1 files changed, 458 insertions, 0 deletions
diff --git a/third_party/rust/memmap2/src/unix.rs b/third_party/rust/memmap2/src/unix.rs
new file mode 100644
index 0000000000..bd8fcf32a8
--- /dev/null
+++ b/third_party/rust/memmap2/src/unix.rs
@@ -0,0 +1,458 @@
+extern crate libc;
+
+use std::fs::File;
+use std::mem::ManuallyDrop;
+use std::os::unix::io::{FromRawFd, RawFd};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::{io, ptr};
+
+#[cfg(any(
+    all(target_os = "linux", not(target_arch = "mips")),
+    target_os = "freebsd",
+    target_os = "android"
+))]
+const MAP_STACK: libc::c_int = libc::MAP_STACK;
+
+#[cfg(not(any(
+    all(target_os = "linux", not(target_arch = "mips")),
+    target_os = "freebsd",
+    target_os = "android"
+)))]
+const MAP_STACK: libc::c_int = 0;
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+const MAP_POPULATE: libc::c_int = libc::MAP_POPULATE;
+
+#[cfg(not(any(target_os = "linux", target_os = "android")))]
+const MAP_POPULATE: libc::c_int = 0;
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+const MAP_HUGETLB: libc::c_int = libc::MAP_HUGETLB;
+
+#[cfg(target_os = "linux")]
+const MAP_HUGE_MASK: libc::c_int = libc::MAP_HUGE_MASK;
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+const MAP_HUGE_SHIFT: libc::c_int = libc::MAP_HUGE_SHIFT;
+
+#[cfg(not(any(target_os = "linux", target_os = "android")))]
+const MAP_HUGETLB: libc::c_int = 0;
+
+#[cfg(not(target_os = "linux"))]
+const MAP_HUGE_MASK: libc::c_int = 0;
+
+#[cfg(not(any(target_os = "linux", target_os = "android")))]
+const MAP_HUGE_SHIFT: libc::c_int = 0;
+
+#[cfg(any(
+    target_os = "android",
+    all(target_os = "linux", not(target_env = "musl"))
+))]
+use libc::{mmap64 as mmap, off64_t as off_t};
+
+#[cfg(not(any(
+    target_os = "android",
+    all(target_os = "linux", not(target_env = "musl"))
+)))]
+use libc::{mmap, off_t};
+
+pub struct MmapInner {
+    ptr: *mut libc::c_void,
+    len: usize,
+}
+
+impl MmapInner {
+    /// Creates a new `MmapInner`.
+    ///
+    /// This is a thin wrapper around the `mmap` system call.
+    fn new(
+        len: usize,
+        prot: libc::c_int,
+        flags: libc::c_int,
+        file: RawFd,
+        offset: u64,
+    ) -> io::Result<MmapInner> {
+        let alignment = offset % page_size() as u64;
+        let aligned_offset = offset - alignment;
+
+        let (map_len, map_offset) = Self::adjust_mmap_params(len, alignment as usize)?;
+
+        unsafe {
+            let ptr = mmap(
+                ptr::null_mut(),
+                map_len as libc::size_t,
+                prot,
+                flags,
+                file,
+                aligned_offset as off_t,
+            );
+
+            if ptr == libc::MAP_FAILED {
+                Err(io::Error::last_os_error())
+            } else {
+                Ok(Self::from_raw_parts(ptr, len, map_offset))
+            }
+        }
+    }
+
+    fn adjust_mmap_params(len: usize, alignment: usize) -> io::Result<(usize, usize)> {
+        use std::isize;
+
+        // Rust's slice cannot be larger than isize::MAX.
+        // See https://doc.rust-lang.org/std/slice/fn.from_raw_parts.html
+        //
+        // This is not a problem on 64-bit targets, but on 32-bit one
+        // having a file or an anonymous mapping larger than 2GB is quite normal
+        // and we have to prevent it.
