Add support for ptrace

Closes #138

3 files changed, 127 insertions, 31 deletions

diff --git a/src/errno.rs b/src/errno.rs
index d9226b96..b41cc834 100644
--- a/src/errno.rs
+++ b/src/errno.rs
@@ -3,44 +3,50 @@ use libc::c_int;
 pub use self::consts::*;
 pub use self::consts::Errno::*;
 
-/// Returns the platform-specific value of errno
-pub fn errno() -> i32 {
-    #[cfg(any(target_os = "macos",
-              target_os = "ios",
-              target_os = "freebsd"))]
-    unsafe fn errno_location() -> *const c_int {
-        extern { fn __error() -> *const c_int; }
-        __error()
-    }
 
-    #[cfg(target_os = "bitrig")]
-    fn errno_location() -> *const c_int {
-        extern {
-            fn __errno() -> *const c_int;
-        }
-        unsafe {
-            __errno()
-        }
-    }
+#[cfg(any(target_os = "macos",
+          target_os = "ios",
+          target_os = "freebsd"))]
+unsafe fn errno_location() -> *mut c_int {
+    extern { fn __error() -> *mut c_int; }
+    __error()
+}
 
-    #[cfg(target_os = "dragonfly")]
-    unsafe fn errno_location() -> *const c_int {
-        extern { fn __dfly_error() -> *const c_int; }
-        __dfly_error()
+#[cfg(target_os = "bitrig")]
+fn errno_location() -> *mut c_int {
+    extern {
+        fn __errno() -> *mut c_int;
     }
-
-    #[cfg(target_os = "openbsd")]
-    unsafe fn errno_location() -> *const c_int {
-        extern { fn __errno() -> *const c_int; }
+    unsafe {
         __errno()
     }
+}
 
-    #[cfg(any(target_os = "linux", target_os = "android"))]
-    unsafe fn errno_location() -> *const c_int {
-        extern { fn __errno_location() -> *const c_int; }
-        __errno_location()
-    }
+#[cfg(target_os = "dragonfly")]
+unsafe fn errno_location() -> *mut c_int {
+    extern { fn __dfly_error() -> *mut c_int; }
+    __dfly_error()
+}
+
+#[cfg(target_os = "openbsd")]
+unsafe fn errno_location() -> *mut c_int {
+    extern { fn __errno() -> *mut c_int; }
+    __errno()
+}
+
+#[cfg(any(target_os = "linux", target_os = "android"))]
+unsafe fn errno_location() -> *mut c_int {
+    extern { fn __errno_location() -> *mut c_int; }
+    __errno_location()
+}
 
+/// Sets the platform-specific errno to no-error
+unsafe fn clear() -> () {
+    *errno_location() = 0;
+}
+
+/// Returns the platform-specific value of errno
+pub fn errno() -> i32 {
     unsafe {
         (*errno_location()) as i32
     }
@@ -60,6 +66,10 @@ macro_rules! impl_errno {
             pub fn from_i32(err: i32) -> Errno {
                 from_i32(err)
             }
+
+            pub unsafe fn clear() -> () {
+                super::clear()
+            }
         }
     }
 }
diff --git a/src/sys/mod.rs b/src/sys/mod.rs
index ac9d6216..c124359d 100644
--- a/src/sys/mod.rs
+++ b/src/sys/mod.rs
@@ -34,3 +34,10 @@ pub mod mman;
 pub mod uio;
 
