Added support for prctl in Linux

Author: DOhlsson

CHANGELOG.md

@@ -30,6 +30,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   (#[1752](https://github.com/nix-rust/nix/pull/1752))
 - Added `signal::SigSet::from_sigset_t_unchecked()`.
   (#[1741](https://github.com/nix-rust/nix/pull/1741))
+- Added support for prctl in Linux.
+  (#[1550](https://github.com/nix-rust/nix/pull/1550))
 
 ### Changed
 

Cargo.toml

@@ -111,6 +111,10 @@ name = "test-mount"
 path = "test/test_mount.rs"
 harness = false
 
+[[test]]
+name = "test-prctl"
+path = "test/sys/test_prctl.rs"
+
 [[test]]
 name = "test-ptymaster-drop"
 path = "test/test_ptymaster_drop.rs"

src/sys/mod.rs

@@ -68,6 +68,12 @@ feature! {
     pub mod personality;
 }
 
+#[cfg(target_os = "linux")]
+feature! {
+    #![feature = "process"]
+    pub mod prctl;
+}
+
 feature! {
     #![feature = "pthread"]
     pub mod pthread;

src/sys/prctl.rs

@@ -0,0 +1,211 @@
+//! prctl is a Linux-only API for performing operations on a process or thread.
+//!
+//! Note that careless use of some prctl() operations can confuse the user-space run-time
+//! environment, so these operations should be used with care.
+//!
+//! For more documentation, please read [prctl(2)](https://man7.org/linux/man-pages/man2/prctl.2.html).
+
+use crate::errno::Errno;
+use crate::sys::signal::Signal;
+use crate::Result;
+
+use libc::{c_int, c_ulong};
+use std::convert::TryFrom;
+use std::ffi::{CStr, CString};
+
+libc_enum! {
+    /// The type of hardware memory corruption kill policy for the thread.
+
+    #[repr(i32)]
+    #[non_exhaustive]
+    #[allow(non_camel_case_types)]
+    pub enum PrctlMCEKillPolicy {
+        /// The thread will receive SIGBUS as soon as a memory corruption is detected.
+        PR_MCE_KILL_EARLY,
+        /// The process is killed only when it accesses a corrupted page.
+        PR_MCE_KILL_LATE,
+        /// Uses the system-wide default.
+        PR_MCE_KILL_DEFAULT,
+    }
+    impl TryFrom<i32>
+}
+
+fn prctl_set_bool(option: c_int, status: bool) -> Result<()> {
+    let res = unsafe { libc::prctl(option, status as c_ulong, 0, 0, 0) };
+    Errno::result(res).map(drop)
+}
+
+fn prctl_get_bool(option: c_int) -> Result<bool> {
+    let res = unsafe { libc::prctl(option, 0, 0, 0, 0) };
+    Errno::result(res).map(|res| res != 0)
+}
+
+/// Set the "child subreaper" attribute for this process
+pub fn set_child_subreaper(attribute: bool) -> Result<()> {
+    prctl_set_bool(libc::PR_SET_CHILD_SUBREAPER, attribute)
+}
+
+/// Get the "child subreaper" attribute for this process
+pub fn get_child_subreaper() -> Result<bool> {
+    // prctl writes into this var
+    let mut subreaper: c_int = 0;
+
+    let res = unsafe { libc::prctl(libc::PR_GET_CHILD_SUBREAPER, &mut subreaper, 0, 0, 0) };
+
+    Errno::result(res).map(|_| subreaper != 0)
+}
+
+/// Set the dumpable attribute which determines if core dumps are created for this process.
+pub fn set_dumpable(attribute: bool) -> Result<()> {
+    prctl_set_bool(libc::PR_SET_DUMPABLE, attribute)
+}
+
+/// Get the dumpable attribute for this process.
+pub fn get_dumpable() -> Result<bool> {
+    prctl_get_bool(libc::PR_GET_DUMPABLE)
+}
+
+/// Set the "keep capabilities" attribute for this process. This causes the thread to retain
+/// capabilities even if it switches its UID to a nonzero value.
+pub fn set_keepcaps(attribute: bool) -> Result<()> {
+    prctl_set_bool(libc::PR_SET_KEEPCAPS, attribute)
+}
+
+/// Get the "keep capabilities" attribute for this process
+pub fn get_keepcaps() -> Result<bool> {
+    prctl_get_bool(libc::PR_GET_KEEPCAPS)
+}
+
+/// Clear the thread memory corruption kill policy and use the system-wide default
+pub fn clear_mce_kill() -> Result<()> {
+    let res = unsafe { libc::prctl(libc::PR_MCE_KILL, libc::PR_MCE_KILL_CLEAR, 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Set the thread memory corruption kill policy
+pub fn set_mce_kill(policy: PrctlMCEKillPolicy) -> Result<()> {
+    let res = unsafe {
