From 6db346c1b8e193f6b8d1861364bb3498c4def4ab Mon Sep 17 00:00:00 2001
From: Damien Zammit via Bug reports for the GNU Hurd <bug-hurd@gnu.org>
Date: Tue, 26 Nov 2024 10:37:58 +0000
Subject: sutils: Add smp tool to run process on slave processors

Until we make gnumach fully parallel, we need a way to execute
on slave processor set on smp-enabled gnumach.

For example:
	$ /sbin/smp /bin/bash
	$

will launch a shell that executes commands only within slave pset,
consisting of all processors except processor 0.

We can thus test parallelism on Hurd in a controlled way.
Message-ID: <20241126103747.353948-1-damien@zamaudio.com>
---
 sutils/Makefile |  2 +-
 sutils/smp.c    | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 sutils/smp.c

diff --git a/sutils/Makefile b/sutils/Makefile
index 5bb92c0b..07d0fb99 100644
--- a/sutils/Makefile
+++ b/sutils/Makefile
@@ -20,7 +20,7 @@
 dir := sutils
 makemode := utilities
 
-progs = reboot halt fsck swapon swapoff bless
+progs = reboot halt fsck swapon swapoff bless smp
 scripts = e2os MAKEDEV losetup
 targets = $(special-targets) $(progs)
 special-targets = $(scripts)
diff --git a/sutils/smp.c b/sutils/smp.c
new file mode 100644
index 00000000..f9147528
--- /dev/null
+++ b/sutils/smp.c
@@ -0,0 +1,80 @@
+/* Run a task on slave_pset
+   Copyright (C) 2024 Free Software Foundation, Inc.
+
+   This file is part of the GNU Hurd.
+
+   The GNU Hurd is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   The GNU Hurd is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <error.h>
+#include <hurd.h>
+#include <version.h>
+#include <mach/mach_types.h>
+#include <mach/mach_host.h>
+
+static void
+smp (char * const argv[])
+{
+  int i;
+  error_t err;
+  mach_msg_type_number_t pset_count;
+  mach_port_t hostpriv;
+  processor_set_name_array_t psets = {0};
+  processor_set_t slave_pset = MACH_PORT_NULL;
+
+  err = get_privileged_ports (&hostpriv, NULL);
+  if (err)
+    error (1, err, "Must be run as root for privileged cpu control");
+
+  err = host_processor_sets (hostpriv, &psets, &pset_count);
+  if (err)
+    error (1, err, "Cannot get list of host processor sets");
+
+  if (pset_count < 2)
+    error (1, ENOSYS, "gnumach does not have the expected processor sets, are you running smp kernel?");
+
+  err = host_processor_set_priv (hostpriv, psets[1], &slave_pset);
+  mach_port_deallocate (mach_task_self (), hostpriv);
+  for (i = 0; i < pset_count; i++)
+    mach_port_deallocate (mach_task_self (), psets[i]);
+  if (err)
+    error (1, err, "Cannot get access to slave processor set");
+
+  err = task_assign (mach_task_self (), slave_pset, FALSE);
+  mach_port_deallocate (mach_task_self (), slave_pset);
+  if (err)
+    error (1, err, "Cannot assign task self to slave processor set");
+
+  /* Drop privileges from suid binary */
+  mach_port_deallocate (mach_task_self (), _hurd_host_priv);
+  setuid (getuid ());
+
+  execve (argv[1], &argv[1], environ);
+
+  /* Fall through if not executed */
+  error (1, errno, "failed to execute %s", argv[1]);
+}
+
+int
+main (int argc, char **argv)
+{
+  if (argc < 2)
+    error (1, 0, "Usage: smp /path/to/executable");
+
+  smp (argv);
+  return 0;
+}
-- 
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