Add process_vm_readv and process_vm_writev

Author: geofft

CHANGELOG.md

@@ -29,6 +29,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - On Linux and Android, added support for receiving `PTRACE_O_TRACESYSGOOD`
   events from `wait` and `waitpid` using `WaitStatus::PtraceSyscall`
   ([#566](https://github.com/nix-rust/nix/pull/566)).
+- 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 ...)` into `ioctl!(write_ptr ...)` and `ioctl!(write_int ..)` variants

src/sys/uio.rs

@@ -56,6 +56,85 @@ pub fn pread(fd: RawFd, buf: &mut [u8], offset: off_t) -> Result<usize>{
     Errno::result(res).map(|r| r as usize)
 }
 
+/// A slice of memory in a remote process, starting at address `base`
+/// and consisting of `len` bytes.
+///
+/// This is the same underlying C structure as [`IoVec`](struct.IoVec.html),
+/// except that it refers to memory in some other process, and is
+/// therefore not represented in Rust by an actual slice as IoVec is. It
+/// is used with [`process_vm_readv`](fn.process_vm_readv.html)
+/// and [`process_vm_writev`](fn.process_vm_writev.html).
+#[cfg(target_os = "linux")]
+#[repr(C)]
+pub struct RemoteIoVec {
+    /// The starting address of this slice (`iov_base`).
+    pub base: usize,
+    /// The number of bytes in this slice (`iov_len`).
+    pub len: usize,
+}
+
+/// Write data directly to another process's virtual memory
+/// (see [`process_vm_writev`(2)]).
+///
+/// `local_iov` is a list of [`IoVec`]s containing the data to be written,
+/// and `remote_iov` is a list of [`RemoteIoVec`]s identifying where the
+/// data should be written in the target process. On success, returns the
+/// number of bytes written, which will always be a whole
+/// number of remote_iov chunks.
+///
+/// This requires the same permissions as debugging the process using
+/// [ptrace]: you must either be a privileged process (with
+/// `CAP_SYS_PTRACE`), or you must be running as the same user as the
+/// target process and the OS must have unprivileged debugging enabled.
+///
+/// This function is only available on Linux.
+///
+/// [`process_vm_writev`(2)]: http://man7.org/linux/man-pages/man2/process_vm_writev.2.html
+/// [ptrace]: ../ptrace/index.html
+/// [`IoVec`]: struct.IoVec.html
+/// [`RemoteIoVec`]: struct.RemoteIoVec.html
+#[cfg(target_os = "linux")]
+pub fn process_vm_writev(pid: ::unistd::Pid, local_iov: &[IoVec<&[u8]>], remote_iov: &[RemoteIoVec]) -> 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, 0)
+    };
+
+    Errno::result(res).map(|r| r as usize)
+}
+
+/// Read data directly from another process's virtual memory
+/// (see [`process_vm_readv`(2)]).
+///
+/// `local_iov` is a list of [`IoVec`]s containing the buffer to copy
+/// data into, and `remote_iov` is a list of [`RemoteIoVec`]s identifying
+/// where the source data is in the target process. On success,
+/// returns the number of bytes written, which will always be a whole
+/// number of remote_iov chunks.
+///
+/// This requires the same permissions as debugging the process using
+/// [ptrace]: you must either be a privileged process (with
+/// `CAP_SYS_PTRACE`), or you must be running as the same user as the
+/// target process and the OS must have unprivileged debugging enabled.
+///
+/// This function is only available on Linux.
+///
+/// [`process_vm_readv`(2)]: http://man7.org/linux/man-pages/man2/process_vm_readv.2.html
+/// [ptrace]: ../ptrace/index.html
+/// [`IoVec`]: struct.IoVec.html
+/// [`RemoteIoVec`]: struct.RemoteIoVec.html
+#[cfg(any(target_os = "linux"))]
+pub fn process_vm_readv(pid: ::unistd::Pid, local_iov: &[IoVec<&mut [u8]>], remote_iov: &[RemoteIoVec]) -> 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, 0)
+    };
+
+    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(target_os = "linux")]
+// 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;
+
+    #[allow(unused_variables)]
+    let m = ::FORK_MTX.lock().expect("Mutex got poisoned by another test");
+
+    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 = RemoteIoVec { base: ptr, len: 4 };
+            let mut buf = vec![0u8; 4];
+
+            let ret = process_vm_readv(child,
+                                       &[IoVec::from_mut_slice(&mut buf)],
+                                       &[remote_iov]);
+
+            kill(child, SIGTERM).unwrap();
+            waitpid(child, None).unwrap();
+
+            assert_eq!(Ok(4), ret);
+            assert_eq!(&buf, b"test");
+        },
+        Ok(Child) => {
+            let _ = close(r);
+            let s = String::from("test");
+            let msg = format!("{}", s.as_bytes().as_ptr() as usize);
+            let _ = write(w, msg.as_bytes());
+            let _ = close(w);
+            loop { let _ = pause(); }
+        },
+        Err(_) => panic!("fork failed")
+    }
+}