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authorJohannes Stoelp <johannes.stoelp@gmail.com>2023-02-27 22:28:40 +0100
committerJohannes Stoelp <johannes.stoelp@gmail.com>2023-02-27 22:40:26 +0100
commit24c9507c2d6529699edca9b2479d7e4f1a3415e6 (patch)
treedd8a81c80b64ca3f8af9ed16536efbfcd87236c9 /src/rt.rs
parentfed6ae454f659f4d2b36520474d1998b526a27dd (diff)
downloadjuicebox-asm-24c9507c2d6529699edca9b2479d7e4f1a3415e6.tar.gz
juicebox-asm-24c9507c2d6529699edca9b2479d7e4f1a3415e6.zip
Add minimal runtime to execute code
Diffstat (limited to 'src/rt.rs')
-rw-r--r--src/rt.rs51
1 files changed, 51 insertions, 0 deletions
diff --git a/src/rt.rs b/src/rt.rs
new file mode 100644
index 0000000..fc8c930
--- /dev/null
+++ b/src/rt.rs
@@ -0,0 +1,51 @@
+use core::ffi::c_void;
+use nix::sys::mman::{mmap, 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: &[u8]) -> Runtime {
+ // Allocate a single page.
+ let len = core::num::NonZeroUsize::new(4096).unwrap();
+ let buf = unsafe {
+ mmap(
+ None,
+ len,
+ ProtFlags::PROT_WRITE | ProtFlags::PROT_READ | ProtFlags::PROT_EXEC,
+ MapFlags::MAP_PRIVATE | MapFlags::MAP_ANONYMOUS,
+ 0, /* fd */
+ 0, /* off */
+ )
+ .unwrap()
+ };
+ {
+ // Copy over code.
+ assert!(code.len() < len.get());
+ unsafe { std::ptr::copy_nonoverlapping(code.as_ptr(), buf.cast(), len.get()) };
+ }
+
+ 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");
+ }
+ }
+}