feat: mmap NonNull

changelog/2000.changed.md

@@ -0,0 +1 @@
+`mmap` and `mmap_anonymous` now return `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.
@@ -427,7 +428,7 @@ pub unsafe fn mmap<F: AsFd>(
     flags: MapFlags,
     f: F,
     offset: off_t,
-) -> Result<*mut c_void> {
+) -> Result<NonNull<c_void>> {
     let ptr = addr.map_or(std::ptr::null_mut(), |a| a.get() as *mut c_void);
 
     let fd = f.as_fd().as_raw_fd();
@@ -436,9 +437,10 @@ pub unsafe fn mmap<F: AsFd>(
 
     if ret == libc::MAP_FAILED {
         Err(Errno::last())
-    } else {
-        Ok(ret)
     }
+    else {
+        Ok(unsafe { NonNull::new_unchecked(ret) })
+    } 
 }
 
 /// Create an anonymous memory mapping.
@@ -456,7 +458,7 @@ pub unsafe fn mmap_anonymous(
     length: NonZeroUsize,
     prot: ProtFlags,
     flags: MapFlags,
-) -> Result<*mut c_void> {
+) -> Result<NonNull<c_void>> {
     let ptr = addr.map_or(std::ptr::null_mut(), |a| a.get() as *mut c_void);
 
     let flags = MapFlags::MAP_ANONYMOUS | flags;
@@ -465,7 +467,7 @@ pub unsafe fn mmap_anonymous(
     if ret == libc::MAP_FAILED {
         Err(Errno::last())
     } else {
-        Ok(ret)
+        Ok(unsafe { NonNull::new_unchecked(ret) })
     }
 }
 
@@ -556,8 +558,8 @@ pub unsafe fn madvise(
 /// 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)
+///     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

@@ -4,16 +4,17 @@ use std::num::NonZeroUsize;
 #[test]
 fn test_mmap_anonymous() {
     unsafe {
-        let ptr = mmap_anonymous(
+        let mut ptr = mmap_anonymous(
             None,
             NonZeroUsize::new(1).unwrap(),
             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;