Don't block in getrandom() detection#26
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newpavlov merged 1 commit intorust-random:masterfrom Jun 10, 2019
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On Linux, we detect if `getrandom` is present by calling getrandom with an empty buffer and seeing if `ENOSYS` is returned. However, even with an empty buffer, this call will block unless we explicitly pass a flag. This can be seen in the source for `getrandom`: https://elixir.bootlin.com/linux/v5.1.8/source/drivers/char/random.c#L2043 This change adds a boolean parameter to `syscall_getrandom` to control the blocking behavior. We now don't block in initialization, but do block when actually reading random data.
dhardy
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Jun 10, 2019
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I think in practice it doesn't make much difference since detection happens on first use. Looks good to me however.
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I also think that blocking is not a big deal. If kernel does not have |
takumi-earth
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Jan 27, 2026
On Linux, we detect if `getrandom` is present by calling getrandom with an empty buffer and seeing if `ENOSYS` is returned. However, even with an empty buffer, this call will block unless we explicitly pass a flag. This can be seen in the source for `getrandom`: https://elixir.bootlin.com/linux/v5.1.8/source/drivers/char/random.c#L2043 This change adds a boolean parameter to `syscall_getrandom` to control the blocking behavior. We now don't block in initialization, but do block when actually reading random data.
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On Linux, we detect if
getrandomis present by callinggetrandomwithan empty buffer and seeing if
ENOSYSis returned. However, even withan empty buffer, this call will block unless we explicitly pass a flag.
This can be seen in the source for
getrandom:https://elixir.bootlin.com/linux/v5.1.8/source/drivers/char/random.c#L2043
This change adds a boolean parameter to
syscall_getrandomto controlthe blocking behavior. We now don't block in initialization, but do
block when actually reading random data.