Re: [PATCH] ntdll: Set rcx and r11 on exit from syscall dispatcher on x64.

[Jinoh Kang]

On 12/1/21 14:34, Jinoh Kang wrote:
> My speculation is that there's a flag that determines whether it's OK to clobber
> RCX/R11 on syscall exit.  If it's enabled, KiFastSystemCall will use SYSRET
> instead of IRETQ.  Issuing NtSetContextThread with CONTEXT_INTEGER on supposedly
> turns this flag off, disabling the use of SYSRET.  From the observations so far,
> this flag more or less corresponds to CONTEXT_CONTROL in

CONTEXT_INTEGER*.  My apologies.
> syscall_frame::restore_flags, but more testing is required...