Module Name: src
Committed By: riastradh
Date: Thu Apr 30 03:29:20 UTC 2020
Modified Files:
src/sys/arch/amd64/amd64: machdep.c
src/sys/arch/i386/i386: machdep.c
src/sys/arch/x86/include: cpu_rng.h
src/sys/arch/x86/x86: cpu_rng.c pmap.c
Log Message:
Simplify Intel RDRAND/RDSEED and VIA C3 RNG API.
Push it all into MD x86 code to keep it simpler, until we have other
examples on other CPUs. Simplify RDSEED-to-RDRAND fallback.
Eliminate cpu_earlyrng in favour of just using entropy_extract, which
is available early now.
To generate a diff of this commit:
cvs rdiff -u -r1.349 -r1.350 src/sys/arch/amd64/amd64/machdep.c
cvs rdiff -u -r1.827 -r1.828 src/sys/arch/i386/i386/machdep.c
cvs rdiff -u -r1.2 -r1.3 src/sys/arch/x86/include/cpu_rng.h
cvs rdiff -u -r1.10 -r1.11 src/sys/arch/x86/x86/cpu_rng.c
cvs rdiff -u -r1.384 -r1.385 src/sys/arch/x86/x86/pmap.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/amd64/amd64/machdep.c
diff -u src/sys/arch/amd64/amd64/machdep.c:1.349 src/sys/arch/amd64/amd64/machdep.c:1.350
--- src/sys/arch/amd64/amd64/machdep.c:1.349 Tue Apr 28 21:35:35 2020
+++ src/sys/arch/amd64/amd64/machdep.c Thu Apr 30 03:29:19 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.349 2020/04/28 21:35:35 jmcneill Exp $ */
+/* $NetBSD: machdep.c,v 1.350 2020/04/30 03:29:19 riastradh Exp $ */
/*
* Copyright (c) 1996, 1997, 1998, 2000, 2006, 2007, 2008, 2011
@@ -110,7 +110,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.349 2020/04/28 21:35:35 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.350 2020/04/30 03:29:19 riastradh Exp $");
#include "opt_modular.h"
#include "opt_user_ldt.h"
@@ -167,6 +167,7 @@ __KERNEL_RCSID(0, "$NetBSD: machdep.c,v
#include <sys/sysctl.h>
#include <machine/cpu.h>
+#include <machine/cpu_rng.h>
#include <machine/cpufunc.h>
#include <machine/gdt.h>
#include <machine/intr.h>
@@ -1682,6 +1683,7 @@ init_x86_64(paddr_t first_avail)
uvm_lwp_setuarea(&lwp0, lwp0uarea);
cpu_probe(&cpu_info_primary);
+ cpu_rng_init();
#ifdef SVS
svs_init();
#endif
Index: src/sys/arch/i386/i386/machdep.c
diff -u src/sys/arch/i386/i386/machdep.c:1.827 src/sys/arch/i386/i386/machdep.c:1.828
--- src/sys/arch/i386/i386/machdep.c:1.827 Sat Apr 25 15:26:17 2020
+++ src/sys/arch/i386/i386/machdep.c Thu Apr 30 03:29:19 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.827 2020/04/25 15:26:17 bouyer Exp $ */
+/* $NetBSD: machdep.c,v 1.828 2020/04/30 03:29:19 riastradh Exp $ */
/*
* Copyright (c) 1996, 1997, 1998, 2000, 2004, 2006, 2008, 2009, 2017
