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
|
//! A simple runtime which can be used to execute emitted instructions.
use core::ffi::c_void;
use nix::sys::mman::{mmap, mprotect, munmap, MapFlags, ProtFlags};
/// A simple `mmap`ed runtime with executable pages.
pub struct Runtime {
buf: *mut c_void,
len: usize,
}
impl Runtime {
/// Create a new [Runtime].
pub fn new(code: impl AsRef<[u8]>) -> Runtime {
// Allocate a single page.
let len = core::num::NonZeroUsize::new(4096).unwrap();
let buf = unsafe {
mmap(
None,
len,
ProtFlags::PROT_WRITE,
MapFlags::MAP_PRIVATE | MapFlags::MAP_ANONYMOUS,
0, /* fd */
0, /* off */
)
.unwrap()
};
{
// Copy over code.
let code = code.as_ref();
assert!(code.len() < len.get());
unsafe { std::ptr::copy_nonoverlapping(code.as_ptr(), buf.cast(), len.get()) };
}
unsafe {
// Remove write permissions from code buffer and allow to read-execute from it.
mprotect(buf, len.get(), ProtFlags::PROT_READ | ProtFlags::PROT_EXEC)
.expect("Failed to RX mprotect Runtime code buffer");
}
Runtime {
buf,
len: len.get(),
}
}
/// Reinterpret the block of code as `F`.
#[inline]
pub unsafe fn as_fn<F>(&self) -> F {
unsafe { std::mem::transmute_copy(&self.buf) }
}
}
impl Drop for Runtime {
fn drop(&mut self) {
unsafe {
munmap(self.buf, self.len).expect("Failed to munmap Runtime");
}
}
}
|
