Module Name: src
Committed By: riastradh
Date: Thu Aug 29 21:54:11 UTC 2013
Modified Files:
src/sys/arch/arm/broadcom: bcm2835_rng.c
Log Message:
Make the rpi hwrng feed data to the entropy pool in a softint.
The two-lock scheme here is excessive but will do provisionally until
rnd(9) gets disentangled.
Tested by Aymeric Vincent.
To generate a diff of this commit:
cvs rdiff -u -r1.8 -r1.9 src/sys/arch/arm/broadcom/bcm2835_rng.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/arm/broadcom/bcm2835_rng.c
diff -u src/sys/arch/arm/broadcom/bcm2835_rng.c:1.8 src/sys/arch/arm/broadcom/bcm2835_rng.c:1.9
--- src/sys/arch/arm/broadcom/bcm2835_rng.c:1.8 Wed Aug 28 18:32:45 2013
+++ src/sys/arch/arm/broadcom/bcm2835_rng.c Thu Aug 29 21:54:11 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: bcm2835_rng.c,v 1.8 2013/08/28 18:32:45 riastradh Exp $ */
+/* $NetBSD: bcm2835_rng.c,v 1.9 2013/08/29 21:54:11 riastradh Exp $ */
/*-
* Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: bcm2835_rng.c,v 1.8 2013/08/28 18:32:45 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bcm2835_rng.c,v 1.9 2013/08/29 21:54:11 riastradh Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -39,6 +39,7 @@ __KERNEL_RCSID(0, "$NetBSD: bcm2835_rng.
#include <sys/bus.h>
#include <sys/rnd.h>
#include <sys/atomic.h>
+#include <sys/intr.h>
#include <arm/broadcom/bcm_amba.h>
#include <arm/broadcom/bcm2835reg.h>
@@ -47,28 +48,30 @@ __KERNEL_RCSID(0, "$NetBSD: bcm2835_rng.
#define RNG_CTRL 0x00
#define RNG_CTRL_EN __BIT(0)
#define RNG_STATUS 0x04
-#define RNG_STATUS_CNT_MASK __BITS(31,24)
-#define RNG_STATUS_CNT_SHIFT 24
+#define RNG_STATUS_CNT __BITS(31,24)
#define RNG_DATA 0x08
#define RNG_DATA_MAX 256
struct bcm2835rng_softc {
- device_t sc_dev;
+ device_t sc_dev;
- bus_space_tag_t sc_iot;
- bus_space_handle_t sc_ioh;
+ bus_space_tag_t sc_iot;
+ bus_space_handle_t sc_ioh;
- krndsource_t sc_rnd;
+ kmutex_t sc_intr_lock;
+ unsigned int sc_bytes_wanted;
+ void *sc_sih;
- kmutex_t sc_mutex;
-
- uint32_t sc_data[RNG_DATA_MAX];
+ kmutex_t sc_rnd_lock;
+ krndsource_t sc_rndsource;
};
-static void bcmrng_get(size_t, void *);
static int bcmrng_match(device_t, cfdata_t, void *);
static void bcmrng_attach(device_t, device_t, void *);
+static void bcmrng_get(struct bcm2835rng_softc *);
+static void bcmrng_get_cb(size_t, void *);
+static void bcmrng_get_intr(void *);
CFATTACH_DECL_NEW(bcmrng_amba, sizeof(struct bcm2835rng_softc),
bcmrng_match, bcmrng_attach, NULL, NULL);
@@ -101,15 +104,9 @@ bcmrng_attach(device_t parent, device_t
if (bus_space_map(aaa->aaa_iot, aaa->aaa_addr, BCM2835_RNG_SIZE, 0,
&sc->sc_ioh)) {
aprint_error_dev(sc->sc_dev, "unable to map device\n");
- return;
+ goto fail0;
}
- mutex_init(&sc->sc_mutex, MUTEX_DEFAULT, IPL_VM);
-
- rndsource_setcb(&sc->sc_rnd, bcmrng_get, sc);
- rnd_attach_source(&sc->sc_rnd, device_xname(self), RND_TYPE_RNG,
- RND_FLAG_NO_ESTIMATE|RND_FLAG_HASCB);
-
/* discard initial numbers, broadcom says they are "less random" */
bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS, 0x40000);
@@ -118,35 +115,88 @@ bcmrng_attach(device_t parent, device_t