+        libc::prctl(
+            libc::PR_MCE_KILL,
+            libc::PR_MCE_KILL_SET,
+            policy as c_ulong,
+            0,
+            0,
+        )
+    };
+
+    Errno::result(res).map(drop)
+}
+
+/// Get the thread memory corruption kill policy
+pub fn get_mce_kill() -> Result<PrctlMCEKillPolicy> {
+    let res = unsafe { libc::prctl(libc::PR_MCE_KILL_GET, 0, 0, 0, 0) };
+
+    match Errno::result(res) {
+        Ok(val) => Ok(PrctlMCEKillPolicy::try_from(val)?),
+        Err(e) => Err(e),
+    }
+}
+
+/// Set the parent-death signal of the calling process. This is the signal that the calling process
+/// will get when its parent dies.
+pub fn set_pdeathsig<T: Into<Option<Signal>>>(signal: T) -> Result<()> {
+    let sig = match signal.into() {
+        Some(s) => s as c_int,
+        None => 0,
+    };
+
+    let res = unsafe { libc::prctl(libc::PR_SET_PDEATHSIG, sig, 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Returns the current parent-death signal
+pub fn get_pdeathsig() -> Result<Option<Signal>> {
+    // prctl writes into this var
+    let mut sig: c_int = 0;
+
+    let res = unsafe { libc::prctl(libc::PR_GET_PDEATHSIG, &mut sig, 0, 0, 0) };
+
+    match Errno::result(res) {
+        Ok(_) => Ok(match sig {
+            0 => None,
+            _ => Some(Signal::try_from(sig)?),
+        }),
+        Err(e) => Err(e),
+    }
+}
+
+/// Set the name of the calling thread. Strings longer than 15 bytes will be truncated.
+pub fn set_name(name: &str) -> Result<()> {
+    let name = CString::new(name.as_bytes()).unwrap();
+
+    let res = unsafe { libc::prctl(libc::PR_SET_NAME, name.as_ptr(), 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Return the name of the calling thread
+pub fn get_name() -> Result<String> {
+    // Size of buffer determined by linux/sched.h TASK_COMM_LEN
+    let buf = [0u8; 16];
+
+    let res = unsafe { libc::prctl(libc::PR_GET_NAME, &buf, 0, 0, 0) };
+
+    let len = buf.iter().position(|&c| c == 0).unwrap_or(buf.len());
+    let cstr = CStr::from_bytes_with_nul(&buf[..=len]).map_err(|_| Errno::EINVAL)?;
+    let name = cstr.to_str().map_err(|_| Errno::EINVAL)?;
+
+    Errno::result(res).map(|_| name.to_owned())
+}
+
+/// Sets the timer slack value for the calling thread. Timer slack is used by the kernel to group
+/// timer expirations and make them the supplied amount of nanoseconds late.
+pub fn set_timerslack(ns: u64) -> Result<()> {
+    let res = unsafe { libc::prctl(libc::PR_SET_TIMERSLACK, ns, 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Get the timerslack for the calling thread.
+pub fn get_timerslack() -> Result<i32> {
+    let res = unsafe { libc::prctl(libc::PR_GET_TIMERSLACK, 0, 0, 0, 0) };
+
+    Errno::result(res)
+}
+
+/// Disable all performance counters attached to the calling process.
+pub fn task_perf_events_disable() -> Result<()> {
+    let res = unsafe { libc::prctl(libc::PR_TASK_PERF_EVENTS_DISABLE, 0, 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Enable all performance counters attached to the calling process.
+pub fn task_perf_events_enable() -> Result<()> {
+    let res = unsafe { libc::prctl(libc::PR_TASK_PERF_EVENTS_ENABLE, 0, 0, 0, 0) };
+
+    Errno::result(res).map(drop)
+}
+
+/// Set the calling threads "no new privs" attribute. Once set this option can not be unset.
+pub fn set_no_new_privs() -> Result<()> {
+    prctl_set_bool(libc::PR_SET_NO_NEW_PRIVS, true) // Cannot be unset
+}
+
+/// Get the "no new privs" attribute for the calling thread.
+pub fn get_no_new_privs() -> Result<bool> {
+    prctl_get_bool(libc::PR_GET_NO_NEW_PRIVS)
+}
+
+/// Set the state of the "THP disable" flag for the calling thread. Setting this disables
+/// transparent huge pages.
+pub fn set_thp_disable(flag: bool) -> Result<()> {
+    prctl_set_bool(libc::PR_SET_THP_DISABLE, flag)
+}
+
+/// Get the "THP disable" flag for the calling thread.
+pub fn get_thp_disable() -> Result<bool> {
+    prctl_get_bool(libc::PR_GET_THP_DISABLE)
+}

