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feat: mman NonNull #2000

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merged 8 commits into from
Nov 13, 2023
Merged

feat: mman NonNull #2000

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e5d99e3
feat: mmap `NonNull`
JonathanWoollett-Light Nov 13, 2023
879c227
feat: munmap `NonNull`
JonathanWoollett-Light Nov 13, 2023
64b9a66
feat: mremap `NonNull`
JonathanWoollett-Light Nov 13, 2023
fffe577
feat: madvise `NonNull`
JonathanWoollett-Light Nov 12, 2023
74c2eb0
feat: msync `NonNull`
JonathanWoollett-Light Nov 12, 2023
85099da
feat: mprotect `NonNull`
JonathanWoollett-Light Nov 12, 2023
7365554
feat: munlock `NonNull`
JonathanWoollett-Light Nov 12, 2023
5756e07
feat mlock `NonNull`
JonathanWoollett-Light Nov 12, 2023
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1 change: 1 addition & 0 deletions changelog/2000.changed.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
`mmap`, `mmap_anonymous`, `munmap`, `mremap`, `madvise`, `msync`, `mprotect`, `munlock` and `mlock` updated to use `NonNull`.
65 changes: 35 additions & 30 deletions src/sys/mman.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,10 +8,8 @@ use crate::Result;
#[cfg(feature = "fs")]
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::{AsFd, AsRawFd},
};
use std::{num::NonZeroUsize, os::unix::io::{AsRawFd, AsFd}};
use std::ptr::NonNull;

libc_bitflags! {
/// Desired memory protection of a memory mapping.
Expand Down Expand Up @@ -377,8 +375,8 @@ libc_bitflags! {
/// `addr` must meet all the requirements described in the [`mlock(2)`] man page.
///
/// [`mlock(2)`]: https://man7.org/linux/man-pages/man2/mlock.2.html
pub unsafe fn mlock(addr: *const c_void, length: size_t) -> Result<()> {
Errno::result(libc::mlock(addr, length)).map(drop)
pub unsafe fn mlock(addr: NonNull<c_void>, length: size_t) -> Result<()> {
Errno::result(libc::mlock(addr.as_ptr(), length)).map(drop)
}

/// Unlocks all memory pages that contain part of the address range with
Expand All @@ -390,8 +388,8 @@ pub unsafe fn mlock(addr: *const c_void, length: size_t) -> Result<()> {
/// page.
///
/// [`munlock(2)`]: https://man7.org/linux/man-pages/man2/munlock.2.html
pub unsafe fn munlock(addr: *const c_void, length: size_t) -> Result<()> {
Errno::result(libc::munlock(addr, length)).map(drop)
pub unsafe fn munlock(addr: NonNull<c_void>, length: size_t) -> Result<()> {
Errno::result(libc::munlock(addr.as_ptr(), length)).map(drop)
}

/// Locks all memory pages mapped into this process' address space.
Expand Down Expand Up @@ -430,7 +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();
Expand All @@ -439,9 +437,12 @@ pub unsafe fn mmap<F: AsFd>(

if ret == libc::MAP_FAILED {
Err(Errno::last())
} else {
Ok(ret)
}
else {
// SAFETY: `libc::mmap` returns a valid non-null pointer or `libc::MAP_FAILED`, thus `ret`
// will be non-null here.
Ok(unsafe { NonNull::new_unchecked(ret) })
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Given that this is unsafe, do you think that we could add a comment stating it is safe, maybe something like:

mmap() will never return a NULL pointer, it is safe to use NonNull::new_unchecked() here

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Added comment.

}
}

/// Create an anonymous memory mapping.
Expand All @@ -459,7 +460,7 @@ 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;
Expand All @@ -468,7 +469,9 @@ pub unsafe fn mmap_anonymous(
if ret == libc::MAP_FAILED {
Err(Errno::last())
} else {
Ok(ret)
// SAFETY: `libc::mmap` returns a valid non-null pointer or `libc::MAP_FAILED`, thus `ret`
// will be non-null here.
Ok(unsafe { NonNull::new_unchecked(ret) })
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Also this one

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Added comment.

}
}

Expand All @@ -481,33 +484,35 @@ pub unsafe fn mmap_anonymous(
/// detailed requirements.
#[cfg(any(target_os = "linux", target_os = "netbsd"))]
pub unsafe fn mremap(
addr: *mut c_void,
addr: NonNull<c_void>,
old_size: size_t,
new_size: size_t,
flags: MRemapFlags,
new_address: Option<*mut c_void>,
) -> Result<*mut c_void> {
new_address: Option<NonNull<c_void>>,
) -> Result<NonNull<c_void>> {
#[cfg(target_os = "linux")]
let ret = libc::mremap(
addr,
addr.as_ptr(),
old_size,
new_size,
flags.bits(),
new_address.unwrap_or(std::ptr::null_mut()),
new_address.map(NonNull::as_ptr).unwrap_or(std::ptr::null_mut()),
);
#[cfg(target_os = "netbsd")]
let ret = libc::mremap(
addr,
addr.as_ptr(),
old_size,
new_address.unwrap_or(std::ptr::null_mut()),
new_address.map(NonNull::as_ptr).unwrap_or(std::ptr::null_mut()),
new_size,
flags.bits(),
);

if ret == libc::MAP_FAILED {
Err(Errno::last())
} else {
Ok(ret)
// SAFETY: `libc::mremap` returns a valid non-null pointer or `libc::MAP_FAILED`, thus `ret`
// will be non-null here.
Ok(unsafe { NonNull::new_unchecked(ret) })
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And this one: mremap() will never return a NULL pointer, it is safe to use NonNull::new_unchecked() here

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Added comment.