 pub mod time;
+
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86",
+              target_arch = "x86_64",
+              target_arch = "arm")),
+          )]
+pub mod ptrace;
diff --git a/src/sys/ptrace.rs b/src/sys/ptrace.rs
new file mode 100644
index 00000000..efda8c4e
--- /dev/null
+++ b/src/sys/ptrace.rs
@@ -0,0 +1,79 @@
+use {Error, Result};
+use errno::Errno;
+use libc::{pid_t, c_void};
+
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86",
+              target_arch = "x86_64",
+              target_arch = "arm")),
+          )]
+pub mod ptrace {
+    use libc::c_int;
+
+    pub type PtraceRequest = c_int;
+
+    pub const PTRACE_TRACEME:     PtraceRequest = 0;
+    pub const PTRACE_PEEKTEXT:    PtraceRequest = 1;
+    pub const PTRACE_PEEKDATA:    PtraceRequest = 2;
+    pub const PTRACE_PEEKUSER:    PtraceRequest = 3;
+    pub const PTRACE_POKETEXT:    PtraceRequest = 4;
+    pub const PTRACE_POKEDATA:    PtraceRequest = 5;
+    pub const PTRACE_POKEUSER:    PtraceRequest = 6;
+    pub const PTRACE_CONT:        PtraceRequest = 7;
+    pub const PTRACE_KILL:        PtraceRequest = 8;
+    pub const PTRACE_SINGLESTEP:  PtraceRequest = 9;
+    pub const PTRACE_GETREGS:     PtraceRequest = 12;
+    pub const PTRACE_SETREGS:     PtraceRequest = 13;
+    pub const PTRACE_GETFPREGS:   PtraceRequest = 14;
+    pub const PTRACE_SETFPREGS:   PtraceRequest = 15;
+    pub const PTRACE_ATTACH:      PtraceRequest = 16;
+    pub const PTRACE_DETACH:      PtraceRequest = 17;
+    pub const PTRACE_GETFPXREGS:  PtraceRequest = 18;
+    pub const PTRACE_SETFPXREGS:  PtraceRequest = 19;
+    pub const PTRACE_SYSCALL:     PtraceRequest = 24;
+    pub const PTRACE_SETOPTIONS:  PtraceRequest = 0x4200;
+    pub const PTRACE_GETEVENTMSG: PtraceRequest = 0x4201;
+    pub const PTRACE_GETSIGINFO:  PtraceRequest = 0x4202;
+    pub const PTRACE_SETSIGINFO:  PtraceRequest = 0x4203;
+    pub const PTRACE_GETREGSET:   PtraceRequest = 0x4204;
+    pub const PTRACE_SETREGSET:   PtraceRequest = 0x4205;
+    pub const PTRACE_SEIZE:       PtraceRequest = 0x4206;
+    pub const PTRACE_INTERRUPT:   PtraceRequest = 0x4207;
+    pub const PTRACE_LISTEN:      PtraceRequest = 0x4208;
+    pub const PTRACE_PEEKSIGINFO: PtraceRequest = 0x4209;
+}
+
+mod ffi {
+    use libc::{pid_t, c_int, c_long, c_void};
+
+    extern {
+        pub fn ptrace(request: c_int, pid: pid_t, addr: * const c_void, data: * const c_void) -> c_long;
+    }
+}
+
+pub fn ptrace(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, data: *mut c_void) -> Result<i64> {
+    use self::ptrace::*;
+
+    match request {
+        PTRACE_PEEKTEXT | PTRACE_PEEKDATA | PTRACE_PEEKUSER => ptrace_peek(request, pid, addr, data),
+        _ => ptrace_other(request, pid, addr, data)
+    }
+}
+
+fn ptrace_peek(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, data: *mut c_void) -> Result<i64> {
+    let ret = unsafe {
+        Errno::clear();
+        ffi::ptrace(request, pid, addr, data)
+    };
+    if ret == -1 && Errno::last() != Errno::UnknownErrno {
+        return Err(Error::Sys(Errno::last()));
+    }
+    Ok::<i64, Error>(ret)
+}
+
+fn ptrace_other(request: ptrace::PtraceRequest, pid: pid_t, addr: *mut c_void, data: *mut c_void) -> Result<i64> {
+    match unsafe { ffi::ptrace(request, pid, addr, data) } {
+        -1 => Err(Error::Sys(Errno::last())),
+        _  => Ok(0)
+    }
+}