Fix user and kernel times on Windows

src/timer/mod.rs

@@ -21,6 +21,7 @@ use std::process::{ChildStdout, Command, ExitStatus};
 
 use anyhow::Result;
 
+#[cfg(not(windows))]
 #[derive(Debug, Copy, Clone)]
 struct CPUTimes {
     /// Total amount of time spent executing in user mode
@@ -74,15 +75,25 @@ fn discard(output: ChildStdout) {
 
 /// Execute the given command and return a timing summary
 pub fn execute_and_measure(mut command: Command) -> Result<TimerResult> {
-    let wallclock_timer = WallClockTimer::start();
-
     #[cfg(not(windows))]
     let cpu_timer = self::unix_timer::CPUTimer::start();
 
+    #[cfg(windows)]
+    {
+        use std::os::windows::process::CommandExt;
+
+        // Create a suspended process
+        command.creation_flags(4);
+    }
+
+    let wallclock_timer = WallClockTimer::start();
     let mut child = command.spawn()?;
 
     #[cfg(windows)]
-    let cpu_timer = self::windows_timer::CPUTimer::start_for_process(&child);
+    let cpu_timer = {
+        // SAFETY: We created a suspended process
+        unsafe { self::windows_timer::CPUTimer::start_suspended_process(&child) }
+    };
 
     if let Some(output) = child.stdout.take() {
         // Handle CommandOutputPolicy::Pipe
@@ -91,8 +102,8 @@ pub fn execute_and_measure(mut command: Command) -> Result<TimerResult> {
 
     let status = child.wait()?;
 
-    let (time_user, time_system) = cpu_timer.stop();
     let time_real = wallclock_timer.stop();
+    let (time_user, time_system) = cpu_timer.stop();
 
     Ok(TimerResult {
         time_real,

src/timer/windows_timer.rs

@@ -1,72 +1,119 @@
 #![cfg(windows)]
+#![warn(unsafe_op_in_unsafe_fn)]
 
-use std::mem;
-use std::os::windows::io::{AsRawHandle, RawHandle};
-use std::process::Child;
+use std::{mem, os::windows::io::AsRawHandle, process, ptr};
 
-use winapi::um::processthreadsapi::GetProcessTimes;
-use winapi::um::winnt::HANDLE;
+use clap::__macro_refs::once_cell::sync::Lazy;
+use winapi::{
+    shared::{ntdef::NTSTATUS, ntstatus::STATUS_SUCCESS},
+    um::{
+        handleapi::CloseHandle,
+        jobapi2::{AssignProcessToJobObject, CreateJobObjectW, QueryInformationJobObject},
+        libloaderapi::{GetModuleHandleA, GetProcAddress},
+        winnt::{
+            JobObjectBasicAccountingInformation, HANDLE, JOBOBJECT_BASIC_ACCOUNTING_INFORMATION,
+        },
+    },
+};
+
+#[cfg(windows_process_extensions_main_thread_handle)]
+use winapi::shared::minwindef::DWORD;
 
-use crate::timer::CPUTimes;
 use crate::util::units::Second;
 
 const HUNDRED_NS_PER_MS: i64 = 10;
 
+#[allow(non_upper_case_globals)]
+static NtResumeProcess: Lazy<unsafe extern "system" fn(ProcessHandle: HANDLE) -> NTSTATUS> =
+    Lazy::new(|| {
+        // SAFETY: Getting the module handle for ntdll.dll is safe
+        let ntdll = unsafe { GetModuleHandleA(b"ntdll.dll\0".as_ptr().cast()) };
+        assert!(!ntdll.is_null(), "GetModuleHandleA failed");
+
+        // SAFETY: The ntdll handle is valid
+        let nt_resume_process =
+            unsafe { GetProcAddress(ntdll, b"NtResumeProcess\0".as_ptr().cast()) };
+        assert!(!nt_resume_process.is_null(), "GetProcAddress failed");
+
+        // SAFETY: We transmute to the correct function signature
+        unsafe { mem::transmute(nt_resume_process) }
+    });
+
 pub struct CPUTimer {
-    handle: RawHandle,
+    job_object: HANDLE,
 }
 
