From: Zhiqiang Liu <[email protected]>
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.
V1->V2:
- remove incorrect Fixes tag
- fix error handling of sysfs_create_link as suggested by Jessica Yu
Signed-off-by: Zhiqiang Liu <[email protected]>
Suggested-by: Jessica Yu <[email protected]>
Reviewed-by: Kang Zhou <[email protected]>
---
kernel/module.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c
index 80c7c09584cf..672abce2222c 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)
{
+ struct module_use *use;
int err;
if (b == NULL || already_uses(a, b))
@@ -866,9 +867,18 @@ 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;
+ }
+
+ 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;
--
2.19.1
Friendly ping ...
On 2019/7/3 10:09, Zhiqiang Liu wrote:
> From: Zhiqiang Liu <[email protected]>
>
> 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.
>
> V1->V2:
> - remove incorrect Fixes tag
> - fix error handling of sysfs_create_link as suggested by Jessica Yu
>
> Signed-off-by: Zhiqiang Liu <[email protected]>
> Suggested-by: Jessica Yu <[email protected]>
> Reviewed-by: Kang Zhou <[email protected]>
> ---
> kernel/module.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 80c7c09584cf..672abce2222c 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)
> {
> + struct module_use *use;
> int err;
>
> if (b == NULL || already_uses(a, b))
> @@ -866,9 +867,18 @@ 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;
> + }
> +
> + 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;
>
+++ Zhiqiang Liu [03/07/19 10:09 +0800]:
>From: Zhiqiang Liu <[email protected]>
>
>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.
>
>V1->V2:
>- remove incorrect Fixes tag
>- fix error handling of sysfs_create_link as suggested by Jessica Yu
>
>Signed-off-by: Zhiqiang Liu <[email protected]>
>Suggested-by: Jessica Yu <[email protected]>
>Reviewed-by: Kang Zhou <[email protected]>
>---
> kernel/module.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 80c7c09584cf..672abce2222c 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)
> {
>+ struct module_use *use;
> int err;
>
> if (b == NULL || already_uses(a, b))
>@@ -866,9 +867,18 @@ 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;
>+ }
>+
>+ err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
Sigh. This ultimately doesn't work because in load_module(), we use
ref_module() in resolve_symbol(), and mod->mkobj.kobj doesn't get
initialized until mod_sysfs_init(), which happens much later in
load_module(). So what happens is that the ref_module(mod, owner) call
in resolve_symbol() returns an error because sysfs_create_link() fails here.
We could *maybe* move sysfs initialization earlier in load_module()
but that is an entirely untested idea and I would need to think about
that more.
> if (err) {
> module_put(b);
>+ list_del(&use->source_list);
>+ list_del(&use->target_list);
>+ kfree(use);
> return err;
> }
> return 0;
>--
>2.19.1
>
On 2019/7/10 0:10, Jessica Yu wrote:
> +++ Zhiqiang Liu [03/07/19 10:09 +0800]:
>> From: Zhiqiang Liu <[email protected]
>>
>> V1->V2:
>> - remove incorrect Fixes tag
>> - fix error handling of sysfs_create_link as suggested by Jessica Yu
>>
>> Signed-off-by: Zhiqiang Liu <[email protected]>
>> Suggested-by: Jessica Yu <[email protected]>
>> Reviewed-by: Kang Zhou <[email protected]>
>> ---
>> kernel/module.c | 18 ++++++++++++++----
>> 1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 80c7c09584cf..672abce2222c 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -837,25 +837,26 @@ static int already_uses(struct module *a, struct module *b)
>> ?0?2*?0?2?0?2?0?2 'b' can walk the list to see who sourced them), and of 'a'
>> ?0?2*?0?2?0?2?0?2 targets (so 'a' can see what modules it targets).
>> ?0?2*/
>> /* Module a uses b: caller needs module_mutex() */
>> int ref_module(struct module *a, struct module *b)
>> {
>> +?0?2?0?2?0?2 struct module_use *use;
>> ?0?2?0?2?0?2?0?2int err;
>>
>> ?0?2?0?2?0?2?0?2if (b == NULL || already_uses(a, b))
>> @@ -866,9 +867,18 @@ int ref_module(struct module *a, struct module *b)
>> ?0?2?0?2?0?2?0?2if (err)
>> ?0?2?0?2?0?2?0?2?0?2?0?2?0?2 return err;
>>
>> -?0?2?0?2?0?2 err = add_module_usage(a, b);
>> +?0?2?0?2?0?2 use = add_module_usage(a, b);
>> +?0?2?0?2?0?2 if (!use) {
>> +?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 -ENOMEM;
>> +?0?2?0?2?0?2 }
>> +
>> +?0?2?0?2?0?2 err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
>
> Sigh. This ultimately doesn't work because in load_module(), we use
> ref_module() in resolve_symbol(), and mod->mkobj.kobj doesn't get
> initialized until mod_sysfs_init(), which happens much later in
> load_module(). So what happens is that the ref_module(mod, owner) call
> in resolve_symbol() returns an error because sysfs_create_link() fails here.
> We could *maybe* move sysfs initialization earlier in load_module()
> but that is an entirely untested idea and I would need to think about
> that more.
Thank you for the reply.
I have tested the patch through livepatch. Maybe I miss somethings.
I will rewrite the patch and test it entirely before sending the v3 patch.
Thanks again.
+++ Zhiqiang Liu [11/07/19 14:03 +0800]:
>
>
>On 2019/7/10 0:10, Jessica Yu wrote:
>> +++ Zhiqiang Liu [03/07/19 10:09 +0800]:
>>> From: Zhiqiang Liu <[email protected]
>>>
>>> V1->V2:
>>> - remove incorrect Fixes tag
>>> - fix error handling of sysfs_create_link as suggested by Jessica Yu
>>>
>>> Signed-off-by: Zhiqiang Liu <[email protected]>
>>> Suggested-by: Jessica Yu <[email protected]>
>>> Reviewed-by: Kang Zhou <[email protected]>
>>> ---
>>> kernel/module.c | 18 ++++++++++++++----
>>> 1 file changed, 14 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/kernel/module.c b/kernel/module.c
>>> index 80c7c09584cf..672abce2222c 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).
>>> ?*/
>>> /* Module a uses b: caller needs module_mutex() */
>>> int ref_module(struct module *a, struct module *b)
>>> {
>>> +??? struct module_use *use;
>>> ????int err;
>>>
>>> ????if (b == NULL || already_uses(a, b))
>>> @@ -866,9 +867,18 @@ 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;
>>> +??? }
>>> +
>>> +??? err = sysfs_create_link(b->holders_dir, &a->mkobj.kobj, a->name);
>>
>> Sigh. This ultimately doesn't work because in load_module(), we use
>> ref_module() in resolve_symbol(), and mod->mkobj.kobj doesn't get
>> initialized until mod_sysfs_init(), which happens much later in
>> load_module(). So what happens is that the ref_module(mod, owner) call
>> in resolve_symbol() returns an error because sysfs_create_link() fails here.
>> We could *maybe* move sysfs initialization earlier in load_module()
>> but that is an entirely untested idea and I would need to think about
>> that more.
>
>Thank you for the reply.
>I have tested the patch through livepatch. Maybe I miss somethings.
>I will rewrite the patch and test it entirely before sending the v3 patch.
Thanks Zhiqiang. A boot test and testing loading modules with
dependencies would be really appreciated.
Thanks!
Jessica