On 02/28, Anton Arapov wrote:
>
> +static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
> +{
> + struct return_uprobe_i *ri;
> + struct uprobe_task *utask;
> + struct xol_area *area;
> + unsigned long rp_trampoline_vaddr = 0;
> + uprobe_opcode_t insn = UPROBE_SWBP_INSN;
> +
> + area = get_xol_area();
> + if (area)
> + rp_trampoline_vaddr = area->rp_trampoline_vaddr;
> + if (!rp_trampoline_vaddr) {
> + rp_trampoline_vaddr = xol_get_insn_slot(&insn);
> + if (!rp_trampoline_vaddr)
> + return;
> + }
> + area->rp_trampoline_vaddr = rp_trampoline_vaddr;
> +
> + ri = kzalloc(sizeof(struct return_uprobe_i), GFP_KERNEL);
> + if (!ri)
> + return;
> +
> + utask = get_utask();
> + ri->orig_ret_vaddr =
> arch_uretprobe_hijack_return_addr(rp_trampoline_vaddr, regs);
> + if (likely(ri->orig_ret_vaddr)) {
> + /* TODO: uretprobe bypass logic */
> + atomic_inc(&uprobe->ref);
OK, but even this is not enough.
Once we inserted "int3" we must ensure that handle_swbp() will be
called even if this uprobe goes away. We have the reference but it
only protects uprobe itself, it can't protect agains delete_uprobe().
IOW, we must ensure that uprobe_pre_sstep_notifier() can't return 0.
So this patch needs the additional change in find_active_uprobe(),
- if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES,
&mm->flags))
+ if (!uprobe && hlist_empty(->return_uprobes) &&
+ test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
Oleg.
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