 impl CPUTimer {
-    pub fn start_for_process(process: &Child) -> Self {
-        CPUTimer {
-            handle: process.as_raw_handle(),
+    pub unsafe fn start_suspended_process(child: &process::Child) -> Self {
+        // SAFETY: Creating a new job object is safe
+        let job_object = unsafe { CreateJobObjectW(ptr::null_mut(), ptr::null_mut()) };
+        assert!(!job_object.is_null(), "CreateJobObjectW failed");
+
+        // SAFETY: The job object handle is valid
+        let ret = unsafe { AssignProcessToJobObject(job_object, child.as_raw_handle()) };
+        assert!(ret != 0, "AssignProcessToJobObject failed");
+
+        #[cfg(windows_process_extensions_main_thread_handle)]
+        {
+            // SAFETY: The main thread handle is valid
+            let ret = unsafe { ResumeThread(child.main_thread_handle().as_raw_handle()) };
+            assert!(ret != -1 as DWORD, "NtResumeProcess failed");
         }
+
+        #[cfg(not(windows_process_extensions_main_thread_handle))]
+        {
+            // Since we can't get the main thread handle on stable rust, we use
+            // the undocumented but widely known `NtResumeProcess` function to
+            // resume a process by it's handle.
+
+            // SAFETY: The process handle is valid
+            let ret = unsafe { NtResumeProcess(child.as_raw_handle()) };
+            assert!(ret == STATUS_SUCCESS, "NtResumeProcess failed");
+        }
+
+        Self { job_object }
     }
 
     pub fn stop(&self) -> (Second, Second) {
-        let times = get_cpu_times(self.handle);
-        (
-            times.user_usec as f64 * 1e-6,
-            times.system_usec as f64 * 1e-6,
-        )
-    }
-}
+        let mut job_object_info =
+            mem::MaybeUninit::<JOBOBJECT_BASIC_ACCOUNTING_INFORMATION>::uninit();
 
-/// Read CPU execution times
-fn get_cpu_times(handle: RawHandle) -> CPUTimes {
-    let (user_usec, system_usec) = {
-        let mut _ctime = unsafe { mem::zeroed() };
-        let mut _etime = unsafe { mem::zeroed() };
-        let mut kernel_time = unsafe { mem::zeroed() };
-        let mut user_time = unsafe { mem::zeroed() };
+        // SAFETY: A valid job object got created in `start_suspended_process`
         let res = unsafe {
-            GetProcessTimes(
-                handle as HANDLE,
-                &mut _ctime,
-                &mut _etime,
-                &mut kernel_time,
-                &mut user_time,
+            QueryInformationJobObject(
+                self.job_object,
+                JobObjectBasicAccountingInformation,
+                job_object_info.as_mut_ptr().cast(),
+                mem::size_of::<JOBOBJECT_BASIC_ACCOUNTING_INFORMATION>() as u32,
+                ptr::null_mut(),
             )
         };
 
-        // GetProcessTimes will exit with non-zero if success as per: https://msdn.microsoft.com/en-us/library/windows/desktop/ms683223(v=vs.85).aspx
         if res != 0 {
-            // Extract times as laid out here: https://support.microsoft.com/en-us/help/188768/info-working-with-the-filetime-structure
-            // Both user_time and kernel_time are spans that the process spent in either.
-            let user: i64 = (((user_time.dwHighDateTime as i64) << 32)
-                + user_time.dwLowDateTime as i64)
-                / HUNDRED_NS_PER_MS;
-            let kernel: i64 = (((kernel_time.dwHighDateTime as i64) << 32)
-                + kernel_time.dwLowDateTime as i64)
-                / HUNDRED_NS_PER_MS;
-            (user, kernel)
-        } else {
-            (0, 0)
-        }
-    };
+            // SAFETY: The job object info got correctly initialized
+            let job_object_info = unsafe { job_object_info.assume_init() };
 
-    CPUTimes {
-        user_usec,
-        system_usec,
+            // SAFETY: The `TotalUserTime` is "The total amount of user-mode execution time for
+            // all active processes associated with the job, as well as all terminated processes no
+            // longer associated with the job, in 100-nanosecond ticks." and is safe to extract
+            let user: i64 = unsafe { job_object_info.TotalUserTime.QuadPart() } / HUNDRED_NS_PER_MS;
+
+            // SAFETY: The `TotalKernelTime` is "The total amount of kernel-mode execution time
+            // for all active processes associated with the job, as well as all terminated
+            // processes no longer associated with the job, in 100-nanosecond ticks." and is safe
+            // to extract
+            let kernel: i64 =
+                unsafe { job_object_info.TotalKernelTime.QuadPart() } / HUNDRED_NS_PER_MS;
+            (user as f64 * 1e-6, kernel as f64 * 1e-6)
+        } else {
+            (0.0, 0.0)
+        }
+    }
+}
+
+impl Drop for CPUTimer {
+    fn drop(self: &mut Self) {
+        // SAFETY: A valid job object got created in `start_suspended_process`
+        unsafe { CloseHandle(self.job_object) };
     }
 }