Re: Request for implementation of KERN_PROC_SIGTRAMP sysctl

["John Marino (NetBSD)" <netbsd%marino.st@localhost>]

So for the purpose of the gdb unwinder, I would pass NULL for the sp
argument?
The unwinder would only be checking the result to see __sigtramp_unwind_np
returns null or not.
John

On Sun, Nov 14, 2021 at 2:49 PM Jason Thorpe <thorpej%me.com@localhost> wrote:

>
> > On Oct 28, 2021, at 8:49 AM, Valery Ushakov <uwe%stderr.spb.ru@localhost> wrote:
> >
> > It is ucontext for the siginfo trampoline and sigcontext for the older
> > one, isn't it?
>
> Ok, I’ve settled on the following:
>
> void *__sigtramp_unwind_np(void *pc, void *sp, int *versp);
>
> Given a program counter and stack pointer, return a pointer to the context
> that will be restored when the signal handler returns.  The signal
> trampoline version is returned in *versp; versp must not be NULL, and
> passing NULL will result in undefined behavior.
>
> Returns NULL if the provided pc is not within the signal trampoline, or if
> the location of the context to restore cannot be determined.
>
> If the returned version is within the range __SIGTRAMP_SIGINFO_VERSION_MIN
> … __SIGTRAMP_SIGINFO_VERSION_MAX, then the returned context points to a
> ucontext_t.
>
> If the returned version is within the range
> __SIGTRAMP_SIGCONTEXT_VERSION_MIN … __SIGTRAMP_SIGCONTEXT_VERSION_MAX, then
> the returned context points to a struct sigcontext.
>
> Note that the layout of the context structures is architecture-dependent
> and may also be version-dependent.
>
> Does this sound good to everyone?
>
> -- thorpej
>
>