| Message ID | 20220717200356.75060-1-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] random: handle archrandom in plural words | expand |
"Jason A. Donenfeld" <Jason@zx2c4.com> writes: > 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 words. On > s390, the CPACF TRNG interface can return between 1 and 32 words for the > same cost as for one word. On UML, the os_getrandom() interface can return > arbitrary amounts. > > So change the api signature to take a "words" parameter designating the > maximum number of words requested, and then return the number of words > generated. On powerpc a word is 32-bits and a doubleword is 64-bits (at least according to the ISA). I think that's also true on other 64-bit architectures. You could avoid any confusion by defining the API in terms of "longs" rather than "words". But that's just a comment, see what others think. > arch/powerpc/include/asm/archrandom.h | 30 ++------ > arch/powerpc/kvm/book3s_hv.c | 2 +- Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) cheers
On Mon, Jul 18, 2022 at 04:31:11PM +1000, Michael Ellerman wrote: > "Jason A. Donenfeld" <Jason@zx2c4.com> writes: > > 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 words. On > > s390, the CPACF TRNG interface can return between 1 and 32 words for the > > same cost as for one word. On UML, the os_getrandom() interface can return > > arbitrary amounts. > > > > So change the api signature to take a "words" parameter designating the > > maximum number of words requested, and then return the number of words > > generated. > > On powerpc a word is 32-bits and a doubleword is 64-bits (at least > according to the ISA). I think that's also true on other 64-bit > architectures. IIRC, this is (or was) not the case on Alpha, where word was defined as 16 bits. All assembly mnemonics had w for 16 bits, l for 32 bits, and q for 64 bits. Blame the PDP-11... Gabriel > > You could avoid any confusion by defining the API in terms of "longs" > rather than "words". > > But that's just a comment, see what others think. > > > arch/powerpc/include/asm/archrandom.h | 30 ++------ > > arch/powerpc/kvm/book3s_hv.c | 2 +- > > Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) > > cheers
On Sun, Jul 17, 2022 at 10:03:56PM +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 words. On > s390, the CPACF TRNG interface can return between 1 and 32 words for the > same cost as for one word. On UML, the os_getrandom() interface can return > arbitrary amounts. > > So change the api signature to take a "words" parameter designating the > maximum number of words requested, and then return the number of words > 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 requested number of words. Additionally, all existing callers > pass in a constant words 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 <will@kernel.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Alexander Gordeev <agordeev@linux.ibm.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: H. Peter Anvin <hpa@zytor.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Heiko Carstens <hca@linux.ibm.com> > Cc: Johannes Berg <johannes@sipsolutions.net> > Cc: Harald Freudenberger <freude@linux.ibm.com> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > 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..7a24fdee3e2f 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_words(unsigned long *v, size_t words) As others have suggested, could we please s/words/longs/? That's a smaller change from the existing name, and avoids amibugity were "word" has an architecture-specific meaning. e.g. the ARM ARM (ARM DDI 0487G.b) defines: Word A 32-bit data item. Words are normally word-aligned in Arm systems. > { > /* > * 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 (words && 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_words(unsigned long *v, size_t words) Likewise, s/words/longs/ woudl be clearer. > { > - 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 (!words) > + 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; > + > + words = min_t(size_t, 3, words); > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); > if ((int)res.a0 >= 0) { > - *v = res.a3; > - return true; > + switch (words) { > + case 3: > + *v++ = res.a1; > + fallthrough; > + case 2: > + *v++ = res.a2; > + fallthrough; > + case 1: > + *v++ = res.a3; > + break; > + } > + return words; > } > } > > @@ -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_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > > + if (!words) > + return 0; > + > if (smccc_trng_available) { > struct arm_smccc_res res; > > - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res); > + words = min_t(size_t, 3, words); > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); > if ((int)res.a0 >= 0) { > - *v = res.a3; > - return true; > + switch (words) { > + case 3: > + *v++ = res.a1; > + fallthrough; > + case 2: > + *v++ = res.a2; > + fallthrough; > + case 1: > + *v++ = res.a3; > + break; > + } > + return words; > } > } > > 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_words_early arch_get_random_seed_words_early > > #endif /* _ASM_ARCHRANDOM_H */ > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c > index 418b2bba1521..ed77afe16121 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_words_early(&raw, 1)) > seed ^= raw; > > if (!seed) { FWIW, other than the naming nits, the arm64 bits look fine to me. Mark. > diff --git a/arch/powerpc/include/asm/archrandom.h b/arch/powerpc/include/asm/archrandom.h > index 25ba65df6b1a..bf2182f80480 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > - 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 (words && 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..18b2d80996b6 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_words(&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..29f1a9bc3867 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > 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, words * sizeof(*v)); > + atomic64_add(words * sizeof(*v), &s390_arch_random_counter); > + return words; > } > - 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..6bcbd47fcb62 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_words(unsigned long *v, size_t words) > { > - 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, words * 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_words(unsigned long *v, size_t words) > { > - return false; > + return 0; > } > > #endif > diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h > index fb235b696175..a1717b81d876 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_words(unsigned long *v, size_t words) > { > - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false; > + return words && 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_words(unsigned long *v, size_t words) > { > - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false; > + return words && 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..f46c9ff3c0d4 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_words(&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..70d8d1d7e2d7 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, words; > > - 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);) { > + words = arch_get_random_seed_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); > + if (words) { > + i += words; > + continue; > + } > + words = arch_get_random_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); > + if (words) { > + i += words; > + 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, words, 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);) { > + words = arch_get_random_seed_words(entropy, ARRAY_SIZE(entropy) - i); > + if (words) { > + _mix_pool_bytes(entropy, sizeof(*entropy) * words); > + i += words; > + continue; > } > - _mix_pool_bytes(&entropy, sizeof(entropy)); > + words = arch_get_random_words(entropy, ARRAY_SIZE(entropy) - i); > + if (words) { > + _mix_pool_bytes(entropy, sizeof(*entropy) * words); > + i += words; > + 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..ae618916c74c 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > - 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..0a327a289f09 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_words_early > +static inline size_t __init arch_get_random_seed_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > - return arch_get_random_seed_long(v); > + return arch_get_random_seed_words(v, words); > } > #endif > > -#ifndef arch_get_random_long_early > -static inline bool __init arch_get_random_long_early(unsigned long *v) > +#ifndef arch_get_random_words_early > +static inline bool __init arch_get_random_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > - return arch_get_random_long(v); > + return arch_get_random_words(v, words); > } > #endif > > -- > 2.35.1 >
Hi Mark, On Tue, Jul 19, 2022 at 2:42 PM Mark Rutland <mark.rutland@arm.com> wrote: > > -static inline bool __must_check arch_get_random_long(unsigned long *v) > > +static inline size_t __must_check arch_get_random_words(unsigned long *v, size_t words) > > As others have suggested, could we please s/words/longs/? That's a smaller > change from the existing name, and avoids amibugity were "word" has an > architecture-specific meaning. e.g. the ARM ARM (ARM DDI 0487G.b) defines: At first I had thought, "erm, I like 'words'" but decided to wait it out, and now it's two people with the same probably good objection to 'words', so I'll send a v+1 with 'longs' instead. Thanks for your feedback. Patch incoming. > FWIW, other than the naming nits, the arm64 bits look fine to me. Oh good. Can you send an Acked-by for v+1? Coming up shortly. Jason
Gabriel Paubert <paubert@iram.es> writes: > On Mon, Jul 18, 2022 at 04:31:11PM +1000, Michael Ellerman wrote: >> "Jason A. Donenfeld" <Jason@zx2c4.com> writes: >> > 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 words. On >> > s390, the CPACF TRNG interface can return between 1 and 32 words for the >> > same cost as for one word. On UML, the os_getrandom() interface can return >> > arbitrary amounts. >> > >> > So change the api signature to take a "words" parameter designating the >> > maximum number of words requested, and then return the number of words >> > generated. >> >> On powerpc a word is 32-bits and a doubleword is 64-bits (at least >> according to the ISA). I think that's also true on other 64-bit >> architectures. > > IIRC, this is (or was) not the case on Alpha, where word was defined as > 16 bits. All assembly mnemonics had w for 16 bits, l for 32 bits, and q > for 64 bits. Yeah I should have said on *some* other 64-bit arches. Seems to be a common feature/hack on arches that have evolved over time, or been inspired by earlier arches. The latest Power ISA has octwords :) cheers
