On Fri, Jan 13, 2023 at 6:43 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>
> 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@xxxxxxxx>
> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Acked-by: Song Liu <song@xxxxxxxxxx>
> ---
> include/linux/module.h | 6 ++++--
> kernel/livepatch/core.c | 10 +---------
> kernel/module/kallsyms.c | 13 ++++++++++++-
> kernel/trace/bpf_trace.c | 2 +-
> kernel/trace/ftrace.c | 2 +-
> 5 files changed, 19 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 8c5909c0076c..514bc81568c5 100644
> --- 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 201f0c0482fb..c973ed9e42f8 100644
> --- 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 4523f99b0358..ab2376a1be88 100644
> --- 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 23ce498bca97..095f7f8d34a1 100644
> --- 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 442438b93fe9..d249a55d9005 100644
> --- 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;
> }
>
> --
> 2.39.0
>
