Added ptrace utilities.

Some ptrace functions return structures through the data argument. This commit adds utilities to return data through this mechanism and function specialisations for a few of these functions (getting event messages or the siginfo_t struct). Once the next version of libc is released these utilities will be expanded to include the fpregs and user_regs structs.

Ptrace requests that are now satisfied by a more specific public function will return an unsupported operation error. This has involved adding an UnsupportedOperation to the nix::Error enum and removed the mapping from Error to Errno and from Error to std::io::Error.

CHANGELOG.md

@@ -18,6 +18,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#556](https://github.com/nix-rust/nix/pull/556)
 - Added `nix::ptr::openpty`
   ([#456](https://github.com/nix-rust/nix/pull/456))
+- Added `nix::ptrace::{ptrace_get_data, ptrace_getsiginfo, ptrace_setsiginfo
+  and nix::Error::UnsupportedOperation}`
+  ([#614](https://github.com/nix-rust/nix/pull/614))
 
 ### Changed
 - Marked `sys::mman::{ mmap, munmap, madvise, munlock, msync }` as unsafe.
@@ -29,6 +32,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Changed type signature of `sys::select::FdSet::contains` to make `self`
   immutable ([#564](https://github.com/nix-rust/nix/pull/564))
 
+### Removed
+- Removed io::Error from nix::Error and conversion from nix::Error to Errno
+  ([#614](https://github.com/nix-rust/nix/pull/614))
+
 ### Fixed
 - Fixed multiple issues compiling under different archetectures and OSes.
   Now compiles on Linux/MIPS ([#538](https://github.com/nix-rust/nix/pull/538)),

src/lib.rs

@@ -75,7 +75,6 @@ use std::{ptr, result};
 use std::ffi::{CStr, OsStr};
 use std::path::{Path, PathBuf};
 use std::os::unix::ffi::OsStrExt;
-use std::io;
 use std::fmt;
 use std::error;
 use libc::PATH_MAX;
@@ -97,6 +96,9 @@ pub enum Error {
     /// The operation involved a conversion to Rust's native String type, which failed because the
     /// string did not contain all valid UTF-8.
     InvalidUtf8,
+    /// The operation is not supported by Nix, in this instance either use the libc bindings or 
+    /// consult the module documentation to see if there is a more appropriate interface available.
+    UnsupportedOperation,
 }
 
 impl Error {
@@ -116,14 +118,6 @@ impl Error {
         Error::Sys(errno::EINVAL)
     }
 
-    /// Get the errno associated with this error
-    pub fn errno(&self) -> errno::Errno {
-        match *self {
-            Error::InvalidPath => errno::Errno::EINVAL,
-            Error::InvalidUtf8 => errno::Errno::UnknownErrno,
-            Error::Sys(errno) => errno,
-        }
-    }
 }
 
 impl From<errno::Errno> for Error {
@@ -139,6 +133,7 @@ impl error::Error for Error {
         match self {
             &Error::InvalidPath => "Invalid path",
             &Error::InvalidUtf8 => "Invalid UTF-8 string",
+            &Error::UnsupportedOperation => "Unsupported Operation",
             &Error::Sys(ref errno) => errno.desc(),
         }
     }
@@ -149,21 +144,12 @@ impl fmt::Display for Error {
         match self {
             &Error::InvalidPath => write!(f, "Invalid path"),
             &Error::InvalidUtf8 => write!(f, "Invalid UTF-8 string"),
+            &Error::UnsupportedOperation => write!(f, "Unsupported Operation"),
             &Error::Sys(errno) => write!(f, "{:?}: {}", errno, errno.desc()),
         }
     }
 }
 
-impl From<Error> for io::Error {
-    fn from(err: Error) -> Self {
-        match err {
-            Error::InvalidPath => io::Error::new(io::ErrorKind::InvalidInput, err),
-            Error::InvalidUtf8 => io::Error::new(io::ErrorKind::Other, err),
-            Error::Sys(errno) => io::Error::from_raw_os_error(errno as i32),
-        }
-    }
-}
-
 pub trait NixPath {
     fn len(&self) -> usize;
 

src/sys/ptrace.rs

@@ -1,5 +1,6 @@
+use std::{mem, ptr};
 use {Errno, Error, Result};
-use libc::{pid_t, c_void, c_long};
+use libc::{pid_t, c_void, c_long, siginfo_t};
 
 #[cfg(all(target_os = "linux",
           any(target_arch = "x86",
@@ -71,11 +72,14 @@ mod ffi {
     }
 }
 
+/// Performs a ptrace request. If the request in question is provided by a specialised function
+/// this function will return an unsupported operation error.
 pub fn ptrace(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, data: *mut c_void) -> Result<c_long> {
     use self::ptrace::*;
 
     match request {
         PTRACE_PEEKTEXT | PTRACE_PEEKDATA | PTRACE_PEEKUSER => ptrace_peek(request, pid, addr, data),
+        PTRACE_GETSIGINFO | PTRACE_GETEVENTMSG | PTRACE_SETSIGINFO | PTRACE_SETOPTIONS => Err(Error::UnsupportedOperation),
         _ => ptrace_other(request, pid, addr, data)
     }
 }
@@ -91,6 +95,20 @@ fn ptrace_peek(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, da
     }
 }
 
+/// Function for ptrace requests that return values from the data field. 
+/// Some ptrace get requests populate structs or larger elements than c_long
+/// and therefore use the data field to return values. This function handles these
+/// requests.
+fn ptrace_get_data<T>(request: ptrace::PtraceRequest, pid: pid_t) -> Result<T> {
+    // Creates an uninitialized pointer to store result in 
+    let data: Box<T> = Box::new(unsafe { mem::uninitialized() });
+    let data: *mut c_void = unsafe { mem::transmute(data) };
+    ptrace(request, pid, ptr::null_mut(), data)?;
+    // Convert back into the original data format and return unboxed value
+    let data: Box<T> = unsafe { mem::transmute(data) };
+    Ok(*data)
+}
+
 fn ptrace_other(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, data: *mut c_void) -> Result<c_long> {
     Errno::result(unsafe { ffi::ptrace(request, pid, addr, data) }).map(|_| 0)
 }
@@ -102,3 +120,28 @@ pub fn ptrace_setoptions(pid: pid_t, options: ptrace::PtraceOptions) -> Result<(
 
     ptrace(PTRACE_SETOPTIONS, pid, ptr::null_mut(), options as *mut c_void).map(drop)
 }
+
+/// Gets a ptrace event as described by `ptrace(PTRACE_GETEVENTMSG,...)`
+pub fn ptrace_getevent(pid: pid_t) -> Result<c_long> {
+    use self::ptrace::*;
+    ptrace_get_data::<c_long>(PTRACE_GETEVENTMSG, pid)
+}
+
+/// Get siginfo as with `ptrace(PTRACE_GETSIGINFO,...)`
+pub fn ptrace_getsiginfo(pid: pid_t) -> Result<siginfo_t> {
+    use self::ptrace::*;
+    ptrace_get_data::<siginfo_t>(PTRACE_GETSIGINFO, pid)
+}
+
+/// Set siginfo as with `ptrace(PTRACE_SETSIGINFO,...)`
+pub fn ptrace_setsiginfo(pid: pid_t, sig: &siginfo_t) -> Result<()> {
+    use self::ptrace::*;
+    let ret = unsafe{
+        Errno::clear();
+        ffi::ptrace(PTRACE_SETSIGINFO, pid, ptr::null_mut(), sig as *const _ as *const c_void)
+    };
+    match Errno::result(ret) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(e),
+    }
+}