LinuxLists.cc - [PATCH v3] random: handle archrandom with multiple longs

2022-07-19 14:21:24

Subject: [PATCH v3] random: handle archrandom with multiple longs

The archrandom interface was originally designed for x86, which supplies
RDRAND/RDSEED for receiving random words into registers, resulting in
one function to generate an int and another to generate a long. However,
other architectures don't follow this.

On arm64, the SMCCC TRNG interface can return between 1 and 3 longs. On
s390, the CPACF TRNG interface can return arbitrary amounts, with 32
longs having the same cost as one. On UML, the os_getrandom() interface
can return arbitrary amounts.

So change the api signature to take a "max_longs" parameter designating
the maximum number of longs requested, and then return the number of
longs generated.

Since callers need to check this return value and loop anyway, each arch
implementation does not bother implementing its own loop to try again to
fill the maximum number of longs. Additionally, all existing callers
pass in a constant max_longs parameter. Taken together, these two things
mean that the codegen doesn't really change much for one-word-at-a-time
platforms, while performance is greatly improved on platforms such as
s390.

Cc: Will Deacon <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Johannes Berg <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Harald Freudenberger <[email protected]>
Acked-by: Michael Ellerman <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>
---
arch/arm64/include/asm/archrandom.h | 102 ++++++++++++--------------
arch/arm64/kernel/kaslr.c | 2 +-
arch/powerpc/include/asm/archrandom.h | 30 ++------
arch/powerpc/kvm/book3s_hv.c | 2 +-
arch/s390/include/asm/archrandom.h | 29 ++------
arch/um/include/asm/archrandom.h | 21 ++----
arch/x86/include/asm/archrandom.h | 41 +----------
arch/x86/kernel/espfix_64.c | 2 +-
drivers/char/random.c | 45 ++++++++----
include/asm-generic/archrandom.h | 18 +----
include/linux/random.h | 12 +--
11 files changed, 116 insertions(+), 188 deletions(-)

diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
index c3b9fa56af67..109e2a4454be 100644
--- a/arch/arm64/include/asm/archrandom.h
+++ b/arch/arm64/include/asm/archrandom.h
@@ -58,7 +58,7 @@ static inline bool __arm64_rndrrs(unsigned long *v)
return ok;
}

-static inline bool __must_check arch_get_random_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
/*
* Only support the generic interface after we have detected
@@ -66,27 +66,15 @@ static inline bool __must_check arch_get_random_long(unsigned long *v)
* cpufeature code and with potential scheduling between CPUs
* with and without the feature.
*/
- if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
- return true;
- return false;
+ if (max_longs && cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
+ return 1;
+ return 0;
}

-static inline bool __must_check arch_get_random_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
- if (cpus_have_const_cap(ARM64_HAS_RNG)) {
- unsigned long val;
-
- if (__arm64_rndr(&val)) {
- *v = val;
- return true;
- }
- }
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-{
- struct arm_smccc_res res;
+ if (!max_longs)
+ return 0;

/*
* We prefer the SMCCC call, since its semantics (return actual
@@ -95,10 +83,23 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
* (the output of a pseudo RNG freshly seeded by a TRNG).
*/
if (smccc_trng_available) {
- arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
+ struct arm_smccc_res res;
+
+ max_longs = min_t(size_t, 3, max_longs);
+ arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
if ((int)res.a0 >= 0) {
- *v = res.a3;
- return true;
+ switch (max_longs) {
+ case 3:
+ *v++ = res.a1;
+ fallthrough;
+ case 2:
+ *v++ = res.a2;
+ fallthrough;
+ case 1:
+ *v++ = res.a3;
+ break;
+ }
+ return max_longs;
}
}

@@ -108,32 +109,9 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
* enough to implement this API if no other entropy source exists.
*/
if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))
- return true;
+ return 1;

- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
-{
- struct arm_smccc_res res;
- unsigned long val;
-
- if (smccc_trng_available) {
- arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 32, &res);
- if ((int)res.a0 >= 0) {
- *v = res.a3 & GENMASK(31, 0);
- return true;
- }
- }
-
- if (cpus_have_const_cap(ARM64_HAS_RNG)) {
- if (__arm64_rndrrs(&val)) {
- *v = val;
- return true;
- }
- }
-
- return false;
+ return 0;
}

static inline bool __init __early_cpu_has_rndr(void)
@@ -143,26 +121,40 @@ static inline bool __init __early_cpu_has_rndr(void)
return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;
}

-static inline bool __init __must_check
-arch_get_random_seed_long_early(unsigned long *v)
+static inline size_t __init __must_check
+arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
{
WARN_ON(system_state != SYSTEM_BOOTING);

+ if (!max_longs)
+ return 0;
+
if (smccc_trng_available) {
struct arm_smccc_res res;

- arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
+ max_longs = min_t(size_t, 3, max_longs);
+ arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
if ((int)res.a0 >= 0) {
- *v = res.a3;
- return true;
+ switch (max_longs) {
+ case 3:
+ *v++ = res.a1;
+ fallthrough;
+ case 2:
+ *v++ = res.a2;
+ fallthrough;
+ case 1:
+ *v++ = res.a3;
+ break;
+ }
+ return max_longs;
}
}

if (__early_cpu_has_rndr() && __arm64_rndr(v))
- return true;
+ return 1;

- return false;
+ return 0;
}
-#define arch_get_random_seed_long_early arch_get_random_seed_long_early
+#define arch_get_random_seed_longs_early arch_get_random_seed_longs_early

#endif /* _ASM_ARCHRANDOM_H */
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 418b2bba1521..c5d541f358d3 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -106,7 +106,7 @@ u64 __init kaslr_early_init(void)
* and supported.
*/

- if (arch_get_random_seed_long_early(&raw))
+ if (arch_get_random_seed_longs_early(&raw, 1))
seed ^= raw;

if (!seed) {
diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
index 25ba65df6b1a..0e365c5b2396 100644
--- a/arch/powerpc/include/asm/archrandom.h
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -4,34 +4,16 @@

#include <asm/machdep.h>

-static inline bool __must_check arch_get_random_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
- return false;
+ return 0;
}

-static inline bool __must_check arch_get_random_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-{
- if (ppc_md.get_random_seed)
- return ppc_md.get_random_seed(v);
-
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
-{
- unsigned long val;
- bool rc;
-
- rc = arch_get_random_seed_long(&val);
- if (rc)
- *v = val;
-
- return rc;
+ if (max_longs && ppc_md.get_random_seed && ppc_md.get_random_seed(v))
+ return 1;
+ return 0;
}

#ifdef CONFIG_PPC_POWERNV
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index e08fb3124dca..631062cde6b4 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1207,7 +1207,7 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
break;
#endif
case H_RANDOM:
- if (!arch_get_random_seed_long(&vcpu->arch.regs.gpr[4]))
+ if (!arch_get_random_seed_longs(&vcpu->arch.regs.gpr[4], 1))
ret = H_HARDWARE;
break;
case H_RPT_INVALIDATE:
diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h
index 0a1c2e66c709..cf5e000df0a1 100644
--- a/arch/s390/include/asm/archrandom.h
+++ b/arch/s390/include/asm/archrandom.h
@@ -18,34 +18,19 @@
DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
extern atomic64_t s390_arch_random_counter;

-static inline bool __must_check arch_get_random_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
- return false;
+ return 0;
}

-static inline bool __must_check arch_get_random_int(unsigned int *v)
-{
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-{
- if (static_branch_likely(&s390_arch_random_available)) {
- cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
- atomic64_add(sizeof(*v), &s390_arch_random_counter);
- return true;
- }
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
if (static_branch_likely(&s390_arch_random_available)) {
- cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
- atomic64_add(sizeof(*v), &s390_arch_random_counter);
- return true;
+ cpacf_trng(NULL, 0, (u8 *)v, max_longs * sizeof(*v));
+ atomic64_add(max_longs * sizeof(*v), &s390_arch_random_counter);
+ return max_longs;
}
- return false;
+ return 0;
}

