diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-11-08 19:12:57 +0100 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2019-11-13 15:36:49 +0100 |
| commit | a3ad1a7e39689005cb04a4f2adb82f9d55b4724f (patch) | |
| tree | 64deafb73e244d233836735dd2fa6a3c41462cc6 | |
| parent | ftrace/x86: Add register_ftrace_direct() for custom trampolines (diff) | |
| download | linux-a3ad1a7e39689005cb04a4f2adb82f9d55b4724f.tar.xz linux-a3ad1a7e39689005cb04a4f2adb82f9d55b4724f.zip | |
ftrace/x86: Add a counter to test function_graph with direct
As testing for direct calls from the function graph tracer adds a little
overhead (which is a lot when tracing every function), add a counter that
can be used to test if function_graph tracer needs to test for a direct
caller or not.
It would have been nicer if we could use a static branch, but the static
branch logic fails when used within the function graph tracer trampoline.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | arch/x86/kernel/ftrace.c | 8 | ||||
| -rw-r--r-- | include/linux/ftrace.h | 2 | ||||
| -rw-r--r-- | kernel/trace/ftrace.c | 4 |
3 files changed, 11 insertions, 3 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index fef283f6341d..060a361d9d11 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -1049,9 +1049,11 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, * return address is actually off by one word, and we * need to adjust for that. */ - if (ftrace_find_direct_func(self_addr + MCOUNT_INSN_SIZE)) { - self_addr = *parent; - parent++; + if (ftrace_direct_func_count) { + if (ftrace_find_direct_func(self_addr + MCOUNT_INSN_SIZE)) { + self_addr = *parent; + parent++; + } } /* diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 2bc7bd6b8387..55647e185141 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -247,10 +247,12 @@ static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { #endif /* CONFIG_FUNCTION_TRACER */ #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +extern int ftrace_direct_func_count; int register_ftrace_direct(unsigned long ip, unsigned long addr); int unregister_ftrace_direct(unsigned long ip, unsigned long addr); struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr); #else +# define ftrace_direct_func_count 0 static inline int register_ftrace_direct(unsigned long ip, unsigned long addr) { return -ENODEV; diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index c4446eabacbe..f9456346ec66 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2364,6 +2364,7 @@ ftrace_find_tramp_ops_new(struct dyn_ftrace *rec) /* Protected by rcu_tasks for reading, and direct_mutex for writing */ static struct ftrace_hash *direct_functions = EMPTY_HASH; static DEFINE_MUTEX(direct_mutex); +int ftrace_direct_func_count; /* * Search the direct_functions hash to see if the given instruction pointer @@ -5056,6 +5057,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr) direct->addr = addr; direct->count = 0; list_add_rcu(&direct->next, &ftrace_direct_funcs); + ftrace_direct_func_count++; } entry->ip = ip; @@ -5081,6 +5083,7 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr) if (free_hash) free_ftrace_hash(free_hash); free_hash = NULL; + ftrace_direct_func_count--; } } else { if (!direct->count) @@ -5141,6 +5144,7 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr) list_del_rcu(&direct->next); synchronize_rcu_tasks(); kfree(direct); + ftrace_direct_func_count--; } } out_unlock: |