feat: mmap NonNull

changelog/2000.changed.md

@@ -0,0 +1 @@
+`Mmap` now returns `Result<NonNull<c_void>>` replacing `Result<*mut c_void>`.

src/sys/mman.rs

@@ -9,6 +9,7 @@ use crate::Result;
 use crate::{fcntl::OFlag, sys::stat::Mode};
 use libc::{self, c_int, c_void, off_t, size_t};
 use std::{num::NonZeroUsize, os::unix::io::{AsRawFd, AsFd}};
+use std::ptr::NonNull;
 
 libc_bitflags! {
     /// Desired memory protection of a memory mapping.
@@ -427,18 +428,20 @@ pub unsafe fn mmap<F: AsFd>(
     flags: MapFlags,
     f: F,
     offset: off_t,
-) -> Result<*mut c_void> {
-    let ptr = addr.map_or(std::ptr::null_mut(), |a| a.get() as *mut c_void);
+) -> Result<NonNull<c_void>> {
+    let ptr =
+        addr.map_or(std::ptr::null_mut(), |a| usize::from(a) as *mut c_void);
 
     let fd = f.as_fd().as_raw_fd();
     let ret =
         libc::mmap(ptr, length.into(), prot.bits(), flags.bits(), fd, offset);
 
     if ret == libc::MAP_FAILED {
         Err(Errno::last())
-    } else {
-        Ok(ret)
     }
+    else {
+        Ok(unsafe { NonNull::new_unchecked(ret) })
+    } 
 }
 
 /// Create an anonymous memory mapping.
@@ -554,10 +557,10 @@ pub unsafe fn madvise(
 /// const ONE_K: size_t = 1024;
 /// let one_k_non_zero = std::num::NonZeroUsize::new(ONE_K).unwrap();
 /// let mut slice: &mut [u8] = unsafe {
-///     let mem = mmap_anonymous(None, one_k_non_zero, ProtFlags::PROT_NONE, MapFlags::MAP_PRIVATE)
-///         .unwrap();
-///     mprotect(mem, ONE_K, ProtFlags::PROT_READ | ProtFlags::PROT_WRITE).unwrap();
-///     std::slice::from_raw_parts_mut(mem as *mut u8, ONE_K)
+///     let mem = mmap::<BorrowedFd>(None, one_k_non_zero, ProtFlags::PROT_NONE,
+///                    MapFlags::MAP_ANON | MapFlags::MAP_PRIVATE, None, 0).unwrap();
+///     mprotect(mem.as_ptr(), ONE_K, ProtFlags::PROT_READ | ProtFlags::PROT_WRITE).unwrap();
+///     std::slice::from_raw_parts_mut(mem.as_ptr().cast(), ONE_K)
 /// };
 /// assert_eq!(slice[0], 0x00);
 /// slice[0] = 0xFF;

test/sys/test_mman.rs

@@ -10,10 +10,11 @@ fn test_mmap_anonymous() {
             ProtFlags::PROT_READ | ProtFlags::PROT_WRITE,
             MapFlags::MAP_PRIVATE,
         )
-        .unwrap() as *mut u8;
-        assert_eq!(*ptr, 0x00u8);
-        *ptr = 0xffu8;
-        assert_eq!(*ptr, 0xffu8);
+        .unwrap()
+        .cast::<u8>();
+        assert_eq!(*ptr.as_ref(), 0x00u8);
+        *ptr.as_mut() = 0xffu8;
+        assert_eq!(*ptr.as_ref(), 0xffu8);
     }
 }
 
@@ -34,7 +35,7 @@ fn test_mremap_grow() {
             MapFlags::MAP_PRIVATE,
         )
         .unwrap();
-        std::slice::from_raw_parts_mut(mem as *mut u8, ONE_K)
+        std::slice::from_raw_parts_mut(mem.as_ptr().cast(), ONE_K)
     };
     assert_eq!(slice[ONE_K - 1], 0x00);
     slice[ONE_K - 1] = 0xFF;
@@ -90,7 +91,7 @@ fn test_mremap_shrink() {
             MapFlags::MAP_PRIVATE,
         )
         .unwrap();
-        std::slice::from_raw_parts_mut(mem as *mut u8, ONE_K)
+        std::slice::from_raw_parts_mut(mem.as_ptr().cast(), ONE_K)
     };
     assert_eq!(slice[ONE_K - 1], 0x00);
     slice[ONE_K - 1] = 0xFF;