From 9ad0eafcf7e2f3e0532666c5353b0f5294401b06 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Tue, 20 Jul 2021 21:38:09 +0200
Subject: per-process virtual memory

VGA is only mapped into the virtual memory because there are no other
ways of interacting with the OS.
---
 src/init/main.c   |  5 ++++-
 src/kernel/main.c | 33 +++++++++++++++------------------
 src/kernel/proc.c | 21 ++++++++++++++++-----
 src/kernel/proc.h |  6 ++++--
 4 files changed, 39 insertions(+), 26 deletions(-)

(limited to 'src')

diff --git a/src/init/main.c b/src/init/main.c
index e6188ac..ce1600c 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -6,5 +6,8 @@ int main() {
 	uint8_t *vga = (void*) 0xB8000;
 	for (int i = 0; i < 80 * 25; i++)
 		vga[(i << 1) + 1] = 0x4e;
-	for (;;);
+
+	// try to mess with kernel memory
+	uint8_t *kernel = (void*) 0x100000;
+	*kernel = 0; // should segfault
 }
diff --git a/src/kernel/main.c b/src/kernel/main.c
index a59c014..729e39d 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -6,32 +6,29 @@
 #include <kernel/util.h>
 #include <stdint.h>
 
-static void setup_paging() {
-	struct pagedir *dir = pagedir_new();
+static void run_init(struct kmain_info *info) {
+	struct process *proc = process_new();
+	void *init_base = (void*) 0x200000;
 
-	// map VGA
-	pagedir_map(dir, 0xB8000, 0xB8000, true, true);
+	// map VGA for testing
+	pagedir_map(proc->pages, 0xB8000, 0xB8000, true, true);
 
-	// map the kernel
-	for (size_t p = 0x100000; p < &_bss_end; p += PAGE_SIZE)
-		pagedir_map(dir, p, p, false, true); // yes, .text is writeable too
+	// map the module as rw
+	for (uintptr_t off = 0; off < info->init.size; off += PAGE_SIZE)
+		pagedir_map(proc->pages, init_base + off, info->init.at + off,
+		            true, true);
+	proc->eip = init_base;
 
-	pagedir_switch(dir);
+	log_const("switching...");
+	process_switch(proc);
 }
 
 void kmain(struct kmain_info info) {
 	log_const("mem...");
 	mem_init(&info);
 
-	log_const("paging...");
-	setup_paging();
-
-	log_const("creating process...");
+	log_const("loading init...");
+	run_init(&info);
 
-	void *init_addr = (void*)0x200000;
-	memcpy(init_addr, info.init.at, info.init.size);
-
-	struct process *proc = process_new(init_addr);
-	log_const("switching...");
-	process_switch(proc);
+	panic();
 }
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 4a931a5..6b80254 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -1,19 +1,30 @@
 #include <kernel/arch/generic.h>
 #include <kernel/mem.h>
 #include <kernel/proc.h>
+#include <stdint.h>
 
 struct process *process_current;
 
-struct process *process_new(void *eip) {
-	struct process *proc;
-	proc = page_alloc(1); // TODO kmalloc
-	proc->stack_top = proc->esp = page_alloc(1) + 1 * PAGE_SIZE;
-	proc->eip = eip;
+struct process *process_new() {
+	struct process *proc = page_alloc(1); // TODO kmalloc
+	proc->pages = pagedir_new();
 
+	// map the stack to the last page in memory
+	pagedir_map(proc->pages, (void*)~PAGE_MASK, page_alloc(1), true, true);
+	proc->stack_top = proc->esp = (void*) ~0;
+
+	// map the kernel
+	//   yup, .text is writeable too. the plan is to not map the kernel
+	//   into user memory at all, but i'll implement that later. TODO
+	for (size_t p = 0x100000; p < &_bss_end; p += PAGE_SIZE)
+		pagedir_map(proc->pages, (void*)p, (void*)p, false, true);
+
+	// the kernel still has to load the executable code and set EIP
 	return proc;
 }
 
 void process_switch(struct process *proc) {
 	process_current = proc;
+	pagedir_switch(proc->pages);
 	sysexit(proc->eip, proc->esp);
 }
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 976b275..745db8d 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -1,13 +1,15 @@
 #pragma once
+#include <kernel/arch/generic.h>
 
 struct process {
 	void *stack_top;
 	void *esp;
-
 	void *eip;
+
+	struct pagedir *pages;
 };
 
 extern struct process *process_current;
 
-struct process *process_new(void *eip);
+struct process *process_new();
 void process_switch(struct process *proc);
-- 
cgit v1.2.3