@@ -67,7 +67,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.827 2020/04/25 15:26:17 bouyer Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.828 2020/04/30 03:29:19 riastradh Exp $");
#include "opt_beep.h"
#include "opt_compat_freebsd.h"
@@ -122,6 +122,7 @@ __KERNEL_RCSID(0, "$NetBSD: machdep.c,v
#include <x86/efi.h>
#include <machine/cpu.h>
+#include <machine/cpu_rng.h>
#include <machine/cpufunc.h>
#include <machine/cpuvar.h>
#include <machine/gdt.h>
@@ -1142,6 +1143,7 @@ init386(paddr_t first_avail)
uvm_lwp_setuarea(&lwp0, lwp0uarea);
cpu_probe(&cpu_info_primary);
+ cpu_rng_init();
cpu_init_msrs(&cpu_info_primary, true);
#ifndef XEN
cpu_speculation_init(&cpu_info_primary);
Index: src/sys/arch/x86/include/cpu_rng.h
diff -u src/sys/arch/x86/include/cpu_rng.h:1.2 src/sys/arch/x86/include/cpu_rng.h:1.3
--- src/sys/arch/x86/include/cpu_rng.h:1.2 Sat Jul 21 06:09:13 2018
+++ src/sys/arch/x86/include/cpu_rng.h Thu Apr 30 03:29:19 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: cpu_rng.h,v 1.2 2018/07/21 06:09:13 maxv Exp $ */
+/* $NetBSD: cpu_rng.h,v 1.3 2020/04/30 03:29:19 riastradh Exp $ */
#ifndef _X86_CPU_RNG_H_
#define _X86_CPU_RNG_H_
@@ -32,12 +32,6 @@
* POSSIBILITY OF SUCH DAMAGE.
*/
-#include <sys/types.h>
-
-typedef uint64_t cpu_rng_t;
-
-bool cpu_rng_init(void);
-size_t cpu_rng(cpu_rng_t *);
-void cpu_earlyrng(void *, size_t);
+void cpu_rng_init(void);
#endif /* _X86_CPU_RNG_H_ */
Index: src/sys/arch/x86/x86/cpu_rng.c
diff -u src/sys/arch/x86/x86/cpu_rng.c:1.10 src/sys/arch/x86/x86/cpu_rng.c:1.11
--- src/sys/arch/x86/x86/cpu_rng.c:1.10 Fri Nov 1 15:01:27 2019
+++ src/sys/arch/x86/x86/cpu_rng.c Thu Apr 30 03:29:20 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: cpu_rng.c,v 1.10 2019/11/01 15:01:27 taca Exp $ */
+/* $NetBSD: cpu_rng.c,v 1.11 2020/04/30 03:29:20 riastradh Exp $ */
/*-
* Copyright (c) 2015 The NetBSD Foundation, Inc.
@@ -33,11 +33,24 @@
* The VIA RNG code in this file is inspired by Jason Wright and
* Theo de Raadt's OpenBSD version but has been rewritten in light of
* comments from Henric Jungheim on the [email protected] mailing list.
+ *
+ * For reference on Intel RDRAND/RDSEED, see the Intel Digital Random
+ * Number Generator Software Implementation Guide (`Intel DRNG SIG'),
+ * Revision 2.1, October 17, 2018.
+ * https://software.intel.com/sites/default/files/managed/98/4a/DRNG_Software_Implementation_Guide_2.1.pdf
+ *
+ * For reference on AMD RDRAND/RDSEED, which are designed to be
+ * compatible with Intel RDRAND/RDSEED, see the somewhat less detailed
+ * AMD Random Number Generator documentation, 2017-06-27.
