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Use more constants and functions from libc #368

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Oct 27, 2024
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Use more constants and functions from libc #368

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5 changes: 2 additions & 3 deletions Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ harness = false
[features]
default = []
force-inprocess = []
memfd = ["sc"]
memfd = []
async = ["futures", "futures-test"]
win32-trace = []

Expand All @@ -33,14 +33,13 @@ fnv = "1.0.3"
futures = { version = "0.3", optional = true }
futures-test = { version = "0.3", optional = true }
lazy_static = "1"
libc = "0.2.12"
libc = "0.2.161"
rand = "0.8"
serde = { version = "1.0", features = ["rc"] }
uuid = { version = "1", features = ["v4"] }

[target.'cfg(any(target_os = "linux", target_os = "openbsd", target_os = "freebsd"))'.dependencies]
mio = { version = "1.0", features = ["os-ext"] }
sc = { version = "0.2.2", optional = true }
tempfile = "3.4"

[dev-dependencies]
Expand Down
103 changes: 19 additions & 84 deletions src/platform/unix/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,21 +11,22 @@ use crate::ipc::{self, IpcMessage};
use bincode;
use fnv::FnvHasher;
use lazy_static::lazy_static;
use libc::{self, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE, SOCK_SEQPACKET, SOL_SOCKET};
use libc::{
self, cmsghdr, linger, CMSG_DATA, CMSG_LEN, CMSG_SPACE, MAP_FAILED, MAP_SHARED, PROT_READ,
PROT_WRITE, SOCK_SEQPACKET, SOL_SOCKET,
};
use libc::{c_char, c_int, c_void, getsockopt, SO_LINGER, S_IFMT, S_IFSOCK};
use libc::{iovec, mode_t, msghdr, off_t, recvmsg, sendmsg};
use libc::{iovec, msghdr, off_t, recvmsg, sendmsg};
use libc::{sa_family_t, setsockopt, size_t, sockaddr, sockaddr_un, socketpair, socklen_t};
use libc::{EAGAIN, EWOULDBLOCK};
use mio::unix::SourceFd;
use mio::{Events, Interest, Poll, Token};
#[cfg(all(feature = "memfd", target_os = "linux"))]
use sc::syscall;
use std::cell::Cell;
use std::cmp;
use std::collections::HashMap;
use std::convert::TryInto;
use std::error::Error as StdError;
use std::ffi::CString;
use std::ffi::{c_uint, CString};
use std::fmt::{self, Debug, Formatter};
use std::hash::BuildHasherDefault;
use std::io;
Expand All @@ -43,8 +44,6 @@ use tempfile::{Builder, TempDir};

const MAX_FDS_IN_CMSG: u32 = 64;

const SCM_RIGHTS: c_int = 0x01;

// The value Linux returns for SO_SNDBUF
// is not the size we are actually allowed to use...
// Empirically, we have to deduct 32 bytes from that.
Expand Down Expand Up @@ -281,15 +280,16 @@ impl OsIpcSender {
len: usize,
) -> Result<(), UnixError> {
let result = unsafe {
let cmsg_length = mem::size_of_val(fds);
let cmsg_length = mem::size_of_val(fds) as c_uint;
let (cmsg_buffer, cmsg_space) = if cmsg_length > 0 {
let cmsg_buffer = libc::malloc(CMSG_SPACE(cmsg_length)) as *mut cmsghdr;
let cmsg_buffer =
libc::malloc(CMSG_SPACE(cmsg_length) as usize) as *mut cmsghdr;
if cmsg_buffer.is_null() {
return Err(UnixError::last());
}
(*cmsg_buffer).cmsg_len = CMSG_LEN(cmsg_length) as MsgControlLen;
(*cmsg_buffer).cmsg_level = libc::SOL_SOCKET;
(*cmsg_buffer).cmsg_type = SCM_RIGHTS;
(*cmsg_buffer).cmsg_type = libc::SCM_RIGHTS;

ptr::copy_nonoverlapping(
fds.as_ptr(),
Expand Down Expand Up @@ -1017,7 +1017,10 @@ fn recv(fd: c_int, blocking_mode: BlockingMode) -> Result<IpcMessage, UnixError>
let channel_length = if cmsg_length == 0 {
0
} else {
(cmsg.cmsg_len() - CMSG_ALIGN(mem::size_of::<cmsghdr>())) / mem::size_of::<c_int>()
// The control header is followed by an array of FDs. The size of the control header is
// determined by CMSG_SPACE. (On Linux this would the same as CMSG_ALIGN, but that isn't
// exposed by libc. CMSG_SPACE(0) is the portable version of that.)
(cmsg.cmsg_len() - CMSG_SPACE(0) as size_t) / mem::size_of::<c_int>()
Comment on lines +1021 to +1023
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If CMSG_ALIGN is not in libc we should add it.

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CMSG_ALIGN isn't portable, though, which is the challenge. CMSG_SPACE(0) should always be the same.

