Added kernel section clear/protect after init

This is a huge security improvement as it prevents potential exploits
of using or modifying internal kernel functions or data.

4 files changed, 54 insertions, 22 deletions

diff --git a/kernel/features/fs.c b/kernel/features/fs.c
index 0ffe80f..cc9949e 100644
--- a/kernel/features/fs.c
+++ b/kernel/features/fs.c
@@ -16,7 +16,7 @@
  * VFS
  */
 
-static struct list *mount_points = NULL;
+PROTECTED static struct list *mount_points = NULL;
 
 static char *vfs_normalize_path(const char *path)
 {
@@ -293,7 +293,7 @@ res vfs_ready(const char *path)
 	return m->dev->vfs->ready(path, m->dev);
 }
 
-void vfs_install(void)
+CLEAR void vfs_install(void)
 {
 	mount_points = list_new();
 }
@@ -302,9 +302,9 @@ void vfs_install(void)
  * Device
  */
 
-static struct list *devices = NULL;
+PROTECTED static struct list *devices = NULL;
 
-void device_add(struct device *dev)
+CLEAR void device_add(struct device *dev)
 {
 	dev->id = rand() + 1;
 	list_add(devices, dev);
@@ -373,7 +373,7 @@ static res devfs_ready(const char *path, struct device *dev)
 	return target->ready();
 }
 
-void device_install(void)
+CLEAR void device_install(void)
 {
 	devices = list_new();
 
diff --git a/kernel/features/mm.c b/kernel/features/mm.c
index 3be798a..86d33c7 100644
--- a/kernel/features/mm.c
+++ b/kernel/features/mm.c
@@ -11,7 +11,7 @@
 #include <print.h>
 #include <random.h>
 
-static struct page_dir kernel_dir ALIGNED(PAGE_SIZE) = { 0 };
+PROTECTED static struct page_dir kernel_dir ALIGNED(PAGE_SIZE) = { 0 };
 static struct page_table kernel_tables[PAGE_KERNEL_COUNT] ALIGNED(PAGE_SIZE) = { 0 };
 
 /**
@@ -23,14 +23,14 @@ static void paging_switch_dir(u32 dir)
 	cr3_set(dir);
 }
 
-extern void paging_invalidate_tlb(void);
+CLEAR extern void paging_invalidate_tlb(void);
 
-void paging_disable(void)
+CLEAR void paging_disable(void)
 {
 	cr0_set(cr0_get() | 0x7fffffff);
 }
 
-void paging_enable(void)
+CLEAR void paging_enable(void)
 {
 	cr0_set(cr0_get() | 0x80010000);
 }
@@ -70,7 +70,7 @@ void page_fault_handler(struct regs *r)
  */
 
 static u32 memory_used = 0;
-static u32 memory_total = 0;
+PROTECTED static u32 memory_total = 0;
 static u32 best_bet = 0;
 static u8 memory[PAGE_COUNT * PAGE_COUNT / 8] = { 0 };
 
@@ -563,7 +563,7 @@ struct memory_range memory_range_around(u32 base, u32 size)
 
 extern u32 kernel_rw_start;
 extern u32 kernel_rw_end;
-static struct memory_range kernel_rw_memory_range(void)
+CLEAR static struct memory_range kernel_rw_memory_range(void)
 {
 	return memory_range_around((u32)&kernel_rw_start,
 				   (u32)&kernel_rw_end - (u32)&kernel_rw_start);
@@ -571,13 +571,44 @@ static struct memory_range kernel_rw_memory_range(void)
 
 extern u32 kernel_ro_start;
 extern u32 kernel_ro_end;
-static struct memory_range kernel_ro_memory_range(void)
+CLEAR static struct memory_range kernel_ro_memory_range(void)
 {
 	return memory_range_around((u32)&kernel_ro_start,
 				   (u32)&kernel_ro_end - (u32)&kernel_ro_start);
 }
 