+ * https://www.amd.com/system/files/TechDocs/amd-random-number-generator.pdf
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/cpu.h>
+#include <sys/rnd.h>
+#include <sys/rndpool.h>
+#include <sys/rndsource.h>
#include <sys/sha2.h>
#include <x86/specialreg.h>
@@ -45,41 +58,66 @@
#include <machine/cpufunc.h>
#include <machine/cpuvar.h>
#include <machine/cpu_rng.h>
+#include <machine/limits.h>
-static enum {
+static enum cpu_rng_mode {
CPU_RNG_NONE = 0,
CPU_RNG_RDRAND,
CPU_RNG_RDSEED,
+ CPU_RNG_RDSEED_RDRAND,
CPU_RNG_VIA
} cpu_rng_mode __read_mostly = CPU_RNG_NONE;
-static bool has_rdrand;
+static const char *const cpu_rng_name[] = {
+ [CPU_RNG_RDRAND] = "rdrand",
+ [CPU_RNG_RDSEED] = "rdseed",
+ [CPU_RNG_RDSEED_RDRAND] = "rdrand/rdseed",
+ [CPU_RNG_VIA] = "via",
+};
-bool
-cpu_rng_init(void)
-{
+static struct krndsource cpu_rng_source __read_mostly;
- if (cpu_feature[5] & CPUID_SEF_RDSEED) {
- cpu_rng_mode = CPU_RNG_RDSEED;
- aprint_normal("cpu_rng: RDSEED\n");
- return true;
- } else if (cpu_feature[1] & CPUID2_RDRAND) {
- cpu_rng_mode = CPU_RNG_RDRAND;
- aprint_normal("cpu_rng: RDRAND\n");
- return true;
- } else if (cpu_feature[4] & CPUID_VIA_HAS_RNG) {
- cpu_rng_mode = CPU_RNG_VIA;
- aprint_normal("cpu_rng: VIA\n");
- return true;
- }
- return false;
+static enum cpu_rng_mode
+cpu_rng_detect(void)
+{
+ bool has_rdseed = (cpu_feature[5] & CPUID_SEF_RDSEED);
+ bool has_rdrand = (cpu_feature[1] & CPUID2_RDRAND);
+ bool has_viarng = (cpu_feature[4] & CPUID_VIA_HAS_RNG);
+
+ if (has_rdseed && has_rdrand)
+ return CPU_RNG_RDSEED_RDRAND;
+ else if (has_rdseed)
+ return CPU_RNG_RDSEED;
+ else if (has_rdrand)
+ return CPU_RNG_RDRAND;
+ else if (has_viarng)
+ return CPU_RNG_VIA;
+ else
+ return CPU_RNG_NONE;
}
static size_t
-cpu_rng_rdrand(cpu_rng_t *out)
+cpu_rng_rdrand(uint64_t *out)
{
uint8_t rndsts;
+ /*
+ * XXX The Intel DRNG SIG recommends (Sec. 5.2.1 `Retry
+ * recommendations', p. 22) that we retry up to ten times
+ * before giving up and panicking because something must be
+ * seriously awry with the CPU.
+ *
+ * XXX The Intel DRNG SIG also recommends (Sec. 5.2.6
+ * `Generating Seeds from RDRAND', p. 28) drawing 1024 64-bit
+ * samples (or, 512 128-bit samples) in order to guarantee that
+ * the CPU has drawn an independent sample from the physical
+ * entropy source, since the AES CTR_DRBG behind RDRAND will be
+ * used to generate at most 511 128-bit samples before it is
+ * reseeded from the physical entropy source. It is unclear
+ * whether the same considerations about RDSEED starvation
+ * apply to this advice.
+ */
+
#ifdef __i386__
uint32_t lo, hi;
@@ -102,19 +140,27 @@ cpu_rng_rdrand(cpu_rng_t *out)
}
static size_t
-cpu_rng_rdseed(cpu_rng_t *out)
+cpu_rng_rdseed(uint64_t *out)
{
uint8_t rndsts;
+ /*
+ * XXX The Intel DRNG SIG recommends (Sec. 5.3.1 `Retry
+ * recommendations', p. 22) that we consider retrying up to 100
+ * times, separated by PAUSE, but offers no guarantees about
+ * success after that many retries. In particular, userland
+ * threads could starve the kernel by issuing RDSEED.
