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authorSteven Rostedt <rostedt@goodmis.org>2008-08-15 02:47:19 (GMT)
committerIngo Molnar <mingo@elte.hu>2008-10-14 08:35:12 (GMT)
commitfed1939c64d2288938fdc1c367d49082da65e195 (patch)
treea4592352d28efcfe82379c71d061b9127e49a115 /kernel/module.c
parent28614889bcb2558a47d02d52394b7fd9795a9547 (diff)
downloadlinux-fed1939c64d2288938fdc1c367d49082da65e195.tar.xz
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 <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/module.c')
-rw-r--r--kernel/module.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/module.c b/kernel/module.c
index d753fd9..7576c2d 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);