+        //
+        // The code below is essentially the same as in Rust's std:
+        // https://github.com/rust-lang/rust/blob/db78ab70a88a0a5e89031d7ee4eccec835dcdbde/library/alloc/src/raw_vec.rs#L495
+        if std::mem::size_of::<usize>() < 8 && len > isize::MAX as usize {
+            return Err(io::Error::new(
+                io::ErrorKind::InvalidData,
+                "memory map length overflows isize",
+            ));
+        }
+
+        let map_len = len + alignment;
+        let map_offset = alignment;
+
+        // `libc::mmap` does not support zero-size mappings. POSIX defines:
+        //
+        // https://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html
+        // > If `len` is zero, `mmap()` shall fail and no mapping shall be established.
+        //
+        // So if we would create such a mapping, crate a one-byte mapping instead:
+        let map_len = map_len.max(1);
+
+        // Note that in that case `MmapInner::len` is still set to zero,
+        // and `Mmap` will still dereferences to an empty slice.
+        //
+        // If this mapping is backed by an empty file, we create a mapping larger than the file.
+        // This is unusual but well-defined. On the same man page, POSIX further defines:
+        //
+        // > The `mmap()` function can be used to map a region of memory that is larger
+        // > than the current size of the object.
+        //
+        // (The object here is the file.)
+        //
+        // > Memory access within the mapping but beyond the current end of the underlying
+        // > objects may result in SIGBUS signals being sent to the process. The reason for this
+        // > is that the size of the object can be manipulated by other processes and can change
+        // > at any moment. The implementation should tell the application that a memory reference
+        // > is outside the object where this can be detected; otherwise, written data may be lost
+        // > and read data may not reflect actual data in the object.
+        //
+        // Because `MmapInner::len` is not incremented, this increment of `aligned_len`
+        // will not allow accesses past the end of the file and will not cause SIGBUS.
+        //
+        // (SIGBUS is still possible by mapping a non-empty file and then truncating it
+        // to a shorter size, but that is unrelated to this handling of empty files.)
+        Ok((map_len, map_offset))
+    }
+
+    /// Get the current memory mapping as a `(ptr, map_len, offset)` tuple.
+    ///
+    /// Note that `map_len` is the length of the memory mapping itself and
+    /// _not_ the one that would be passed to `from_raw_parts`.
+    fn as_mmap_params(&self) -> (*mut libc::c_void, usize, usize) {
+        let offset = self.ptr as usize % page_size();
+        let len = self.len + offset;
+
+        // There are two possible memory layouts we could have, depending on
+        // the length and offset passed when constructing this instance:
+        //
+        // 1. The "normal" memory layout looks like this:
+        //
+        //         |<------------------>|<---------------------->|
+        //     mmap ptr    offset      ptr     public slice
+        //
+        //    That is, we have
+        //    - The start of the page-aligned memory mapping returned by mmap,
+        //      followed by,
+        //    - Some number of bytes that are memory mapped but ignored since
+        //      they are before the byte offset requested by the user, followed
+        //      by,
+        //    - The actual memory mapped slice requested by the user.
+        //
+        //    This maps cleanly to a (ptr, len, offset) tuple.
+        //
+        // 2. Then, we have the case where the user requested a zero-length
+        //    memory mapping. mmap(2) does not support zero-length mappings so
+        //    this crate works around that by actually making a mapping of
+        //    length one. This means that we have
+        //    - A length zero slice, followed by,
+        //    - A single memory mapped byte
+        //
+        //    Note that this only happens if the offset within the page is also
+        //    zero. Otherwise, we have a memory map of offset bytes and not a
+        //    zero-length memory map.
+        //
+        //    This doesn't fit cleanly into a (ptr, len, offset) tuple. Instead,
+        //    we fudge it slightly: a zero-length memory map turns into a
+        //    mapping of length one and can't be told apart outside of this
+        //    method without knowing the original length.
+        if len == 0 {
+            (self.ptr, 1, 0)
+        } else {
+            (unsafe { self.ptr.offset(-(offset as isize)) }, len, offset)
+        }
+    }
+
+    /// Construct this `MmapInner` from its raw components
+    ///
+    /// # Safety
+    ///
+    /// - `ptr` must point to the start of memory mapping that can be freed
+    ///   using `munmap(2)` (i.e. returned by `mmap(2)` or `mremap(2)`)
+    /// - The memory mapping at `ptr` must have a length of `len + offset`.