+ */
+
#ifdef __i386__
uint32_t lo, hi;
__asm __volatile("rdseed %0; setc %1" : "=r"(lo), "=qm"(rndsts));
if (rndsts != 1)
- goto exhausted;
+ return 0;
__asm __volatile("rdseed %0; setc %1" : "=r"(hi), "=qm"(rndsts));
if (rndsts != 1)
- goto exhausted;
+ return 0;
*out = (uint64_t)lo | ((uint64_t)hi << 32);
explicit_memset(&lo, 0, sizeof(lo));
@@ -123,24 +169,24 @@ cpu_rng_rdseed(cpu_rng_t *out)
__asm __volatile("rdseed %0; setc %1" : "=r"(*out), "=qm"(rndsts));
#endif
if (rndsts != 1)
- goto exhausted;
+ return 0;
return sizeof(*out) * NBBY;
+}
- /*
- * Userspace could have exhausted RDSEED, but the
- * CPU-internal generator feeding RDRAND is guaranteed
- * to be seeded even in this case.
- */
-exhausted:
- if (has_rdrand)
- return cpu_rng_rdrand(out);
- else
- return 0;
+static size_t
+cpu_rng_rdseed_rdrand(uint64_t *out)
+{
+ size_t n = cpu_rng_rdseed(out);
+
+ if (n == 0)
+ n = cpu_rng_rdrand(out);
+
+ return n;
}
static size_t
-cpu_rng_via(cpu_rng_t *out)
+cpu_rng_via(uint64_t *out)
{
uint32_t creg0, rndsts;
@@ -179,72 +225,64 @@ cpu_rng_via(cpu_rng_t *out)
* 0.75 bits of entropy per output bit and advises users to
* be "even more conservative".
*/
- return rndsts & 0xf ? 0 : sizeof(cpu_rng_t) * NBBY / 2;
+ return (rndsts & 0xf) ? 0 : sizeof(uint64_t) * NBBY/2;
}
-size_t
-cpu_rng(cpu_rng_t *out)
+static size_t
+cpu_rng(enum cpu_rng_mode mode, uint64_t *out)
{
- switch (cpu_rng_mode) {
+ switch (mode) {
case CPU_RNG_NONE:
return 0;
case CPU_RNG_RDSEED:
return cpu_rng_rdseed(out);
case CPU_RNG_RDRAND:
return cpu_rng_rdrand(out);
+ case CPU_RNG_RDSEED_RDRAND:
+ return cpu_rng_rdseed_rdrand(out);
case CPU_RNG_VIA:
return cpu_rng_via(out);
default:
- panic("cpu_rng: unknown mode %d", (int)cpu_rng_mode);
+ panic("cpu_rng: unknown mode %d", (int)mode);
}
}
-/* -------------------------------------------------------------------------- */
-
-static uint64_t earlyrng_state;
-
-/*
- * Small PRNG, that can be used very early. The only requirement is that
- * cpu_probe got called before.
- */
-void __noasan
-cpu_earlyrng(void *out, size_t sz)
+static void
+cpu_rng_get(size_t nbytes, void *cookie)
{
- uint8_t digest[SHA512_DIGEST_LENGTH];
- SHA512_CTX ctx;
- cpu_rng_t buf[8];
- uint64_t val;
- int i;
-
- bool has_rdseed = (cpu_feature[5] & CPUID_SEF_RDSEED) != 0;
- has_rdrand = (cpu_feature[1] & CPUID2_RDRAND) != 0;
-
- KASSERT(sz + sizeof(uint64_t) <= SHA512_DIGEST_LENGTH);
-
- SHA512_Init(&ctx);
-
- SHA512_Update(&ctx, (uint8_t *)&earlyrng_state, sizeof(earlyrng_state));
- if (has_rdseed) {
- for (i = 0; i < 8; i++) {
- if (cpu_rng_rdseed(&buf[i]) == 0) {
- break;
- }
- }
- SHA512_Update(&ctx, (uint8_t *)buf, i * sizeof(cpu_rng_t));
- } else if (has_rdrand) {
- for (i = 0; i < 8; i++) {
- if (cpu_rng_rdrand(&buf[i]) == 0) {
- break;
- }
- }
- SHA512_Update(&ctx, (uint8_t *)buf, i * sizeof(cpu_rng_t));
+ const unsigned N = howmany(RND_POOLBITS, 64);
+ uint64_t buf[2*N];
+ unsigned i, nbits = 0;
+
+ /*
+ * Draw a sample large enough to (a) fill the pool if it had
+ * full entropy, and (b) run a repeated-output test; then test
+ * it. If RND_POOLBITS is at least 256, the fraction of
+ * outputs this rejects in correct operation is 1/2^256, which
+ * is close enough to zero that we round it to having no effect
+ * on the number of bits of entropy.
