Messages in this thread Patch in this message | | | From | Adrian Hunter <> | Subject | [PATCH V7 06/15] ftrace: Add symbols for ftrace trampolines | Date | Tue, 12 May 2020 15:19:13 +0300 |
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Symbols are needed for tools to describe instruction addresses. Pages allocated for ftrace's purposes need symbols to be created for them. Add such symbols to be visible via /proc/kallsyms.
Example on x86 with CONFIG_DYNAMIC_FTRACE=y
# echo function > /sys/kernel/debug/tracing/current_tracer # cat /proc/kallsyms | grep '\[__builtin__ftrace\]' ffffffffc0238000 t ftrace_trampoline [__builtin__ftrace]
Note: This patch adds "__builtin__ftrace" as a module name in /proc/kallsyms for symbols for pages allocated for ftrace's purposes, even though "__builtin__ftrace" is not a module.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- include/linux/ftrace.h | 12 ++++--- kernel/kallsyms.c | 5 +++ kernel/trace/ftrace.c | 77 ++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 88 insertions(+), 6 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index db95244a62d4..ea726ad1fa83 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -58,9 +58,6 @@ struct ftrace_direct_func; const char * ftrace_mod_address_lookup(unsigned long addr, unsigned long *size, unsigned long *off, char **modname, char *sym); -int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, - char *type, char *name, - char *module_name, int *exported); #else static inline const char * ftrace_mod_address_lookup(unsigned long addr, unsigned long *size, @@ -68,6 +65,13 @@ ftrace_mod_address_lookup(unsigned long addr, unsigned long *size, { return NULL; } +#endif + +#if defined(CONFIG_FUNCTION_TRACER) && defined(CONFIG_DYNAMIC_FTRACE) +int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, + char *type, char *name, + char *module_name, int *exported); +#else static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name, char *module_name, int *exported) @@ -76,7 +80,6 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val } #endif - #ifdef CONFIG_FUNCTION_TRACER extern int ftrace_enabled; @@ -207,6 +210,7 @@ struct ftrace_ops { struct ftrace_ops_hash old_hash; unsigned long trampoline; unsigned long trampoline_size; + struct list_head list; #endif }; diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index c6cc293c0e67..834bfdc43235 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -482,6 +482,11 @@ static int get_ksymbol_mod(struct kallsym_iter *iter) return 1; } +/* + * ftrace_mod_get_kallsym() may also get symbols for pages allocated for ftrace + * purposes. In that case "__builtin__ftrace" is used as a module name, even + * though "__builtin__ftrace" is not a module. + */ static int get_ksymbol_ftrace_mod(struct kallsym_iter *iter) { int ret = ftrace_mod_get_kallsym(iter->pos - iter->pos_mod_end, diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 041694a1eb74..9b0baeb4f0bb 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2775,6 +2775,38 @@ void __weak arch_ftrace_trampoline_free(struct ftrace_ops *ops) { } +/* List of trace_ops that have allocated trampolines */ +static LIST_HEAD(ftrace_ops_trampoline_list); + +static void ftrace_add_trampoline_to_kallsyms(struct ftrace_ops *ops) +{ + lockdep_assert_held(&ftrace_lock); + list_add_rcu(&ops->list, &ftrace_ops_trampoline_list); +} + +static void ftrace_remove_trampoline_from_kallsyms(struct ftrace_ops *ops) +{ + lockdep_assert_held(&ftrace_lock); + list_del_rcu(&ops->list); +} + +/* + * "__builtin__ftrace" is used as a module name in /proc/kallsyms for symbols + * for pages allocated for ftrace purposes, even though "__builtin__ftrace" is + * not a module. + */ +#define FTRACE_TRAMPOLINE_MOD "__builtin__ftrace" +#define FTRACE_TRAMPOLINE_SYM "ftrace_trampoline" + +static void ftrace_trampoline_free(struct ftrace_ops *ops) +{ + if (ops && (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP) && + ops->trampoline) + ftrace_remove_trampoline_from_kallsyms(ops); + + arch_ftrace_trampoline_free(ops); +} + static void ftrace_startup_enable(int command) { if (saved_ftrace_func != ftrace_trace_function) { @@ -2945,7 +2977,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command) synchronize_rcu_tasks(); free_ops: - arch_ftrace_trampoline_free(ops); + ftrace_trampoline_free(ops); } return 0; @@ -6188,6 +6220,27 @@ struct ftrace_mod_map { unsigned int num_funcs; }; +static int ftrace_get_trampoline_kallsym(unsigned int symnum, + unsigned long *value, char *type, + char *name, char *module_name, + int *exported) +{ + struct ftrace_ops *op; + + list_for_each_entry_rcu(op, &ftrace_ops_trampoline_list, list) { + if (!op->trampoline || symnum--) + continue; + *value = op->trampoline; + *type = 't'; + strlcpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN); + strlcpy(module_name, FTRACE_TRAMPOLINE_MOD, MODULE_NAME_LEN); + *exported = 0; + return 0; + } + + return -ERANGE; +} + #ifdef CONFIG_MODULES #define next_to_ftrace_page(p) container_of(p, struct ftrace_page, next) @@ -6524,6 +6577,7 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, { struct ftrace_mod_map *mod_map; struct ftrace_mod_func *mod_func; + int ret; preempt_disable(); list_for_each_entry_rcu(mod_map, &ftrace_mod_maps, list) { @@ -6550,8 +6604,10 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, WARN_ON(1); break; } + ret = ftrace_get_trampoline_kallsym(symnum, value, type, name, + module_name, exported); preempt_enable(); - return -ERANGE; + return ret; } #else @@ -6563,6 +6619,18 @@ allocate_ftrace_mod_map(struct module *mod, { return NULL; } +int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value, + char *type, char *name, char *module_name, + int *exported) +{ + int ret; + + preempt_disable(); + ret = ftrace_get_trampoline_kallsym(symnum, value, type, name, + module_name, exported); + preempt_enable(); + return ret; +} #endif /* CONFIG_MODULES */ struct ftrace_init_func { @@ -6743,7 +6811,12 @@ void __weak arch_ftrace_update_trampoline(struct ftrace_ops *ops) static void ftrace_update_trampoline(struct ftrace_ops *ops) { + unsigned long trampoline = ops->trampoline; + arch_ftrace_update_trampoline(ops); + if (ops->trampoline && ops->trampoline != trampoline && + (ops->flags & FTRACE_OPS_FL_ALLOC_TRAMP)) + ftrace_add_trampoline_to_kallsyms(ops); } void ftrace_init_trace_array(struct trace_array *tr) -- 2.17.1
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