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random: remove CONFIG_ARCH_RANDOM

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When RDRAND was introduced, there was much discussion on whether it
should be trusted and how the kernel should handle that. Initially, two
mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and
"nordrand", a boot-time switch.

Later the thinking evolved. With a properly designed RNG, using RDRAND
values alone won't harm anything, even if the outputs are malicious.
Rather, the issue is whether those values are being *trusted* to be good
or not. And so a new set of options were introduced as the real
ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu".
With these options, RDRAND is used, but it's not always credited. So in
the worst case, it does nothing, and in the best case, maybe it helps.

Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the
center and became something certain platforms force-select.

The old options don't really help with much, and it's a bit odd to have
special handling for these instructions when the kernel can deal fine
with the existence or untrusted existence or broken existence or
non-existence of that CPU capability.

Simplify the situation by removing CONFIG_ARCH_RANDOM and using the
ordinary asm-generic fallback pattern instead, keeping the two options
that are actually used. For now it leaves "nordrand" for now, as the
removal of that will take a different route.

Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Borislav Petkov <bp@suse.de>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2022-07-05 20:48:41 +02:00
parent 829d680e82
commit 9592eef7c1
24 changed files with 34 additions and 93 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
arch/arm/include/asm/archrandom.h
View file

@ -7,4 +7,6 @@ static inline bool __init smccc_probe_trng(void)
return false;
}
#include <asm-generic/archrandom.h>
#endif /* _ASM_ARCHRANDOM_H */

8
arch/arm64/Kconfig
View file

@ -1858,14 +1858,6 @@ config ARM64_E0PD
This option enables E0PD for TTBR1 where available.
config ARCH_RANDOM
bool "Enable support for random number generation"
default y
help
Random number generation (part of the ARMv8.5 Extensions)
provides a high bandwidth, cryptographically secure
hardware random number generator.
config ARM64_AS_HAS_MTE
# Initial support for MTE went in binutils 2.32.0, checked with
# ".arch armv8.5-a+memtag" below. However, this was incomplete

10
arch/arm64/include/asm/archrandom.h
View file

@ -2,8 +2,6 @@
#ifndef _ASM_ARCHRANDOM_H
#define _ASM_ARCHRANDOM_H
#ifdef CONFIG_ARCH_RANDOM
#include <linux/arm-smccc.h>
#include <linux/bug.h>
#include <linux/kernel.h>
@ -167,12 +165,4 @@ arch_get_random_seed_long_early(unsigned long *v)
}
#define arch_get_random_seed_long_early arch_get_random_seed_long_early
#else /* !CONFIG_ARCH_RANDOM */
static inline bool __init smccc_probe_trng(void)
{
return false;
}
#endif /* CONFIG_ARCH_RANDOM */
#endif /* _ASM_ARCHRANDOM_H */

2
arch/arm64/kernel/cpufeature.c
View file

@ -2416,7 +2416,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.cpu_enable = cpu_enable_e0pd,
},
#endif
#ifdef CONFIG_ARCH_RANDOM
{
.desc = "Random Number Generator",
.capability = ARM64_HAS_RNG,
@ -2428,7 +2427,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.sign = FTR_UNSIGNED,
.min_field_value = 1,
},
#endif
#ifdef CONFIG_ARM64_BTI
{
.desc = "Branch Target Identification",

3
arch/powerpc/Kconfig
View file

@ -1252,9 +1252,6 @@ config PHYSICAL_START
default "0x00000000"
endif
config ARCH_RANDOM
def_bool n
config PPC_LIB_RHEAP
bool

3
arch/powerpc/include/asm/archrandom.h
View file

@ -2,8 +2,6 @@
#ifndef _ASM_POWERPC_ARCHRANDOM_H
#define _ASM_POWERPC_ARCHRANDOM_H
#ifdef CONFIG_ARCH_RANDOM
#include <asm/machdep.h>
static inline bool __must_check arch_get_random_long(unsigned long *v)
@ -35,7 +33,6 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
return rc;
}
#endif /* CONFIG_ARCH_RANDOM */
#ifdef CONFIG_PPC_POWERNV
int powernv_hwrng_present(void);

2
arch/powerpc/include/asm/machdep.h
View file

@ -200,9 +200,7 @@ struct machdep_calls {
ssize_t (*cpu_release)(const char *, size_t);
#endif
#ifdef CONFIG_ARCH_RANDOM
int (*get_random_seed)(unsigned long *v);
#endif
};
extern void e500_idle(void);

1
arch/powerpc/platforms/microwatt/Kconfig
View file

@ -6,7 +6,6 @@ config PPC_MICROWATT
select PPC_ICS_NATIVE
select PPC_ICP_NATIVE
select PPC_UDBG_16550
select ARCH_RANDOM
help
This option enables support for FPGA-based Microwatt implementations.