+ */
+ for (i = 0; i < __arraycount(buf); i++)
+ nbits += cpu_rng(cpu_rng_mode, &buf[i]);
+ if (consttime_memequal(buf, buf + N, N)) {
+ printf("cpu_rng %s: failed repetition test\n",
+ cpu_rng_name[cpu_rng_mode]);
+ nbits = 0;
}
- val = rdtsc();
- SHA512_Update(&ctx, (uint8_t *)&val, sizeof(val));
- SHA512_Final(digest, &ctx);
+ rnd_add_data_sync(&cpu_rng_source, buf, sizeof buf, nbits);
+}
+
+void
+cpu_rng_init(void)
+{
- memcpy(out, digest, sz);
- memcpy(&earlyrng_state, &digest[sz], sizeof(earlyrng_state));
+ cpu_rng_mode = cpu_rng_detect();
+ if (cpu_rng_mode == CPU_RNG_NONE)
+ return;
+ aprint_normal("cpu_rng: %s\n", cpu_rng_name[cpu_rng_mode]);
+ rndsource_setcb(&cpu_rng_source, cpu_rng_get, NULL);
+ rnd_attach_source(&cpu_rng_source, cpu_rng_name[cpu_rng_mode],
+ RND_TYPE_RNG, RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
}
Index: src/sys/arch/x86/x86/pmap.c
diff -u src/sys/arch/x86/x86/pmap.c:1.384 src/sys/arch/x86/x86/pmap.c:1.385
--- src/sys/arch/x86/x86/pmap.c:1.384 Tue Apr 28 21:35:35 2020
+++ src/sys/arch/x86/x86/pmap.c Thu Apr 30 03:29:20 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.384 2020/04/28 21:35:35 jmcneill Exp $ */
+/* $NetBSD: pmap.c,v 1.385 2020/04/30 03:29:20 riastradh Exp $ */
/*
* Copyright (c) 2008, 2010, 2016, 2017, 2019, 2020 The NetBSD Foundation, Inc.
@@ -130,7 +130,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.384 2020/04/28 21:35:35 jmcneill Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.385 2020/04/30 03:29:20 riastradh Exp $");
#include "opt_user_ldt.h"
#include "opt_lockdebug.h"
@@ -153,6 +153,7 @@ __KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.3
#include <sys/kcore.h>
#include <sys/asan.h>
#include <sys/msan.h>
+#include <sys/entropy.h>
#include <uvm/uvm.h>
#include <uvm/pmap/pmap_pvt.h>
@@ -164,7 +165,6 @@ __KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.3
#include <machine/isa_machdep.h>
#include <machine/cpuvar.h>
#include <machine/cputypes.h>
-#include <machine/cpu_rng.h>
#include <x86/pmap.h>
#include <x86/pmap_pv.h>
@@ -1478,7 +1478,7 @@ slotspace_rand(int type, size_t sz, size
}
/* Select a hole. */
- cpu_earlyrng(&hole, sizeof(hole));
+ entropy_extract(&hole, sizeof(hole), 0);
#ifdef NO_X86_ASLR
hole = 0;
#endif
@@ -1488,7 +1488,7 @@ slotspace_rand(int type, size_t sz, size
startva = VA_SIGN_NEG(startsl * NBPD_L4);
/* Select an area within the hole. */
- cpu_earlyrng(&va, sizeof(va));
+ entropy_extract(&va, sizeof(va), 0);
#ifdef NO_X86_ASLR
va = 0;
#endif
