feat(sys): High-level personality(2) wrappers

Adds a high level `Persona` bitflags enum, as well as `personality::get()`
and `personality::set()` for interacting with `libc::personality()`.

3 files changed, 75 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 719d84dc..473ff454 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 - Added `mremap` (#[1306](https://github.com/nix-rust/nix/pull/1306))
 
+- Added `personality` (#[1331](https://github.com/nix-rust/nix/pull/1331))
 ### Fixed
 ### Changed
 
@@ -70,7 +71,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - Derived `Ord`, `PartialOrd` for `unistd::Pid` (#[1189](https://github.com/nix-rust/nix/pull/1189))
 - Added `select::FdSet::fds` method to iterate over file descriptors in a set.
   ([#1207](https://github.com/nix-rust/nix/pull/1207))
-- Added support for UDP generic segmentation offload (GSO) and generic 
+- Added support for UDP generic segmentation offload (GSO) and generic
   receive offload (GRO) ([#1209](https://github.com/nix-rust/nix/pull/1209))
 - Added support for `sendmmsg` and `recvmmsg` calls
   (#[1208](https://github.com/nix-rust/nix/pull/1208))
diff --git a/src/sys/mod.rs b/src/sys/mod.rs
index bf7f5412..438fb4fd 100644
--- a/src/sys/mod.rs
+++ b/src/sys/mod.rs
@@ -38,6 +38,9 @@ pub mod memfd;
 #[cfg(not(target_os = "redox"))]
 pub mod mman;
 
+#[cfg(target_os = "linux")]
+pub mod personality;
+
 pub mod pthread;
 
 #[cfg(any(target_os = "android",
diff --git a/src/sys/personality.rs b/src/sys/personality.rs
new file mode 100644
index 00000000..6548b654
--- /dev/null
+++ b/src/sys/personality.rs
@@ -0,0 +1,70 @@
+use crate::Result;
+use crate::errno::Errno;
+
+use libc::{self, c_int, c_ulong};
+
+libc_bitflags! {
+    /// Flags used and returned by [`get()`](fn.get.html) and
+    /// [`set()`](fn.set.html).
+    pub struct Persona: c_int {
+        ADDR_COMPAT_LAYOUT;
+        ADDR_NO_RANDOMIZE;
+        ADDR_LIMIT_32BIT;
+        ADDR_LIMIT_3GB;
+        #[cfg(not(target_env = "musl"))]
+        FDPIC_FUNCPTRS;
+        MMAP_PAGE_ZERO;
+        READ_IMPLIES_EXEC;
+        SHORT_INODE;
+        STICKY_TIMEOUTS;
+        #[cfg(not(target_env = "musl"))]
+        UNAME26;
+        WHOLE_SECONDS;
+    }
+}
+
+/// Retrieve the current process personality.
+///
+/// Returns a Result containing a Persona instance.
+///
+/// Example:
+///
+/// ```
+/// # use nix::sys::personality::{self, Persona};
+/// let pers = personality::get().unwrap();
+/// assert!(!pers.contains(Persona::WHOLE_SECONDS));
+/// ```
+pub fn get() -> Result<Persona> {
+    let res = unsafe {
+        libc::personality(0xFFFFFFFF)
+    };
+
+    Errno::result(res).map(|r| Persona::from_bits_truncate(r))
+}
+
+/// Set the current process personality.
+///
+/// Returns a Result containing the *previous* personality for the
+/// process, as a Persona.
+///
+/// For more information, see [personality(2)](https://man7.org/linux/man-pages/man2/personality.2.html)
+///
+/// **NOTE**: This call **replaces** the current personality entirely.
+/// To **update** the personality, first call `get()` and then `set()`
+/// with the modified persona.
+///
+/// Example:
+///
+/// ```
+/// # use nix::sys::personality::{self, Persona};
+/// let mut pers = personality::get().unwrap();
+/// assert!(!pers.contains(Persona::ADDR_NO_RANDOMIZE));
+/// personality::set(pers | Persona::ADDR_NO_RANDOMIZE);
+/// ```
+pub fn set(persona: Persona) -> Result<Persona> {
+    let res = unsafe {
+        libc::personality(persona.bits() as c_ulong)
+    };
+
+    Errno::result(res).map(|r| Persona::from_bits_truncate(r))
+}