-void memory_install(struct mem_info *mem_info, struct vid_info *vid_info)
+extern u32 kernel_temp_clear_start;
+extern u32 kernel_temp_clear_end;
+static void memory_temp_clear(void)
+{
+	u8 *data = (u8 *)&kernel_temp_clear_start;
+	u32 size = (u32)&kernel_temp_clear_end - (u32)&kernel_temp_clear_start;
+	memset(data, 0, size);
+	memory_free(&kernel_dir, memory_range_around((u32)data, size));
+	printf("Cleared %dKiB\n", size >> 10);
+}
+
+extern u32 kernel_temp_protect_start;
+extern u32 kernel_temp_protect_end;
+CLEAR static void memory_temp_protect(void)
+{
+	u32 data = (u32)&kernel_temp_protect_start;
+	u32 size = (u32)&kernel_temp_protect_end - (u32)&kernel_temp_protect_start;
+	memory_map_identity(&kernel_dir, memory_range_around((u32)data, size), MEMORY_READONLY);
+	printf("Protected %dKiB\n", size >> 10);
+}
+
+void memory_user_hook(void)
+{
+	PROTECTED static u8 called = 0;
+	if (!called) {
+		called = 1;
+		memory_temp_protect();
+		memory_temp_clear();
+	}
+}
+
+CLEAR void memory_install(struct mem_info *mem_info, struct vid_info *vid_info)
 {
 	for (struct mmap_boot *p = mem_info->start; (u32)(p - mem_info->start) < mem_info->size;
 	     p++) {
diff --git a/kernel/features/proc.c b/kernel/features/proc.c
index 8625e7d..6d07945 100644
--- a/kernel/features/proc.c
+++ b/kernel/features/proc.c
@@ -18,12 +18,12 @@
 
 static u32 locked = 0;
 static u32 current_pid = 0;
-static struct node *idle_proc = NULL;
 static struct node *current = NULL;
+PROTECTED static struct node *idle_proc = NULL;
 
-static struct list *proc_list_running = NULL;
-static struct list *proc_list_blocked = NULL;
-static struct list *proc_list_idle = NULL;
+PROTECTED static struct list *proc_list_running = NULL;
+PROTECTED static struct list *proc_list_blocked = NULL;
+PROTECTED static struct list *proc_list_idle = NULL;
 
 // TODO: Use less memcpy and only copy relevant registers
 // TODO: 20 priority queues (https://www.kernel.org/doc/html/latest/scheduler/sched-nice-design.html)
@@ -111,7 +111,7 @@ struct proc *proc_from_pid(u32 pid)
 	return NULL;
 }
 
-void proc_set_quantum(struct proc *proc, u32 value)
+CLEAR void proc_set_quantum(struct proc *proc, u32 value)
 {
 	proc->quantum.val = value;
 }
@@ -552,8 +552,10 @@ NORETURN void proc_init(void)
 	_eip = init->regs.eip;
 	_esp = init->regs.useresp;
 
-	memory_switch_dir(init->page_dir);
+	// We'll shortly jump to usermode. Clear and protect every secret!
+	memory_user_hook();
 
+	memory_switch_dir(init->page_dir);
 	printf("Jumping to userspace!\n");
 
 	// You're waiting for a train. A train that will take you far away...
diff --git a/kernel/features/syscall.c b/kernel/features/syscall.c
index ab14539..6a64996 100644
--- a/kernel/features/syscall.c
+++ b/kernel/features/syscall.c
@@ -24,8 +24,7 @@ static void syscall_handler(struct regs *r)
 
 	switch (num) {
 	case SYS_LOOP: {
-		loop();
-		panic("Fell out of the looping!\n");
+		panic("Loop is deprecated!\n");
 		break;
 	}
 	case SYS_ALLOC: {
@@ -134,7 +133,7 @@ static void syscall_handler(struct regs *r)
 	}
 }
 
-void syscall_init(void)
+CLEAR void syscall_init(void)
 {
 	idt_set_gate(0x80, (u32)isr128, 0x08, 0x8E);
 	isr_install_handler(0x80, syscall_handler);