#endif /* _ASM_S390_ARCHRANDOM_H */
diff --git a/arch/um/include/asm/archrandom.h b/arch/um/include/asm/archrandom.h
index 2f24cb96391d..24e16c979c51 100644
--- a/arch/um/include/asm/archrandom.h
+++ b/arch/um/include/asm/archrandom.h
@@ -7,24 +7,19 @@
/* This is from <os.h>, but better not to #include that in a global header here. */
ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);

-static inline bool __must_check arch_get_random_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
- return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
-}
+ ssize_t ret;

-static inline bool __must_check arch_get_random_int(unsigned int *v)
-{
- return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-{
- return false;
+ ret = os_getrandom(v, max_longs * sizeof(*v), 0);
+ if (ret < 0)
+ return 0;
+ return ret / sizeof(*v);
}

-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
- return false;
+ return 0;
}

#endif
diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
index fb235b696175..02bae8e0758b 100644
--- a/arch/x86/include/asm/archrandom.h
+++ b/arch/x86/include/asm/archrandom.h
@@ -31,20 +31,6 @@ static inline bool __must_check rdrand_long(unsigned long *v)
return false;
}

-static inline bool __must_check rdrand_int(unsigned int *v)
-{
- bool ok;
- unsigned int retry = RDRAND_RETRY_LOOPS;
- do {
- asm volatile("rdrand %[out]"
- CC_SET(c)
- : CC_OUT(c) (ok), [out] "=r" (*v));
- if (ok)
- return true;
- } while (--retry);
- return false;
-}
-
static inline bool __must_check rdseed_long(unsigned long *v)
{
bool ok;
@@ -54,38 +40,19 @@ static inline bool __must_check rdseed_long(unsigned long *v)
return ok;
}

-static inline bool __must_check rdseed_int(unsigned int *v)
-{
- bool ok;
- asm volatile("rdseed %[out]"
- CC_SET(c)
- : CC_OUT(c) (ok), [out] "=r" (*v));
- return ok;
-}
-
/*
* These are the generic interfaces; they must not be declared if the
* stubs in <linux/random.h> are to be invoked.
*/

-static inline bool __must_check arch_get_random_long(unsigned long *v)
-{
- return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
-}
-
-static inline bool __must_check arch_get_random_int(unsigned int *v)
-{
- return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
- return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
+ return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
}

-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
- return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
+ return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
}

#ifndef CONFIG_UML
diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
index 4fe7af58cfe1..9417d5aa7305 100644
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -100,7 +100,7 @@ static void init_espfix_random(void)
* This is run before the entropy pools are initialized,
* but this is hopefully better than nothing.
*/
- if (!arch_get_random_long(&rand)) {
+ if (!arch_get_random_longs(&rand, 1)) {
/* The constant is an arbitrary large prime */
rand = rdtsc();
rand *= 0xc345c6b72fd16123UL;
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0c6568ae5f68..7bf11fa66265 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -596,12 +596,20 @@ static void extract_entropy(void *buf, size_t len)
unsigned long rdseed[32 / sizeof(long)];
size_t counter;
} block;
- size_t i;
+ size_t i, longs;

- for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) {
- if (!arch_get_random_seed_long(&block.rdseed[i]) &&
- !arch_get_random_long(&block.rdseed[i]))
- block.rdseed[i] = random_get_entropy();
+ for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
+ longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
+ if (longs) {
+ i += longs;
+ continue;
+ }
+ longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
+ if (longs) {
+ i += longs;
+ continue;
+ }
+ block.rdseed[i++] = random_get_entropy();
}

spin_lock_irqsave(&input_pool.lock, flags);
@@ -776,22 +784,31 @@ static struct notifier_block pm_notifier = { .notifier_call = random_pm_notifica
int __init random_init(const char *command_line)
{
ktime_t now = ktime_get_real();
- unsigned int i, arch_bits;
- unsigned long entropy;
+ size_t i, longs, arch_bits;
+ unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];

#if defined(LATENT_ENTROPY_PLUGIN)
static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
_mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
#endif

- for (i = 0, arch_bits = BLAKE2S_BLOCK_SIZE * 8;
- i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) {
- if (!arch_get_random_seed_long_early(&entropy) &&
- !arch_get_random_long_early(&entropy)) {
- entropy = random_get_entropy();
- arch_bits -= sizeof(entropy) * 8;
+ for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
+ longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
+ if (longs) {
+ _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
+ i += longs;
+ continue;
}
- _mix_pool_bytes(&entropy, sizeof(entropy));
+ longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
+ if (longs) {
+ _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
+ i += longs;
+ continue;
+ }
+ entropy[0] = random_get_entropy();
+ _mix_pool_bytes(entropy, sizeof(*entropy));
+ arch_bits -= sizeof(*entropy) * 8;
+ ++i;
}
_mix_pool_bytes(&now, sizeof(now));
_mix_pool_bytes(utsname(), sizeof(*(utsname())));
diff --git a/include/asm-generic/archrandom.h b/include/asm-generic/archrandom.h
index 3a5ee202dd86..3cd7f980cfdc 100644
--- a/include/asm-generic/archrandom.h
+++ b/include/asm-generic/archrandom.h
@@ -2,24 +2,14 @@
#ifndef __ASM_GENERIC_ARCHRANDOM_H__
#define __ASM_GENERIC_ARCHRANDOM_H__

-static inline bool __must_check arch_get_random_long(unsigned long *v)
+static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
- return false;
+ return 0;
}

-static inline bool __must_check arch_get_random_int(unsigned int *v)
+static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
-{
- return false;
-}
-
-static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
-{
- return false;
+ return 0;
}

#endif
diff --git a/include/linux/random.h b/include/linux/random.h
index 865770e29f3e..3fec206487f6 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -112,19 +112,19 @@ declare_get_random_var_wait(long, unsigned long)
* Called from the boot CPU during startup; not valid to call once
* secondary CPUs are up and preemption is possible.
*/
-#ifndef arch_get_random_seed_long_early
-static inline bool __init arch_get_random_seed_long_early(unsigned long *v)
+#ifndef arch_get_random_seed_longs_early
+static inline size_t __init arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
{
WARN_ON(system_state != SYSTEM_BOOTING);
- return arch_get_random_seed_long(v);
+ return arch_get_random_seed_longs(v, max_longs);
}
#endif

-#ifndef arch_get_random_long_early
-static inline bool __init arch_get_random_long_early(unsigned long *v)
+#ifndef arch_get_random_longs_early
+static inline bool __init arch_get_random_longs_early(unsigned long *v, size_t max_longs)
{
WARN_ON(system_state != SYSTEM_BOOTING);
- return arch_get_random_long(v);
+ return arch_get_random_longs(v, max_longs);
}
#endif

--
2.35.1

2022-07-19 14:52:01

by Mark Rutland

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

On Tue, Jul 19, 2022 at 03:02:07PM +0200, Jason A. Donenfeld wrote:
> The archrandom interface was originally designed for x86, which supplies
> RDRAND/RDSEED for receiving random words into registers, resulting in
> one function to generate an int and another to generate a long. However,
> other architectures don't follow this.
>
> On arm64, the SMCCC TRNG interface can return between 1 and 3 longs. On
> s390, the CPACF TRNG interface can return arbitrary amounts, with 32
> longs having the same cost as one. On UML, the os_getrandom() interface
> can return arbitrary amounts.
>
> So change the api signature to take a "max_longs" parameter designating
> the maximum number of longs requested, and then return the number of
> longs generated.
>
> Since callers need to check this return value and loop anyway, each arch
> implementation does not bother implementing its own loop to try again to
> fill the maximum number of longs. Additionally, all existing callers
> pass in a constant max_longs parameter. Taken together, these two things
> mean that the codegen doesn't really change much for one-word-at-a-time
> platforms, while performance is greatly improved on platforms such as
> s390.
>
> Cc: Will Deacon <[email protected]>
> Cc: Alexander Gordeev <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: H. Peter Anvin <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Heiko Carstens <[email protected]>
> Cc: Johannes Berg <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Harald Freudenberger <[email protected]>
> Acked-by: Michael Ellerman <[email protected]>
> Signed-off-by: Jason A. Donenfeld <[email protected]>

The arm64 bits looks good to me, so FWIW:

Acked-by: Mark Rutland <[email protected]>

Mark.

