* Anton Arapov <an...@redhat.com> [2013-04-03 18:00:36]:
> Uretprobe handlers are invoked when the trampoline is hit, on completion the
> trampoline is replaced with the saved return address and the uretprobe
> instance
> deleted.
>
> v1 changes:
> * pass bp_vaddr to ret_handler()
> * simplify handle_uretprobe()
>
> RFCv6 changes:
> * rework handle_uretprobe()
>
> RFCv5 changes:
> * switch to simply linked list ->return_uprobes
> * rework handle_uretprobe()
>
> RFCv4 changes:
> * check, whether utask is not NULL in handle_uretprobe()
> * get rid of area->rp_trampoline_vaddr
> * minor handle_uretprobe() fixups
>
> RFCv3 changes:
> * protected uprobe with refcounter. See put_uprobe() in handle_uretprobe()
> that reflects increment in prepare_uretprobe()
>
> RFCv2 changes:
> * get rid of ->return_consumers member from struct uprobe, introduce
> ret_handler() in consumer instead
>
> Signed-off-by: Anton Arapov <an...@redhat.com>
> ---
> kernel/events/uprobes.c | 60
> ++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 08ecfff..d129c1d 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1609,6 +1609,57 @@ static void handler_chain(struct uprobe *uprobe,
> struct pt_regs *regs)
> up_read(&uprobe->register_rwsem);
> }
>
> +static void
> +handler_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs)
> +{
> + struct uprobe *uprobe = ri->uprobe;
> + struct uprobe_consumer *uc;
> +
> + down_read(&uprobe->register_rwsem);
> + for (uc = uprobe->consumers; uc; uc = uc->next) {
> + if (uc->ret_handler)
> + uc->ret_handler(uc, ri->func, regs);
> + }
> + up_read(&uprobe->register_rwsem);
> +}
> +
> +static bool handler_uretprobe(struct pt_regs *regs)
Nit: can this be renamed to handle_trampoline
> +{
> + struct uprobe_task *utask;
> + struct return_instance *ri, *tmp;
> + bool chained;
> +
> + utask = current->utask;
> + if (!utask)
> + return false;
> +
> + ri = utask->return_instances;
> + if (!ri)
> + return false;
> +
> + instruction_pointer_set(regs, ri->orig_ret_vaddr);
Should we a check here before using top most ri.
What if the application had done a longjmp and the trampoline he hit
corresponds to something thats below in the stack?
Not sure if this what you meant by leaking return instances in your next
patch.
> +
> + for (;;) {
> + handler_uretprobe_chain(ri, regs);
> +
> + chained = ri->chained;
> + put_uprobe(ri->uprobe);
> +
> + tmp = ri;
> + ri = ri->next;
> + kfree(tmp);
> +
> + if (!chained)
> + break;
> +
> + BUG_ON(!ri);
> + }
> +
> + utask->return_instances = ri;
> +
> + return true;
> +}
> +
> /*
> * Run handler and ask thread to singlestep.
> * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
> @@ -1620,8 +1671,15 @@ static void handle_swbp(struct pt_regs *regs)
> int uninitialized_var(is_swbp);
>
> bp_vaddr = uprobe_get_swbp_addr(regs);
> - uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
> + if (bp_vaddr == get_trampoline_vaddr()) {
> + if (handler_uretprobe(regs))
> + return;
>
> + pr_warn("uprobe: unable to handle uretprobe pid/tgid=%d/%d\n",
> + current->pid, current->tgid);
> + }
> +
> + uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
> if (!uprobe) {
> if (is_swbp > 0) {
> /* No matching uprobe; signal SIGTRAP. */
> --
> 1.8.1.4
>
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