1
arch/powerpc/platforms/powernv/Kconfig
View file

@ -12,7 +12,6 @@ config PPC_POWERNV
select EPAPR_BOOT
select PPC_INDIRECT_PIO
select PPC_UDBG_16550
select ARCH_RANDOM
select CPU_FREQ
select PPC_DOORBELL
select MMU_NOTIFIER

1
arch/powerpc/platforms/pseries/Kconfig
View file

@ -19,7 +19,6 @@ config PPC_PSERIES
select PPC_UDBG_16550
select PPC_DOORBELL
select HOTPLUG_CPU
select ARCH_RANDOM
select FORCE_SMP
select SWIOTLB
default y

15
arch/s390/Kconfig
View file

@ -507,21 +507,6 @@ config KEXEC_SIG
verification for the corresponding kernel image type being
loaded in order for this to work.
config ARCH_RANDOM
def_bool y
prompt "s390 architectural random number generation API"
help
Enable the s390 architectural random number generation API
to provide random data for all consumers within the Linux
kernel.
When enabled the arch_random_* functions declared in linux/random.h
are implemented. The implementation is based on the s390 CPACF
instruction subfunction TRNG which provides a real true random
number generator.
If unsure, say Y.
config KERNEL_NOBP
def_bool n
prompt "Enable modified branch prediction for the kernel by default"

1
arch/s390/configs/zfcpdump_defconfig
View file

@ -15,7 +15,6 @@ CONFIG_TUNE_ZEC12=y
# CONFIG_COMPAT is not set
CONFIG_NR_CPUS=2
CONFIG_HZ_100=y
# CONFIG_ARCH_RANDOM is not set
# CONFIG_RELOCATABLE is not set
# CONFIG_CHSC_SCH is not set
# CONFIG_SCM_BUS is not set

2
arch/s390/crypto/Makefile
View file

@ -15,7 +15,7 @@ obj-$(CONFIG_CRYPTO_CHACHA_S390) += chacha_s390.o
obj-$(CONFIG_S390_PRNG) += prng.o
obj-$(CONFIG_CRYPTO_GHASH_S390) += ghash_s390.o
obj-$(CONFIG_CRYPTO_CRC32_S390) += crc32-vx_s390.o
obj-$(CONFIG_ARCH_RANDOM) += arch_random.o
obj-y += arch_random.o
crc32-vx_s390-y := crc32-vx.o crc32le-vx.o crc32be-vx.o
chacha_s390-y := chacha-glue.o chacha-s390.o

3
arch/s390/include/asm/archrandom.h
View file

@ -11,8 +11,6 @@
#ifndef _ASM_S390_ARCHRANDOM_H
#define _ASM_S390_ARCHRANDOM_H
#ifdef CONFIG_ARCH_RANDOM
#include <linux/static_key.h>
#include <linux/atomic.h>
#include <asm/cpacf.h>
@ -50,5 +48,4 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
return false;
}
#endif /* CONFIG_ARCH_RANDOM */
#endif /* _ASM_S390_ARCHRANDOM_H */

2
arch/s390/kernel/setup.c
View file

@ -876,10 +876,8 @@ static void __init setup_randomness(void)
add_device_randomness(&vmms->vm, sizeof(vmms->vm[0]) * vmms->count);
memblock_free(vmms, PAGE_SIZE);
#ifdef CONFIG_ARCH_RANDOM
if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG))
static_branch_enable(&s390_arch_random_available);
#endif
}
/*

9
arch/x86/Kconfig
View file

@ -1810,15 +1810,6 @@ config ARCH_USES_PG_UNCACHED
def_bool y
depends on X86_PAT
config ARCH_RANDOM
def_bool y
prompt "x86 architectural random number generator" if EXPERT
help
Enable the x86 architectural RDRAND instruction
(Intel Bull Mountain technology) to generate random numbers.
If supported, this is a high bandwidth, cryptographically
secure hardware random number generator.
config X86_UMIP
def_bool y
prompt "User Mode Instruction Prevention" if EXPERT

