* [PATCH v2 06/28] module: Use RCU in find_module_all().
[not found] <20241220174731.514432-1-bigeasy@linutronix.de>
@ 2024-12-20 17:41 ` Sebastian Andrzej Siewior
2025-01-02 14:16 ` Petr Mladek
0 siblings, 1 reply; 2+ messages in thread
From: Sebastian Andrzej Siewior @ 2024-12-20 17:41 UTC (permalink / raw)
To: linux-modules, linux-kernel
Cc: Daniel Gomez, Luis Chamberlain, Paul E . 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,
live-patching
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 <jikos@kernel.org>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Miroslav Benes <mbenes@suse.cz>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-trace-kernel@vger.kernel.org
Cc: live-patching@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
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
--
2.45.2
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