kernel/linux.git/include/linux/random.h, branch v6.19.11

random: remove unused get_random_var_wait functions

2025-11-02T12:40:13+00:00

None of these functions are used, so remove them. This renders the two bugs moot: - get_random_u64_wait() used the wrong pointer type, making it provide only 32 bits. - The '#undef' directive used the wrong identifier, leaving the helper macro defined. Signed-off-by: Eric Biggers Signed-off-by: Jason A. Donenfeld

random: Do not include in

2024-10-03T16:20:55+00:00

Files that use prandom infrastructure are now converted to use header instead of . Remove the legacy inclusion of from . This is the "nice cleanup" part, wished in c0842fbc1b18. Signed-off-by: Uros Bizjak Fixes: c0842fbc1b18 ("random32: move the pseudo-random 32-bit definitions to prandom.h") Cc: Theodore Ts'o Cc: Jason A. Donenfeld Cc: Linus Torvalds Signed-off-by: Jason A. Donenfeld

random: do not include from random.h

2022-12-20T02:13:45+00:00

The header is a random.c private detail, not something to be called by other code. As such, don't make it automatically available by way of random.h. Cc: Michael Ellerman Acked-by: Heiko Carstens Reviewed-by: Christophe Leroy Signed-off-by: Jason A. Donenfeld

random: include in the right header

2022-12-04T13:37:08+00:00

uses DO_ONCE(), so it should include directly. In contrast, does not use code from , so it should be removed. Move the `#include ` line into the right file. Signed-off-by: Christophe JAILLET Fixes: c0842fbc1b18 ("random32: move the pseudo-random 32-bit definitions to prandom.h") Signed-off-by: Jason A. Donenfeld

random: add back async readiness notifier

2022-11-22T13:53:00+00:00

This is required by vsprint, because it can't do things synchronously from hardirq context, and it will be useful for an EFI notifier as well. I didn't initially want to do this, but with two potential consumers now, it seems worth it. Signed-off-by: Jason A. Donenfeld

random: always mix cycle counter in add_latent_entropy()

2022-11-18T01:18:10+00:00

add_latent_entropy() is called every time a process forks, in kernel_clone(). This in turn calls add_device_randomness() using the latent entropy global state. add_device_randomness() does two things: 2) Mixes into the input pool the latent entropy argument passed; and 1) Mixes in a cycle counter, a sort of measurement of when the event took place, the high precision bits of which are presumably difficult to predict. (2) is impossible without CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y. But (1) is always possible. However, currently CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n disables both (1) and (2), instead of just (2). This commit causes the CONFIG_GCC_PLUGIN_LATENT_ENTROPY=n case to still do (1) by passing NULL (len 0) to add_device_randomness() when add_latent_ entropy() is called. Cc: Dominik Brodowski Cc: PaX Team Cc: Emese Revfy Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin") Signed-off-by: Jason A. Donenfeld

hw_random: use add_hwgenerator_randomness() for early entropy

2022-11-18T01:18:10+00:00

Rather than calling add_device_randomness(), the add_early_randomness() function should use add_hwgenerator_randomness(), so that the early entropy can be potentially credited, which allows for the RNG to initialize earlier without having to wait for the kthread to come up. This requires some minor API refactoring, by adding a `sleep_after` parameter to add_hwgenerator_randomness(), so that we don't hit a blocking sleep from add_early_randomness(). Tested-by: AngeloGioacchino Del Regno Tested-by: Marek Szyprowski Reviewed-by: AngeloGioacchino Del Regno Reviewed-by: Dominik Brodowski Acked-by: Herbert Xu Signed-off-by: Jason A. Donenfeld

random: remove early archrandom abstraction

2022-11-18T01:18:10+00:00

The arch_get_random*_early() abstraction is not completely useful and adds complexity, because it's not a given that there will be no calls to arch_get_random*() between random_init_early(), which uses arch_get_random*_early(), and init_cpu_features(). During that gap, crng_reseed() might be called, which uses arch_get_random*(), since it's mostly not init code. Instead we can test whether we're in the early phase in arch_get_random*() itself, and in doing so avoid all ambiguity about where we are. Fortunately, the only architecture that currently implements arch_get_random*_early() also has an alternatives-based cpu feature system, one flag of which determines whether the other flags have been initialized. This makes it possible to do the early check with zero cost once the system is initialized. Reviewed-by: Catalin Marinas Cc: Will Deacon Cc: Ard Biesheuvel Cc: Jean-Philippe Brucker Signed-off-by: Jason A. Donenfeld

stackprotector: move get_random_canary() into stackprotector.h

2022-11-18T01:18:10+00:00

This has nothing to do with random.c and everything to do with stack protectors. Yes, it uses randomness. But many things use randomness. random.h and random.c are concerned with the generation of randomness, not with each and every use. So move this function into the more specific stackprotector.h file where it belongs. Acked-by: Greg Kroah-Hartman Signed-off-by: Jason A. Donenfeld

random: add helpers for random numbers with given floor or range

2022-11-18T01:15:12+00:00

Now that we have get_random_u32_below(), it's nearly trivial to make inline helpers to compute get_random_u32_above() and get_random_u32_inclusive(), which will help clean up open coded loops and manual computations throughout the tree. One snag is that in order to make get_random_u32_inclusive() operate on closed intervals, we have to do some (unlikely) special case handling if get_random_u32_inclusive(0, U32_MAX) is called. The least expensive way of doing this is actually to adjust the slowpath of get_random_u32_below() to have its undefined 0 result just return the output of get_random_u32(). We can make this basically free by calling get_random_u32() before the branch, so that the branch latency gets interleaved. Cc: stable@vger.kernel.org # to ease future backports that use this api Reviewed-by: Kees Cook Signed-off-by: Jason A. Donenfeld