From d0f81e3d2afdf7a89fd466799f2d900da9f2ac40 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 14 Mar 2024 20:57:12 -0400
Subject: kernel: sched: Add exit routine

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/include/sys/sched.h |  1 +
 sys/kern/kern_sched.c   | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

(limited to 'sys')

diff --git a/sys/include/sys/sched.h b/sys/include/sys/sched.h
index d803df0..f06c104 100644
--- a/sys/include/sys/sched.h
+++ b/sys/include/sys/sched.h
@@ -38,6 +38,7 @@
 #include <machine/frame.h>
 
 void sched_init(void);
+void sched_exit(void);
 void sched_context_switch(struct trapframe *tf);
 
 __noreturn
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index f985f62..c3d1e09 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -280,6 +280,50 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
     return td;
 }
 
+static void
+sched_destroy_td(struct proc *td)
+{
+    processor_free_pcb(td);
+
+    /*
+     * User stacks are allocated with vm_alloc_pageframe(),
+     * while kernel stacks are allocated with dynalloc().
+     * We want to check if we are a user program or kernel
+     * program to perform the proper deallocation method.
+     */
+    if (td->is_user) {
+        vm_free_pageframe(td->stack_base, STACK_PAGES);
+    } else {
+        dynfree((void *)td->stack_base);
+    }
+
+    pmap_free_vas(vm_get_ctx(), td->addrsp);
+    dynfree(td);
+}
+
+void
+sched_exit(void)
+{
+    struct sched_state *state;
+    struct cpu_info *ci;
+    struct proc *td;
+    struct vas kvas = vm_get_kvas();
+
+    intr_mask();
+
+    /* Get the thread running on the current processor */
+    ci = this_cpu();
+    state = &ci->sched_state;
+    td = state->td;
+
+    /* Switch back to the kernel address space and destroy ourself */
+    pmap_switch_vas(vm_get_ctx(), kvas);
+    sched_destroy_td(td);
+
+    intr_unmask();
+    sched_enter();
+}
+
 /*
  * Thread context switch routine
  */
-- 
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