On Tue, Jul 07, 2015 at 03:22:50AM +0200, Oleg Nesterov wrote:
> No functional changes, preparation.
>
> Add the new helper, find_next_ret_chain(), which finds the first !chained
> entry and returns its ->next. Yes, it is suboptimal. We probably want to
> turn ->chained into ->start_of_this_chain pointer and avoid another loop.
> But this needs the boring changes in dup_utask(), so lets do this later.
>
> Change the main loop in handle_trampoline() to unwind the stack until ri
> is equal to the pointer returned by this new helper.
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
> Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
Acked-by: Anton Arapov <ara...@gmail.com>
> ---
> kernel/events/uprobes.c | 27 ++++++++++++++++-----------
> 1 files changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 4c941fe..98e4d97 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1766,11 +1766,22 @@ handle_uretprobe_chain(struct return_instance *ri,
> struct pt_regs *regs)
> up_read(&uprobe->register_rwsem);
> }
>
> +static struct return_instance *find_next_ret_chain(struct return_instance
> *ri)
> +{
> + bool chained;
> +
> + do {
> + chained = ri->chained;
> + ri = ri->next; /* can't be NULL if chained */
> + } while (chained);
> +
> + return ri;
> +}
> +
> static void handle_trampoline(struct pt_regs *regs)
> {
> struct uprobe_task *utask;
> - struct return_instance *ri;
> - bool chained;
> + struct return_instance *ri, *next;
>
> utask = current->utask;
> if (!utask)
> @@ -1780,24 +1791,18 @@ static void handle_trampoline(struct pt_regs *regs)
> if (!ri)
> goto sigill;
>
> + next = find_next_ret_chain(ri);
> /*
> * TODO: we should throw out return_instance's invalidated by
> * longjmp(), currently we assume that the probed function always
> * returns.
> */
> instruction_pointer_set(regs, ri->orig_ret_vaddr);
> -
> - for (;;) {
> + do {
> handle_uretprobe_chain(ri, regs);
> -
> - chained = ri->chained;
> ri = free_ret_instance(ri);
> utask->depth--;
> -
> - if (!chained)
> - break;
> - BUG_ON(!ri);
> - }
> + } while (ri != next);
>
> utask->return_instances = ri;
> return;
> --
> 1.5.5.1
>
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