30 lines
1.0 KiB
Rust
30 lines
1.0 KiB
Rust
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//! Implementation for Hermit
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use crate::Error;
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use core::{mem::MaybeUninit, num::NonZeroU32};
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/// Minimum return value which we should get from syscalls in practice,
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/// because Hermit uses positive `i32`s for error codes:
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/// https://github.com/hermitcore/libhermit-rs/blob/main/src/errno.rs
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const MIN_RET_CODE: isize = -(i32::MAX as isize);
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extern "C" {
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fn sys_read_entropy(buffer: *mut u8, length: usize, flags: u32) -> isize;
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}
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pub fn getrandom_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
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while !dest.is_empty() {
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let res = unsafe { sys_read_entropy(dest.as_mut_ptr() as *mut u8, dest.len(), 0) };
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// Positive `isize`s can be safely casted to `usize`
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if res > 0 && (res as usize) <= dest.len() {
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dest = &mut dest[res as usize..];
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} else {
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let err = match res {
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MIN_RET_CODE..=-1 => NonZeroU32::new(-res as u32).unwrap().into(),
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_ => Error::UNEXPECTED,
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};
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return Err(err);
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}
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}
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Ok(())
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}
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