsigned long *retp); + /* * Sometimes we don't want to trace a function with the function * graph tracer but we want them to keep traced by the usual function @@ -875,6 +878,13 @@ static inline int task_curr_ret_stack(struct task_struct *tsk) return -1; } +static inline unsigned long +ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret, + unsigned long *retp) +{ + return ret; +} + static inline void pause_graph_tracing(void) { } static inline void unpause_graph_tracing(void) { } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ -- cgit v1.2.3