From bc828883c51c3c0f35872019f4db632e4ce82dc5 Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Wed, 11 Dec 2024 14:56:58 +0100
Subject: procfs: Add a procfs

Userland can now interface with processes by writing/reading from
`/proc/<pid>/<entry>`

It can send signals, for example `echo 15 > /proc/1/signal`
---
 kernel/sched/scheduler.c | 12 ++++++++++++
 kernel/sched/scheduler.h |  3 +++
 2 files changed, 15 insertions(+)

(limited to 'kernel/sched')

diff --git a/kernel/sched/scheduler.c b/kernel/sched/scheduler.c
index d0452fd..1b36e8a 100644
--- a/kernel/sched/scheduler.c
+++ b/kernel/sched/scheduler.c
@@ -98,6 +98,7 @@ process_t *create_process(process_t *p, u32 esp, u32 eip) {
   if (!r) {
     return NULL;
   }
+  r->reference_count = 1;
   r->tcb = kcalloc(1, sizeof(struct TCB));
   if (!r->tcb) {
     kfree(r);
@@ -147,6 +148,9 @@ process_t *create_process(process_t *p, u32 esp, u32 eip) {
     r->cr3 = get_active_pagedirectory();
   }
   r->parent = p;
+  if (p) {
+    p->reference_count++;
+  }
 
   r->tcb->CR3 = r->cr3->physical_address;
 
@@ -205,6 +209,14 @@ void free_process(process_t *p) {
   mmu_free_pagedirectory(p->cr3);
 }
 
+void process_remove_reference(process_t *p) {
+  assert(0 != p->reference_count);
+  p->reference_count--;
+  if (0 == p->reference_count) {
+    kfree(p);
+  }
+}
+
 void exit_process(process_t *p, int status) {
   assert(p->pid != 1);
   disable_interrupts();
diff --git a/kernel/sched/scheduler.h b/kernel/sched/scheduler.h
index 9d548a3..d03277e 100644
--- a/kernel/sched/scheduler.h
+++ b/kernel/sched/scheduler.h
@@ -69,6 +69,8 @@ struct Process {
   struct list write_list;
   struct list disconnect_list;
 
+  int reference_count;
+
   struct list event_queue;
 
   struct stack restore_context_stack;
@@ -98,4 +100,5 @@ int get_task_from_pid(pid_t pid, process_t **out);
 void free_process(process_t *p);
 void *get_free_virtual_memory(size_t length);
 void signal_process(process_t *p, int sig);
+void process_remove_reference(process_t *p);
 #endif
-- 
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