dtrace_sdt: Don't ignore the first stack frame in sdt probes.

The aframes argument to dtrace_probe_create gives the number of stack
frames that are ignored in stack(), the first frame of which is
`caller'.

This is for, e.g., profiler interrupts where the interrupt frame
itself isn't interesting; it's the code that was interrupted that was
interesting (hence profile_aframes = PROF_ARTIFICIAL_FRAMES is often
nonzero, or even several frames deep).

But for sdt, the direct caller is the interesting part -- when we
have something like:

foo()
{
	...
	bar();
	...
}

bar()
{
	...
	SDT_PROBE1(...);
	...
}

We want `caller' to be the return address in bar of SDT_PROBE1(...),
not the return address in foo of bar().

PR kern/59934: dtrace_sdt: caller is off by a frame

Author: riastradh

external/cddl/osnet/dev/sdt/sdt.c

@@ -39,7 +39,7 @@
  * unloaded; in particular, probes may not span multiple kernel modules.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sdt.c,v 1.24 2022/08/31 12:34:04 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sdt.c,v 1.25 2026/01/22 04:14:08 riastradh Exp $");
 
 #include <sys/cdefs.h>
 #include <sys/proc.h>
@@ -250,7 +250,7 @@ sdt_create_probe(struct sdt_probe *probe)
 	if (dtrace_probe_lookup(prov->id, mod, func, name) != DTRACE_IDNONE)
 		return;
 
-	(void)dtrace_probe_create(prov->id, mod, func, name, 1, probe);
+	(void)dtrace_probe_create(prov->id, mod, func, name, 0, probe);
 }
 
 /*