Sometimes, device drivers are bound into each other via try_module_get(), making such references invisible when looking at /proc/modules or lsmod.
Add a function to allow setting up module references for such cases, and call it when try_module_get() is used. Reviewed-by: Dan Williams <dan.j.willi...@intel.com> Reviewed-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> Signed-off-by: Mauro Carvalho Chehab <mche...@kernel.org> --- See [PATCH v6 0/4] at: https://lore.kernel.org/all/cover.1652113087.git.mche...@kernel.org/ include/linux/module.h | 8 +++-- kernel/module/main.c | 73 ++++++++++++++++++++++++++++++++++-------- 2 files changed, 64 insertions(+), 17 deletions(-) diff --git a/include/linux/module.h b/include/linux/module.h index 77961f5773b6..a66b9be92ef5 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -618,12 +618,12 @@ extern void __module_get(struct module *module); /* This is the Right Way to get a module: if it fails, it's being removed, * so pretend it's not there. */ -extern bool try_module_get(struct module *module); +extern bool try_module_get_owner(struct module *module, struct module *this); extern void module_put(struct module *module); #else /*!CONFIG_MODULE_UNLOAD*/ -static inline bool try_module_get(struct module *module) +static inline bool try_module_get_owner(struct module *module, struct module *this) { return !module || module_is_live(module); } @@ -752,7 +752,7 @@ static inline void __module_get(struct module *module) { } -static inline bool try_module_get(struct module *module) +static inline bool try_module_get_owner(struct module *module, struct module *this) { return true; } @@ -893,6 +893,8 @@ static inline bool module_sig_ok(struct module *module) } #endif /* CONFIG_MODULE_SIG */ +#define try_module_get(mod) try_module_get_owner(mod, THIS_MODULE) + int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, unsigned long), void *data); diff --git a/kernel/module/main.c b/kernel/module/main.c index fe44d46c378b..6044aeba0f18 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -139,6 +139,24 @@ int unregister_module_notifier(struct notifier_block *nb) } EXPORT_SYMBOL(unregister_module_notifier); +static bool __try_module_get(struct module *module) +{ + bool ret = true; + + if (module) { + preempt_disable(); + /* Note: here, we can fail to get a reference */ + if (likely(module_is_live(module) && + atomic_inc_not_zero(&module->refcnt) != 0)) + trace_module_get(module, _RET_IP_); + else + ret = false; + + preempt_enable(); + } + return ret; +} + /* * We require a truly strong try_module_get(): 0 means success. * Otherwise an error is returned due to ongoing or failed @@ -149,7 +167,7 @@ static inline int strong_try_module_get(struct module *mod) BUG_ON(mod && mod->state == MODULE_STATE_UNFORMED); if (mod && mod->state == MODULE_STATE_COMING) return -EBUSY; - if (try_module_get(mod)) + if (__try_module_get(mod)) return 0; else return -ENOENT; @@ -620,6 +638,41 @@ static int ref_module(struct module *a, struct module *b) return 0; } +static int ref_module_dependency(struct module *mod, struct module *this) +{ + int ret = 0; + + if (!this || !mod || !this->name || !mod->holders_dir) + return -EINVAL; + + if (mod == this) + return 0; + + mutex_lock(&module_mutex); + + if (already_uses(this, mod)) + goto ret; + + ret = strong_try_module_get(mod); + if (ret) + goto ret; + + ret = add_module_usage(this, mod); + if (ret) { + module_put(mod); + goto ret; + } + +#ifdef CONFIG_MODULE_UNLOAD + ret = sysfs_create_link(mod->holders_dir, + &this->mkobj.kobj, this->name); +#endif + +ret: + mutex_unlock(&module_mutex); + return ret; +} + /* Clear the unload stuff of the module. */ static void module_unload_free(struct module *mod) { @@ -830,24 +883,16 @@ void __module_get(struct module *module) } EXPORT_SYMBOL(__module_get); -bool try_module_get(struct module *module) +bool try_module_get_owner(struct module *module, struct module *this) { - bool ret = true; + int ret = __try_module_get(module); - if (module) { - preempt_disable(); - /* Note: here, we can fail to get a reference */ - if (likely(module_is_live(module) && - atomic_inc_not_zero(&module->refcnt) != 0)) - trace_module_get(module, _RET_IP_); - else - ret = false; + if (ret) + ref_module_dependency(module, this); - preempt_enable(); - } return ret; } -EXPORT_SYMBOL(try_module_get); +EXPORT_SYMBOL(try_module_get_owner); void module_put(struct module *module) { -- 2.35.3
