Re: Request for implementation of KERN_PROC_SIGTRAMP sysctl

[Jason Thorpe <thorpej%me.com@localhost>]

> On Oct 27, 2021, at 4:01 PM, Jason Thorpe <thorpej%me.com@localhost> wrote:
> 
> 
>> On Oct 27, 2021, at 3:44 PM, Valery Ushakov <uwe%stderr.spb.ru@localhost> wrote:
>> 
>> On Wed, Oct 27, 2021 at 07:50:55 -0700, Jason Thorpe wrote:
>> 
>> I was wondering if it might be easier to not put the onus onto the
>> caller and instead have a function that returns the interrupted
>> ucontext (or NULL, if the pc is not in a trampoline).
>> 
>> ucontext_t *__unwind_sigtramp(return_pc, return_sp)
> 
> That would certainly be a nicer API.

Thought about it a little more.

To make this really work, we’d definitely have to version sigaction() so that it fully de-supported sigcontext handlers.  Otherwise, it’s a toss-up whether you have a sigcontext or a ucontext on the stack.  I do think a __sigtramp_unwind() would also be a good addition.  But I also see some value in the basic check (which you need to have to __sigtramp_unwind() anyway…).

-- thorpej