Implement switching to usermode.

6 files changed, 72 insertions, 7 deletions

diff --git a/src/kernel/core/gdt.c b/src/kernel/core/gdt.c
index eadde5f..97e6661 100644
--- a/src/kernel/core/gdt.c
+++ b/src/kernel/core/gdt.c
@@ -60,6 +60,7 @@ typedef struct tss_entry tss_entry_t;
 
 static gdt_entry_t gdt_entries[GDT_ENTRIES];
 static gdt_ptr_t gdt_ptr;
+static tss_entry_t tss_entry;
 
 /*	For internal use only. Writes one entry of the GDT with given parameters. */
 static void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran) {
@@ -84,7 +85,27 @@ void gdt_init() {
 	gdt_set_gate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF);		//User code segment		0x18
 	gdt_set_gate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF);		//User data segment		0x20
 
-	asm volatile ("lgdt %0"::"m"(gdt_ptr):"memory");
+	// Write TSS
+	memset(&tss_entry, 0, sizeof(tss_entry));
+
+	tss_entry.ss0  = 0x10;
+	tss_entry.esp0 = 0;
+
+	tss_entry.cs   = 0x0b;
+	tss_entry.ss = tss_entry.ds = tss_entry.es = tss_entry.fs = tss_entry.gs = 0x13;
+
+	uint32_t tss_base = (uint32_t)&tss_entry;
+	uint32_t tss_limit = tss_base + sizeof(tss_entry_t);
+
+	gdt_set_gate(5, tss_base, tss_limit, 0xE9, 0x00);
+
+	asm volatile("lgdt %0"::"m"(gdt_ptr):"memory");
+
+	asm volatile("movw $0x2b, %%ax; ltr %%ax":::"%eax");
+}
+
+void set_kernel_stack(void* addr) {
+	tss_entry.esp0 = (uint32_t)addr;
 }
 
 /* vim: set ts=4 sw=4 tw=0 noet :*/
diff --git a/src/kernel/core/thread.c b/src/kernel/core/thread.c
index 9d11da2..519ba41 100644
--- a/src/kernel/core/thread.c
+++ b/src/kernel/core/thread.c
@@ -2,6 +2,7 @@
 #include <malloc.h>
 #include <dbglog.h>
 #include <idt.h>
+#include <gdt.h>
 
 #include <frame.h>
 #include <paging.h>
@@ -88,6 +89,7 @@ void run_scheduler() {
 
 	current_thread = dequeue_thread();
 	if (current_thread != 0) {
+		set_kernel_stack(current_thread->stack_region->addr + current_thread->stack_region->size);
 		resume_context(&current_thread->ctx);
 	} else {
 		// Wait for an IRQ
@@ -146,7 +148,6 @@ thread_t *new_thread(entry_t entry, void* data) {
 
 	// used by user processes
 	t->proc = 0;
-	t->usermem_pf_handler = 0;
 	t->kmem_violation_handler = 0;
 
 	return t;
diff --git a/src/kernel/include/gdt.h b/src/kernel/include/gdt.h
index a62d0db..048accd 100644
--- a/src/kernel/include/gdt.h
+++ b/src/kernel/include/gdt.h
@@ -9,6 +9,8 @@
 
 void gdt_init();
 
+void set_kernel_stack(void* addr);
+
 #define K_CODE_SEGMENT 0x08
 #define K_DATA_SEGMENT 0x10
 #define U_CODE_SEGMENT 0x18
diff --git a/src/kernel/include/process.h b/src/kernel/include/process.h
index 30e24db..d67ede6 100644
--- a/src/kernel/include/process.h
+++ b/src/kernel/include/process.h
@@ -21,6 +21,9 @@
 #define MM_WRITE	(0x02)
 #define MM_EXEC		(0x04)
 
+#define USERSTACK_ADDR	0xB8000000
+#define USERSTACK_SIZE	0x00020000		// 32 KB
+
 struct process;
 typedef struct process process_t;
 
diff --git a/src/kernel/user/process.c b/src/kernel/user/process.c
index 7b51370..9f3e2b1 100644
--- a/src/kernel/user/process.c
+++ b/src/kernel/user/process.c
@@ -66,12 +66,50 @@ process_t *new_process(process_t *parent) {
 	return proc;
 }
 
-static void run_user_code(void* data) {
-	// TODO
-	exit();
+static void run_user_code(void* entry) {
+	process_t *proc = current_thread->proc;
+	ASSERT(proc != 0);
+
+	switch_pagedir(proc->pd);
+
+	void* esp = (void*)USERSTACK_ADDR + USERSTACK_SIZE;
+
+	asm volatile("
+			cli;
+
+			mov $0x23, %%ax;
+			mov %%ax, %%ds;
+			mov %%ax, %%es;
+			mov %%ax, %%fs;
+			mov %%ax, %%gs;
+
+			pushl $0x23;
+			pushl %%ebx;
+			pushf;
+			pop %%eax;
+			or $0x200, %%eax;
+			pushl %%eax;
+			pushl $0x1B;
+			pushl %%ecx;
+			iret
+		"::"b"(esp),"c"(entry));
 }
 bool start_process(process_t *p, void* entry) {
-	// TODO
+	bool stack_ok = mmap(p, (void*)USERSTACK_ADDR, USERSTACK_SIZE, MM_READ | MM_WRITE);
+	if (!stack_ok) return false;
+
+	thread_t *th = new_thread(run_user_code, entry);
+	if (th == 0) {
+		munmap(p, (void*)USERSTACK_ADDR);
+		return false;
+	}
+
+	th->proc = p;
+	th->kmem_violation_handler = proc_kmem_violation;
+	
+	resume_thread(th, false);
+
+	return true;
 }
 
 // ================================== //
diff --git a/src/rules.make b/src/rules.make
index acd1c62..6c02313 100644
--- a/src/rules.make
+++ b/src/rules.make
@@ -28,7 +28,7 @@ all: $(OUT)
 #	$(CXX) -c $< -o $@ $(CXFLAGS)
 
 clean:
-	rm */*.o || true
+	rm *.o */*.o || true
 mrproper: clean
 	rm $(OUT) || true