Commit d349ab99 authored by Jason A. Donenfeld's avatar Jason A. Donenfeld
Browse files

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 one and three
longs. On s390, the CPACF TRNG interface can return arbitrary amounts,
with four 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.

Acked-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Acked-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
parent 0b9ba613

arch/arm64/include/asm/archrandom.h

+47 −55
Original line number Diff line number Diff line
@@ -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 false;

}

		return 1;



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 */

arch/arm64/kernel/kaslr.c

+1 −1
Original line number Diff line number Diff line
@@ -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) {

arch/powerpc/include/asm/archrandom.h

+6 −24
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kvm/book3s_hv.c

+1 −1
Original line number Diff line number Diff line
@@ -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:

arch/s390/include/asm/archrandom.h

+7 −22
Original line number Diff line number Diff line
@@ -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 */