Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack

[Al Viro]

On Mon, Jun 21, 2021 at 02:01:18PM +1200, Michael Schmitz wrote:
> Hi Eric,
> 
> instrumenting get_reg on m68k and using a similar patch to yours to warn
> when unsaved registers are accessed on the switch stack, I get a hit from
> getegid and getegid32, just by running a simple ptrace on ls.
> 
> Going to wack those two moles now ...

Explain, please.  get_reg() is called by tracer; whose state are you checking?
Because you are *not* accessing the switch stack of the caller of get_reg().
And tracee should be in something like syscall_trace() or do_notify_resume();
both have SAVE_SWITCH_STACK done by the glue...