[PATCH v3 2/3] prandom: Convert prandom_u32_state() to __always_inline
From: Ryan Roberts <ryan.roberts@arm.com>
Date: 2026-01-02 13:12:16
Also in:
linux-arm-kernel, linux-hardening, linux-riscv, linux-s390, lkml, loongarch
Subsystem:
library code, networking [general], the rest · Maintainers:
Andrew Morton, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
We will shortly use prandom_u32_state() to implement kstack offset randomization and some arches need to call it from non-instrumentable context. Given the function is just a handful of operations and doesn't call out to any other functions, let's take the easy path and make it __always_inline. Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> --- include/linux/prandom.h | 19 ++++++++++++++++++- lib/random32.c | 19 ------------------- 2 files changed, 18 insertions(+), 20 deletions(-)
diff --git a/include/linux/prandom.h b/include/linux/prandom.h
index ff7dcc3fa105..e797b3709f5c 100644
--- a/include/linux/prandom.h
+++ b/include/linux/prandom.h@@ -17,7 +17,24 @@ struct rnd_state { __u32 s1, s2, s3, s4; }; -u32 prandom_u32_state(struct rnd_state *state); +/** + * prandom_u32_state - seeded pseudo-random number generator. + * @state: pointer to state structure holding seeded state. + * + * This is used for pseudo-randomness with no outside seeding. + * For more random results, use get_random_u32(). + */ +static __always_inline u32 prandom_u32_state(struct rnd_state *state) +{ +#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) + state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); + state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); + state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); + state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); + + return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); +} + void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state);
diff --git a/lib/random32.c b/lib/random32.c
index 24e7acd9343f..d57baf489d4a 100644
--- a/lib/random32.c
+++ b/lib/random32.c@@ -42,25 +42,6 @@ #include <linux/slab.h> #include <linux/unaligned.h> -/** - * prandom_u32_state - seeded pseudo-random number generator. - * @state: pointer to state structure holding seeded state. - * - * This is used for pseudo-randomness with no outside seeding. - * For more random results, use get_random_u32(). - */ -u32 prandom_u32_state(struct rnd_state *state) -{ -#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) - state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); - state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); - state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); - state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); - - return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); -} -EXPORT_SYMBOL(prandom_u32_state); - /** * prandom_bytes_state - get the requested number of pseudo-random bytes *
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2.43.0