Re: [PATCH v5 06/10] Uprobes: Support SDT markers having reference count (semaphore)
From: Srikar Dronamraju
Date: Mon Jul 02 2018 - 12:02:19 EST
> Implement the reference counter logic in core uprobe. User will be
> able to use it from trace_uprobe as well as from kernel module. New
> trace_uprobe definition with reference counter will now be:
> where ref_ctr_offset is an optional field. For kernel module, new
> variant of uprobe_register() has been introduced:
> uprobe_register_refctr(inode, offset, ref_ctr_offset, consumer)
Sorry for bringing this again, but I would actually think the ref_ctr is
a consumer property. i.e the ref_ctr_offset should be part of
The advantages of doing that would be
1. Dont need to expose uprobe structure and just update our
uprobe_consumer which is already an exported structure.
- Exporting uprobe structure would expose some of our internal
implementation details, basically reduce the freedom of changing stuff
- we came up with uprobe_arch for the parts that we wanted to expose
to archs. exposing uprobe and uprobe_arch looks weird.
2. ref_ctr_offset is necessarily a consumer property, its not a uprobe
property at all.
3. We dont need to change/add new uprobe_register functions.
The way I look at it is.
Based on the ref_ctr_offset field in consumer, we update_ref_ctr()
> +static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm)
> + struct delayed_uprobe *du;
> + if (delayed_uprobe_check(uprobe, mm))
> + return 0;
> + du = kzalloc(sizeof(*du), GFP_KERNEL);
> + if (!du)
> + return -ENOMEM;
> + du->uprobe = uprobe;
> + du->mm = mm;
> + list_add(&du->list, &delayed_uprobe_list);
> + return 0;
If I understood the delayed_uprobe stuff, its when we could insert a
breakpoint but the vma that has the ref_ctr_offset is not loaded. Is