Re: Crash when attaching uretprobes to processes running in Docker

[Oleg Nesterov]

On 01/14, Masami Hiramatsu wrote:
>
> On Tue, 14 Jan 2025 10:22:20 +0100
> Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> > @@ -418,6 +439,9 @@ SYSCALL_DEFINE0(uretprobe)
> >  	regs->r11 = regs->flags;
> >  	regs->cx  = regs->ip;
> >
> > +	/* zero rbx to signal trampoline that uretprobe syscall was executed */
> > +	regs->bx  = 0;
>
> Can we just return -ENOSYS as like as other syscall instead of
> using rbx as a side channel?
> We can carefully check the return address is not -ERRNO when set up
> and reserve the -ENOSYS for this use case.

Not sure I understand...

But please not that the uretprobed function can return any value
including -ENOSYS, and this is what sys_uretprobe() has to return.

Oleg.