ctrl |= RNG_CTRL_EN;
bus_space_write_4(sc->sc_iot, sc->sc_ioh, RNG_CTRL, ctrl);
+ /* set up a softint for adding data */
+ mutex_init(&sc->sc_intr_lock, MUTEX_DEFAULT, IPL_SERIAL);
+ sc->sc_bytes_wanted = 0;
+ sc->sc_sih = softint_establish(SOFTINT_SERIAL|SOFTINT_MPSAFE,
+ &bcmrng_get_intr, sc);
+ if (sc->sc_sih == NULL) {
+ aprint_error_dev(sc->sc_dev, "unable to establish softint");
+ goto fail1;
+ }
+
+ /* set up an rndsource */
+ mutex_init(&sc->sc_rnd_lock, MUTEX_DEFAULT, IPL_SERIAL);
+ rndsource_setcb(&sc->sc_rndsource, &bcmrng_get_cb, sc);
+ rnd_attach_source(&sc->sc_rndsource, device_xname(self), RND_TYPE_RNG,
+ RND_FLAG_NO_ESTIMATE|RND_FLAG_HASCB);
+
/* get some initial entropy ASAP */
- bcmrng_get(RND_POOLBITS / NBBY, sc);
+ bcmrng_get_cb(RND_POOLBITS / NBBY, sc);
+
+ /* Success! */
+ return;
+
+fail1: mutex_destroy(&sc->sc_intr_lock);
+ bus_space_unmap(aaa->aaa_iot, sc->sc_ioh, BCM2835_RNG_SIZE);
+fail0: return;
}
static void
-bcmrng_get(size_t bytes, void *priv)
+bcmrng_get(struct bcm2835rng_softc *sc)
{
- struct bcm2835rng_softc *sc = priv;
- uint32_t status;
- int need = bytes, cnt;
-
- mutex_spin_enter(&sc->sc_mutex);
-
- if (__predict_false(need < 1)) {
- mutex_spin_exit(&sc->sc_mutex);
- return;
- }
+ uint32_t status, cnt;
+ uint32_t buf[RNG_DATA_MAX]; /* 1k on the stack */
- while (need > 0) {
+ mutex_spin_enter(&sc->sc_intr_lock);
+ while (sc->sc_bytes_wanted) {
status = bus_space_read_4(sc->sc_iot, sc->sc_ioh, RNG_STATUS);
- cnt = (status & RNG_STATUS_CNT_MASK) >> RNG_STATUS_CNT_SHIFT;
- if (cnt > 0) {
- bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh,
- RNG_DATA, sc->sc_data, cnt);
- rnd_add_data(&sc->sc_rnd, sc->sc_data,
- cnt * 4, cnt * 4 * NBBY);
- }
-
- need -= cnt * 4;
+ cnt = __SHIFTOUT(status, RNG_STATUS_CNT);
+ KASSERT(cnt < RNG_DATA_MAX);
+ if (cnt == 0)
+ continue; /* XXX Busy-waiting seems wrong... */
+ bus_space_read_multi_4(sc->sc_iot, sc->sc_ioh, RNG_DATA, buf,
+ cnt);
+
+ /*
+ * This lock dance is necessary because rnd_add_data
+ * may call bcmrng_get_cb which takes the intr lock.
+ */
+ mutex_spin_exit(&sc->sc_intr_lock);
+ mutex_spin_enter(&sc->sc_rnd_lock);
+ rnd_add_data(&sc->sc_rndsource, buf, (cnt * 4),
+ (cnt * 4 * NBBY));
+ mutex_spin_exit(&sc->sc_rnd_lock);
+ mutex_spin_enter(&sc->sc_intr_lock);
+ sc->sc_bytes_wanted -= MIN(sc->sc_bytes_wanted, (cnt * 4));
}
- mutex_spin_exit(&sc->sc_mutex);
+ explicit_memset(buf, 0, sizeof(buf));
+ mutex_spin_exit(&sc->sc_intr_lock);
+}
+
+static void
+bcmrng_get_cb(size_t bytes_wanted, void *arg)
+{
+ struct bcm2835rng_softc *sc = arg;
+
+ /*
+ * Deferring to a softint is necessary until the rnd(9) locking
+ * is fixed.
+ */
+ mutex_spin_enter(&sc->sc_intr_lock);
+ if (sc->sc_bytes_wanted == 0)
+ softint_schedule(sc->sc_sih);
+ if (bytes_wanted > (UINT_MAX - sc->sc_bytes_wanted))
+ sc->sc_bytes_wanted = UINT_MAX;
+ else
+ sc->sc_bytes_wanted += bytes_wanted;
+ mutex_spin_exit(&sc->sc_intr_lock);
+}
+
+static void
+bcmrng_get_intr(void *arg)
+{
+ struct bcm2835rng_softc *const sc = arg;
+
+ bcmrng_get(sc);
}