Hi Jason, On 17/07/2022 22:03, 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 words. On > s390, the CPACF TRNG interface can return between 1 and 32 words for the > same cost as for one word. On UML, the os_getrandom() interface can return > arbitrary amounts. > > So change the api signature to take a "words" parameter designating the > maximum number of words requested, and then return the number of words > generated. Why not changing the API to take bytes instead of words? Sure, at the moment it looks like all platforms with TRNG support are able to deliver at least one word, but bytes would be more flexible. > 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 requested number of words. Additionally, all existing callers > pass in a constant words 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 <will@kernel.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Alexander Gordeev <agordeev@linux.ibm.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: H. Peter Anvin <hpa@zytor.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Heiko Carstens <hca@linux.ibm.com> > Cc: Johannes Berg <johannes@sipsolutions.net> > Cc: Harald Freudenberger <freude@linux.ibm.com> > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > 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..7a24fdee3e2f 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_words(unsigned long *v, size_t words) > { > /* > * 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 (words && 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_words(unsigned long *v, size_t words) > { > - 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 (!words) > + 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; > + > + words = min_t(size_t, 3, words); > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); > if ((int)res.a0 >= 0) { > - *v = res.a3; > - return true; > + switch (words) { > + case 3: > + *v++ = res.a1; > + fallthrough; > + case 2: > + *v++ = res.a2; > + fallthrough; > + case 1: > + *v++ = res.a3; > + break; > + } > + return words; > } > } > > @@ -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_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > > + if (!words) > + return 0; > + > if (smccc_trng_available) { > struct arm_smccc_res res; > > - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res); > + words = min_t(size_t, 3, words); > + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); > if ((int)res.a0 >= 0) { > - *v = res.a3; > - return true; > + switch (words) { > + case 3: > + *v++ = res.a1; > + fallthrough; > + case 2: > + *v++ = res.a2; > + fallthrough; > + case 1: > + *v++ = res.a3; > + break; > + } > + return words; > } > } > > 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_words_early arch_get_random_seed_words_early > > #endif /* _ASM_ARCHRANDOM_H */ > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c > index 418b2bba1521..ed77afe16121 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_words_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..bf2182f80480 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > - 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 (words && 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..18b2d80996b6 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_words(&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..29f1a9bc3867 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > 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, words * sizeof(*v)); > + atomic64_add(words * sizeof(*v), &s390_arch_random_counter); > + return words; > } > - 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..6bcbd47fcb62 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_words(unsigned long *v, size_t words) > { > - 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, words * 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_words(unsigned long *v, size_t words) > { > - return false; > + return 0; > } > > #endif > diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h > index fb235b696175..a1717b81d876 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_words(unsigned long *v, size_t words) > { > - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false; > + return words && 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_words(unsigned long *v, size_t words) > { > - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false; > + return words && 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..f46c9ff3c0d4 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_words(&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..70d8d1d7e2d7 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, words; > > - 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);) { > + words = arch_get_random_seed_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); > + if (words) { > + i += words; > + continue; > + } > + words = arch_get_random_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); > + if (words) { > + i += words; > + 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, words, 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);) { > + words = arch_get_random_seed_words(entropy, ARRAY_SIZE(entropy) - i); > + if (words) { > + _mix_pool_bytes(entropy, sizeof(*entropy) * words); > + i += words; > + continue; > } > - _mix_pool_bytes(&entropy, sizeof(entropy)); > + words = arch_get_random_words(entropy, ARRAY_SIZE(entropy) - i); > + if (words) { > + _mix_pool_bytes(entropy, sizeof(*entropy) * words); > + i += words; > + 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..ae618916c74c 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_words(unsigned long *v, size_t words) > { > - 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_words(unsigned long *v, size_t words) > { > - 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..0a327a289f09 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_words_early > +static inline size_t __init arch_get_random_seed_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > - return arch_get_random_seed_long(v); > + return arch_get_random_seed_words(v, words); > } > #endif > > -#ifndef arch_get_random_long_early > -static inline bool __init arch_get_random_long_early(unsigned long *v) > +#ifndef arch_get_random_words_early > +static inline bool __init arch_get_random_words_early(unsigned long *v, size_t words) > { > WARN_ON(system_state != SYSTEM_BOOTING); > - return arch_get_random_long(v); > + return arch_get_random_words(v, words); > } > #endif >
Hi Holger, On Fri, Jul 22, 2022 at 10:08:05AM +0200, Holger Dengler wrote: > Why not changing the API to take bytes instead of words? Sure, at the > moment it looks like all platforms with TRNG support are able to > deliver at least one word, but bytes would be more flexible. The idea is to strike a sweet spot between capabilities. S390x is fine with byte-level granularity up to arbitrary lengths, while x86 is best with word-level granularity of length 1. The happy intersection between the two is just word-level granularity of arbitrary length. Yes we _could_ introduce a lot of code complexity by cascading the x86 case down into smaller and smaller registers, ignoring the fact that it's no longer efficient below 32- or 64-bit registers depending on vendor. But then we're relying on the inliner to remove all of that extra code, since all callers actually only ever want 32 or 64 bytes. Why bloat for nothing? The beauty of this approach is that it translates very naturally over all the various quirks of architectures without having to have a lot of coupling code. The other reason is that it's simply not necessary. The primary use for this in random.c is to fill a 32- or 64-*byte* block with "some stuff", preferring RDSEED, then RDRAND, and finally falling back to RDTSC. These correspond with arch_get_random_seed_longs(), arch_get_random_longs(), and random_get_entropy() (which is usually get_cycles() underneath), respectively. With the cycle counter being (at least) ~word-sized on all platforms, keeping the granularity of the arch_get_random_*_longs() functions the same lets us fill these with a basic cascade that doesn't require a lot of code: 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(); } By using a word as the underlying unit, the above cascade generates optimal code on basically all archrandom platforms, no matter what their byte-vs-word or one-vs-three-vs-many semantics are. That's a bit long winded, but hopefully that gives a bit of insight on why going from _long -> _longs is so "lazy" looking. Jason
Hi Jason, On 22/07/2022 13:22, Jason A. Donenfeld wrote: > On Fri, Jul 22, 2022 at 10:08:05AM +0200, Holger Dengler wrote: >> Why not changing the API to take bytes instead of words? Sure, at the >> moment it looks like all platforms with TRNG support are able to >> deliver at least one word, but bytes would be more flexible. > > The idea is to strike a sweet spot between capabilities. S390x is fine > with byte-level granularity up to arbitrary lengths, while x86 is best > with word-level granularity of length 1. The happy intersection between > the two is just word-level granularity of arbitrary length. Yes we > _could_ introduce a lot of code complexity by cascading the x86 case > down into smaller and smaller registers, ignoring the fact that it's no > longer efficient below 32- or 64-bit registers depending on vendor. But > then we're relying on the inliner to remove all of that extra code, > since all callers actually only ever want 32 or 64 bytes. Why bloat for > nothing? The beauty of this approach is that it translates very > naturally over all the various quirks of architectures without having to > have a lot of coupling code. You're absolutely right. Your solution addresses all needs of current architectures. My proposal was just meant as preparation for the case, that new (smaller) architectures may come up in the future with a TRNG support, but with other granularity. But anyhow: we can handle it as soon as it happens, fine with me.
