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https://github.com/ghostty-org/ghostty.git
synced 2025-07-15 00:06:09 +03:00
Use clone3 / CLONE_INTO_CGROUP on Linux
Use clone3 / CLONE_INTO_CGROUP to have the Linux kernel create the process in the correct cgroup rather than move the process into the cgroup after it is created.
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@ -19,6 +19,7 @@ const Command = @This();
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const std = @import("std");
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const builtin = @import("builtin");
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const internal_os = @import("os/main.zig");
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const termio = @import("termio.zig");
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const windows = internal_os.windows;
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const TempDir = internal_os.TempDir;
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const mem = std.mem;
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@ -32,6 +33,8 @@ const EnvMap = std.process.EnvMap;
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const PreExecFn = fn (*Command) void;
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const log = std.log.scoped(.command);
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/// Path to the command to run. This must be an absolute path. This
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/// library does not do PATH lookup.
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path: []const u8,
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@ -61,6 +64,8 @@ stderr: ?File = null,
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/// exec process takes over, such as signal handlers, setsid, setuid, etc.
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pre_exec: ?*const PreExecFn = null,
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linux_cgroup: termio.Options.LinuxCgroup = termio.Options.linux_cgroup_default,
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/// If set, then the process will be created attached to this pseudo console.
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/// `stdin`, `stdout`, and `stderr` will be ignored if set.
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pseudo_console: if (builtin.os.tag == .windows) ?windows.exp.HPCON else void =
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@ -133,8 +138,11 @@ fn startPosix(self: *Command, arena: Allocator) !void {
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else
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@compileError("missing env vars");
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// Fork
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const pid = try posix.fork();
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const pid: linux.pid_t = switch (builtin.os.tag) {
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.linux => if (self.linux_cgroup) |cgroup| try internal_os.cgroup.cloneInto(cgroup) else try posix.fork(),
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else => try posix.fork(),
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};
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if (pid != 0) {
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// Parent, return immediately.
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self.pid = @intCast(pid);
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@ -1,7 +1,11 @@
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const std = @import("std");
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const assert = std.debug.assert;
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const linux = std.os.linux;
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const posix = std.posix;
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const Allocator = std.mem.Allocator;
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const log = std.log.scoped(.@"linux-cgroup");
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/// Returns the path to the cgroup for the given pid.
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pub fn current(alloc: Allocator, pid: std.os.linux.pid_t) !?[]const u8 {
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var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined;
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@ -64,6 +68,65 @@ pub fn moveInto(
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try file.writer().print("{}", .{pid});
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}
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/// Use clone3 to have the kernel create a new process with the correct cgroup
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/// rather than moving the process to the correct cgroup later.
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pub fn cloneInto(cgroup: []const u8) !posix.pid_t {
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var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined;
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const path = try std.fmt.bufPrintZ(&buf, "/sys/fs/cgroup{s}", .{cgroup});
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// Get a file descriptor that refers to the cgroup directory in the cgroup
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// sysfs to pass to the kernel in clone3.
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const fd: linux.fd_t = fd: {
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const rc = linux.open(path, linux.O{ .PATH = true, .DIRECTORY = true }, 0);
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switch (posix.errno(rc)) {
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.SUCCESS => {
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break :fd @as(linux.fd_t, @intCast(rc));
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},
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else => |errno| {
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log.err("unable to open cgroup dir {s}: {}", .{ path, errno });
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break :fd -1;
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},
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}
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};
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const args: extern struct {
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flags: u64,
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pidfd: u64,
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child_tid: u64,
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parent_tid: u64,
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exit_signal: u64,
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stack: u64,
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stack_size: u64,
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tls: u64,
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set_tid: u64,
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set_tid_size: u64,
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cgroup: u64,
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} = .{
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.flags = if (fd >= 0) linux.CLONE.INTO_CGROUP else 0,
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.pidfd = 0,
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.child_tid = 0,
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.parent_tid = 0,
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.exit_signal = linux.SIG.CHLD,
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.stack = 0,
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.stack_size = 0,
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.tls = 0,
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.set_tid = 0,
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.set_tid_size = 0,
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.cgroup = if (fd >= 0) @intCast(fd) else 0,
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};
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const rc = linux.syscall2(linux.SYS.clone3, @intFromPtr(&args), @sizeOf(@TypeOf(args)));
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switch (posix.errno(rc)) {
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.SUCCESS => {
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return @as(posix.pid_t, @intCast(rc));
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},
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else => |errno| {
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log.err("unable to clone: {}", .{errno});
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return error.CloneError;
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},
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}
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}
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/// Returns all available cgroup controllers for the given cgroup.
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/// The cgroup should have a '/'-prefix.
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///
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@ -1315,6 +1315,7 @@ const Subprocess = struct {
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}
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}).callback,
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.data = self,
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.linux_cgroup = self.linux_cgroup,
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};
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try cmd.start(alloc);
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errdefer killCommand(&cmd) catch |err| {
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@ -1345,13 +1346,6 @@ const Subprocess = struct {
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fn childPreExec(self: *Subprocess) !void {
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// Setup our pty
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try self.pty.?.childPreExec();
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// If we have a cgroup set, then we want to move into that cgroup.
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if (comptime builtin.os.tag == .linux) {
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if (self.linux_cgroup) |cgroup| {
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try internal_os.cgroup.moveInto(cgroup, 0);
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}
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}
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}
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/// Called to notify that we exited externally so we can unset our
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