Messages in this thread Patch in this message | | | Subject | [PATCH] ftrace: fix race between ftrace and insmod | From | "Qiu, PeiyangX" <> | Date | Mon, 14 Dec 2015 10:59:02 +0800 |
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We hit ftrace_bug report when booting Android on a 64bit ATOM SOC chip. Basically, there is a race between insmod and ftrace_run_update_code.
After load_module=>ftrace_module_init, another thread jumps in to call ftrace_run_update_code=>ftrace_arch_code_modify_prepare =>set_all_modules_text_rw, to change all modules as RW. Since the new module is at MODULE_STATE_UNFORMED, the text attribute is not changed. Then, the 2nd thread goes ahead to change codes. However, load_module continues to call complete_formation=>set_section_ro_nx, then 2nd thread would fail when probing the module's TEXT.
Below patch tries to resolve it.
commit a949ae560a511fe4e3adf48fa44fefded93e5c2b Author: Steven Rostedt (Red Hat) <rostedt@goodmis.org> Date: Thu Apr 24 10:40:12 2014 -0400
ftrace/module: Hardcode ftrace_module_init() call into load_module()
But it can't fully resolve the issue.
THis patch holds ftrace_mutex across ftrace_module_init and complete_formation.
Signed-off-by: Qiu Peiyang <peiyangx.qiu@intel.com> Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com> --- include/linux/ftrace.h | 6 ++++-- kernel/module.c | 3 ++- kernel/trace/ftrace.c | 33 ++++++++++++++++++++++----------- 3 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index eae6548..4adc279 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -585,7 +585,8 @@ static inline int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_a extern int ftrace_arch_read_dyn_info(char *buf, int size);
extern int skip_trace(unsigned long ip); -extern void ftrace_module_init(struct module *mod); +extern void ftrace_module_init_start(struct module *mod); +extern void ftrace_module_init_end(struct module *mod);
extern void ftrace_disable_daemon(void); extern void ftrace_enable_daemon(void); @@ -595,7 +596,8 @@ static inline int ftrace_force_update(void) { return 0; } static inline void ftrace_disable_daemon(void) { } static inline void ftrace_enable_daemon(void) { } static inline void ftrace_release_mod(struct module *mod) {} -static inline void ftrace_module_init(struct module *mod) {} +static inline void ftrace_module_init_start(struct module *mod) {} +static inline void ftrace_module_init_end(struct module *mod) {} static inline __init int register_ftrace_command(struct ftrace_func_command *cmd) { return -EINVAL; diff --git a/kernel/module.c b/kernel/module.c index 8f051a1..324c5c6 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3506,10 +3506,11 @@ static int load_module(struct load_info *info, const char __user *uargs, dynamic_debug_setup(info->debug, info->num_debug);
/* Ftrace init must be called in the MODULE_STATE_UNFORMED state */ - ftrace_module_init(mod); + ftrace_module_init_start(mod);
/* Finally it's fully formed, ready to start executing. */ err = complete_formation(mod, info); + ftrace_module_init_end(mod); if (err) goto ddebug_cleanup;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 3f743b1..436c199 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -4795,7 +4795,7 @@ static int ftrace_cmp_ips(const void *a, const void *b) return 0; }
-static int ftrace_process_locs(struct module *mod, +static int ftrace_process_locs_nolock(struct module *mod, unsigned long *start, unsigned long *end) { @@ -4820,8 +4820,6 @@ static int ftrace_process_locs(struct module *mod, if (!start_pg) return -ENOMEM;
- mutex_lock(&ftrace_lock); - /* * Core and each module needs their own pages, as * modules will free them when they are removed. @@ -4889,8 +4887,18 @@ static int ftrace_process_locs(struct module *mod, local_irq_restore(flags); ret = 0; out: - mutex_unlock(&ftrace_lock); + return ret; +}
+static int ftrace_process_locs(struct module *mod, + unsigned long *start, + unsigned long *end) +{ + int ret; + + mutex_lock(&ftrace_lock); + ret = ftrace_process_locs_nolock(mod, start, end); + mutex_unlock(&ftrace_lock); return ret; }
@@ -4940,19 +4948,22 @@ void ftrace_release_mod(struct module *mod) mutex_unlock(&ftrace_lock); }
-static void ftrace_init_module(struct module *mod, - unsigned long *start, unsigned long *end) +void ftrace_module_init_start(struct module *mod) { + unsigned long *start = mod->ftrace_callsites; + unsigned long *end = mod->ftrace_callsites + mod->num_ftrace_callsites; + + mutex_lock(&ftrace_lock); + if (ftrace_disabled || start == end) return; - ftrace_process_locs(mod, start, end); + + ftrace_process_locs_nolock(mod, start, end); }
-void ftrace_module_init(struct module *mod) +void ftrace_module_init_end(struct module *mod) { - ftrace_init_module(mod, mod->ftrace_callsites, - mod->ftrace_callsites + - mod->num_ftrace_callsites); + mutex_unlock(&ftrace_lock); }
static int ftrace_module_notify_exit(struct notifier_block *self, -- 1.9.1
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