# Re: \[PATCH v19 3/7\] x86/cet/ibt: Handle signals for Indirect Branch Tracking

- From: Kees Cook \<hidden\>
- Date: 2021-02-04 20:17:52 
- List: linux-arch
- Page: https://ratatoskr.run/linux-arch/2021/02/6259121
- Thread: https://ratatoskr.run/linux-doc/2021/02/6257808/t.md

```text
On Wed, Feb 03, 2021 at 02:58:58PM -0800, Yu-cheng Yu wrote:
> When an indirect CALL/JMP instruction is executed and before it reaches
> the target, it is in 'WAIT_ENDBR' status, which can be read from
> MSR_IA32_U_CET.  The status is part of a task's status before a signal is
> raised and preserved in the signal frame.  It is restored for sigreturn.
> 
> IBT state machine is described in Intel SDM Vol. 1, Sec. 18.3.
> 
> Signed-off-by: Yu-cheng Yu <redacted>

Reviewed-by: Kees Cook <redacted>

-- 
Kees Cook
```