livepatch: Improve the search performance of module_kallsyms_on_each_symbol()

Currently we traverse all symbols of all modules to find the specified
function for the specified module. But in reality, we just need to find
the given module and then traverse all the symbols in it.

Let's add a new parameter 'const char *modname' to function
module_kallsyms_on_each_symbol(), then we can compare the module names
directly in this function and call hook 'fn' after matching. If 'modname'
is NULL, the symbols of all modules are still traversed for compatibility
with other usage cases.

Phase1: mod1-->mod2..(subsequent modules do not need to be compared)
                |
Phase2:          -->f1-->f2-->f3

Assuming that there are m modules, each module has n symbols on average,
then the time complexity is reduced from O(m * n) to O(m) + O(n).

Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20230116101009.23694-2-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/module.h b/include/linux/module.h
index 8c5909c0076c6e1e75fde683574769085cef6cc5..514bc81568c52205a3da8047505dd302b0a14e37 100644 (file)
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -879,11 +879,13 @@ static inline bool module_sig_ok(struct module *module)
 #endif /* CONFIG_MODULE_SIG */
 
 #if defined(CONFIG_MODULES) && defined(CONFIG_KALLSYMS)
-int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+int module_kallsyms_on_each_symbol(const char *modname,
+                                  int (*fn)(void *, const char *,
                                             struct module *, unsigned long),
                                   void *data);
 #else
-static inline int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+static inline int module_kallsyms_on_each_symbol(const char *modname,
+                                                int (*fn)(void *, const char *,
                                                 struct module *, unsigned long),
                                                 void *data)
 {

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 201f0c0482fb56dbaccb5c4eeb414c4dd3de9aba..c973ed9e42f8177b116d22549bb348315f1edcd1 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -118,7 +118,6 @@ static struct klp_object *klp_find_object(struct klp_patch *patch,
 }
 
 struct klp_find_arg {
-       const char *objname;
        const char *name;
        unsigned long addr;
        unsigned long count;
@@ -148,15 +147,9 @@ static int klp_find_callback(void *data, const char *name,
 {
        struct klp_find_arg *args = data;
 
-       if ((mod && !args->objname) || (!mod && args->objname))
-               return 0;
-
        if (strcmp(args->name, name))
                return 0;
 
-       if (args->objname && strcmp(args->objname, mod->name))
-               return 0;
-
        return klp_match_callback(data, addr);
 }
 
@@ -164,7 +157,6 @@ static int klp_find_object_symbol(const char *objname, const char *name,
                                  unsigned long sympos, unsigned long *addr)
 {
        struct klp_find_arg args = {
-               .objname = objname,
                .name = name,
                .addr = 0,
                .count = 0,
@@ -172,7 +164,7 @@ static int klp_find_object_symbol(const char *objname, const char *name,
        };
 
        if (objname)
-               module_kallsyms_on_each_symbol(klp_find_callback, &args);
+               module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
        else
                kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
 

diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 4523f99b03589e3cdfe20a80c57cb1fa589ca9de..ab2376a1be88e7e6960d9544e08fdb83a5cba484 100644 (file)
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -494,7 +494,8 @@ unsigned long module_kallsyms_lookup_name(const char *name)
        return ret;
 }
 
-int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
+int module_kallsyms_on_each_symbol(const char *modname,
+                                  int (*fn)(void *, const char *,
                                             struct module *, unsigned long),
                                   void *data)
 {
@@ -509,6 +510,9 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
                if (mod->state == MODULE_STATE_UNFORMED)
                        continue;
 
+               if (modname && strcmp(modname, mod->name))
+                       continue;
+
                /* Use rcu_dereference_sched() to remain compliant with the sparse tool */
                preempt_disable();
                kallsyms = rcu_dereference_sched(mod->kallsyms);
@@ -525,6 +529,13 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *,
                        if (ret != 0)
                                goto out;
                }
+
+               /*
+                * The given module is found, the subsequent modules do not
+                * need to be compared.
+                */
+               if (modname)
+                       break;
        }
 out:
        mutex_unlock(&module_mutex);

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 23ce498bca975bb317c5c0627533f8999575e893..095f7f8d34a1d7fd51fe5646ad954e3b316a9db7 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2735,7 +2735,7 @@ static int get_modules_for_addrs(struct module ***mods, unsigned long *addrs, u3
        int err;
 
        /* We return either err < 0 in case of error, ... */
-       err = module_kallsyms_on_each_symbol(module_callback, &args);
+       err = module_kallsyms_on_each_symbol(NULL, module_callback, &args);
        if (err) {
                kprobe_multi_put_modules(args.mods, args.mods_cnt);
                kfree(args.mods);

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 442438b93fe98040349ec5c33161c1d550212e5c..d249a55d9005765b8042669fd877c8c25dfaa241 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -8324,7 +8324,7 @@ int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *a
        found_all = kallsyms_on_each_symbol(kallsyms_callback, &args);
        if (found_all)
                return 0;
-       found_all = module_kallsyms_on_each_symbol(kallsyms_callback, &args);
+       found_all = module_kallsyms_on_each_symbol(NULL, kallsyms_callback, &args);
        return found_all ? 0 : -ESRCH;
 }