> ---
> arch/arm64/include/asm/archrandom.h | 102 ++++++++++++--------------
> arch/arm64/kernel/kaslr.c | 2 +-
> arch/powerpc/include/asm/archrandom.h | 30 ++------
> arch/powerpc/kvm/book3s_hv.c | 2 +-
> arch/s390/include/asm/archrandom.h | 29 ++------
> arch/um/include/asm/archrandom.h | 21 ++----
> arch/x86/include/asm/archrandom.h | 41 +----------
> arch/x86/kernel/espfix_64.c | 2 +-
> drivers/char/random.c | 45 ++++++++----
> include/asm-generic/archrandom.h | 18 +----
> include/linux/random.h | 12 +--
> 11 files changed, 116 insertions(+), 188 deletions(-)
>
> diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
> index c3b9fa56af67..109e2a4454be 100644
> --- a/arch/arm64/include/asm/archrandom.h
> +++ b/arch/arm64/include/asm/archrandom.h
> @@ -58,7 +58,7 @@ static inline bool __arm64_rndrrs(unsigned long *v)
> return ok;
> }
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> /*
> * Only support the generic interface after we have detected
> @@ -66,27 +66,15 @@ static inline bool __must_check arch_get_random_long(unsigned long *v)
> * cpufeature code and with potential scheduling between CPUs
> * with and without the feature.
> */
> - if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
> - return true;
> - return false;
> + if (max_longs && cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
> + return 1;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> - if (cpus_have_const_cap(ARM64_HAS_RNG)) {
> - unsigned long val;
> -
> - if (__arm64_rndr(&val)) {
> - *v = val;
> - return true;
> - }
> - }
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> -{
> - struct arm_smccc_res res;
> + if (!max_longs)
> + return 0;
>
> /*
> * We prefer the SMCCC call, since its semantics (return actual
> @@ -95,10 +83,23 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> * (the output of a pseudo RNG freshly seeded by a TRNG).
> */
> if (smccc_trng_available) {
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
> + struct arm_smccc_res res;
> +
> + max_longs = min_t(size_t, 3, max_longs);
> + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
> if ((int)res.a0 >= 0) {
> - *v = res.a3;
> - return true;
> + switch (max_longs) {
> + case 3:
> + *v++ = res.a1;
> + fallthrough;
> + case 2:
> + *v++ = res.a2;
> + fallthrough;
> + case 1:
> + *v++ = res.a3;
> + break;
> + }
> + return max_longs;
> }
> }
>
> @@ -108,32 +109,9 @@ static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> * enough to implement this API if no other entropy source exists.
> */
> if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))
> - return true;
> + return 1;
>
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> -{
> - struct arm_smccc_res res;
> - unsigned long val;
> -
> - if (smccc_trng_available) {
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 32, &res);
> - if ((int)res.a0 >= 0) {
> - *v = res.a3 & GENMASK(31, 0);
> - return true;
> - }
> - }
> -
> - if (cpus_have_const_cap(ARM64_HAS_RNG)) {
> - if (__arm64_rndrrs(&val)) {
> - *v = val;
> - return true;
> - }
> - }
> -
> - return false;
> + return 0;
> }
>
> static inline bool __init __early_cpu_has_rndr(void)
> @@ -143,26 +121,40 @@ static inline bool __init __early_cpu_has_rndr(void)
> return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;
> }
>
> -static inline bool __init __must_check
> -arch_get_random_seed_long_early(unsigned long *v)
> +static inline size_t __init __must_check
> +arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
>
> + if (!max_longs)
> + return 0;
> +
> if (smccc_trng_available) {
> struct arm_smccc_res res;
>
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
> + max_longs = min_t(size_t, 3, max_longs);
> + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
> if ((int)res.a0 >= 0) {
> - *v = res.a3;
> - return true;
> + switch (max_longs) {
> + case 3:
> + *v++ = res.a1;
> + fallthrough;
> + case 2:
> + *v++ = res.a2;
> + fallthrough;
> + case 1:
> + *v++ = res.a3;
> + break;
> + }
> + return max_longs;
> }
> }
>
> if (__early_cpu_has_rndr() && __arm64_rndr(v))
> - return true;
> + return 1;
>
> - return false;
> + return 0;
> }
> -#define arch_get_random_seed_long_early arch_get_random_seed_long_early
> +#define arch_get_random_seed_longs_early arch_get_random_seed_longs_early
>
> #endif /* _ASM_ARCHRANDOM_H */
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index 418b2bba1521..c5d541f358d3 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -106,7 +106,7 @@ u64 __init kaslr_early_init(void)
> * and supported.
> */
>
> - if (arch_get_random_seed_long_early(&raw))
> + if (arch_get_random_seed_longs_early(&raw, 1))
> seed ^= raw;
>
> if (!seed) {
> diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
> index 25ba65df6b1a..0e365c5b2396 100644
> --- a/arch/powerpc/include/asm/archrandom.h
> +++ b/arch/powerpc/include/asm/archrandom.h
> @@ -4,34 +4,16 @@
>
> #include <asm/machdep.h>
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> -{
> - if (ppc_md.get_random_seed)
> - return ppc_md.get_random_seed(v);
> -
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> -{
> - unsigned long val;
> - bool rc;
> -
> - rc = arch_get_random_seed_long(&val);
> - if (rc)
> - *v = val;
> -
> - return rc;
> + if (max_longs && ppc_md.get_random_seed && ppc_md.get_random_seed(v))
> + return 1;
> + return 0;
> }
>
> #ifdef CONFIG_PPC_POWERNV
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index e08fb3124dca..631062cde6b4 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1207,7 +1207,7 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
> break;
> #endif
> case H_RANDOM:
> - if (!arch_get_random_seed_long(&vcpu->arch.regs.gpr[4]))
> + if (!arch_get_random_seed_longs(&vcpu->arch.regs.gpr[4], 1))
> ret = H_HARDWARE;
> break;
> case H_RPT_INVALIDATE:
> diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h
> index 0a1c2e66c709..cf5e000df0a1 100644
> --- a/arch/s390/include/asm/archrandom.h
> +++ b/arch/s390/include/asm/archrandom.h
> @@ -18,34 +18,19 @@
> DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
> extern atomic64_t s390_arch_random_counter;
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> -{
> - if (static_branch_likely(&s390_arch_random_available)) {
> - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
> - atomic64_add(sizeof(*v), &s390_arch_random_counter);
> - return true;
> - }
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> if (static_branch_likely(&s390_arch_random_available)) {
> - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
> - atomic64_add(sizeof(*v), &s390_arch_random_counter);
> - return true;
> + cpacf_trng(NULL, 0, (u8 *)v, max_longs * sizeof(*v));
> + atomic64_add(max_longs * sizeof(*v), &s390_arch_random_counter);
> + return max_longs;
> }
> - return false;
> + return 0;
> }
>
> #endif /* _ASM_S390_ARCHRANDOM_H */
> diff --git a/arch/um/include/asm/archrandom.h b/arch/um/include/asm/archrandom.h
> index 2f24cb96391d..24e16c979c51 100644
> --- a/arch/um/include/asm/archrandom.h
> +++ b/arch/um/include/asm/archrandom.h
> @@ -7,24 +7,19 @@
> /* This is from <os.h>, but better not to #include that in a global header here. */
> ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> - return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
> -}
> + ssize_t ret;
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> -{
> - return false;
> + ret = os_getrandom(v, max_longs * sizeof(*v), 0);
> + if (ret < 0)
> + return 0;
> + return ret / sizeof(*v);
> }
>
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> #endif
> diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
> index fb235b696175..02bae8e0758b 100644
> --- a/arch/x86/include/asm/archrandom.h
> +++ b/arch/x86/include/asm/archrandom.h
> @@ -31,20 +31,6 @@ static inline bool __must_check rdrand_long(unsigned long *v)
> return false;
> }
>
> -static inline bool __must_check rdrand_int(unsigned int *v)
> -{
> - bool ok;
> - unsigned int retry = RDRAND_RETRY_LOOPS;
> - do {
> - asm volatile("rdrand %[out]"
> - CC_SET(c)
> - : CC_OUT(c) (ok), [out] "=r" (*v));
> - if (ok)
> - return true;
> - } while (--retry);
> - return false;
> -}
> -
> static inline bool __must_check rdseed_long(unsigned long *v)
> {
> bool ok;
> @@ -54,38 +40,19 @@ static inline bool __must_check rdseed_long(unsigned long *v)
> return ok;
> }
>
> -static inline bool __must_check rdseed_int(unsigned int *v)
> -{
> - bool ok;
> - asm volatile("rdseed %[out]"
> - CC_SET(c)
> - : CC_OUT(c) (ok), [out] "=r" (*v));
> - return ok;
> -}
> -
> /*
> * These are the generic interfaces; they must not be declared if the
> * stubs in <linux/random.h> are to be invoked.
> */
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> -{
> - return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
> -}
> -
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
> + return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
> }
>
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
> + return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
> }
>
> #ifndef CONFIG_UML
> diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
> index 4fe7af58cfe1..9417d5aa7305 100644
> --- a/arch/x86/kernel/espfix_64.c
> +++ b/arch/x86/kernel/espfix_64.c
> @@ -100,7 +100,7 @@ static void init_espfix_random(void)
> * This is run before the entropy pools are initialized,
> * but this is hopefully better than nothing.
> */
> - if (!arch_get_random_long(&rand)) {
> + if (!arch_get_random_longs(&rand, 1)) {
> /* The constant is an arbitrary large prime */
> rand = rdtsc();
> rand *= 0xc345c6b72fd16123UL;
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 0c6568ae5f68..7bf11fa66265 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -596,12 +596,20 @@ static void extract_entropy(void *buf, size_t len)
> unsigned long rdseed[32 / sizeof(long)];
> size_t counter;
> } block;
> - size_t i;
> + size_t i, longs;
>
> - for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) {
> - if (!arch_get_random_seed_long(&block.rdseed[i]) &&
> - !arch_get_random_long(&block.rdseed[i]))
> - block.rdseed[i] = random_get_entropy();
> + for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
> + longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
> + if (longs) {
> + i += longs;
> + continue;
> + }
> + longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
> + if (longs) {
> + i += longs;
> + continue;
> + }
> + block.rdseed[i++] = random_get_entropy();
> }
>
> spin_lock_irqsave(&input_pool.lock, flags);
> @@ -776,22 +784,31 @@ static struct notifier_block pm_notifier = { .notifier_call = random_pm_notifica
> int __init random_init(const char *command_line)
> {
> ktime_t now = ktime_get_real();
> - unsigned int i, arch_bits;
> - unsigned long entropy;
> + size_t i, longs, arch_bits;
> + unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];
>
> #if defined(LATENT_ENTROPY_PLUGIN)
> static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
> _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
> #endif
>
> - for (i = 0, arch_bits = BLAKE2S_BLOCK_SIZE * 8;
> - i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) {
> - if (!arch_get_random_seed_long_early(&entropy) &&
> - !arch_get_random_long_early(&entropy)) {
> - entropy = random_get_entropy();
> - arch_bits -= sizeof(entropy) * 8;
> + for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
> + longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
> + if (longs) {
> + _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
> + i += longs;
> + continue;
> }
> - _mix_pool_bytes(&entropy, sizeof(entropy));
> + longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
> + if (longs) {
> + _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
> + i += longs;
> + continue;
> + }
> + entropy[0] = random_get_entropy();
> + _mix_pool_bytes(entropy, sizeof(*entropy));
> + arch_bits -= sizeof(*entropy) * 8;
> + ++i;
> }
> _mix_pool_bytes(&now, sizeof(now));
> _mix_pool_bytes(utsname(), sizeof(*(utsname())));
> diff --git a/include/asm-generic/archrandom.h b/include/asm-generic/archrandom.h
> index 3a5ee202dd86..3cd7f980cfdc 100644
> --- a/include/asm-generic/archrandom.h
> +++ b/include/asm-generic/archrandom.h
> @@ -2,24 +2,14 @@
> #ifndef __ASM_GENERIC_ARCHRANDOM_H__
> #define __ASM_GENERIC_ARCHRANDOM_H__
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned long *v)
> -{
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
> -{
> - return false;
> + return 0;
> }
>
> #endif
> diff --git a/include/linux/random.h b/include/linux/random.h
> index 865770e29f3e..3fec206487f6 100644
> --- a/include/linux/random.h
> +++ b/include/linux/random.h
> @@ -112,19 +112,19 @@ declare_get_random_var_wait(long, unsigned long)
> * Called from the boot CPU during startup; not valid to call once
> * secondary CPUs are up and preemption is possible.
> */
> -#ifndef arch_get_random_seed_long_early
> -static inline bool __init arch_get_random_seed_long_early(unsigned long *v)
> +#ifndef arch_get_random_seed_longs_early
> +static inline size_t __init arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
> - return arch_get_random_seed_long(v);
> + return arch_get_random_seed_longs(v, max_longs);
> }
> #endif
>
> -#ifndef arch_get_random_long_early
> -static inline bool __init arch_get_random_long_early(unsigned long *v)
> +#ifndef arch_get_random_longs_early
> +static inline bool __init arch_get_random_longs_early(unsigned long *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
> - return arch_get_random_long(v);
> + return arch_get_random_longs(v, max_longs);
> }
> #endif
>
> --
> 2.35.1
>