+    /// - If `len + offset == 0` then the memory mapping must be of length 1.
+    /// - `offset` must be less than the current page size.
+    unsafe fn from_raw_parts(ptr: *mut libc::c_void, len: usize, offset: usize) -> Self {
+        debug_assert_eq!(ptr as usize % page_size(), 0, "ptr not page-aligned");
+        debug_assert!(offset < page_size(), "offset larger than page size");
+
+        Self {
+            ptr: ptr.add(offset),
+            len,
+        }
+    }
+
+    pub fn map(len: usize, file: RawFd, offset: u64, populate: bool) -> io::Result<MmapInner> {
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        MmapInner::new(
+            len,
+            libc::PROT_READ,
+            libc::MAP_SHARED | populate,
+            file,
+            offset,
+        )
+    }
+
+    pub fn map_exec(len: usize, file: RawFd, offset: u64, populate: bool) -> io::Result<MmapInner> {
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        MmapInner::new(
+            len,
+            libc::PROT_READ | libc::PROT_EXEC,
+            libc::MAP_SHARED | populate,
+            file,
+            offset,
+        )
+    }
+
+    pub fn map_mut(len: usize, file: RawFd, offset: u64, populate: bool) -> io::Result<MmapInner> {
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        MmapInner::new(
+            len,
+            libc::PROT_READ | libc::PROT_WRITE,
+            libc::MAP_SHARED | populate,
+            file,
+            offset,
+        )
+    }
+
+    pub fn map_copy(len: usize, file: RawFd, offset: u64, populate: bool) -> io::Result<MmapInner> {
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        MmapInner::new(
+            len,
+            libc::PROT_READ | libc::PROT_WRITE,
+            libc::MAP_PRIVATE | populate,
+            file,
+            offset,
+        )
+    }
+
+    pub fn map_copy_read_only(
+        len: usize,
+        file: RawFd,
+        offset: u64,
+        populate: bool,
+    ) -> io::Result<MmapInner> {
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        MmapInner::new(
+            len,
+            libc::PROT_READ,
+            libc::MAP_PRIVATE | populate,
+            file,
+            offset,
+        )
+    }
+
+    /// Open an anonymous memory map.
+    pub fn map_anon(
+        len: usize,
+        stack: bool,
+        populate: bool,
+        huge: Option<u8>,
+    ) -> io::Result<MmapInner> {
+        let stack = if stack { MAP_STACK } else { 0 };
+        let populate = if populate { MAP_POPULATE } else { 0 };
+        let hugetlb = if huge.is_some() { MAP_HUGETLB } else { 0 };
+        let offset = huge
+            .map(|mask| ((mask as u64) & (MAP_HUGE_MASK as u64)) << MAP_HUGE_SHIFT)
+            .unwrap_or(0);
+        MmapInner::new(
+            len,
+            libc::PROT_READ | libc::PROT_WRITE,
+            libc::MAP_PRIVATE | libc::MAP_ANON | stack | populate | hugetlb,
+            -1,
+            offset,
+        )
+    }
+
+    pub fn flush(&self, offset: usize, len: usize) -> io::Result<()> {
+        let alignment = (self.ptr as usize + offset) % page_size();
+        let offset = offset as isize - alignment as isize;
+        let len = len + alignment;
+        let result =
+            unsafe { libc::msync(self.ptr.offset(offset), len as libc::size_t, libc::MS_SYNC) };
+        if result == 0 {
+            Ok(())
+        } else {
+            Err(io::Error::last_os_error())
+        }
+    }
+
+    pub fn flush_async(&self, offset: usize, len: usize) -> io::Result<()> {
+        let alignment = (self.ptr as usize + offset) % page_size();
+        let offset = offset as isize - alignment as isize;
+        let len = len + alignment;
+        let result =
+            unsafe { libc::msync(self.ptr.offset(offset), len as libc::size_t, libc::MS_ASYNC) };
+        if result == 0 {
+            Ok(())
+        } else {
+            Err(io::Error::last_os_error())
+        }
+    }
+
