Greatly reduce needed memory when retrieving process arguments and en…

…vironment

src/unix/apple/macos/process.rs

@@ -6,7 +6,7 @@ use std::path::{Path, PathBuf};
 
 use std::borrow::Borrow;
 
-use libc::{c_int, c_void, kill, size_t};
+use libc::{c_int, c_void, kill};
 
 use crate::{DiskUsage, Gid, Pid, Process, ProcessRefreshKind, ProcessStatus, Signal, Uid};
 
@@ -363,7 +363,6 @@ unsafe fn convert_node_path_info(node: &libc::vnode_info_path) -> PathBuf {
 
 unsafe fn create_new_process(
     pid: Pid,
-    mut arg_max: size_t,
     now: u64,
     refresh_kind: ProcessRefreshKind,
     info: Option<libc::proc_bsdinfo>,
@@ -417,8 +416,6 @@ unsafe fn create_new_process(
         p => Some(Pid(p)),
     };
 
-    let mut proc_args: Vec<u8> = Vec::with_capacity(arg_max as _);
-    let mut mib = [libc::CTL_KERN, libc::KERN_PROCARGS2, pid.0 as _];
     /*
      * /---------------\ 0x00000000
      * | ::::::::::::: |
@@ -449,6 +446,26 @@ unsafe fn create_new_process(
      * :               :
      * \---------------/ 0xffffffff
      */
+    let mut mib = [libc::CTL_KERN, libc::KERN_PROCARGS2, pid.0 as _];
+    let mut arg_max = 0;
+    // First we retrieve the size we will need for our data (in `arg_max`).
+    if libc::sysctl(
+        mib.as_mut_ptr(),
+        mib.len() as _,
+        std::ptr::null_mut(),
+        &mut arg_max,
+        std::ptr::null_mut(),
+        0,
+    ) == -1
+    {
+        sysinfo_debug!(
+            "couldn't get arguments and environment size for PID {}",
+            pid.0
+        );
+        return Err(()); // not enough rights I assume?
+    }
+
+    let mut proc_args: Vec<u8> = Vec::with_capacity(arg_max as _);
     if libc::sysctl(
         mib.as_mut_ptr(),
         mib.len() as _,
@@ -459,7 +476,7 @@ unsafe fn create_new_process(
     ) == -1
     {
         sysinfo_debug!("couldn't get arguments and environment for PID {}", pid.0);
-        return Err(()); // not enough rights I assume?
+        return Err(()); // What changed since the previous call? Dark magic!
     }
 
     proc_args.set_len(arg_max);
@@ -577,7 +594,6 @@ fn get_environ(mut data: &[u8]) -> Vec<String> {
 pub(crate) fn update_process(
     wrap: &Wrap,
     pid: Pid,
-    size: size_t,
     time_interval: Option<f64>,
     now: u64,
     refresh_kind: ProcessRefreshKind,
@@ -600,7 +616,7 @@ pub(crate) fn update_process(
                     // We don't it to be removed, just replaced.
                     p.updated = true;
                     // The owner of this PID changed.
-                    return create_new_process(pid, size, now, refresh_kind, Some(info));
+                    return create_new_process(pid, now, refresh_kind, Some(info));
                 }
             }
             let task_info = get_task_info(pid);
@@ -640,7 +656,7 @@ pub(crate) fn update_process(
             p.updated = true;
             return Ok(None);
         }
-        create_new_process(pid, size, now, refresh_kind, get_bsd_info(pid))
+        create_new_process(pid, now, refresh_kind, get_bsd_info(pid))
     }
 }
 

src/unix/apple/system.rs

@@ -13,9 +13,6 @@ use std::mem;
 #[cfg(all(target_os = "macos", not(feature = "apple-sandbox")))]
 use std::time::SystemTime;
 
-#[cfg(all(target_os = "macos", not(feature = "apple-sandbox")))]
-use libc::size_t;
-
 use libc::{
     c_int, c_void, host_statistics64, mach_port_t, sysconf, sysctl, timeval, vm_statistics64,
     _SC_PAGESIZE,
@@ -182,7 +179,6 @@ impl SystemInner {
         }
         if let Some(pids) = get_proc_list() {
             let now = get_now();
-            let arg_max = get_arg_max();
             let port = self.port;
             let time_interval = self.clock_info.as_mut().map(|c| c.get_time_interval(port));
             let entries: Vec<Process> = {
@@ -193,15 +189,7 @@ impl SystemInner {
 
                 into_iter(pids)
                     .flat_map(|pid| {
-                        match update_process(
-                            wrap,
-                            pid,
-                            arg_max as size_t,
-                            time_interval,
-                            now,
-                            refresh_kind,
-                            false,
-                        ) {
+                        match update_process(wrap, pid, time_interval, now, refresh_kind, false) {
                             Ok(x) => x,
                             _ => None,
                         }
@@ -232,7 +220,6 @@ impl SystemInner {
         refresh_kind: ProcessRefreshKind,
     ) -> bool {
         let mut time_interval = None;
-        let arg_max = get_arg_max();
         let now = get_now();
 
         if refresh_kind.cpu() {
@@ -241,15 +228,7 @@ impl SystemInner {
         }
         match {
             let wrap = Wrap(UnsafeCell::new(&mut self.process_list));
-            update_process(
-                &wrap,
-                pid,
-                arg_max as size_t,
-                time_interval,
-                now,
-                refresh_kind,
-                true,
-            )
+            update_process(&wrap, pid, time_interval, now, refresh_kind, true)
         } {
             Ok(Some(p)) => {
                 self.process_list.insert(p.pid(), p);
@@ -430,28 +409,6 @@ impl SystemInner {
     }
 }
 
-#[cfg(all(target_os = "macos", not(feature = "apple-sandbox")))]
-fn get_arg_max() -> usize {
-    let mut mib = [libc::CTL_KERN, libc::KERN_ARGMAX];
-    let mut arg_max = 0i32;
-    let mut size = mem::size_of::<c_int>();
-    unsafe {
-        if sysctl(
-            mib.as_mut_ptr(),
-            mib.len() as _,
-            (&mut arg_max) as *mut i32 as *mut c_void,
-            &mut size,
-            std::ptr::null_mut(),
-            0,
-        ) == -1
-        {
-            4096 // We default to this value
-        } else {
-            arg_max as usize
-        }
-    }
-}
-
 fn get_system_info(value: c_int, default: Option<&str>) -> Option<String> {
     let mut mib: [c_int; 2] = [libc::CTL_KERN, value];
     let mut size = 0;