lkml.org 
[lkml]   [2019]   [Sep]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH v3] module: add link_flag pram in ref_module func to decide whether add usage link
+++ 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

\
 
 \ /
  Last update: 2019-09-11 22:04    [W:0.044 / U:5.140 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site