On Fri, Nov 06, 2015 at 06:55:18PM -0800, Jeremiah Mahler wrote:
> Jarkko,
>
> On Fri, Oct 16, 2015 at 09:40:22PM +0300, Jarkko Sakkinen wrote:
> > Added a new function __compat_only_sysfs_link_group_to_kobj() that adds
> > a symlink from attribute or group to a kobject. This needed for
> > maintaining backwards compatibility with PPI attributes in the TPM
> > driver.
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
> > ---
> > fs/sysfs/group.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> > include/linux/sysfs.h | 11 +++++++++++
> > 2 files changed, 55 insertions(+)
> >
> > diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
> > index 39a0199..e123659 100644
> > --- a/fs/sysfs/group.c
> > +++ b/fs/sysfs/group.c
> > @@ -352,3 +352,47 @@ void sysfs_remove_link_from_group(struct kobject
> > *kobj, const char *group_name,
> > }
> > }
> > EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
> > +
> > +/**
> > + * __compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject
> > pointing
> > + * to a group or an attribute
> > + * @kobj: The kobject containing the group.
> > + * @target_kobj: The target kobject.
> > + * @target_name: The name of the target group or attribute.
> > + */
> > +int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
> > + struct kobject *target_kobj,
> > + const char *target_name)
> > +{
> > + struct kernfs_node *target;
> > + struct kernfs_node *entry;
> > + struct kernfs_node *link;
> > +
> > + /*
> > + * We don't own @target_kobj and it may be removed at any time.
> > + * Synchronize using sysfs_symlink_target_lock. See sysfs_remove_dir()
> > + * for details.
> > + */
> > + spin_lock(&sysfs_symlink_target_lock);
> > + target = target_kobj->sd;
> > + if (target)
> > + kernfs_get(target);
> > + spin_unlock(&sysfs_symlink_target_lock);
> > + if (!target)
> > + return -ENOENT;
> > +
> > + entry = kernfs_find_and_get(target_kobj->sd, target_name);
> > + if (!entry) {
> > + kernfs_put(target);
> > + return -ENOENT;
> > + }
> > +
>
> On an Acer C720 this call to kernfs_find_and_get fails resulting in
> a failed resume after suspend.
>
> Apparently it can't find an object for the name "ppi".
>
> This bug does not appear until the next patch is applied which
> calls __compat_only_sysfs_link_entry_to_kobj.
I think I might have found something thanks to your help
First I found this old bug:
https://bugzilla.redhat.com/show_bug.cgi?id=1096511
What is happening is that DSM is not found and therefore tpm_add_ppi()
does not add ppi to sysfs groups array.
__compat_only_sysfs_link_entry_to_kobj() is called after tpm_add_ppi
unconditionally for TPM1.
I'll implement a fix for this ASAP.
Thank you for great effort on finding tis!
> --
> - Jeremiah Mahler
/Jarkko
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