On Tue, 2 Sep 2025 16:34:54 +0200 Jiri Olsa <[email protected]> wrote:
> Adding unique flag to uprobe consumer to ensure it's the only consumer > attached on the uprobe. > > This is helpful for use cases when consumer wants to change user space > registers, which might confuse other consumers. With this change we can > ensure there's only one consumer on specific uprobe. nit: Does this mean one callback (consumer) is exclusively attached? If so, "exclusive" will be better wording? The logic looks good to me. Thanks, > > Signed-off-by: Jiri Olsa <[email protected]> > --- > include/linux/uprobes.h | 1 + > kernel/events/uprobes.c | 30 ++++++++++++++++++++++++++++-- > 2 files changed, 29 insertions(+), 2 deletions(-) > > diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h > index 08ef78439d0d..0df849dee720 100644 > --- a/include/linux/uprobes.h > +++ b/include/linux/uprobes.h > @@ -60,6 +60,7 @@ struct uprobe_consumer { > struct list_head cons_node; > > __u64 id; /* set when uprobe_consumer is registered */ > + bool is_unique; /* the only consumer on uprobe */ > }; > > #ifdef CONFIG_UPROBES > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index 996a81080d56..b9b088f7333a 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1024,14 +1024,35 @@ static struct uprobe *alloc_uprobe(struct inode > *inode, loff_t offset, > return uprobe; > } > > -static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) > +static bool consumer_can_add(struct list_head *head, struct uprobe_consumer > *uc) > +{ > + /* Uprobe has no consumer, we can add any. */ > + if (list_empty(head)) > + return true; > + /* Uprobe has consumer/s, we can't add unique one. */ > + if (uc->is_unique) > + return false; > + /* > + * Uprobe has consumer/s, we can add nother consumer only if the > + * current consumer is not unique. > + **/ > + return !list_first_entry(head, struct uprobe_consumer, > cons_node)->is_unique; > +} > + > +static int consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) > { > static atomic64_t id; > + int ret = -EBUSY; > > down_write(&uprobe->consumer_rwsem); > + if (!consumer_can_add(&uprobe->consumers, uc)) > + goto unlock; > list_add_rcu(&uc->cons_node, &uprobe->consumers); > uc->id = (__u64) atomic64_inc_return(&id); > + ret = 0; > +unlock: > up_write(&uprobe->consumer_rwsem); > + return ret; > } > > /* > @@ -1420,7 +1441,12 @@ struct uprobe *uprobe_register(struct inode *inode, > return uprobe; > > down_write(&uprobe->register_rwsem); > - consumer_add(uprobe, uc); > + ret = consumer_add(uprobe, uc); > + if (ret) { > + put_uprobe(uprobe); > + up_write(&uprobe->register_rwsem); > + return ERR_PTR(ret); > + } > ret = register_for_each_vma(uprobe, uc); > up_write(&uprobe->register_rwsem); > > -- > 2.51.0 > -- Masami Hiramatsu (Google) <[email protected]>