}
}

Expand All @@ -519,8 +524,8 @@ pub unsafe fn mremap(
/// page.
///
/// [`munmap(2)`]: https://man7.org/linux/man-pages/man2/munmap.2.html
pub unsafe fn munmap(addr: *mut c_void, len: size_t) -> Result<()> {
Errno::result(libc::munmap(addr, len)).map(drop)
pub unsafe fn munmap(addr: NonNull<c_void>, len: size_t) -> Result<()> {
Errno::result(libc::munmap(addr.as_ptr(), len)).map(drop)
}

/// give advice about use of memory
Expand All @@ -532,11 +537,11 @@ pub unsafe fn munmap(addr: *mut c_void, len: size_t) -> Result<()> {
///
/// [`madvise(2)`]: https://man7.org/linux/man-pages/man2/madvise.2.html
pub unsafe fn madvise(
addr: *mut c_void,
addr: NonNull<c_void>,
length: size_t,
advise: MmapAdvise,
) -> Result<()> {
Errno::result(libc::madvise(addr, length, advise as i32)).map(drop)
Errno::result(libc::madvise(addr.as_ptr(), length, advise as i32)).map(drop)
}

/// Set protection of memory mapping.
Expand All @@ -560,18 +565,18 @@ pub unsafe fn madvise(
/// 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)
/// std::slice::from_raw_parts_mut(mem.as_ptr().cast(), ONE_K)
/// };
/// assert_eq!(slice[0], 0x00);
/// slice[0] = 0xFF;
/// assert_eq!(slice[0], 0xFF);
/// ```
pub unsafe fn mprotect(
addr: *mut c_void,
addr: NonNull<c_void>,
length: size_t,
prot: ProtFlags,
) -> Result<()> {
Errno::result(libc::mprotect(addr, length, prot.bits())).map(drop)
Errno::result(libc::mprotect(addr.as_ptr(), length, prot.bits())).map(drop)
}

/// synchronize a mapped region
Expand All @@ -583,11 +588,11 @@ pub unsafe fn mprotect(
///
/// [`msync(2)`]: https://man7.org/linux/man-pages/man2/msync.2.html
pub unsafe fn msync(
addr: *mut c_void,
addr: NonNull<c_void>,
length: size_t,
flags: MsFlags,
) -> Result<()> {
Errno::result(libc::msync(addr, length, flags.bits())).map(drop)
Errno::result(libc::msync(addr.as_ptr(), length, flags.bits())).map(drop)
}

#[cfg(not(target_os = "android"))]
Expand Down
31 changes: 18 additions & 13 deletions test/sys/test_mman.rs
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Original file line number Diff line number Diff line change
@@ -1,19 +1,22 @@
#![allow(clippy::redundant_slicing)]

use nix::sys::mman::{mmap_anonymous, MapFlags, ProtFlags};
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);
}
}

Expand All @@ -22,6 +25,7 @@ fn test_mmap_anonymous() {
fn test_mremap_grow() {
use nix::libc::size_t;
use nix::sys::mman::{mremap, MRemapFlags};
use std::ptr::NonNull;

const ONE_K: size_t = 1024;
let one_k_non_zero = NonZeroUsize::new(ONE_K).unwrap();
Expand All @@ -34,7 +38,7 @@ 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;
Expand All @@ -43,7 +47,7 @@ fn test_mremap_grow() {
let slice: &mut [u8] = unsafe {
#[cfg(target_os = "linux")]
let mem = mremap(
slice.as_mut_ptr().cast(),
NonNull::from(&mut slice[..]).cast(),
ONE_K,
10 * ONE_K,
MRemapFlags::MREMAP_MAYMOVE,
Expand All @@ -52,14 +56,14 @@ fn test_mremap_grow() {
.unwrap();
#[cfg(target_os = "netbsd")]
let mem = mremap(
slice.as_mut_ptr().cast(),
NonNull::from(&mut slice[..]).cast(),
ONE_K,
10 * ONE_K,
MRemapFlags::MAP_REMAPDUP,
None,
)
.unwrap();
std::slice::from_raw_parts_mut(mem as *mut u8, 10 * ONE_K)
std::slice::from_raw_parts_mut(mem.cast().as_ptr(), 10 * ONE_K)
};

// The first KB should still have the old data in it.
Expand All @@ -79,6 +83,7 @@ fn test_mremap_shrink() {
use nix::libc::size_t;
use nix::sys::mman::{mremap, MRemapFlags};
use std::num::NonZeroUsize;
use std::ptr::NonNull;

const ONE_K: size_t = 1024;
let ten_one_k = NonZeroUsize::new(10 * ONE_K).unwrap();
Expand All @@ -90,15 +95,15 @@ 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;
assert_eq!(slice[ONE_K - 1], 0xFF);

let slice: &mut [u8] = unsafe {
let mem = mremap(
slice.as_mut_ptr().cast(),
NonNull::from(&mut slice[..]).cast(),
ten_one_k.into(),
ONE_K,
MRemapFlags::empty(),
Expand All @@ -107,8 +112,8 @@ fn test_mremap_shrink() {
.unwrap();
// Since we didn't supply MREMAP_MAYMOVE, the address should be the
// same.
assert_eq!(mem, slice.as_mut_ptr().cast());
std::slice::from_raw_parts_mut(mem as *mut u8, ONE_K)
assert_eq!(mem.as_ptr(), NonNull::from(&mut slice[..]).cast().as_ptr());
std::slice::from_raw_parts_mut(mem.as_ptr().cast(), ONE_K)
};

// The first KB should still be accessible and have the old data in it.
Expand Down