From ea806eb3eab35528b578a061b2c4b28f0f92c465 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Sun, 17 Nov 2019 17:04:15 -0500 Subject: ftrace: Add a helper function to modify_ftrace_direct() to allow arch optimization If a direct ftrace callback is at a location that does not have any other ftrace helpers attached to it, it is possible to simply just change the text to call the new caller (if the architecture supports it). But this requires special architecture code. Currently, modify_ftrace_direct() uses a trick to add a stub ftrace callback to the location forcing it to call the ftrace iterator. Then it can change the direct helper to call the new function in C, and then remove the stub. Removing the stub will have the location now call the new location that the direct helper is using. The new helper function does the registering the stub trick, but is a weak function, allowing an architecture to override it to do something a bit more direct. Link: https://lore.kernel.org/r/20191115215125.mbqv7taqnx376yed@ast-mbp.dhcp.thefacebook.com Suggested-by: Alexei Starovoitov Signed-off-by: Steven Rostedt (VMware) --- include/linux/ftrace.h | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 73eb2e93593f..dfaa37e1943d 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -246,12 +246,24 @@ static inline void ftrace_free_init_mem(void) { } static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { } #endif /* CONFIG_FUNCTION_TRACER */ +struct ftrace_func_entry { + struct hlist_node hlist; + unsigned long ip; + unsigned long direct; /* for direct lookup only */ +}; + +struct dyn_ftrace; + #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); int modify_ftrace_direct(unsigned long ip, unsigned long old_addr, unsigned long new_addr); struct ftrace_direct_func *ftrace_find_direct_func(unsigned long addr); +int ftrace_modify_direct_caller(struct ftrace_func_entry *entry, + struct dyn_ftrace *rec, + unsigned long old_addr, + unsigned long new_addr); #else # define ftrace_direct_func_count 0 static inline int register_ftrace_direct(unsigned long ip, unsigned long addr) @@ -271,6 +283,13 @@ static inline struct ftrace_direct_func *ftrace_find_direct_func(unsigned long a { return NULL; } +static inline int ftrace_modify_direct_caller(struct ftrace_func_entry *entry, + struct dyn_ftrace *rec, + unsigned long old_addr, + unsigned long new_addr) +{ + return -ENODEV; +} #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS @@ -343,8 +362,6 @@ static inline void stack_tracer_enable(void) { } int ftrace_arch_code_modify_prepare(void); int ftrace_arch_code_modify_post_process(void); -struct dyn_ftrace; - enum ftrace_bug_type { FTRACE_BUG_UNKNOWN, FTRACE_BUG_INIT, -- cgit v1.2.3