Messages in this thread Patch in this message | | | Date | Wed, 11 Sep 2019 22:03:29 +0200 | From | Jessica Yu <> | Subject | Re: [PATCH v3] module: add link_flag pram in ref_module func to decide whether add usage link |
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+++ Zhiqiang Liu [20/07/19 22:40 +0800]: >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 <liuzhiqiang26@huawei.com> >Suggested-by: Jessica Yu <jeyu@kernel.org> >Reviewed-by: Kang Zhou <zhoukang7@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);
Thanks a lot for pinging me. If I'm remembering correctly, we had to do this because sysfs intialization is being done too late in load_module(). The last time I was tinkering with a solution, I think I was able to avoid needing this extra link_flag param by moving the mod_sysfs_setup() call earlier in load_module(). It just looks a lot cleaner that way, without that extra param. Have you looked into trying that? I would prefer that solution rather than adding another argument to ref_module().
Thanks,
Jessica
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