2022-07-19 15:02:23

by Catalin Marinas

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

2022-07-22 12:20:52

by Heiko Carstens

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

2022-07-24 23:02:20

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

Hey Borislav (or other x86ers),

On Tue, Jul 19, 2022 at 3:02 PM Jason A. Donenfeld <[email protected]> wrote:
>
> The archrandom interface was originally designed for x86, which supplies
> RDRAND/RDSEED for receiving random words into registers, resulting in
> one function to generate an int and another to generate a long. However,
> other architectures don't follow this.
>
> On arm64, the SMCCC TRNG interface can return between 1 and 3 longs. On
> s390, the CPACF TRNG interface can return arbitrary amounts, with 32
> longs having the same cost as one. On UML, the os_getrandom() interface
> can return arbitrary amounts.
>
> So change the api signature to take a "max_longs" parameter designating
> the maximum number of longs requested, and then return the number of
> longs generated.
>
> Since callers need to check this return value and loop anyway, each arch
> implementation does not bother implementing its own loop to try again to
> fill the maximum number of longs. Additionally, all existing callers
> pass in a constant max_longs parameter. Taken together, these two things
> mean that the codegen doesn't really change much for one-word-at-a-time
> platforms, while performance is greatly improved on platforms such as
> s390.

This patch now has acks from Heiko, Catalin, Mark, and Michael,
covering the arm, ppc, and s390 changes. The changes to s390 and arm
were non-trivial so those acks were quite meaningful. On x86 and ppc,
the code compiles down to basically the same assembly and the change
really doesn't matter at all. Nonetheless, I thought I should give you
a final poke in case you want to ack or nack this, lest I step on the
tip.git of your shoes.

Jason

2022-07-25 09:21:29

by Borislav Petkov

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

On Tue, Jul 19, 2022 at 03:02:07PM +0200, Jason A. Donenfeld wrote:
> Since callers need to check this return value and loop anyway, each arch
> implementation does not bother implementing its own loop to try again to
> fill the maximum number of longs. Additionally, all existing callers
> pass in a constant max_longs parameter.

Hmm, maybe this has come up already but it reads weird.

If I have a function arch_get_random_longs(), I'd expect it to give me
the number of longs I requested or say, error.

Why do the callers need to loop?

If I have to loop, I'd call the "get me one long" function and loop N
times.

--
Regards/Gruss,
Boris.

