Create an [`MmapRegion`] using `mmap` of a file descriptor.
(
len: u64,
prot: c_int,
fd: BorrowedFd,
offset1: u64,
offset2: u64,
)
| 50 | |
| 51 | /// Create an [`MmapRegion`] using `mmap` of a file descriptor. |
| 52 | pub fn mmap( |
| 53 | len: u64, |
| 54 | prot: c_int, |
| 55 | fd: BorrowedFd, |
| 56 | offset1: u64, |
| 57 | offset2: u64, |
| 58 | ) -> std::io::Result<Self> { |
| 59 | const BAD_LENGTH: &str = "Offsets must fit in libc::off_t"; |
| 60 | const BAD_OFFSET: &str = "Mapping length must fit \ |
| 61 | in both isize and libc::size_t"; |
| 62 | let Some(offset) = offset1.checked_add(offset2) else { |
| 63 | return Err(Error::new(ErrorKind::InvalidInput, BAD_OFFSET)); |
| 64 | }; |
| 65 | let Ok(offset) = libc::off_t::try_from(offset) else { |
| 66 | return Err(Error::new(ErrorKind::InvalidInput, BAD_OFFSET)); |
| 67 | }; |
| 68 | if isize::try_from(len).is_err() { |
| 69 | return Err(Error::new(ErrorKind::InvalidInput, BAD_LENGTH)); |
| 70 | } |
| 71 | let Ok(len) = libc::size_t::try_from(len) else { |
| 72 | return Err(Error::new(ErrorKind::InvalidInput, BAD_LENGTH)); |
| 73 | }; |
| 74 | |
| 75 | assert!( |
| 76 | (prot & !(libc::PROT_READ | libc::PROT_WRITE | libc::PROT_EXEC)) == 0, |
| 77 | "bad protection" |
| 78 | ); |
| 79 | let flags = libc::MAP_SHARED; |
| 80 | // SAFETY: FFI call with correct parameters. |
| 81 | let addr = unsafe { libc::mmap(null_mut(), len, prot, flags, fd.as_raw_fd(), offset) }; |
| 82 | if addr == libc::MAP_FAILED { |
| 83 | Err(Error::last_os_error()) |
| 84 | } else { |
| 85 | let addr = addr.cast(); |
| 86 | Ok(Self { addr, len }) |
| 87 | } |
| 88 | } |
| 89 | } |