diff --git a/arch/arm64/include/asm/archrandom.h b/arch/arm64/include/asm/archrandom.h index c3b9fa56af67..7a24fdee3e2f 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_words(unsigned long *v, size_t words) { /* * 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 (words && 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_words(unsigned long *v, size_t words) { - 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 (!words) + 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; + + words = min_t(size_t, 3, words); + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); if ((int)res.a0 >= 0) { - *v = res.a3; - return true; + switch (words) { + case 3: + *v++ = res.a1; + fallthrough; + case 2: + *v++ = res.a2; + fallthrough; + case 1: + *v++ = res.a3; + break; + } + return words; } } @@ -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_words_early(unsigned long *v, size_t words) { WARN_ON(system_state != SYSTEM_BOOTING); + if (!words) + return 0; + if (smccc_trng_available) { struct arm_smccc_res res; - arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, 64, &res); + words = min_t(size_t, 3, words); + arm_smccc_1_1_invoke(ARM_SMCCC_TRNG_RND64, words * 64, &res); if ((int)res.a0 >= 0) { - *v = res.a3; - return true; + switch (words) { + case 3: + *v++ = res.a1; + fallthrough; + case 2: + *v++ = res.a2; + fallthrough; + case 1: + *v++ = res.a3; + break; + } + return words; } } 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_words_early arch_get_random_seed_words_early #endif /* _ASM_ARCHRANDOM_H */ diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index 418b2bba1521..ed77afe16121 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_words_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..bf2182f80480 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_words(unsigned long *v, size_t words) { - 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_words(unsigned long *v, size_t words) { - 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 (words && 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..18b2d80996b6 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_words(&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..29f1a9bc3867 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_words(unsigned long *v, size_t words) { - 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_words(unsigned long *v, size_t words) { 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, words * sizeof(*v)); + atomic64_add(words * sizeof(*v), &s390_arch_random_counter); + return words; } - 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..6bcbd47fcb62 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_words(unsigned long *v, size_t words) { - 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, words * 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_words(unsigned long *v, size_t words) { - return false; + return 0; } #endif diff --git a/arch/x86/include/asm/archrandom.h b/arch/x86/include/asm/archrandom.h index fb235b696175..a1717b81d876 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_words(unsigned long *v, size_t words) { - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_long(v) : false; + return words && 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_words(unsigned long *v, size_t words) { - return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false; + return words && 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..f46c9ff3c0d4 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_words(&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..70d8d1d7e2d7 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, words; - 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);) { + words = arch_get_random_seed_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (words) { + i += words; + continue; + } + words = arch_get_random_words(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i); + if (words) { + i += words; + 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, words, 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);) { + words = arch_get_random_seed_words(entropy, ARRAY_SIZE(entropy) - i); + if (words) { + _mix_pool_bytes(entropy, sizeof(*entropy) * words); + i += words; + continue; } - _mix_pool_bytes(&entropy, sizeof(entropy)); + words = arch_get_random_words(entropy, ARRAY_SIZE(entropy) - i); + if (words) { + _mix_pool_bytes(entropy, sizeof(*entropy) * words); + i += words; + 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..ae618916c74c 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_words(unsigned long *v, size_t words) { - 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_words(unsigned long *v, size_t words) { - 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..0a327a289f09 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_words_early +static inline size_t __init arch_get_random_seed_words_early(unsigned long *v, size_t words) { WARN_ON(system_state != SYSTEM_BOOTING); - return arch_get_random_seed_long(v); + return arch_get_random_seed_words(v, words); } #endif -#ifndef arch_get_random_long_early -static inline bool __init arch_get_random_long_early(unsigned long *v) +#ifndef arch_get_random_words_early +static inline bool __init arch_get_random_words_early(unsigned long *v, size_t words) { WARN_ON(system_state != SYSTEM_BOOTING); - return arch_get_random_long(v); + return arch_get_random_words(v, words); } #endif
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 words. On s390, the CPACF TRNG interface can return between 1 and 32 words for the same cost as for one word. On UML, the os_getrandom() interface can return arbitrary amounts. So change the api signature to take a "words" parameter designating the maximum number of words requested, and then return the number of words 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 requested number of words. Additionally, all existing callers pass in a constant words 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 <will@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Borislav Petkov <bp@suse.de> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Harald Freudenberger <freude@linux.ibm.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- 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(-)