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.
