On Wed, May 18, 2022 at 3:53 PM Xu Kuohai [off-list ref] wrote:

Add ftrace direct support for arm64.

1. When there is custom trampoline only, replace the fentry nop to a
   jump instruction that jumps directly to the custom trampoline.

2. When ftrace trampoline and custom trampoline coexist, jump from
   fentry to ftrace trampoline first, then jump to custom trampoline
   when ftrace trampoline exits. The current unused register
   pt_regs->orig_x0 is used as an intermediary for jumping from ftrace
   trampoline to custom trampoline.

Signed-off-by: Xu Kuohai <redacted>
Acked-by: Song Liu <redacted>

Acked-by: KP Singh <kpsingh@kernel.org>