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Index: sys/dev/random/randomdev.c
===================================================================
--- sys/dev/random/randomdev.c
+++ sys/dev/random/randomdev.c
@@ -257,6 +257,12 @@
if (len == 0)
return;
+#ifdef INVARIANTS
+ if ((curthread->td_pflags & TDP_RNG_SEEDED) == 0)
+ WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
+ "read_random may block once");
+#endif
+
/* (Un)Blocking logic */
if (__predict_false(!p_random_alg_context->ra_seeded())) {
if (random_bypass_before_seeding) {
@@ -300,7 +306,18 @@
bool
IS_RANDOM_SEEDED(void)
{
- return (p_random_alg_context->ra_seeded());
+ bool seeded;
+
+ seeded = p_random_alg_context->ra_seeded();
+#ifdef INVARIANTS
+ /*
+ * Mute false-positive WITNESS_WARNs for threads that have already
+ * confirmed seeded status.
+ */
+ if (seeded)
+ curthread->td_pflags |= TDP_RNG_SEEDED;
+#endif
+ return (seeded);
}
static __inline void
Index: sys/libkern/arc4random.c
===================================================================
--- sys/libkern/arc4random.c
+++ sys/libkern/arc4random.c
@@ -36,6 +36,7 @@
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
+#include <sys/proc.h>
#include <sys/random.h>
#include <sys/smp.h>
#include <sys/time.h>
@@ -177,6 +178,12 @@
u_int length;
u_int8_t *p;
+#ifdef INVARIANTS
+ if ((curthread->td_pflags & TDP_RNG_SEEDED) == 0)
+ WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
+ "arc4rand may block once");
+#endif
+
if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))
CHACHA20_FOREACH(chacha20)
chacha20_randomstir(chacha20);
Index: sys/sys/proc.h
===================================================================
--- sys/sys/proc.h
+++ sys/sys/proc.h
@@ -492,6 +492,7 @@
#define TDP_UIOHELD 0x10000000 /* Current uio has pages held in td_ma */
#define TDP_FORKING 0x20000000 /* Thread is being created through fork() */
#define TDP_EXECVMSPC 0x40000000 /* Execve destroyed old vmspace */
+#define TDP_RNG_SEEDED 0x80000000 /* This thread verified random seeded */
/*
* Reasons that the current thread can not be run yet.

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