[src/trunk]: src/sys/kern New sysctl kern.entropy.gather=1 to trigger entropy...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/600a68c3b661
branches:  trunk
changeset: 1009858:600a68c3b661
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue May 05 15:31:42 2020 +0000

description:
New sysctl kern.entropy.gather=1 to trigger entropy gathering.

Invokes all on-demand RNG sources.  This enables HWRNG driver
developers to use a dtrace probe on rnd_add_data to examine the data
coming out of the HWRNG:

dtrace -n 'fbt::rnd_add_data:entry /args[0]->name == "amdccp0"/ {
   ...examine buffer args[1] length args[2]...
}'

diffstat:

 sys/kern/kern_entropy.c |  38 ++++++++++++++++++++++++++++++++++++--
 1 files changed, 36 insertions(+), 2 deletions(-)

diffs (73 lines):

diff -r 640e96133c9b -r 600a68c3b661 sys/kern/kern_entropy.c
--- a/sys/kern/kern_entropy.c   Tue May 05 15:25:18 2020 +0000
+++ b/sys/kern/kern_entropy.c   Tue May 05 15:31:42 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_entropy.c,v 1.9 2020/05/03 06:33:59 riastradh Exp $       */
+/*     $NetBSD: kern_entropy.c,v 1.10 2020/05/05 15:31:42 riastradh Exp $      */
 
 /*-
  * Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -77,7 +77,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.9 2020/05/03 06:33:59 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.10 2020/05/05 15:31:42 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -245,6 +245,7 @@
 static void    entropy_gather_xc(void *, void *);
 static void    entropy_notify(void);
 static int     sysctl_entropy_consolidate(SYSCTLFN_ARGS);
+static int     sysctl_entropy_gather(SYSCTLFN_ARGS);
 static void    filt_entropy_read_detach(struct knote *);
 static int     filt_entropy_read_event(struct knote *, long);
 static void    entropy_request(size_t);
@@ -362,6 +363,10 @@
            CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "consolidate",
            SYSCTL_DESCR("Trigger entropy consolidation now"),
            sysctl_entropy_consolidate, 0, NULL, 0, CTL_CREATE, CTL_EOL);
+       sysctl_createv(&entropy_sysctllog, 0, &entropy_sysctlroot, NULL,
+           CTLFLAG_PERMANENT|CTLFLAG_READWRITE, CTLTYPE_INT, "gather",
+           SYSCTL_DESCR("Trigger entropy gathering from sources now"),
+           sysctl_entropy_gather, 0, NULL, 0, CTL_CREATE, CTL_EOL);
        /* XXX These should maybe not be readable at securelevel>0.  */
        sysctl_createv(&entropy_sysctllog, 0, &entropy_sysctlroot, NULL,
            CTLFLAG_PERMANENT|CTLFLAG_READONLY|CTLFLAG_PRIVATE, CTLTYPE_INT,
@@ -1171,6 +1176,35 @@
 }
 
 /*
+ * sysctl -w kern.entropy.gather=1
+ *
+ *     Trigger gathering entropy from all on-demand sources, and wait
+ *     for synchronous sources (but not asynchronous sources) to
+ *     complete.  Writable only by superuser.
+ */
+static int
+sysctl_entropy_gather(SYSCTLFN_ARGS)
+{
+       struct sysctlnode node = *rnode;
+       int arg;
+       int error;
+
+       KASSERT(E->stage == ENTROPY_HOT);
+
+       node.sysctl_data = &arg;
+       error = sysctl_lookup(SYSCTLFN_CALL(&node));
+       if (error || newp == NULL)
+               return error;
+       if (arg) {
+               mutex_enter(&E->lock);
+               entropy_request(ENTROPY_CAPACITY);
+               mutex_exit(&E->lock);
+       }
+
+       return 0;
+}
+
+/*
  * entropy_extract(buf, len, flags)
  *
  *     Extract len bytes from the global entropy pool into buf.