Friendly Ping...
On 2019/7/20 22:40, Zhiqiang Liu wrote:
> Users can call ref_module func in their modules to construct
> relationships with other modules. However, the holders
> '/sys/module/<mod-name>/holders' of the target module donot include
> the users` module. So lsmod command misses detailed info of 'Used by'.
>
> When load module, the process is given as follows,
> load_module()
> -> mod_sysfs_setup()
> -> add_usage_links
> -> do_init_module
> -> mod->init()
>
> add_usage_links func creates holders of target modules linking to
> this module. If ref_module is called in mod->init() func, the usage
> links cannot be added.
>
> Consider that add_module_usage and add usage_link may separate, the
> link_flag pram is added in ref_module func to decide whether add usage
> link after add_module_usage. If link_flag is true, it means usage link
> of a to b's holder_dir should be created immediately after add_module_usage.
>
> V2->V3:
> - add link_flag pram in ref_module func to decide whether add usage link
>
> V1->V2:
> - remove incorrect Fixes tag
> - fix error handling of sysfs_create_link as suggested by Jessica Yu
>
> Signed-off-by: Zhiqiang Liu <liuzhiqian...@huawei.com>
> Suggested-by: Jessica Yu <j...@kernel.org>
> Reviewed-by: Kang Zhou <zhouka...@huawei.com>
> ---
> include/linux/module.h | 2 +-
> kernel/module.c | 27 ++++++++++++++++++++-------
> 2 files changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 188998d3dca9..9ec04b9e93e8 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -632,7 +632,7 @@ static inline void __module_get(struct module *module)
> #define symbol_put_addr(p) do { } while (0)
>
> #endif /* CONFIG_MODULE_UNLOAD */
> -int ref_module(struct module *a, struct module *b);
> +int ref_module(struct module *a, struct module *b, bool link_flag);
>
> /* This is a #define so the string doesn't get put in every .o file */
> #define module_name(mod) \
> diff --git a/kernel/module.c b/kernel/module.c
> index 80c7c09584cf..00e4862a8ef7 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -837,25 +837,26 @@ static int already_uses(struct module *a, struct module
> *b)
> * 'b' can walk the list to see who sourced them), and of 'a'
> * targets (so 'a' can see what modules it targets).
> */
> -static int add_module_usage(struct module *a, struct module *b)
> +static struct module_use *add_module_usage(struct module *a, struct module
> *b)
> {
> struct module_use *use;
>
> pr_debug("Allocating new usage for %s.\n", a->name);
> use = kmalloc(sizeof(*use), GFP_ATOMIC);
> if (!use)
> - return -ENOMEM;
> + return NULL;
>
> use->source = a;
> use->target = b;
> list_add(&use->source_list, &b->source_list);
> list_add(&use->target_list, &a->target_list);
> - return 0;
> + return use;
> }
>
> /* Module a uses b: caller needs module_mutex() */
> -int ref_module(struct module *a, struct module *b)
> +int ref_module(struct module *a, struct module *b, bool link_flag)
> {
> + struct module_use *use;
> int err;
>
> if (b == NULL || already_uses(a, b))
> @@ -866,9 +867,21 @@ int ref_module(struct module *a, struct module *b)
> if (err)
> return err;
>
> - err = add_module_usage(a, b);
> + use = add_module_usage(a, b);
> + if (!use) {
> + module_put(b);
> + return -ENOMEM;
> + }
> +
> + if (!link_flag)
> + return 0;
> +
> + err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
> if (err) {
> module_put(b);
> + list_del(&use->source_list);
> + list_del(&use->target_list);
> + kfree(use);
> return err;
> }
> return 0;
> @@ -1152,7 +1165,7 @@ static inline void module_unload_free(struct module
> *mod)
> {
> }
>
> -int ref_module(struct module *a, struct module *b)
> +int ref_module(struct module *a, struct module *b, bool link_flag)
> {
> return strong_try_module_get(b);
> }
> @@ -1407,7 +1420,7 @@ static const struct kernel_symbol
> *resolve_symbol(struct module *mod,
> goto getname;
> }
>
> - err = ref_module(mod, owner);
> + err = ref_module(mod, owner, false);
> if (err) {
> sym = ERR_PTR(err);
> goto getname;
>
