From fed1939c64d2288938fdc1c367d49082da65e195 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 14 Aug 2008 22:47:19 -0400 Subject: ftrace: remove old pointers to mcount When a mcount pointer is recorded into a table, it is used to add or remove calls to mcount (replacing them with nops). If the code is removed via removing a module, the pointers still exist. At modifying the code a check is always made to make sure the code being replaced is the code expected. In-other-words, the code being replaced is compared to what it is expected to be before being replaced. There is a very small chance that the code being replaced just happens to look like code that calls mcount (very small since the call to mcount is relative). To remove this chance, this patch adds ftrace_release to allow module unloading to remove the pointers to mcount within the module. Another change for init calls is made to not trace calls marked with __init. The tracing can not be started until after init is done anyway. Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- kernel/module.c | 12 ++++++++---- kernel/trace/ftrace.c | 32 ++++++++++++++++++++++++++++++-- 2 files changed, 38 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/module.c b/kernel/module.c index d753fd9d83e..7576c2d9462 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1431,6 +1431,9 @@ static void free_module(struct module *mod) /* Module unload stuff */ module_unload_free(mod); + /* release any pointers to mcount in this module */ + ftrace_release(mod->module_core, mod->core_size); + /* This may be NULL, but that's OK */ module_free(mod, mod->module_init); kfree(mod->args); @@ -1839,6 +1842,7 @@ static noinline struct module *load_module(void __user *umod, struct module *mod; long err = 0; void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */ + void *mseg; struct exception_table_entry *extable; mm_segment_t old_fs; @@ -2190,10 +2194,9 @@ static noinline struct module *load_module(void __user *umod, #endif } - if (mcountindex) { - void *mseg = (void *)sechdrs[mcountindex].sh_addr; - ftrace_init_module(mseg, mseg + sechdrs[mcountindex].sh_size); - } + /* sechdrs[0].sh_size is always zero */ + mseg = (void *)sechdrs[mcountindex].sh_addr; + ftrace_init_module(mseg, mseg + sechdrs[mcountindex].sh_size); err = module_finalize(hdr, sechdrs, mod); if (err < 0) @@ -2264,6 +2267,7 @@ static noinline struct module *load_module(void __user *umod, cleanup: kobject_del(&mod->mkobj.kobj); kobject_put(&mod->mkobj.kobj); + ftrace_release(mod->module_core, mod->core_size); free_unload: module_unload_free(mod); module_free(mod, mod->module_init); diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 8affb6d00ec..eadd0eaea9b 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -294,13 +294,37 @@ static inline void ftrace_del_hash(struct dyn_ftrace *node) static void ftrace_free_rec(struct dyn_ftrace *rec) { - /* no locking, only called from kstop_machine */ - rec->ip = (unsigned long)ftrace_free_records; ftrace_free_records = rec; rec->flags |= FTRACE_FL_FREE; } +void ftrace_release(void *start, unsigned long size) +{ + struct dyn_ftrace *rec; + struct ftrace_page *pg; + unsigned long s = (unsigned long)start; + unsigned long e = s + size; + int i; + + if (!start) + return; + + /* No interrupt should call this */ + spin_lock(&ftrace_lock); + + for (pg = ftrace_pages_start; pg; pg = pg->next) { + for (i = 0; i < pg->index; i++) { + rec = &pg->records[i]; + + if ((rec->ip >= s) && (rec->ip < e)) + ftrace_free_rec(rec); + } + } + spin_unlock(&ftrace_lock); + +} + static struct dyn_ftrace *ftrace_alloc_dyn_node(unsigned long ip) { struct dyn_ftrace *rec; @@ -1527,7 +1551,9 @@ static int ftrace_convert_nops(unsigned long *start, p = start; while (p < end) { addr = ftrace_call_adjust(*p++); + spin_lock(&ftrace_lock); ftrace_record_ip(addr); + spin_unlock(&ftrace_lock); ftrace_shutdown_replenish(); } @@ -1541,6 +1567,8 @@ static int ftrace_convert_nops(unsigned long *start, void ftrace_init_module(unsigned long *start, unsigned long *end) { + if (start == end) + return; ftrace_convert_nops(start, end); } -- cgit v1.2.3-70-g09d2