Remove syscall module.

This module merely contained FFI declarations, and only enough to
implement memfd_create() and pivot_root() wrapper functions in
nix. Since these declarations are redundant with equivalent FFI
declarations in libc, we'll remove them here. In the future, any
syscall-related wrapper function will be implemented directly and
utilize libc for FFI declarations as we cannot generically expose
a type-safe `syscall()` because of its variadic argument list.

CHANGELOG.md

@@ -52,6 +52,11 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Fix compilation and tests for OpenBSD targets
   ([#688](https://github.com/nix-rust/nix/pull/688))
 
+# Removed
+- The syscall module has been removed. This only exposed enough functionality for
+  `memfd_create()` and `pivot_root()`, which are still exposed as separate functions.
+  ([#747](https://github.com/nix-rust/nix/pull/747))
+
 ## [0.9.0] 2017-07-23
 
 ### Added

src/sys/memfd.rs

@@ -11,8 +11,9 @@ bitflags!(
 );
 
 pub fn memfd_create(name: &CStr, flags: MemFdCreateFlag) -> Result<RawFd> {
-    use sys::syscall::{syscall, MEMFD_CREATE};
-    let res = unsafe { syscall(MEMFD_CREATE, name.as_ptr(), flags.bits()) };
+    let res = unsafe {
+        libc::syscall(libc::SYS_memfd_create, name.as_ptr(), flags.bits())
+    };
 
     Errno::result(res).map(|r| r as RawFd)
 }

src/sys/mod.rs

@@ -31,9 +31,6 @@ pub mod socket;
 
 pub mod stat;
 
-#[cfg(any(target_os = "linux", target_os = "android"))]
-pub mod syscall;
-
 #[cfg(any(target_os = "linux"))]
 pub mod reboot;
 

src/unistd.rs

@@ -16,7 +16,7 @@ use sys::stat::Mode;
 use std::fmt;
 
 #[cfg(any(target_os = "android", target_os = "linux"))]
-pub use self::linux::*;
+pub use self::pivot_root::*;
 
 #[cfg(any(target_os = "android", target_os = "freebsd",
           target_os = "linux", target_os = "openbsd"))]
@@ -1647,16 +1647,16 @@ pub fn sysconf(var: SysconfVar) -> Result<Option<c_long>> {
 }
 
 #[cfg(any(target_os = "android", target_os = "linux"))]
-mod linux {
-    use sys::syscall::{syscall, SYSPIVOTROOT};
+mod pivot_root {
+    use libc;
     use {Errno, Result, NixPath};
 
     pub fn pivot_root<P1: ?Sized + NixPath, P2: ?Sized + NixPath>(
             new_root: &P1, put_old: &P2) -> Result<()> {
         let res = try!(try!(new_root.with_nix_path(|new_root| {
             put_old.with_nix_path(|put_old| {
                 unsafe {
-                    syscall(SYSPIVOTROOT, new_root.as_ptr(), put_old.as_ptr())
+                    libc::syscall(libc::SYS_pivot_root, new_root.as_ptr(), put_old.as_ptr())
                 }
             })
         })));