+    fn mprotect(&mut self, prot: libc::c_int) -> io::Result<()> {
+        unsafe {
+            let alignment = self.ptr as usize % page_size();
+            let ptr = self.ptr.offset(-(alignment as isize));
+            let len = self.len + alignment;
+            let len = len.max(1);
+            if libc::mprotect(ptr, len, prot) == 0 {
+                Ok(())
+            } else {
+                Err(io::Error::last_os_error())
+            }
+        }
+    }
+
+    pub fn make_read_only(&mut self) -> io::Result<()> {
+        self.mprotect(libc::PROT_READ)
+    }
+
+    pub fn make_exec(&mut self) -> io::Result<()> {
+        self.mprotect(libc::PROT_READ | libc::PROT_EXEC)
+    }
+
+    pub fn make_mut(&mut self) -> io::Result<()> {
+        self.mprotect(libc::PROT_READ | libc::PROT_WRITE)
+    }
+
+    #[inline]
+    pub fn ptr(&self) -> *const u8 {
+        self.ptr as *const u8
+    }
+
+    #[inline]
+    pub fn mut_ptr(&mut self) -> *mut u8 {
+        self.ptr as *mut u8
+    }
+
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    pub fn advise(&self, advice: libc::c_int, offset: usize, len: usize) -> io::Result<()> {
+        let alignment = (self.ptr as usize + offset) % page_size();
+        let offset = offset as isize - alignment as isize;
+        let len = len + alignment;
+        unsafe {
+            if libc::madvise(self.ptr.offset(offset), len, advice) != 0 {
+                Err(io::Error::last_os_error())
+            } else {
+                Ok(())
+            }
+        }
+    }
+
+    #[cfg(target_os = "linux")]
+    pub fn remap(&mut self, new_len: usize, options: crate::RemapOptions) -> io::Result<()> {
+        let (old_ptr, old_len, offset) = self.as_mmap_params();
+        let (map_len, offset) = Self::adjust_mmap_params(new_len, offset)?;
+
+        unsafe {
+            let new_ptr = libc::mremap(old_ptr, old_len, map_len, options.into_flags());
+
+            if new_ptr == libc::MAP_FAILED {
+                Err(io::Error::last_os_error())
+            } else {
+                // We explicitly don't drop self since the pointer within is no longer valid.
+                ptr::write(self, Self::from_raw_parts(new_ptr, new_len, offset));
+                Ok(())
+            }
+        }
+    }
+
+    pub fn lock(&self) -> io::Result<()> {
+        unsafe {
+            if libc::mlock(self.ptr, self.len) != 0 {
+                Err(io::Error::last_os_error())
+            } else {
+                Ok(())
+            }
+        }
+    }
+
+    pub fn unlock(&self) -> io::Result<()> {
+        unsafe {
+            if libc::munlock(self.ptr, self.len) != 0 {
+                Err(io::Error::last_os_error())
+            } else {
+                Ok(())
+            }
+        }
+    }
+}
+
+impl Drop for MmapInner {
+    fn drop(&mut self) {
+        let (ptr, len, _) = self.as_mmap_params();
+
+        // Any errors during unmapping/closing are ignored as the only way
+        // to report them would be through panicking which is highly discouraged
+        // in Drop impls, c.f. https://github.com/rust-lang/lang-team/issues/97
+        unsafe { libc::munmap(ptr, len as libc::size_t) };
+    }
+}
+
+unsafe impl Sync for MmapInner {}
+unsafe impl Send for MmapInner {}
+
+fn page_size() -> usize {
+    static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
+
+    match PAGE_SIZE.load(Ordering::Relaxed) {
+        0 => {
+            let page_size = unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize };
+
+            PAGE_SIZE.store(page_size, Ordering::Relaxed);
+
+            page_size
+        }
+        page_size => page_size,
+    }
+}
+
+pub fn file_len(file: RawFd) -> io::Result<u64> {
+    // SAFETY: We must not close the passed-in fd by dropping the File we create,
+    // we ensure this by immediately wrapping it in a ManuallyDrop.
+    unsafe {
+        let file = ManuallyDrop::new(File::from_raw_fd(file));
+        Ok(file.metadata()?.len())
+    }
+}