Merge #686

686: Fix special ptraces r=Susurrus

In #614 we added specializations of `ptrace()` that added more type safety. As part of this, the `UnsupportedOperation` error was introduced for the requests that are covered by specialized versions so they couldn't be used with the general `ptrace()`. Unfortunately, no tests were added with this PR and so it slipped through that you could not do those operations at all anymore: `ptrace()` reported `UnsupportedOperation` for them and `ptrace_*` called `ptrace`, not `ffi::ptrace` and so also reported `UnsupportedOperation`! Whoops!

This minimally-invasive surgery corrects this by adding tests that call all the specialized `ptrace_*` ignoring the return value save checking for `UnsupportedOperation`. It also changes the functions calls to use `ffi::ptrace()` directly to fix the bug.

As this was never a bug in a released version of `nix`, there's no need for a changelog entry here.

src/sys/ptrace.rs

@@ -91,18 +91,16 @@ fn ptrace_peek(request: ptrace::PtraceRequest, pid: Pid, addr: *mut c_void, data
     }
 }
 
-/// Function for ptrace requests that return values from the data field. 
+/// 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) -> 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)
+    // Creates an uninitialized pointer to store result in
+    let data: T = unsafe { mem::uninitialized() };
+    let res = unsafe { ffi::ptrace(request, pid.into(), ptr::null_mut(), &data as *const _ as *const c_void) };
+    Errno::result(res)?;
+    Ok(data)
 }
 
 fn ptrace_other(request: ptrace::PtraceRequest, pid: Pid, addr: *mut c_void, data: *mut c_void) -> Result<c_long> {
@@ -114,7 +112,8 @@ pub fn ptrace_setoptions(pid: Pid, options: ptrace::PtraceOptions) -> Result<()>
     use self::ptrace::*;
     use std::ptr;
 
-    ptrace(PTRACE_SETOPTIONS, pid, ptr::null_mut(), options as *mut c_void).map(drop)
+    let res = unsafe { ffi::ptrace(PTRACE_SETOPTIONS, pid.into(), ptr::null_mut(), options as *mut c_void) };
+    Errno::result(res).map(|_| ())
 }
 
 /// Gets a ptrace event as described by `ptrace(PTRACE_GETEVENTMSG,...)`

test/sys/test_ptrace.rs

@@ -3,7 +3,8 @@ use nix::errno::*;
 use nix::unistd::*;
 use nix::sys::ptrace::*;
 use nix::sys::ptrace::ptrace::*;
-use std::ptr;
+
+use std::{mem, ptr};
 
 #[test]
 fn test_ptrace() {
@@ -12,3 +13,36 @@ fn test_ptrace() {
     let err = ptrace(PTRACE_ATTACH, getpid(), ptr::null_mut(), ptr::null_mut()).unwrap_err();
     assert!(err == Error::Sys(Errno::EPERM) || err == Error::Sys(Errno::ENOSYS));
 }
+
+// Just make sure ptrace_setoptions can be called at all, for now.
+#[test]
+fn test_ptrace_setoptions() {
+    let err = ptrace_setoptions(getpid(), PTRACE_O_TRACESYSGOOD).unwrap_err();
+    assert!(err != Error::UnsupportedOperation);
+}
+
+// Just make sure ptrace_getevent can be called at all, for now.
+#[test]
+fn test_ptrace_getevent() {
+    let err = ptrace_getevent(getpid()).unwrap_err();
+    assert!(err != Error::UnsupportedOperation);
+}
+
+// Just make sure ptrace_getsiginfo can be called at all, for now.
+#[test]
+fn test_ptrace_getsiginfo() {
+    match ptrace_getsiginfo(getpid()) {
+        Err(Error::UnsupportedOperation) => panic!("ptrace_getsiginfo returns Error::UnsupportedOperation!"),
+        _ => (),
+    }
+}
+
+// Just make sure ptrace_setsiginfo can be called at all, for now.
+#[test]
+fn test_ptrace_setsiginfo() {
+    let siginfo = unsafe { mem::uninitialized() };
+    match ptrace_setsiginfo(getpid(), &siginfo) {
+        Err(Error::UnsupportedOperation) => panic!("ptrace_setsiginfo returns Error::UnsupportedOperation!"),
+        _ => (),
+    }
+}