On Tue, Jul 07, 2015 at 03:22:58AM +0200, Oleg Nesterov wrote:
> Add the x86-specific version of arch_uretprobe_is_alive() helper.
> It returns true if the stack frame mangled by prepare_uretprobe()
> is still on stack. So if it returns false, we know that the probed
> function has already returned.
>
> We add the new return_instance->stack member and change the generic
> code to initialize it in prepare_uretprobe, but it should be equally
> useful for other architectures.
>
> TODO: this assumes that the probed application can't use multiple
> stacks (say sigaltstack). We will try to improve this logic later.
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Anton Arapov <ara...@gmail.com>
> ---
> arch/x86/kernel/uprobes.c | 5 +++++
> include/linux/uprobes.h | 1 +
> kernel/events/uprobes.c | 1 +
> 3 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 0b81ad6..9d5f570 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -993,3 +993,8 @@ arch_uretprobe_hijack_return_addr(unsigned long
> trampoline_vaddr, struct pt_regs
>
> return -1;
> }
> +
> +bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs
> *regs)
> +{
> + return regs->sp <= ret->stack;
> +}
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 50d2764..7ab6d2c 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -95,6 +95,7 @@ struct uprobe_task {
> struct return_instance {
> struct uprobe *uprobe;
> unsigned long func;
> + unsigned long stack; /* stack pointer */
> unsigned long orig_ret_vaddr; /* original return address */
> bool chained; /* true, if instance is nested
> */
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 1c71b62..c5f316e 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1562,6 +1562,7 @@ static void prepare_uretprobe(struct uprobe *uprobe,
> struct pt_regs *regs)
>
> ri->uprobe = get_uprobe(uprobe);
> ri->func = instruction_pointer(regs);
> + ri->stack = user_stack_pointer(regs);
> ri->orig_ret_vaddr = orig_ret_vaddr;
> ri->chained = chained;
>
> --
> 1.5.5.1
>
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