Enable getregs/setregs on musl

Update CHANGELOG for nix-rust#1198

CHANGELOG.md

@@ -17,6 +17,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Derived `Ord`, `PartialOrd` for `unistd::Pid` (#[1189](https://github.com/nix-rust/nix/pull/1189))
 
 ### Changed
+
+- Enabled `sys::ptrace::setregs` and `sys::ptrace::getregs` on x86_64-unknown-linux-musl target
+  (#[1198](https://github.com/nix-rust/nix/pull/1198))
+
 ### Fixed
 ### Removed
 

src/sys/ptrace/linux.rs

@@ -9,10 +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"))]
+#[cfg(all(
+    target_os = "linux",
+    any(all(target_arch = "x86_64",
+            any(target_env = "gnu", target_env = "musl")),
+        all(target_arch = "x86", target_env = "gnu"))
+))]
 use libc::user_regs_struct;
 
 cfg_if! {
@@ -199,19 +201,23 @@ 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"))]
+#[cfg(all(
+    target_os = "linux",
+    any(all(target_arch = "x86_64",
+            any(target_env = "gnu", target_env = "musl")),
+        all(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"))]
+#[cfg(all(
+    target_os = "linux",
+    any(all(target_arch = "x86_64",
+            any(target_env = "gnu", target_env = "musl")),
+        all(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,