On 01/09, Anton Arapov wrote:
>
> The first time a uprobe with return consumer is hit for a process, a
> trampoline slot is obtained in the xol_area and initialized with a
> breakpoint instruction. This slot is subsequently used by all
> uretprobes.
See my reply to 0/4, I think we do not really need this.
> todo:
> unify with xol_take_insn_slot()
>
> Signed-off-by: Anton Arapov <an...@redhat.com>
> ---
> include/linux/uprobes.h | 1 +
> kernel/events/uprobes.c | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 95d0002..bddfad6 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -91,6 +91,7 @@ struct xol_area {
> * the vma go away, and we must handle that reasonably gracefully.
> */
> unsigned long vaddr; /* Page(s) of instruction slots
> */
> + unsigned long rp_trampoline_vaddr; /* address of trampolines
> */
> };
>
> struct uprobes_state {
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 473db3f..0ad2ac3 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1208,6 +1208,39 @@ static unsigned long xol_get_insn_slot(struct uprobe
> *uprobe)
> return xol_vaddr;
> }
>
> +/*
> + * xol_get_trampoline_slot - A trampoline slot is obtained the first
> + * time a uprobe with return consumer is hit for a process. Use one
> + * trampoline slot for all probes pertaining to a process, i.e.
> + * one per xol_area.
> + */
> +static unsigned long xol_get_trampoline_slot(void)
> +{
> + struct xol_area *area;
> + unsigned long offset;
> + uprobe_opcode_t bp_insn = UPROBE_SWBP_INSN;
> + void *vaddr;
> +
> + area = get_xol_area();
> + if (!area)
> + return 0;
> +
> + if (!area->rp_trampoline_vaddr)
> + area->rp_trampoline_vaddr = xol_take_insn_slot(area);
> +
> + if (unlikely(!area->rp_trampoline_vaddr))
> + return 0;
> +
> + offset = area->rp_trampoline_vaddr & ~PAGE_MASK;
> + vaddr = kmap_atomic(area->page);
> + memcpy(vaddr + offset, &bp_insn, UPROBE_SWBP_INSN_SIZE);
> + kunmap_atomic(vaddr);
> +
> + flush_dcache_page(area->page);
> +
> + return area->rp_trampoline_vaddr;
> +}
> +
> /*
> * xol_free_insn_slot - If slot was earlier allocated by
> * @xol_get_insn_slot(), make the slot available for
> --
> 1.8.0.2
>
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