SUSE Software Solutions Germany GmbH
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman
(HRB 36809, AG Nürnberg)

2022-07-25 09:34:01

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

Hi Boris,

On Mon, Jul 25, 2022 at 11:19:01AM +0200, Borislav Petkov wrote:
> On Tue, Jul 19, 2022 at 03:02:07PM +0200, Jason A. Donenfeld wrote:
> > Since callers need to check this return value and loop anyway, each arch
> > implementation does not bother implementing its own loop to try again to
> > fill the maximum number of longs. Additionally, all existing callers
> > pass in a constant max_longs parameter.
>
> Hmm, maybe this has come up already but it reads weird.
>
> If I have a function arch_get_random_longs(), I'd expect it to give me
> the number of longs I requested or say, error.
>
> Why do the callers need to loop?
>
> If I have to loop, I'd call the "get me one long" function and loop N
> times.

Answered partially in the commit message you quoted and partially here:
https://lore.kernel.org/lkml/[email protected]/

Note that arch_get_random_longs() is not a general purpose function. For
that there used to be get_random_bytes_arch(), but that no longer exists
as people shouldn't be using this stuff directly. arch_get_random_longs()
is a special purpose function mainly intended for use by the RNG itself.

More directly, the reason we don't want to error is because the use case
has fallbacks meant to handle errors. The cascade looks like this
(quoting from the other email):

unsigned long array[whatever];
for (i = 0; i < ARRAY_SIZE(array);) {
longs = arch_get_random_seed_longs(&array[i], ARRAY_SIZE(array) - i);
if (longs) {
i += longs;
continue;
}
longs = arch_get_random_longs(&array[i], ARRAY_SIZE(array) - i);
if (longs) {
i += longs;
continue;
}
array[i++] = random_get_entropy();
}

It tries to get the best that it can as much as it can, but isn't going
to block or do anything too nuts for that.

Anyway, from an x86 perspective, I can't imagine you object to this
change, right? Codegen is the same.

Jason

2022-07-25 09:53:07

by David Laight

[permalink] [raw]

Subject: RE: [PATCH v3] random: handle archrandom with multiple longs

...
> More directly, the reason we don't want to error is because the use case
> has fallbacks meant to handle errors. The cascade looks like this
> (quoting from the other email):
>
> unsigned long array[whatever];
> for (i = 0; i < ARRAY_SIZE(array);) {
> longs = arch_get_random_seed_longs(&array[i], ARRAY_SIZE(array) - i);
> if (longs) {
> i += longs;
> continue;
> }
> longs = arch_get_random_longs(&array[i], ARRAY_SIZE(array) - i);
> if (longs) {
> i += longs;
> continue;
> }
> array[i++] = random_get_entropy();
> }
>
> It tries to get the best that it can as much as it can, but isn't going
> to block or do anything too nuts for that.

Do you really want to retry the earlier calls that returned no data?

David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

2022-07-25 10:09:33

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

On Mon, Jul 25, 2022 at 11:36 AM David Laight <[email protected]> wrote:
>
> ...
> > More directly, the reason we don't want to error is because the use case
> > has fallbacks meant to handle errors. The cascade looks like this
> > (quoting from the other email):
> >
> > unsigned long array[whatever];
> > for (i = 0; i < ARRAY_SIZE(array);) {
> > longs = arch_get_random_seed_longs(&array[i], ARRAY_SIZE(array) - i);
> > if (longs) {
> > i += longs;
> > continue;
> > }
> > longs = arch_get_random_longs(&array[i], ARRAY_SIZE(array) - i);
> > if (longs) {
> > i += longs;
> > continue;
> > }
> > array[i++] = random_get_entropy();
> > }
> >
> > It tries to get the best that it can as much as it can, but isn't going
> > to block or do anything too nuts for that.
>
> Do you really want to retry the earlier calls that returned no data?

Does the above code do that?

2022-07-25 12:03:49

by Borislav Petkov

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

2022-07-25 12:03:55

by Jason A. Donenfeld

[permalink] [raw]

Subject: [PATCH] random: discourage use of archrandom outside of rng

Borislav pointed out during the review of "random: handle archrandom
with multiple longs" that people might actually use this function, which
might not be good because the function has surprising semantics. This of
course was also the case before that patch, and indeed RDSEED-like
functions across architectures often behave surprisingly, failing often.
While random.c has been written specifically to work with that behavior,
not much else is well equipped for that.

So add a comment suggesting that this is not for general consumption.
Fortunately, nobody uses this for general consumption anyway, and people
who try quickly find themselves in trouble. But adding this comment out
of an abundance of caution was nonetheless suggested, and it at least
means there will be easier justification for cleaning up potential
misuses of the function later.

Cc: Borislav Petkov <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Johannes Berg <[email protected]>
Suggested-by: Borislav Petkov <[email protected]>
Signed-off-by: Jason A. Donenfeld <[email protected]>
---
arch/arm64/include/asm/archrandom.h | 13 +++++++++++++
arch/powerpc/include/asm/archrandom.h | 8 ++++++++
arch/s390/include/asm/archrandom.h | 8 ++++++++
arch/um/include/asm/archrandom.h | 8 ++++++++
arch/x86/include/asm/archrandom.h | 9 ++++++---
include/asm-generic/archrandom.h | 8 ++++++++
6 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
index 109e2a4454be..0b5ee0e12a13 100644
--- a/arch/arm64/include/asm/archrandom.h
+++ b/arch/arm64/include/asm/archrandom.h
@@ -58,6 +58,10 @@ static inline bool __arm64_rndrrs(unsigned long *v)
return ok;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
/*
@@ -71,6 +75,10 @@ static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t
return 0;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
if (!max_longs)
@@ -121,6 +129,11 @@ static inline bool __init __early_cpu_has_rndr(void)
return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;
}

+
+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __init __must_check
arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
{
diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
index 0e365c5b2396..7accfe346d49 100644
--- a/arch/powerpc/include/asm/archrandom.h
+++ b/arch/powerpc/include/asm/archrandom.h
@@ -4,11 +4,19 @@

#include <asm/machdep.h>

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
return 0;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
if (max_longs && ppc_md.get_random_seed && ppc_md.get_random_seed(v))
diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h
index cf5e000df0a1..ae1efdd6f3a9 100644
--- a/arch/s390/include/asm/archrandom.h
+++ b/arch/s390/include/asm/archrandom.h
@@ -18,11 +18,19 @@
DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
extern atomic64_t s390_arch_random_counter;

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
return 0;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
if (static_branch_likely(&s390_arch_random_available)) {
diff --git a/arch/um/include/asm/archrandom.h b/arch/um/include/asm/archrandom.h
index 24e16c979c51..d2b20bb0ed53 100644
--- a/arch/um/include/asm/archrandom.h
+++ b/arch/um/include/asm/archrandom.h
@@ -7,6 +7,10 @@
/* This is from <os.h>, but better not to #include that in a global header here. */
ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
ssize_t ret;
@@ -17,6 +21,10 @@ static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t
return ret / sizeof(*v);
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
return 0;
diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
index 02bae8e0758b..8352948e6412 100644
--- a/arch/x86/include/asm/archrandom.h
+++ b/arch/x86/include/asm/archrandom.h
@@ -41,15 +41,18 @@ static inline bool __must_check rdseed_long(unsigned long *v)
}

/*
- * These are the generic interfaces; they must not be declared if the
- * stubs in <linux/random.h> are to be invoked.
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
*/
-
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
diff --git a/include/asm-generic/archrandom.h b/include/asm-generic/archrandom.h
index 3cd7f980cfdc..800b41639dd7 100644
--- a/include/asm-generic/archrandom.h
+++ b/include/asm-generic/archrandom.h
@@ -2,11 +2,19 @@
#ifndef __ASM_GENERIC_ARCHRANDOM_H__
#define __ASM_GENERIC_ARCHRANDOM_H__

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
{
return 0;
}

+/*
+ * This should only be used by drivers/char/random.c. Other drivers *must*
+ * use get_random_bytes() instead.
+ */
static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
{
return 0;
--
2.35.1

2022-07-25 13:09:59

by Mark Rutland

[permalink] [raw]