};
for index in 0..channel_length {
let fd = *cmsg_fds.add(index);
Expand Down Expand Up @@ -1122,7 +1125,7 @@ fn create_shmem(name: CString, length: usize) -> c_int {
#[cfg(all(feature = "memfd", target_os = "linux"))]
fn create_shmem(name: CString, length: usize) -> c_int {
unsafe {
let fd = memfd_create(name.as_ptr(), libc::MFD_CLOEXEC as usize);
let fd = libc::memfd_create(name.as_ptr(), libc::MFD_CLOEXEC);
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Oh hmm, glibc support was only added in 2.27. Not sure what the glibc policy of ipc-channel is.

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@sunshowers sunshowers Oct 18, 2024 •
edited
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FWIW I think the old call was incorrect, since it passed in a usize but the syscall is a cint: https://github.com/torvalds/linux/blob/4d939780b70592e0f4bc6c397e52e518f8fb7916/mm/memfd.c#L332

This worked presumably because of little-endianness, but it wasn't correct as far as I can tell.

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Looks like glibc 2.27 came out in 2018: https://sourceware.org/glibc/wiki/Release/2.27.

assert!(fd >= 0);
assert!(libc::ftruncate(fd, length as off_t) == 0);
fd
Expand All @@ -1146,8 +1149,8 @@ impl Drop for UnixCmsg {

impl UnixCmsg {
unsafe fn new(iovec: &mut [iovec]) -> Result<UnixCmsg, UnixError> {
let cmsg_length = CMSG_SPACE(MAX_FDS_IN_CMSG as usize * mem::size_of::<c_int>());
let cmsg_buffer = libc::malloc(cmsg_length) as *mut cmsghdr;
let cmsg_length = CMSG_SPACE(MAX_FDS_IN_CMSG * (mem::size_of::<c_int>() as c_uint));
let cmsg_buffer = libc::malloc(cmsg_length as usize) as *mut cmsghdr;
if cmsg_buffer.is_null() {
return Err(UnixError::last());
}
Expand All @@ -1165,17 +1168,7 @@ impl UnixCmsg {
}
},
BlockingMode::Timeout(duration) => {
#[cfg(target_os = "linux")]
const POLLRDHUP: libc::c_short = libc::POLLRDHUP;

// It's rather unfortunate that Rust's libc doesn't know that
// FreeBSD has POLLRDHUP, but in the mean time we can add
// the value ourselves.
// https://cgit.freebsd.org/src/tree/sys/sys/poll.h#n72
#[cfg(target_os = "freebsd")]
const POLLRDHUP: libc::c_short = 0x4000;

let events = libc::POLLIN | libc::POLLPRI | POLLRDHUP;
let events = libc::POLLIN | libc::POLLPRI | libc::POLLRDHUP;

let mut fd = [libc::pollfd {
fd,
Expand Down Expand Up @@ -1224,64 +1217,6 @@ fn is_socket(fd: c_int) -> bool {
if libc::fstat(fd, st.as_mut_ptr()) != 0 {
return false;
}
S_ISSOCK(st.assume_init().st_mode as mode_t)
(st.assume_init().st_mode & S_IFMT) == S_IFSOCK
}
}

// FFI stuff follows:

#[cfg(all(feature = "memfd", target_os = "linux"))]
unsafe fn memfd_create(name: *const c_char, flags: usize) -> c_int {
syscall!(MEMFD_CREATE, name, flags) as c_int
}

#[allow(non_snake_case)]
fn CMSG_LEN(length: size_t) -> size_t {
CMSG_ALIGN(mem::size_of::<cmsghdr>()) + length
}

#[allow(non_snake_case)]
unsafe fn CMSG_DATA(cmsg: *mut cmsghdr) -> *mut c_void {
(cmsg as *mut libc::c_uchar).add(CMSG_ALIGN(mem::size_of::<cmsghdr>())) as *mut c_void
}

#[allow(non_snake_case)]
fn CMSG_ALIGN(length: size_t) -> size_t {
(length + mem::size_of::<size_t>() - 1) & !(mem::size_of::<size_t>() - 1)
}

#[allow(non_snake_case)]
fn CMSG_SPACE(length: size_t) -> size_t {
CMSG_ALIGN(length) + CMSG_ALIGN(mem::size_of::<cmsghdr>())
}

#[allow(non_snake_case)]
fn S_ISSOCK(mode: mode_t) -> bool {
(mode & S_IFMT) == S_IFSOCK
}

#[cfg(target_env = "gnu")]
#[repr(C)]
struct cmsghdr {
cmsg_len: MsgControlLen,
cmsg_level: c_int,
cmsg_type: c_int,
}

#[cfg(not(target_env = "gnu"))]
#[repr(C)]
struct cmsghdr {
#[cfg(target_endian = "big")]
__pad1: c_int,
cmsg_len: MsgControlLen,
#[cfg(target_endian = "little")]
__pad1: c_int,
cmsg_level: c_int,
cmsg_type: c_int,
}

#[repr(C)]
struct linger {
l_onoff: c_int,
l_linger: c_int,
}