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kern: harvest entropy from callouts

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74cf7cae4d ("softclock: Use dedicated ithreads for running callouts.")
switched callouts away from the swi infrastructure.  It turns out that
this was a major source of entropy in early boot, which we've now lost.

As a result, first boot on hardware without a 'fast' entropy source
would block waiting for fortuna to be seeded with little hope of
progressing without manual intervention.

Let's resolve it by explicitly harvesting entropy in callout_process()
if we've handled any callouts.  cc/curthread/now seem to be reasonable
sources of entropy, so use those.

Discussed with:	jhb (also proposed initial patch)
Reported by:	many
Reviewed by:	cem, markm (both csprng)
Differential Revision:	https://reviews.freebsd.org/D34150
This commit is contained in:
Kyle Evans 2022-02-03 10:05:06 -06:00
parent f026275e26
commit 642701abc8
4 changed files with 18 additions and 2 deletions
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3
sys/dev/random/fenestrasX/fx_pool.c
View file

@ -164,6 +164,9 @@ static const struct fxrng_ent_char {
[RANDOM_UMA] = {
.entc_cls = &fxrng_lo_push,
},
[RANDOM_CALLOUT] = {
.entc_cls = &fxrng_lo_push,
},
[RANDOM_PURE_OCTEON] = {
.entc_cls = &fxrng_hi_push, /* Could be made pull. */
},

3
sys/dev/random/random_harvestq.c
View file

@ -349,7 +349,8 @@ static const char *random_source_descr[ENTROPYSOURCE] = {
[RANDOM_INTERRUPT] = "INTERRUPT",
[RANDOM_SWI] = "SWI",
[RANDOM_FS_ATIME] = "FS_ATIME",
[RANDOM_UMA] = "UMA", /* ENVIRONMENTAL_END */
[RANDOM_UMA] = "UMA",
[RANDOM_CALLOUT] = "CALLOUT", /* ENVIRONMENTAL_END */
[RANDOM_PURE_OCTEON] = "PURE_OCTEON", /* PURE_START */
[RANDOM_PURE_SAFE] = "PURE_SAFE",
[RANDOM_PURE_GLXSB] = "PURE_GLXSB",

11
sys/kern/kern_timeout.c
View file

@ -57,6 +57,7 @@ __FBSDID("$FreeBSD$");
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/random.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/sleepqueue.h>
@ -430,6 +431,11 @@ callout_get_bucket(sbintime_t sbt)
void
callout_process(sbintime_t now)
{
struct callout_entropy {
struct callout_cpu *cc;
struct thread *td;
sbintime_t now;
} entropy;
struct callout *tmp, *tmpn;
struct callout_cpu *cc;
struct callout_list *sc;
@ -545,6 +551,11 @@ next:
avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
#endif
if (!TAILQ_EMPTY(&cc->cc_expireq)) {
entropy.cc = cc;
entropy.td = curthread;
entropy.now = now;
random_harvest_queue(&entropy, sizeof(entropy), RANDOM_CALLOUT);
td = cc->cc_thread;
if (TD_AWAITING_INTR(td)) {
thread_lock_block_wait(td);

3
sys/sys/random.h
View file

@ -86,7 +86,8 @@ enum random_entropy_source {
RANDOM_SWI,
RANDOM_FS_ATIME,
RANDOM_UMA, /* Special!! UMA/SLAB Allocator */
RANDOM_ENVIRONMENTAL_END = RANDOM_UMA,
RANDOM_CALLOUT,
RANDOM_ENVIRONMENTAL_END = RANDOM_CALLOUT,
/* Fast hardware random-number sources from here on. */
RANDOM_PURE_START,
RANDOM_PURE_OCTEON = RANDOM_PURE_START,