14
arch/x86/include/asm/archrandom.h
View file

@ -65,10 +65,8 @@ static inline bool __must_check rdseed_int(unsigned int *v)
/*
* These are the generic interfaces; they must not be declared if the
* stubs in <linux/random.h> are to be invoked,
* i.e. CONFIG_ARCH_RANDOM is not defined.
* stubs in <linux/random.h> are to be invoked.
*/
#ifdef CONFIG_ARCH_RANDOM
static inline bool __must_check arch_get_random_long(unsigned long *v)
{
@ -90,12 +88,8 @@ static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
return static_cpu_has(X86_FEATURE_RDSEED) ? rdseed_int(v) : false;
}
extern void x86_init_rdrand(struct cpuinfo_x86 *c);
#else /* !CONFIG_ARCH_RANDOM */
static inline void x86_init_rdrand(struct cpuinfo_x86 *c) { }
#endif /* !CONFIG_ARCH_RANDOM */
#ifndef CONFIG_UML
void x86_init_rdrand(struct cpuinfo_x86 *c);
#endif
#endif /* ASM_X86_ARCHRANDOM_H */

2
arch/x86/kernel/cpu/rdrand.c
View file

@ -26,7 +26,6 @@ __setup("nordrand", x86_rdrand_setup);
*/
#define SANITY_CHECK_LOOPS 8
#ifdef CONFIG_ARCH_RANDOM
void x86_init_rdrand(struct cpuinfo_x86 *c)
{
unsigned int changed = 0;
@ -63,4 +62,3 @@ void x86_init_rdrand(struct cpuinfo_x86 *c)
"RDRAND gives funky smelling output, might consider not using it by booting with \"nordrand\"");
}
#endif

1
drivers/char/Kconfig
View file

@ -431,7 +431,6 @@ config ADI
config RANDOM_TRUST_CPU
bool "Initialize RNG using CPU RNG instructions"
default y
depends on ARCH_RANDOM
help
Initialize the RNG using random numbers supplied by the CPU's
RNG instructions (e.g. RDRAND), if supported and available. These

9
drivers/char/hw_random/s390-trng.c
View file

@ -108,7 +108,6 @@ static ssize_t trng_counter_show(struct device *dev,
{
u64 dev_counter = atomic64_read(&trng_dev_counter);
u64 hwrng_counter = atomic64_read(&trng_hwrng_counter);
#if IS_ENABLED(CONFIG_ARCH_RANDOM)
u64 arch_counter = atomic64_read(&s390_arch_random_counter);
return sysfs_emit(buf,
@ -118,14 +117,6 @@ static ssize_t trng_counter_show(struct device *dev,
"total: %llu\n",
dev_counter, hwrng_counter, arch_counter,
dev_counter + hwrng_counter + arch_counter);
#else
return sysfs_emit(buf,
"trng: %llu\n"
"hwrng: %llu\n"
"total: %llu\n",
dev_counter, hwrng_counter,
dev_counter + hwrng_counter);
#endif
}
static DEVICE_ATTR(byte_counter, 0444, trng_counter_show, NULL);

1
include/asm-generic/Kbuild
View file

@ -5,6 +5,7 @@
# asm headers from the host architecutre.)
mandatory-y += atomic.h
mandatory-y += archrandom.h
mandatory-y += barrier.h
mandatory-y += bitops.h
mandatory-y += bug.h

25
include/asm-generic/archrandom.h Normal file
View file

@ -0,0 +1,25 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_GENERIC_ARCHRANDOM_H__
#define __ASM_GENERIC_ARCHRANDOM_H__
static inline bool __must_check arch_get_random_long(unsigned long *v)
{
return false;
}
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)
{
return false;
}
static inline bool __must_check arch_get_random_seed_int(unsigned int *v)
{
return false;
}
#endif

9
include/linux/random.h
View file

@ -106,14 +106,7 @@ declare_get_random_var_wait(long, unsigned long)
*/
#include <linux/prandom.h>
#ifdef CONFIG_ARCH_RANDOM
# include <asm/archrandom.h>
#else
static inline bool __must_check arch_get_random_long(unsigned long *v) { return false; }
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) { return false; }
static inline bool __must_check arch_get_random_seed_int(unsigned int *v) { return false; }
#endif
#include <asm/archrandom.h>
/*
* Called from the boot CPU during startup; not valid to call once

1
tools/testing/selftests/wireguard/qemu/kernel.config
View file

@ -58,7 +58,6 @@ CONFIG_NO_HZ_IDLE=y
CONFIG_NO_HZ_FULL=n
CONFIG_HZ_PERIODIC=n
CONFIG_HIGH_RES_TIMERS=y
CONFIG_ARCH_RANDOM=y
CONFIG_FILE_LOCKING=y
CONFIG_POSIX_TIMERS=y
CONFIG_DEVTMPFS=y