From 3c8cc57cd1d7b04ab92dc80bc0e0c9a481d905f8 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Mon, 26 Jul 2021 19:39:57 +0200
Subject: exit() now switches to the first running process

i used a linked list because it's the simplest way to implement this
---
 src/kernel/proc.c     | 15 ++++++++++++++-
 src/kernel/proc.h     | 13 ++++++++++++-
 src/kernel/syscalls.c |  6 ++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index b165878..36c88b5 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -4,11 +4,16 @@
 #include <kernel/util.h>
 #include <stdint.h>
 
+struct process *process_first;
 struct process *process_current;
 
 struct process *process_new() {
 	struct process *proc = page_alloc(1); // TODO kmalloc
 	proc->pages = pagedir_new();
+	proc->state = PS_RUNNING;
+	proc->next = NULL;
+
+	process_first = proc;
 
 	// map the stack to the last page in memory
 	pagedir_map(proc->pages, (void*)~PAGE_MASK, page_alloc(1), true, true);
@@ -24,10 +29,11 @@ struct process *process_new() {
 	return proc;
 }
 
-struct process *process_clone(const struct process *orig) {
+struct process *process_clone(struct process *orig) {
 	struct process *clone = page_alloc(1);
 	memcpy(clone, orig, sizeof(struct process));
 	clone->pages = pagedir_copy(orig->pages);
+	orig->next = clone;
 
 	return clone;
 }
@@ -37,3 +43,10 @@ void process_switch(struct process *proc) {
 	pagedir_switch(proc->pages);
 	sysexit(proc->regs);
 }
+
+struct process *process_find(enum process_state target) {
+	struct process *iter = process_first;
+	while (iter && (iter->state != target))
+		iter = iter->next;
+	return iter;
+}
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 71880e6..6d1ed8c 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -1,14 +1,25 @@
 #pragma once
 #include <kernel/arch/generic.h>
 
+enum process_state {
+	PS_RUNNING,
+	PS_DEAD,
+};
+
 struct process {
 	void *stack_top;
 	struct pagedir *pages;
 	struct registers regs;
+	enum process_state state;
+
+	struct process *next;
 };
 
+extern struct process *process_first;
 extern struct process *process_current;
 
 struct process *process_new();
-struct process *process_clone(const struct process *orig);
+struct process *process_clone(struct process *orig);
 _Noreturn void process_switch(struct process *proc);
+
+struct process *process_find(enum process_state);
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index eff670e..3d35a4a 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -5,6 +5,12 @@
 #include <stdint.h>
 
 _Noreturn void sc_exit(const char *msg, size_t len) {
+	process_current->state = PS_DEAD;
+
+	process_current = process_find(PS_RUNNING);
+	if (process_current)
+		process_switch(process_current);
+
 	log_const("last process returned. ");
 	panic();
 }
-- 
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