Merge #1010

1010: Added `ptrace::{getregs, setregs}` r=asomers a=wpovell

I needed `ptrace`'s `getregs` and `setregs` for a project I was working on, so I added them! First time contributor, so let me know if I should change / fix anything. Things work fine in my project which uses both functions, let me know if further testing is needed.

Co-authored-by: Will Povell <william_povell@brown.edu>

CHANGELOG.md

@@ -13,6 +13,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
   ([#972](https://github.com/nix-rust/nix/pull/972))
 - Added `symlinkat` wrapper.
   ([#997](https://github.com/nix-rust/nix/pull/997))
+- Added `ptrace::{getregs, setregs}`.
+  ([#1010](https://github.com/nix-rust/nix/pull/1010))
 
 ### Changed
 ### Fixed
@@ -46,7 +48,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Added a `fchownat` wrapper.
   ([#955](https://github.com/nix-rust/nix/pull/955))
 - Added support for `ptrace` on BSD operating systems ([#949](https://github.com/nix-rust/nix/pull/949))
-- Added `ptrace` functions for reads and writes to tracee memory and ptrace kill 
+- Added `ptrace` functions for reads and writes to tracee memory and ptrace kill
   ([#949](https://github.com/nix-rust/nix/pull/949)) ([#958](https://github.com/nix-rust/nix/pull/958))
 - Added a `acct` wrapper module for enabling and disabling process accounting
   ([#952](https://github.com/nix-rust/nix/pull/952))

src/sys/ptrace/linux.rs

@@ -9,6 +9,12 @@ use sys::signal::Signal;
 
 pub type AddressType = *mut ::libc::c_void;
 
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86_64",
+              target_arch = "x86"),
+          target_env = "gnu"))]
+use libc::user_regs_struct;
+
 cfg_if! {
     if #[cfg(any(all(target_os = "linux", target_arch = "s390x"),
                  all(target_os = "linux", target_env = "gnu")))] {
@@ -192,6 +198,30 @@ fn ptrace_peek(request: Request, pid: Pid, addr: AddressType, data: *mut c_void)
     }
 }
 
+/// Get user registers, as with `ptrace(PTRACE_GETREGS, ...)`
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86_64",
+              target_arch = "x86"),
+          target_env = "gnu"))]
+pub fn getregs(pid: Pid) -> Result<user_regs_struct> {
+    ptrace_get_data::<user_regs_struct>(Request::PTRACE_GETREGS, pid)
+}
+
+/// Set user registers, as with `ptrace(PTRACE_SETREGS, ...)`
+#[cfg(all(target_os = "linux",
+          any(target_arch = "x86_64",
+              target_arch = "x86"),
+          target_env = "gnu"))]
+pub fn setregs(pid: Pid, regs: user_regs_struct) -> Result<()> {
+    let res = unsafe {
+        libc::ptrace(Request::PTRACE_SETREGS as RequestType,
+                     libc::pid_t::from(pid),
+                     ptr::null_mut::<c_void>(),
+                     &regs as *const _ as *const c_void)
+    };
+    Errno::result(res).map(drop)
+}
+
 /// 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
@@ -215,8 +245,6 @@ unsafe fn ptrace_other(request: Request, pid: Pid, addr: AddressType, data: *mut
 
 /// Set options, as with `ptrace(PTRACE_SETOPTIONS,...)`.
 pub fn setoptions(pid: Pid, options: Options) -> Result<()> {
-    use std::ptr;
-
     let res = unsafe {
         libc::ptrace(Request::PTRACE_SETOPTIONS as RequestType,
                      libc::pid_t::from(pid),