module: add within_module_core() and within_module_init()

This series of patches allows kprobes to probe module's __init and __exit
functions.  This means, you can probe driver initialization and
terminating.

Currently, kprobes can't probe __init function because these functions are
freed after module initialization.  And it also can't probe module __exit
functions because kprobe increments reference count of target module and
user can't unload it.  this means __exit functions never be called unless
removing probes from the module.

To solve both cases, this series of patches introduces GONE flag and sets
it when the target code is freed(for this purpose, kprobes hooks
MODULE_STATE_* events).  This also removes refcount incrementing for
allowing user to unload target module.  Users can check which probes are
GONE by debugfs interface.  For taking timing of freeing module's .init
text, these also include a patch which adds module's notifier of
MODULE_STATE_LIVE event.

This patch:

Add within_module_core() and within_module_init() for checking whether an
address is in the module .init.text section or .text section, and replace
within() local inline functions in kernel/module.c with them.

kprobes uses these functions to check where the kprobe is inserted.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 20 insertions, 8 deletions

diff --git a/include/linux/module.h b/include/linux/module.h
index 03cb93d..4f7ea12 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -365,6 +365,18 @@ struct module *module_text_address(unsigned long addr);
 struct module *__module_text_address(unsigned long addr);
 int is_module_address(unsigned long addr);
 
+static inline int within_module_core(unsigned long addr, struct module *mod)
+{
+	return (unsigned long)mod->module_core <= addr &&
+	       addr < (unsigned long)mod->module_core + mod->core_size;
+}
+
+static inline int within_module_init(unsigned long addr, struct module *mod)
+{
+	return (unsigned long)mod->module_init <= addr &&
+	       addr < (unsigned long)mod->module_init + mod->init_size;
+}
+
 /* Returns 0 and fills in value, defined and namebuf, or -ERANGE if
    symnum out of range. */
 int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
diff --git a/kernel/module.c b/kernel/module.c
index 34b56cf..cc79c94 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2390,7 +2390,7 @@ static const char *get_ksymbol(struct module *mod,
 	unsigned long nextval;
 
 	/* At worse, next value is at end of module */
-	if (within(addr, mod->module_init, mod->init_size))
+	if (within_module_init(addr, mod))
 		nextval = (unsigned long)mod->module_init+mod->init_text_size;
 	else
 		nextval = (unsigned long)mod->module_core+mod->core_text_size;
@@ -2438,8 +2438,8 @@ const char *module_address_lookup(unsigned long addr,
 
 	preempt_disable();
 	list_for_each_entry_rcu(mod, &modules, list) {
-		if (within(addr, mod->module_init, mod->init_size)
-		    || within(addr, mod->module_core, mod->core_size)) {
+		if (within_module_init(addr, mod) ||
+		    within_module_core(addr, mod)) {
 			if (modname)
 				*modname = mod->name;
 			ret = get_ksymbol(mod, addr, size, offset);
@@ -2461,8 +2461,8 @@ int lookup_module_symbol_name(unsigned long addr, char *symname)
 
 	preempt_disable();
 	list_for_each_entry_rcu(mod, &modules, list) {
-		if (within(addr, mod->module_init, mod->init_size) ||
-		    within(addr, mod->module_core, mod->core_size)) {
+		if (within_module_init(addr, mod) ||
+		    within_module_core(addr, mod)) {
 			const char *sym;
 
 			sym = get_ksymbol(mod, addr, NULL, NULL);
@@ -2485,8 +2485,8 @@ int lookup_module_symbol_attrs(unsigned long addr, unsigned long *size,
 
 	preempt_disable();
 	list_for_each_entry_rcu(mod, &modules, list) {
-		if (within(addr, mod->module_init, mod->init_size) ||
-		    within(addr, mod->module_core, mod->core_size)) {
+		if (within_module_init(addr, mod) ||
+		    within_module_core(addr, mod)) {
 			const char *sym;
 
 			sym = get_ksymbol(mod, addr, size, offset);
@@ -2705,7 +2705,7 @@ int is_module_address(unsigned long addr)
 	preempt_disable();
 
 	list_for_each_entry_rcu(mod, &modules, list) {
-		if (within(addr, mod->module_core, mod->core_size)) {
+		if (within_module_core(addr, mod)) {
 			preempt_enable();
 			return 1;
 		}