Subject: Re: [PATCH] random: discourage use of archrandom outside of rng

On Mon, Jul 25, 2022 at 01:10:38PM +0200, Jason A. Donenfeld wrote:
> Borislav pointed out during the review of "random: handle archrandom
> with multiple longs" that people might actually use this function, which
> might not be good because the function has surprising semantics. This of
> course was also the case before that patch, and indeed RDSEED-like
> functions across architectures often behave surprisingly, failing often.
> While random.c has been written specifically to work with that behavior,
> not much else is well equipped for that.
>
> So add a comment suggesting that this is not for general consumption.
> Fortunately, nobody uses this for general consumption anyway, and people
> who try quickly find themselves in trouble. But adding this comment out
> of an abundance of caution was nonetheless suggested, and it at least
> means there will be easier justification for cleaning up potential
> misuses of the function later.
>
> Cc: Borislav Petkov <[email protected]>
> Cc: Heiko Carstens <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Michael Ellerman <[email protected]>
> Cc: Johannes Berg <[email protected]>
> Suggested-by: Borislav Petkov <[email protected]>
> Signed-off-by: Jason A. Donenfeld <[email protected]>

FWIW:

Acked-by: Mark Rutland <[email protected]>

Mark.

> ---
> arch/arm64/include/asm/archrandom.h | 13 +++++++++++++
> arch/powerpc/include/asm/archrandom.h | 8 ++++++++
> arch/s390/include/asm/archrandom.h | 8 ++++++++
> arch/um/include/asm/archrandom.h | 8 ++++++++
> arch/x86/include/asm/archrandom.h | 9 ++++++---
> include/asm-generic/archrandom.h | 8 ++++++++
> 6 files changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h
> index 109e2a4454be..0b5ee0e12a13 100644
> --- a/arch/arm64/include/asm/archrandom.h
> +++ b/arch/arm64/include/asm/archrandom.h
> @@ -58,6 +58,10 @@ static inline bool __arm64_rndrrs(unsigned long *v)
> return ok;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> /*
> @@ -71,6 +75,10 @@ static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t
> return 0;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> if (!max_longs)
> @@ -121,6 +129,11 @@ static inline bool __init __early_cpu_has_rndr(void)
> return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;
> }
>
> +
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __init __must_check
> arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
> {
> diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h
> index 0e365c5b2396..7accfe346d49 100644
> --- a/arch/powerpc/include/asm/archrandom.h
> +++ b/arch/powerpc/include/asm/archrandom.h
> @@ -4,11 +4,19 @@
>
> #include <asm/machdep.h>
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> return 0;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> if (max_longs && ppc_md.get_random_seed && ppc_md.get_random_seed(v))
> diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h
> index cf5e000df0a1..ae1efdd6f3a9 100644
> --- a/arch/s390/include/asm/archrandom.h
> +++ b/arch/s390/include/asm/archrandom.h
> @@ -18,11 +18,19 @@
> DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
> extern atomic64_t s390_arch_random_counter;
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> return 0;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> if (static_branch_likely(&s390_arch_random_available)) {
> diff --git a/arch/um/include/asm/archrandom.h b/arch/um/include/asm/archrandom.h
> index 24e16c979c51..d2b20bb0ed53 100644
> --- a/arch/um/include/asm/archrandom.h
> +++ b/arch/um/include/asm/archrandom.h
> @@ -7,6 +7,10 @@
> /* This is from <os.h>, but better not to #include that in a global header here. */
> ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> ssize_t ret;
> @@ -17,6 +21,10 @@ static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t
> return ret / sizeof(*v);
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> return 0;
> diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h
> index 02bae8e0758b..8352948e6412 100644
> --- a/arch/x86/include/asm/archrandom.h
> +++ b/arch/x86/include/asm/archrandom.h
> @@ -41,15 +41,18 @@ static inline bool __must_check rdseed_long(unsigned long *v)
> }
>
> /*
> - * These are the generic interfaces; they must not be declared if the
> - * stubs in <linux/random.h> are to be invoked.
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> */
> -
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> return max_longs && static_cpu_has(X86_FEATURE_RDRAND) && rdrand_long(v) ? 1 : 0;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> return max_longs && static_cpu_has(X86_FEATURE_RDSEED) && rdseed_long(v) ? 1 : 0;
> diff --git a/include/asm-generic/archrandom.h b/include/asm-generic/archrandom.h
> index 3cd7f980cfdc..800b41639dd7 100644
> --- a/include/asm-generic/archrandom.h
> +++ b/include/asm-generic/archrandom.h
> @@ -2,11 +2,19 @@
> #ifndef __ASM_GENERIC_ARCHRANDOM_H__
> #define __ASM_GENERIC_ARCHRANDOM_H__
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_longs(unsigned long *v, size_t max_longs)
> {
> return 0;
> }
>
> +/*
> + * This should only be used by drivers/char/random.c. Other drivers *must*
> + * use get_random_bytes() instead.
> + */
> static inline size_t __must_check arch_get_random_seed_longs(unsigned long *v, size_t max_longs)
> {
> return 0;
> --
> 2.35.1
>

