From: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Exports base_crng.generation to vDSO and adds getrandom() to the vDSO. Based on Jason A. Donenfeld <Jason@xxxxxxxxx> patch [1] "[PATCH v14 6/7] random: introduce generic vDSO getrandom() implementation", but deal only with GRND_TIMESTAMP in vDSO: generating random stream is left to the getrandom() syscall. [1] https://lore.kernel.org/all/20230101162910.710293-7-Jason@xxxxxxxxx/ Link: https://lore.kernel.org/all/cover.1673539719.git.ydroneaud@xxxxxxxxxx/ Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx> --- MAINTAINERS | 1 + drivers/char/random.c | 6 +++++ include/vdso/datapage.h | 9 ++++++++ lib/vdso/Kconfig | 5 ++++ lib/vdso/getrandom.c | 51 +++++++++++++++++++++++++++++++++++++++++ 5 files changed, 72 insertions(+) create mode 100644 lib/vdso/getrandom.c diff --git a/MAINTAINERS b/MAINTAINERS index 7f86d02cb427..20e1fabcb2e9 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17521,6 +17521,7 @@ T: git https://git.kernel.org/pub/scm/linux/kernel/git/crng/random.git S: Maintained F: drivers/char/random.c F: drivers/virt/vmgenid.c +F: lib/vdso/getrandom.c RAPIDIO SUBSYSTEM M: Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx> diff --git a/drivers/char/random.c b/drivers/char/random.c index 9e2a37e432c0..a60f50c95ab1 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -56,6 +56,9 @@ #include <linux/sched/isolation.h> #include <crypto/chacha.h> #include <crypto/blake2s.h> +#ifdef CONFIG_VDSO_GETRANDOM +#include <vdso/datapage.h> +#endif #include <asm/archrandom.h> #include <asm/processor.h> #include <asm/irq.h> @@ -271,6 +274,9 @@ static void crng_reseed(struct work_struct *work) if (next_gen == ULONG_MAX) ++next_gen; WRITE_ONCE(base_crng.generation, next_gen); +#ifdef CONFIG_VDSO_GETRANDOM + smp_store_release(&_vdso_rng_data.generation, next_gen); +#endif if (!static_branch_likely(&crng_is_ready)) crng_init = CRNG_READY; spin_unlock_irqrestore(&base_crng.lock, flags); diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h index 73eb622e7663..7ae8e7ffe3ba 100644 --- a/include/vdso/datapage.h +++ b/include/vdso/datapage.h @@ -109,6 +109,14 @@ struct vdso_data { struct arch_vdso_data arch_data; }; +/** + * struct vdso_rng_data - vdso RNG state information + * @generation: counter representing the number of RNG reseeds + */ +struct vdso_rng_data { + u64 generation; +}; + /* * We use the hidden visibility to prevent the compiler from generating a GOT * relocation. Not only is going through a GOT useless (the entry couldn't and @@ -120,6 +128,7 @@ struct vdso_data { */ extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden"))); extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden"))); +extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden"))); /* * The generic vDSO implementation requires that gettimeofday.h diff --git a/lib/vdso/Kconfig b/lib/vdso/Kconfig index d883ac299508..3b394fa83f65 100644 --- a/lib/vdso/Kconfig +++ b/lib/vdso/Kconfig @@ -31,3 +31,8 @@ config GENERIC_VDSO_TIME_NS VDSO endif + +config VDSO_GETRANDOM + bool + help + Selected by architectures that support vDSO getrandom(). diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c new file mode 100644 index 000000000000..827351a87002 --- /dev/null +++ b/lib/vdso/getrandom.c @@ -0,0 +1,51 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2022 Jason A. Donenfeld <Jason@xxxxxxxxx>. All Rights Reserved. + */ + +#include <linux/cache.h> +#include <linux/kernel.h> +#include <linux/time64.h> +#include <vdso/datapage.h> +#include <asm/vdso/getrandom.h> +#include <asm/vdso/vsyscall.h> + +/** + * __cvdso_getrandom_data - Generic vDSO implementation of getrandom() syscall. + * @rng_info: Describes state of kernel RNG, memory shared with kernel. + * @buffer: Input/Output buffer. + * @len: Size of @buffer in bytes. + * @flags: Zero or more GRND_* flags. + */ +static __always_inline ssize_t +__cvdso_getrandom_data(const struct vdso_rng_data *rng_info, void *buffer, size_t len, + unsigned int flags) +{ + if (flags != GRND_TIMESTAMP) + goto fallback; + + if (unlikely(!buffer)) + goto fallback; + + /* want aligned access */ + if (unlikely(!IS_ALIGNED((uintptr_t)buffer, __alignof__(u64)))) + goto fallback; + + if (unlikely(len != sizeof(u64))) + goto fallback; + + if (!get_random_timestamp_update((u64 *)buffer, + READ_ONCE(rng_info->generation))) + return 0; + + return sizeof(u64); + +fallback: + return getrandom_syscall(buffer, len, flags); +} + +static __always_inline ssize_t +__cvdso_getrandom(void *buffer, size_t len, unsigned int flags) +{ + return __cvdso_getrandom_data(__arch_get_vdso_rng_data(), buffer, len, flags); +} -- 2.37.2
