From a8b2282eb88f24c3c5f461e1557fa2cf76ebc251 Mon Sep 17 00:00:00 2001
From: turret <turret@duck.com>
Date: Sun, 19 Nov 2023 18:57:55 -0600
Subject: Initial commit

- create subsystem system using clone syscall, shared memory, shared
  file descriptors
- printk-like logging facility (TODO: console loglevel)
- initcall system (like linux kernel)

TODO: determine license
factors: linker.ld, linux kernel licensing (some ideas are more
  liberally taken rather than paraphrased)
---
 init/subsys.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 init/subsys.c

(limited to 'init/subsys.c')

diff --git a/init/subsys.c b/init/subsys.c
new file mode 100644
index 0000000..0435f1a
--- /dev/null
+++ b/init/subsys.c
@@ -0,0 +1,55 @@
+#include <errno.h>
+#include <sched.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <config.h>
+#include <log.h>
+#include <util.h>
+
+#define STACK_SIZE 8192 * 512
+
+struct subsystem_info {
+    char *fn_name;
+    int (*fn)(void);
+};
+
+int __subsystem_entry(struct subsystem_info *info)
+{
+
+    char *name = malloc(16 * sizeof(char));
+    snprintf(name, 16, NAME_SHORTHAND ": %s", info->fn_name);
+    name[15] = '\0';
+    prctl(PR_SET_NAME, name);
+    free(name);
+
+    int ret = info->fn();
+
+    free(info);
+
+    return ret;
+}
+
+int __impl_start_subsystem(char *fn_name, int (*fn)(void))
+{
+    void *stack = mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_GROWSDOWN | MAP_STACK | MAP_PRIVATE, -1, 0);
+    if((long)stack < 0)
+        die("subsys mmap:");
+
+    struct subsystem_info *info = malloc(sizeof(struct subsystem_info));
+    info->fn_name = fn_name;
+    info->fn = fn;
+
+    int pid = clone((int (*)(void *))__subsystem_entry, stack, CLONE_FILES | CLONE_VM, info);
+    if(pid < 0) {
+        munmap(stack, STACK_SIZE);
+        die("subsys clone:");
+    }
+
+    return 0;
+}
-- 
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