2022-08-01 15:17:25

by Harald Freudenberger

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

On 2022-07-19 15:02, Jason A. Donenfeld wrote:
> The archrandom interface was originally designed for x86, which
> supplies
> RDRAND/RDSEED for receiving random words into registers, resulting in
> one function to generate an int and another to generate a long.
> However,
> other architectures don't follow this.
>
> On arm64, the SMCCC TRNG interface can return between 1 and 3 longs. On
> s390, the CPACF TRNG interface can return arbitrary amounts, with 32
> longs having the same cost as one. On UML, the os_getrandom() interface
> can return arbitrary amounts.
>
> So change the api signature to take a "max_longs" parameter designating
> the maximum number of longs requested, and then return the number of
> longs generated.
>
> Since callers need to check this return value and loop anyway, each
> arch
> implementation does not bother implementing its own loop to try again
> to
> fill the maximum number of longs. Additionally, all existing callers
> pass in a constant max_longs parameter. Taken together, these two
> things
> mean that the codegen doesn't really change much for one-word-at-a-time
> platforms, while performance is greatly improved on platforms such as
> s390.
>
> Cc: Will Deacon <[email protected]>
> Cc: Alexander Gordeev <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: H. Peter Anvin <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Heiko Carstens <[email protected]>
> Cc: Johannes Berg <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Cc: Harald Freudenberger <[email protected]>
> Acked-by: Michael Ellerman <[email protected]>
> Signed-off-by: Jason A. Donenfeld <[email protected]>
> ---
> arch/arm64/include/asm/archrandom.h | 102 ++++++++++++--------------
> arch/arm64/kernel/kaslr.c | 2 +-
> arch/powerpc/include/asm/archrandom.h | 30 ++------
> arch/powerpc/kvm/book3s_hv.c | 2 +-
> arch/s390/include/asm/archrandom.h | 29 ++------
> arch/um/include/asm/archrandom.h | 21 ++----
> arch/x86/include/asm/archrandom.h | 41 +----------
> arch/x86/kernel/espfix_64.c | 2 +-
> drivers/char/random.c | 45 ++++++++----
> include/asm-generic/archrandom.h | 18 +----
> include/linux/random.h | 12 +--
> 11 files changed, 116 insertions(+), 188 deletions(-)
>
> diff --git a/arch/arm64/include/asm/archrandom.h
> b/arch/arm64/include/asm/archrandom.h
> index c3b9fa56af67..109e2a4454be 100644
> --- a/arch/arm64/include/asm/archrandom.h
> +++ b/arch/arm64/include/asm/archrandom.h
> @@ -58,7 +58,7 @@ static inline bool __arm64_rndrrs(unsigned long *v)
> return ok;
> }
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> /*
> * Only support the generic interface after we have detected
> @@ -66,27 +66,15 @@ static inline bool __must_check
> arch_get_random_long(unsigned long *v)
> * cpufeature code and with potential scheduling between CPUs
> * with and without the feature.
> */
> - if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndr(v))
> - return true;
> - return false;
> + if (max_longs && cpus_have_const_cap(ARM64_HAS_RNG) &&
> __arm64_rndr(v))
> + return 1;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> - if (cpus_have_const_cap(ARM64_HAS_RNG)) {
> - unsigned long val;
> -
> - if (__arm64_rndr(&val)) {
> - *v = val;
> - return true;
> - }
> - }
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> -{
> - struct arm_smccc_res res;
> + if (!max_longs)
> + return 0;
>
> /*
> * We prefer the SMCCC call, since its semantics (return actual
> @@ -95,10 +83,23 @@ static inline bool __must_check
> arch_get_random_seed_long(unsigned long *v)
> * (the output of a pseudo RNG freshly seeded by a TRNG).
> */
> if (smccc_trng_available) {
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
> + struct arm_smccc_res res;
> +
> + max_longs = min_t(size_t, 3, max_longs);
> + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
> if ((int)res.a0 >= 0) {
> - *v = res.a3;
> - return true;
> + switch (max_longs) {
> + case 3:
> + *v++ = res.a1;
> + fallthrough;
> + case 2:
> + *v++ = res.a2;
> + fallthrough;
> + case 1:
> + *v++ = res.a3;
> + break;
> + }
> + return max_longs;
> }
> }
>
> @@ -108,32 +109,9 @@ static inline bool __must_check
> arch_get_random_seed_long(unsigned long *v)
> * enough to implement this API if no other entropy source exists.
> */
> if (cpus_have_const_cap(ARM64_HAS_RNG) && __arm64_rndrrs(v))
> - return true;
> + return 1;
>
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> -{
> - struct arm_smccc_res res;
> - unsigned long val;
> -
> - if (smccc_trng_available) {
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 32, &res);
> - if ((int)res.a0 >= 0) {
> - *v = res.a3 & GENMASK(31, 0);
> - return true;
> - }
> - }
> -
> - if (cpus_have_const_cap(ARM64_HAS_RNG)) {
> - if (__arm64_rndrrs(&val)) {
> - *v = val;
> - return true;
> - }
> - }
> -
> - return false;
> + return 0;
> }
>
> static inline bool __init __early_cpu_has_rndr(void)
> @@ -143,26 +121,40 @@ static inline bool __init
> __early_cpu_has_rndr(void)
> return (ftr >> ID_AA64ISAR0_EL1_RNDR_SHIFT) & 0xf;
> }
>
> -static inline bool __init __must_check
> -arch_get_random_seed_long_early(unsigned long *v)
> +static inline size_t __init __must_check
> +arch_get_random_seed_longs_early(unsigned long *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
>
> + if (!max_longs)
> + return 0;
> +
> if (smccc_trng_available) {
> struct arm_smccc_res res;
>
> - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res);
> + max_longs = min_t(size_t, 3, max_longs);
> + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, max_longs * 64, &res);
> if ((int)res.a0 >= 0) {
> - *v = res.a3;
> - return true;
> + switch (max_longs) {
> + case 3:
> + *v++ = res.a1;
> + fallthrough;
> + case 2:
> + *v++ = res.a2;
> + fallthrough;
> + case 1:
> + *v++ = res.a3;
> + break;
> + }
> + return max_longs;
> }
> }
>
> if (__early_cpu_has_rndr() && __arm64_rndr(v))
> - return true;
> + return 1;
>
> - return false;
> + return 0;
> }
> -#define arch_get_random_seed_long_early
> arch_get_random_seed_long_early
> +#define arch_get_random_seed_longs_early
> arch_get_random_seed_longs_early
>
> #endif /* _ASM_ARCHRANDOM_H */
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index 418b2bba1521..c5d541f358d3 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -106,7 +106,7 @@ u64 __init kaslr_early_init(void)
> * and supported.
> */
>
> - if (arch_get_random_seed_long_early(&raw))
> + if (arch_get_random_seed_longs_early(&raw, 1))
> seed ^= raw;
>
> if (!seed) {
> diff --git a/arch/powerpc/include/asm/archrandom.h
> b/arch/powerpc/include/asm/archrandom.h
> index 25ba65df6b1a..0e365c5b2396 100644
> --- a/arch/powerpc/include/asm/archrandom.h
> +++ b/arch/powerpc/include/asm/archrandom.h
> @@ -4,34 +4,16 @@
>
> #include <asm/machdep.h>
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> -{
> - if (ppc_md.get_random_seed)
> - return ppc_md.get_random_seed(v);
> -
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> -{
> - unsigned long val;
> - bool rc;
> -
> - rc = arch_get_random_seed_long(&val);
> - if (rc)
> - *v = val;
> -
> - return rc;
> + if (max_longs && ppc_md.get_random_seed && ppc_md.get_random_seed(v))
> + return 1;
> + return 0;
> }
>
> #ifdef CONFIG_PPC_POWERNV
> diff --git a/arch/powerpc/kvm/book3s_hv.c
> b/arch/powerpc/kvm/book3s_hv.c
> index e08fb3124dca..631062cde6b4 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -1207,7 +1207,7 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu
> *vcpu)
> break;
> #endif
> case H_RANDOM:
> - if (!arch_get_random_seed_long(&vcpu->arch.regs.gpr[4]))
> + if (!arch_get_random_seed_longs(&vcpu->arch.regs.gpr[4], 1))
> ret = H_HARDWARE;
> break;
> case H_RPT_INVALIDATE:
> diff --git a/arch/s390/include/asm/archrandom.h
> b/arch/s390/include/asm/archrandom.h
> index 0a1c2e66c709..cf5e000df0a1 100644
> --- a/arch/s390/include/asm/archrandom.h
> +++ b/arch/s390/include/asm/archrandom.h
> @@ -18,34 +18,19 @@
> DECLARE_STATIC_KEY_FALSE(s390_arch_random_available);
> extern atomic64_t s390_arch_random_counter;
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> -{
> - if (static_branch_likely(&s390_arch_random_available)) {
> - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
> - atomic64_add(sizeof(*v), &s390_arch_random_counter);
> - return true;
> - }
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> if (static_branch_likely(&s390_arch_random_available)) {
> - cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v));
> - atomic64_add(sizeof(*v), &s390_arch_random_counter);
> - return true;
> + cpacf_trng(NULL, 0, (u8 *)v, max_longs * sizeof(*v));
> + atomic64_add(max_longs * sizeof(*v), &s390_arch_random_counter);
> + return max_longs;
> }
> - return false;
> + return 0;
> }
>
> #endif /* _ASM_S390_ARCHRANDOM_H */
> diff --git a/arch/um/include/asm/archrandom.h
