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McKenney" , Peter Zijlstra , Petr Pavlu , Sami Tolvanen , Thomas Gleixner , Sebastian Andrzej Siewior , Jiri Kosina , Joe Lawrence , Josh Poimboeuf , Masami Hiramatsu , Mathieu Desnoyers , Miroslav Benes , Petr Mladek , Steven Rostedt , linux-trace-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: [PATCH v2 06/28] module: Use RCU in find_module_all(). Date: Fri, 20 Dec 2024 18:41:20 +0100 Message-ID: <20241220174731.514432-7-bigeasy@linutronix.de> In-Reply-To: <20241220174731.514432-1-bigeasy@linutronix.de> References: <20241220174731.514432-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 The modules list and module::kallsyms can be accessed under RCU assumption. Remove module_assert_mutex_or_preempt() from find_module_all() so it can be used under RCU protection without warnings. Update its callers to use RCU protection instead of preempt_disable(). Cc: Jiri Kosina Cc: Joe Lawrence Cc: Josh Poimboeuf Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Miroslav Benes Cc: Petr Mladek Cc: Steven Rostedt Cc: linux-trace-kernel@vger.kernel.org Cc: live-patching@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior --- include/linux/module.h | 2 +- kernel/livepatch/core.c | 4 +--- kernel/module/kallsyms.c | 1 + kernel/module/main.c | 6 ++---- kernel/trace/trace_kprobe.c | 9 +++------ 5 files changed, 8 insertions(+), 14 deletions(-) diff --git a/include/linux/module.h b/include/linux/module.h index 94acbacdcdf18..5c1f7ea76c8cb 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -663,7 +663,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod) return within_module_init(addr, mod) || within_module_core(addr, mod); } -/* Search for module by name: must be in a RCU-sched critical section. */ +/* Search for module by name: must be in a RCU critical section. */ struct module *find_module(const char *name); extern void __noreturn __module_put_and_kthread_exit(struct module *mod, diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 3c21c31796db0..f8932c63b08e3 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -59,7 +59,7 @@ static void klp_find_object_module(struct klp_object *obj) if (!klp_is_module(obj)) return; - rcu_read_lock_sched(); + guard(rcu)(); /* * We do not want to block removal of patched modules and therefore * we do not take a reference here. The patches are removed by @@ -75,8 +75,6 @@ static void klp_find_object_module(struct klp_object *obj) */ if (mod && mod->klp_alive) obj->mod = mod; - - rcu_read_unlock_sched(); } static bool klp_initialized(void) diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c index 4eef518204eb5..3cba9f933b24f 100644 --- a/kernel/module/kallsyms.c +++ b/kernel/module/kallsyms.c @@ -450,6 +450,7 @@ unsigned long module_kallsyms_lookup_name(const char *name) unsigned long ret; /* Don't lock: we're in enough trouble already. */ + guard(rcu)(); preempt_disable(); ret = __module_kallsyms_lookup_name(name); preempt_enable(); diff --git a/kernel/module/main.c b/kernel/module/main.c index 5cce4a92d7ba3..5aa56ec8e203e 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -374,16 +374,14 @@ bool find_symbol(struct find_symbol_arg *fsa) } /* - * Search for module by name: must hold module_mutex (or preempt disabled - * for read-only access). + * Search for module by name: must hold module_mutex (or RCU for read-only + * access). */ struct module *find_module_all(const char *name, size_t len, bool even_unformed) { struct module *mod; - module_assert_mutex_or_preempt(); - list_for_each_entry_rcu(mod, &modules, list, lockdep_is_held(&module_mutex)) { if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 263fac44d3ca3..c7db326f4e88e 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -123,9 +123,8 @@ static nokprobe_inline bool trace_kprobe_module_exist(struct trace_kprobe *tk) if (!p) return true; *p = '\0'; - rcu_read_lock_sched(); - ret = !!find_module(tk->symbol); - rcu_read_unlock_sched(); + scoped_guard(rcu) + ret = !!find_module(tk->symbol); *p = ':'; return ret; @@ -800,12 +799,10 @@ static struct module *try_module_get_by_name(const char *name) { struct module *mod; - rcu_read_lock_sched(); + guard(rcu)(); mod = find_module(name); if (mod && !try_module_get(mod)) mod = NULL; - rcu_read_unlock_sched(); - return mod; } #else