[PATCH v2 04/28] module: Use RCU in find_kallsyms_symbol().

[Sebastian Andrzej Siewior]

The modules list and module::kallsyms can be accessed under RCU
assumption.

Use rcu_dereference() to reference the kallsyms pointer in
find_kallsyms_symbol().  Use a RCU section instead of preempt_disable in
callers of find_kallsyms_symbol(). Keep the preempt-disable in
module_address_lookup() due to __module_address().

Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
 kernel/module/kallsyms.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 45846ae4042d1..3f59d04795572 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -257,7 +257,7 @@ static const char *find_kallsyms_symbol(struct module *mod,
 {
        unsigned int i, best = 0;
        unsigned long nextval, bestval;
-       struct mod_kallsyms *kallsyms = rcu_dereference_sched(mod->kallsyms);
+       struct mod_kallsyms *kallsyms = rcu_dereference(mod->kallsyms);
        struct module_memory *mod_mem;
 
        /* At worse, next value is at end of module */
@@ -329,6 +329,7 @@ int module_address_lookup(unsigned long addr,
        int ret = 0;
        struct module *mod;
 
+       guard(rcu)();
        preempt_disable();
        mod = __module_address(addr);
        if (mod) {
@@ -356,7 +357,7 @@ int lookup_module_symbol_name(unsigned long addr, char 
*symname)
 {
        struct module *mod;
 
-       preempt_disable();
+       guard(rcu)();
        list_for_each_entry_rcu(mod, &modules, list) {
                if (mod->state == MODULE_STATE_UNFORMED)
                        continue;
@@ -368,12 +369,10 @@ int lookup_module_symbol_name(unsigned long addr, char 
*symname)
                                goto out;
 
                        strscpy(symname, sym, KSYM_NAME_LEN);
-                       preempt_enable();
                        return 0;
                }
        }
 out:
-       preempt_enable();
        return -ERANGE;
 }
 
-- 
2.45.2