> b/arch/um/include/asm/archrandom.h
> index 2f24cb96391d..24e16c979c51 100644
> --- a/arch/um/include/asm/archrandom.h
> +++ b/arch/um/include/asm/archrandom.h
> @@ -7,24 +7,19 @@
> /* This is from <os.h>, but better not to #include that in a global
> header here. */
> ssize_t os_getrandom(void *buf, size_t len, unsigned int flags);
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> - return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
> -}
> + ssize_t ret;
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return os_getrandom(v, sizeof(*v), 0) == sizeof(*v);
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> -{
> - return false;
> + ret = os_getrandom(v, max_longs * sizeof(*v), 0);
> + if (ret < 0)
> + return 0;
> + return ret / sizeof(*v);
> }
>
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> #endif
> diff --git a/arch/x86/include/asm/archrandom.h
> b/arch/x86/include/asm/archrandom.h
> index fb235b696175..02bae8e0758b 100644
> --- a/arch/x86/include/asm/archrandom.h
> +++ b/arch/x86/include/asm/archrandom.h
> @@ -31,20 +31,6 @@ static inline bool __must_check rdrand_long(unsigned
> long *v)
> return false;
> }
>
> -static inline bool __must_check rdrand_int(unsigned int *v)
> -{
> - bool ok;
> - unsigned int retry = RDRAND_RETRY_LOOPS;
> - do {
> - asm volatile("rdrand %[out]"
> - CC_SET(c)
> - : CC_OUT(c) (ok), [out] "=r" (*v));
> - if (ok)
> - return true;
> - } while (--retry);
> - return false;
> -}
> -
> static inline bool __must_check rdseed_long(unsigned long *v)
> {
> bool ok;
> @@ -54,38 +40,19 @@ static inline bool __must_check
> rdseed_long(unsigned long *v)
> return ok;
> }
>
> -static inline bool __must_check rdseed_int(unsigned int *v)
> -{
> - bool ok;
> - asm volatile("rdseed %[out]"
> - CC_SET(c)
> - : CC_OUT(c) (ok), [out] "=r" (*v));
> - return ok;
> -}
> -
> /*
> * These are the generic interfaces; they must not be declared if the
> * stubs in <linux/random.h> are to be invoked.
> */
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> -{
> - return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_long(v) : false;
> -}
> -
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> -{
> - return static_cpu_has(X86_FEATURE_RDRAND) ? rdrand_int(v) : false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false;
> + return max_longs && static_cpu_has(X86_FEATURE_RDRAND) &&
> rdrand_long(v) ? 1 : 0;
> }
>
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
> + return max_longs && static_cpu_has(X86_FEATURE_RDSEED) &&
> rdseed_long(v) ? 1 : 0;
> }
>
> #ifndef CONFIG_UML
> diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
> index 4fe7af58cfe1..9417d5aa7305 100644
> --- a/arch/x86/kernel/espfix_64.c
> +++ b/arch/x86/kernel/espfix_64.c
> @@ -100,7 +100,7 @@ static void init_espfix_random(void)
> * This is run before the entropy pools are initialized,
> * but this is hopefully better than nothing.
> */
> - if (!arch_get_random_long(&rand)) {
> + if (!arch_get_random_longs(&rand, 1)) {
> /* The constant is an arbitrary large prime */
> rand = rdtsc();
> rand *= 0xc345c6b72fd16123UL;
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 0c6568ae5f68..7bf11fa66265 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -596,12 +596,20 @@ static void extract_entropy(void *buf, size_t
> len)
> unsigned long rdseed[32 / sizeof(long)];
> size_t counter;
> } block;
> - size_t i;
> + size_t i, longs;
>
> - for (i = 0; i < ARRAY_SIZE(block.rdseed); ++i) {
> - if (!arch_get_random_seed_long(&block.rdseed[i]) &&
> - !arch_get_random_long(&block.rdseed[i]))
> - block.rdseed[i] = random_get_entropy();
> + for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
> + longs = arch_get_random_seed_longs(&block.rdseed[i],
> ARRAY_SIZE(block.rdseed) - i);
> + if (longs) {
> + i += longs;
> + continue;
> + }
> + longs = arch_get_random_longs(&block.rdseed[i],
> ARRAY_SIZE(block.rdseed) - i);
> + if (longs) {
> + i += longs;
> + continue;
> + }
> + block.rdseed[i++] = random_get_entropy();
> }
>
> spin_lock_irqsave(&input_pool.lock, flags);
> @@ -776,22 +784,31 @@ static struct notifier_block pm_notifier = {
> .notifier_call = random_pm_notifica
> int __init random_init(const char *command_line)
> {
> ktime_t now = ktime_get_real();
> - unsigned int i, arch_bits;
> - unsigned long entropy;
> + size_t i, longs, arch_bits;
> + unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];
>
> #if defined(LATENT_ENTROPY_PLUGIN)
> static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst
> __latent_entropy;
> _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
> #endif
>
> - for (i = 0, arch_bits = BLAKE2S_BLOCK_SIZE * 8;
> - i < BLAKE2S_BLOCK_SIZE; i += sizeof(entropy)) {
> - if (!arch_get_random_seed_long_early(&entropy) &&
> - !arch_get_random_long_early(&entropy)) {
> - entropy = random_get_entropy();
> - arch_bits -= sizeof(entropy) * 8;
> + for (i = 0, arch_bits = sizeof(entropy) * 8; i <
> ARRAY_SIZE(entropy);) {
> + longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) -
> i);
> + if (longs) {
> + _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
> + i += longs;
> + continue;
> }
> - _mix_pool_bytes(&entropy, sizeof(entropy));
> + longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
> + if (longs) {
> + _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
> + i += longs;
> + continue;
> + }
> + entropy[0] = random_get_entropy();
> + _mix_pool_bytes(entropy, sizeof(*entropy));
> + arch_bits -= sizeof(*entropy) * 8;
> + ++i;
> }
> _mix_pool_bytes(&now, sizeof(now));
> _mix_pool_bytes(utsname(), sizeof(*(utsname())));
> diff --git a/include/asm-generic/archrandom.h
> b/include/asm-generic/archrandom.h
> index 3a5ee202dd86..3cd7f980cfdc 100644
> --- a/include/asm-generic/archrandom.h
> +++ b/include/asm-generic/archrandom.h
> @@ -2,24 +2,14 @@
> #ifndef __ASM_GENERIC_ARCHRANDOM_H__
> #define __ASM_GENERIC_ARCHRANDOM_H__
>
> -static inline bool __must_check arch_get_random_long(unsigned long *v)
> +static inline size_t __must_check arch_get_random_longs(unsigned long
> *v, size_t max_longs)
> {
> - return false;
> + return 0;
> }
>
> -static inline bool __must_check arch_get_random_int(unsigned int *v)
> +static inline size_t __must_check arch_get_random_seed_longs(unsigned
> long *v, size_t max_longs)
> {
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_long(unsigned
> long *v)
> -{
> - return false;
> -}
> -
> -static inline bool __must_check arch_get_random_seed_int(unsigned int
> *v)
> -{
> - return false;
> + return 0;
> }
>
> #endif
> diff --git a/include/linux/random.h b/include/linux/random.h
> index 865770e29f3e..3fec206487f6 100644
> --- a/include/linux/random.h
> +++ b/include/linux/random.h
> @@ -112,19 +112,19 @@ declare_get_random_var_wait(long, unsigned long)
> * Called from the boot CPU during startup; not valid to call once
> * secondary CPUs are up and preemption is possible.
> */
> -#ifndef arch_get_random_seed_long_early
> -static inline bool __init arch_get_random_seed_long_early(unsigned
> long *v)
> +#ifndef arch_get_random_seed_longs_early
> +static inline size_t __init arch_get_random_seed_longs_early(unsigned
> long *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
> - return arch_get_random_seed_long(v);
> + return arch_get_random_seed_longs(v, max_longs);
> }
> #endif
>
> -#ifndef arch_get_random_long_early
> -static inline bool __init arch_get_random_long_early(unsigned long *v)
> +#ifndef arch_get_random_longs_early
> +static inline bool __init arch_get_random_longs_early(unsigned long
> *v, size_t max_longs)
> {
> WARN_ON(system_state != SYSTEM_BOOTING);
> - return arch_get_random_long(v);
> + return arch_get_random_longs(v, max_longs);
> }
> #endif

Nice interface :-)
Here is my
Acked-by: Harald Freudenberger <[email protected]>
but please keep in mind that your patch does not apply cleanly as there
is my other patch
918e75f77af7 ("s390/archrandom: prevent CPACF trng invocations in
interrupt context")
in between.
Thanks for your work
Harald

2022-08-01 15:17:56

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3] random: handle archrandom with multiple longs

Hi Harald,

On Mon, Aug 1, 2022 at 4:47 PM Harald Freudenberger
<[email protected]> wrote:
>
> Nice interface :-)
> Here is my
> Acked-by: Harald Freudenberger <[email protected]>

You're too late; I already sent in my pull request. But that's okay; I
received Heiko's ack on this for s390.

> but please keep in mind that your patch does not apply cleanly as there
> is my other patch
> 918e75f77af7 ("s390/archrandom: prevent CPACF trng invocations in
> interrupt context")
> in between.

Yea, this was a late addition to 5.19, and my random tree was based on
an earlier rc of 5.19. That kind of thing happens and is fine; Stephen
caught it when doing the next merge and carries the merge conflict
resolution there. I mentioned it to Linus in my pull, so he'll be able
to work it out.

Jason