From: Zhiqiang Liu <[email protected]>
Problem: 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.
Here, we will add usage link of a to b's holder_dir.
Fixes: 9bea7f239 ("module: fix bne2 "gave up waiting for init of module libcrc32c")
Signed-off-by: Zhiqiang Liu <[email protected]>
---
kernel/module.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..11c6aff37b1f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -871,6 +871,11 @@ int ref_module(struct module *a, struct module *b)
module_put(b);
return err;
}
+
+ err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
+ if (err)
+ return err;
+
return 0;
}
EXPORT_SYMBOL_GPL(ref_module);
--
2.19.1
+++ Zhiqiang Liu [28/06/19 20:32 +0800]:
>From: Zhiqiang Liu <[email protected]>
>
>Problem: 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.
>
>Here, we will add usage link of a to b's holder_dir.
>
>Fixes: 9bea7f239 ("module: fix bne2 "gave up waiting for init of module libcrc32c")
I think we can drop this tag; it doesn't fix a bug specifically
introduced by that particular commit.
>Signed-off-by: Zhiqiang Liu <[email protected]>
>---
> kernel/module.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 80c7c09584cf..11c6aff37b1f 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -871,6 +871,11 @@ int ref_module(struct module *a, struct module *b)
> module_put(b);
> return err;
> }
>+
>+ err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
>+ if (err)
>+ return err;
We need to fix the error handling here - the module_use struct
allocated in the call to add_module_usage() needs to be freed (you
could just modify add_module_usage() to return the use pointer so that
it's easier to free from within ref_module()), module_put() needs to
be called, and the use struct should be removed from its respective
lists (see module_unload_free()).
Thanks,
Jessica
On 2019/7/1 21:55, Jessica Yu wrote:
> +++ Zhiqiang Liu [28/06/19 20:32 +0800]:
>> From: Zhiqiang Liu <[email protected]>
>>
>> Problem: 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'.
>>
>> Here, we will add usage link of a to b's holder_dir.
>>
>> Fixes: 9bea7f239 ("module: fix bne2 "gave up waiting for init of module libcrc32c")
>
> I think we can drop this tag; it doesn't fix a bug specifically
> introduced by that particular commit.
>
Thanks for your reply.
I will remove the Fixes tag in v2 patch.
>> Signed-off-by: Zhiqiang Liu <[email protected]>
>> ---
>> kernel/module.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 80c7c09584cf..11c6aff37b1f 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -871,6 +871,11 @@ int ref_module(struct module *a, struct module *b)
>> ?0?2?0?2?0?2?0?2?0?2?0?2?0?2 module_put(b);
>> ?0?2?0?2?0?2?0?2?0?2?0?2?0?2 return err;
>> ?0?2?0?2?0?2?0?2}
>> +
>> +?0?2?0?2?0?2 err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
>> +?0?2?0?2?0?2 if (err)
>> +?0?2?0?2?0?2?0?2?0?2?0?2?0?2 return err;
>
> We need to fix the error handling here - the module_use struct
> allocated in the call to add_module_usage() needs to be freed (you
> could just modify add_module_usage() to return the use pointer so that
> it's easier to free from within ref_module()), module_put() needs to
> be called, and the use struct should be removed from its respective
> lists (see module_unload_free()).
>
Thanks again for your advice.
We will modify add_module_usage func to return the use pointer as your suggestion.
In the error handling, We will call module_put() and call list_del() to remove the use.
> Thanks,
>
> Jessica
>
>
> .
>