atlas-define-syscall 4.0.2

Atlas define_syscall macro and core syscall definitions.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101

#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]

pub mod definitions;

#[cfg(any(
    target_feature = "static-syscalls",
    all(target_arch = "bpf", feature = "unstable-static-syscalls")
))]
#[macro_export]
macro_rules! define_syscall {
    (fn $name:ident($($arg:ident: $typ:ty),*) -> $ret:ty) => {
        #[inline]
        pub unsafe fn $name($($arg: $typ),*) -> $ret {
            // this enum is used to force the hash to be computed in a const context
            #[repr(usize)]
            enum Syscall {
                Code = $crate::sys_hash(stringify!($name)),
            }

            let syscall: extern "C" fn($($arg: $typ),*) -> $ret = core::mem::transmute(Syscall::Code);
            syscall($($arg),*)
        }

    };
    (fn $name:ident($($arg:ident: $typ:ty),*)) => {
        define_syscall!(fn $name($($arg: $typ),*) -> ());
    }
}

#[cfg(not(any(
    target_feature = "static-syscalls",
    all(target_arch = "bpf", feature = "unstable-static-syscalls")
)))]
#[macro_export]
macro_rules! define_syscall {
    (fn $name:ident($($arg:ident: $typ:ty),*) -> $ret:ty) => {
        extern "C" {
            pub fn $name($($arg: $typ),*) -> $ret;
        }
    };
    (fn $name:ident($($arg:ident: $typ:ty),*)) => {
        define_syscall!(fn $name($($arg: $typ),*) -> ());
    }
}

#[cfg(any(
    target_feature = "static-syscalls",
    all(target_arch = "bpf", feature = "unstable-static-syscalls")
))]
pub const fn sys_hash(name: &str) -> usize {
    murmur3_32(name.as_bytes(), 0) as usize
}

#[cfg(any(
    target_feature = "static-syscalls",
    all(target_arch = "bpf", feature = "unstable-static-syscalls")
))]
const fn murmur3_32(buf: &[u8], seed: u32) -> u32 {
    const fn pre_mix(buf: [u8; 4]) -> u32 {
        u32::from_le_bytes(buf)
            .wrapping_mul(0xcc9e2d51)
            .rotate_left(15)
            .wrapping_mul(0x1b873593)
    }

    let mut hash = seed;

    let mut i = 0;
    while i < buf.len() / 4 {
        let buf = [buf[i * 4], buf[i * 4 + 1], buf[i * 4 + 2], buf[i * 4 + 3]];
        hash ^= pre_mix(buf);
        hash = hash.rotate_left(13);
        hash = hash.wrapping_mul(5).wrapping_add(0xe6546b64);

        i += 1;
    }

    match buf.len() % 4 {
        0 => {}
        1 => {
            hash = hash ^ pre_mix([buf[i * 4], 0, 0, 0]);
        }
        2 => {
            hash = hash ^ pre_mix([buf[i * 4], buf[i * 4 + 1], 0, 0]);
        }
        3 => {
            hash = hash ^ pre_mix([buf[i * 4], buf[i * 4 + 1], buf[i * 4 + 2], 0]);
        }
        _ => { /* unreachable!() */ }
    }

    hash = hash ^ buf.len() as u32;
    hash = hash ^ (hash.wrapping_shr(16));
    hash = hash.wrapping_mul(0x85ebca6b);
    hash = hash ^ (hash.wrapping_shr(13));
    hash = hash.wrapping_mul(0xc2b2ae35);
    hash = hash ^ (hash.wrapping_shr(16));

    hash
}