Add process_vm_readv and process_vm_writev

Author: geofft

CHANGELOG.md

@@ -24,6 +24,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   and nix::Error::UnsupportedOperation}`
   ([#614](https://github.com/nix-rust/nix/pull/614))
 - Added `cfmakeraw`, `cfsetspeed`, and `tcgetsid`. ([#527](https://github.com/nix-rust/nix/pull/527))
+- Added `nix::sys::uio::{process_vm_readv, process_vm_writev}` on Linux
+  ([#568](https://github.com/nix-rust/nix/pull/568))
 
 ### Changed
 - Changed `ioctl!(write ...)` to take argument by value instead as pointer.

src/sys/uio.rs

@@ -1,7 +1,10 @@
 // Silence invalid warnings due to rust-lang/rust#16719
 #![allow(improper_ctypes)]
+// Silence warning from empty bitflags
+#![allow(unused_imports)]
 
 use {Errno, Result};
+use unistd::Pid;
 use libc::{self, c_int, c_void, size_t, off_t};
 use std::marker::PhantomData;
 use std::os::unix::io::RawFd;
@@ -56,6 +59,38 @@ pub fn pread(fd: RawFd, buf: &mut [u8], offset: off_t) -> Result<usize>{
     Errno::result(res).map(|r| r as usize)
 }
 
+// process_vm_{read,write}v currently doesn't use flags, but we define this
+// type for forwards-compatibility.
+#[cfg(any(target_os = "linux"))]
+bitflags!(
+    pub struct CmaFlags: libc::c_ulong {
+        // The bitflags! macro requires at least one variant. any() evaluates
+        // to false, so this symbol never actually exists.
+        #[cfg(any())]
+        const CMA_DUMMY = 0;
+    }
+);
+
+#[cfg(any(target_os = "linux"))]
+pub fn process_vm_writev(pid: Pid, local_iov: &[IoVec<&[u8]>], remote_iov: &mut [IoVec<&mut [u8]>], flags: CmaFlags) -> Result<usize> {
+    let res = unsafe {
+        libc::process_vm_writev(pid.into(), local_iov.as_ptr() as *const libc::iovec, local_iov.len() as libc::c_ulong,
+                                            remote_iov.as_ptr() as *const libc::iovec, remote_iov.len() as libc::c_ulong, flags.bits())
+    };
+
+    Errno::result(res).map(|r| r as usize)
+}
+
+#[cfg(any(target_os = "linux"))]
+pub fn process_vm_readv(pid: Pid, local_iov: &mut [IoVec<&mut [u8]>], remote_iov: &[IoVec<&[u8]>], flags: CmaFlags) -> Result<usize> {
+    let res = unsafe {
+        libc::process_vm_readv(pid.into(), local_iov.as_ptr() as *const libc::iovec, local_iov.len() as libc::c_ulong,
+                                           remote_iov.as_ptr() as *const libc::iovec, remote_iov.len() as libc::c_ulong, flags.bits())
+    };
+
+    Errno::result(res).map(|r| r as usize)
+}
+
 #[repr(C)]
 pub struct IoVec<T>(libc::iovec, PhantomData<T>); 
 

test/sys/test_uio.rs

@@ -190,3 +190,51 @@ fn test_preadv() {
     let all = buffers.concat();
     assert_eq!(all, expected);
 }
+
+#[test]
+#[cfg(any(target_os = "linux", target_os = "android"))]
+// FIXME: qemu-user doesn't implement process_vm_readv/writev on most arches
+#[cfg_attr(not(any(target_arch = "x86", target_arch = "x86_64")), ignore)]
+fn test_process_vm_readv() {
+    use nix::unistd::ForkResult::*;
+    use nix::sys::signal::*;
+    use nix::sys::wait::*;
+    use std::{str, slice};
+
+    let (r, w) = pipe().unwrap();
+    match fork() {
+        Ok(Parent { child }) => {
+            close(w).unwrap();
+            let mut msg = vec![0u8; 32];
+            let bytes_read = read(r, &mut msg).unwrap();
+            msg.truncate(bytes_read);
+            close(r).unwrap();
+
+            let ptr: usize = str::from_utf8(&msg).unwrap().parse().unwrap();
+            let remote_iov = IoVec::from_slice(unsafe {
+                slice::from_raw_parts(ptr as *const _, 4)
+            });
+            let mut buf = vec![0u8; 4];
+
+            let ret = process_vm_readv(child,
+                                       &mut [IoVec::from_mut_slice(&mut buf)],
+                                       &[remote_iov],
+                                       CmaFlags::empty());
+
+            kill(child, SIGTERM).unwrap();
+            waitpid(child, None).unwrap();
+
+            assert_eq!(Ok(4), ret);
+            assert_eq!(&buf, b"test");
+        },
+        Ok(Child) => {
+            close(r).unwrap();
+            let s = String::from("test");
+            let msg = format!("{}", s.as_bytes().as_ptr() as usize);
+            write(w, msg.as_bytes()).unwrap();
+            close(w).unwrap();
+            pause().unwrap();
+        },
+        Err(_) => panic!("fork failed")
+    }
+}