kernel: proc: Do not introduce fork()main

Simplicity is divine, fork() may be powerful but is no longer simple. It
became a thing in the late 70s during the early days of UNIX when computing
was simple, when CPUs were only 16-bits, MMUs were not prevalent and RAM was
only 512 KB. However it isn't 1971 anymore, process management, CPUs and memory
architecture has advanced significantly since. This commit ceases work on the
fork() syscall as implementing it would only introduce unnecessary complexity,
security issues, hefty processing overhead and would perpetuate what should
now be considered legacy. The current best alternative would be providing
a form of process spawning as well as a mechanism to wait for the child
process to complete.

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 96 insertions, 0 deletions

diff --git a/sys/kern/kern_spawn.c b/sys/kern/kern_spawn.c
new file mode 100644
index 0000000..6adf726
--- /dev/null
+++ b/sys/kern/kern_spawn.c
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/proc.h>
+#include <sys/mman.h>
+#include <sys/errno.h>
+#include <sys/syslog.h>
+#include <sys/atomic.h>
+#include <sys/signal.h>
+#include <sys/sched.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+#define pr_trace(fmt, ...) kprintf("spawn: " fmt, ##__VA_ARGS__)
+#define pr_error(...) pr_trace(__VA_ARGS__)
+
+static volatile size_t nthreads = 0;
+
+/*
+ * Spawn a new process
+ *
+ * @cur: Parent (current) process.
+ * @flags: Spawn flags.
+ * @ip: Location for process to start
+ * @newprocp: If not NULL, will contain the new process.
+ */
+int
+spawn(struct proc *cur, int flags, void(*ip)(void), struct proc **newprocp)
+{
+    struct proc *newproc;
+    struct mmap_lgdr *mlgdr;
+    int error;
+
+    newproc = dynalloc(sizeof(*newproc));
+    if (newproc == NULL) {
+        pr_error("could not alloc proc (-ENOMEM)\n");
+        return -ENOMEM;
+    }
+
+    mlgdr = dynalloc(sizeof(*mlgdr));
+    if (mlgdr == NULL) {
+        dynfree(newproc);
+        pr_error("could not alloc proc mlgdr (-ENOMEM)\n");
+        return -ENOMEM;
+    }
+
+    memset(newproc, 0, sizeof(*newproc));
+    error = md_spawn(newproc, cur, (uintptr_t)ip);
+    if (error < 0) {
+        dynfree(newproc);
+        dynfree(mlgdr);
+        pr_error("error initializing proc\n");
+        return error;
+    }
+
+    /* Set proc output if we can */
+    if (newprocp != NULL) {
+        *newprocp = newproc;
+    }
+
+    /* Initialize the mmap ledger */
+    mlgdr->nbytes = 0;
+    RBT_INIT(lgdr_entries, &mlgdr->hd);
+    newproc->mlgdr = mlgdr;
+
+    newproc->pid = ++nthreads;
+    signals_init(newproc);
+    sched_enqueue_td(newproc);
+    return 0;
+}