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.

1 files changed, 44 insertions, 1 deletions

diff --git a/src/sys/ptrace.rs b/src/sys/ptrace.rs
index edbc9734..bf6ee8bb 100644
--- a/src/sys/ptrace.rs
+++ b/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),
+    }
+}