test/sys/test_prctl.rs

@@ -0,0 +1,122 @@
+#[cfg(target_os = "linux")]
+#[cfg(feature = "process")]
+mod test_prctl {
+    use nix::sys::prctl;
+
+    #[cfg_attr(qemu, ignore)]
+    #[test]
+    fn test_get_set_subreaper() {
+        let original = prctl::get_child_subreaper().unwrap();
+
+        prctl::set_child_subreaper(true).unwrap();
+        let subreaper = prctl::get_child_subreaper().unwrap();
+        assert!(subreaper);
+
+        prctl::set_child_subreaper(original).unwrap();
+    }
+
+    #[test]
+    fn test_get_set_dumpable() {
+        let original = prctl::get_dumpable().unwrap();
+
+        prctl::set_dumpable(false).unwrap();
+        let dumpable = prctl::get_dumpable().unwrap();
+        assert!(!dumpable);
+
+        prctl::set_dumpable(original).unwrap();
+    }
+
+    #[test]
+    fn test_get_set_keepcaps() {
+        let original = prctl::get_keepcaps().unwrap();
+
+        prctl::set_keepcaps(true).unwrap();
+        let keepcaps = prctl::get_keepcaps().unwrap();
+        assert!(keepcaps);
+
+        prctl::set_keepcaps(original).unwrap();
+    }
+
+    #[test]
+    fn test_get_set_clear_mce_kill() {
+        use prctl::PrctlMCEKillPolicy::*;
+
+        prctl::set_mce_kill(PR_MCE_KILL_LATE).unwrap();
+        let mce = prctl::get_mce_kill().unwrap();
+        assert_eq!(mce, PR_MCE_KILL_LATE);
+
+        prctl::clear_mce_kill().unwrap();
+        let mce = prctl::get_mce_kill().unwrap();
+        assert_eq!(mce, PR_MCE_KILL_DEFAULT);
+    }
+
+    #[cfg_attr(qemu, ignore)]
+    #[test]
+    fn test_get_set_pdeathsig() {
+        use nix::sys::signal::Signal;
+
+        let original = prctl::get_pdeathsig().unwrap();
+
+        prctl::set_pdeathsig(Signal::SIGUSR1).unwrap();
+        let sig = prctl::get_pdeathsig().unwrap();
+        assert_eq!(sig, Some(Signal::SIGUSR1));
+
+        prctl::set_pdeathsig(original).unwrap();
+    }
+
+    #[test]
+    fn test_get_set_name() {
+        let original = prctl::get_name().unwrap();
+
+        let long_name = String::from("0123456789abcdefghijklmn");
+        prctl::set_name(&long_name).unwrap();
+        let res = prctl::get_name().unwrap();
+
+        // name truncated by kernel to TASK_COMM_LEN
+        assert_eq!(&long_name[..15], res);
+
+        let short_name = String::from("01234567");
+        prctl::set_name(&short_name).unwrap();
+        let res = prctl::get_name().unwrap();
+        assert_eq!(short_name, res);
+
+        prctl::set_name(&original).unwrap();
+    }
+
+    #[cfg_attr(qemu, ignore)]
+    #[test]
+    fn test_get_set_timerslack() {
+        let original = prctl::get_timerslack().unwrap();
+
+        let slack = 60_000;
+        prctl::set_timerslack(slack).unwrap();
+        let res = prctl::get_timerslack().unwrap();
+        assert_eq!(slack, res as u64);
+
+        prctl::set_timerslack(original as u64).unwrap();
+    }
+
+    #[test]
+    fn test_disable_enable_perf_events() {
+        prctl::task_perf_events_disable().unwrap();
+        prctl::task_perf_events_enable().unwrap();
+    }
+
+    #[test]
+    fn test_get_set_no_new_privs() {
+        prctl::set_no_new_privs().unwrap();
+        let no_new_privs = prctl::get_no_new_privs().unwrap();
+        assert!(no_new_privs);
+    }
+
+    #[test]
+    fn test_get_set_thp_disable() {
+        let original = prctl::get_thp_disable().unwrap();
+
+        prctl::set_thp_disable(true).unwrap();
+        let thp_disable = prctl::get_thp_disable().unwrap();
+        assert!(thp_disable);
+
+        prctl::set_thp_disable(original).unwrap();
+    }
+}