Instead of only iterating over the set of known SDT probes when sdt.ko is

loaded and unloaded, also have sdt.ko register callbacks with kern_sdt.c
that will be called when a newly loaded KLD module adds more probes or
a module with probes is unloaded.

This fixes two issues: first, if a module with SDT probes was loaded after
sdt.ko was loaded, those new probes would not be available in DTrace.
Second, if a module with SDT probes was unloaded while sdt.ko was loaded,
the kernel would panic the next time DTrace had cause to try and do
anything with the no-longer-existent probes.

This makes it possible to create SDT probes in KLD modules, although there
are still two caveats: first, any SDT probes in a KLD module must be part
of a DTrace provider that is defined in that module.  At present DTrace
only destroys probes when the provider is destroyed, so you can still
panic the system if a KLD module creates new probes in a provider from a
different module(including the kernel) and then unload the the first module.

Second, the system will panic if you unload a module containing SDT probes
while there is an active D script that has enabled those probes.

MFC after:	1 month

1 files changed, 5 insertions, 2 deletions

diff --git a/sys/cddl/dev/sdt/sdt.c b/sys/cddl/dev/sdt/sdt.c
index d5d4172..395daf7 100644
--- a/sys/cddl/dev/sdt/sdt.c
+++ b/sys/cddl/dev/sdt/sdt.c
@@ -52,6 +52,8 @@ static void	sdt_destroy(void *, dtrace_id_t, void *);
 static void	sdt_enable(void *, dtrace_id_t, void *);
 static void	sdt_disable(void *, dtrace_id_t, void *);
 static void	sdt_load(void *);
+static int	sdt_provider_unreg_callback(struct sdt_provider *prov, 
+		    void *arg);
 
 static struct cdevsw sdt_cdevsw = {
 	.d_version	= D_VERSION,
@@ -190,7 +192,8 @@ sdt_load(void *dummy)
 
 	sdt_probe_func = dtrace_probe;
 
-	(void) sdt_provider_listall(sdt_provider_reg_callback, NULL);
+	sdt_register_callbacks(sdt_provider_reg_callback, NULL,
+	    sdt_provider_unreg_callback, NULL, sdt_probe_callback, NULL);
 }
 
 static int
@@ -206,7 +209,7 @@ sdt_unload()
 
 	sdt_probe_func = sdt_probe_stub;
 
-	(void) sdt_provider_listall(sdt_provider_unreg_callback, NULL);
+	sdt_deregister_callbacks();
 	
 	destroy_dev(sdt_cdev);