syscalls + userland process with its own page directory pointer table - working protection

TwoUnderscorez · TwoUnderscorez · commit a62d45ea4430 · 2018-01-24T20:32:54.000+02:00
diff --git a/iso/kernel/kernel.sys b/iso/kernel/kernel.sys
diff --git a/os.iso b/os.iso
diff --git a/src/Makefile b/src/Makefile
@@ -5,8 +5,8 @@ LDFLAGS:=-T linker.ld -o kernel.sys -m elf_i386
 ASM:=nasm
 ASMFLAGS:=-f elf
 
-all: kernel.o boot.o
-	$(LD) $(LDFLAGS) boot.o kernel.o screen.o keyboard.o asmio.o asmisr.o gdt.o idt.o descriptors.o isr.o string.o memoryasm.o memory.o heap.o task.o syscall.o
+all: kernel.o boot.o testuserapp.o
+	$(LD) $(LDFLAGS) boot.o kernel.o screen.o keyboard.o asmio.o asmisr.o gdt.o idt.o descriptors.o isr.o string.o memoryasm.o memory.o heap.o task.o syscall.o testuserapp.o
 
 kernel.o: screen.o keyboard.o asmio.o descriptors.o memory.o heap.o
 	$(CC) $(CFLAGS) kernel/kernel.c
@@ -59,6 +59,9 @@ task.o: syscall.o
 syscall.o:
 	$(CC) $(CFLAGS) kernel/syscall.c
 
+testuserapp.o:
+	$(ASM) $(ASMFLAGS) -o testuserapp.o asm/testuserapp.asm
+
 clean:
 	$(shell rm -rf *.o kernel.sys)
 	$(shell rm ../os.iso)
diff --git a/src/asm/asmio.asm b/src/asm/asmio.asm
@@ -2,6 +2,7 @@ global in_byte
 global out_byte
 global in_word
 global out_word
+global io_wait
 global asmcli
 global asmsti
 
@@ -44,6 +45,16 @@ out_word:
     pop     ebp
     ret
 
+io_wait:
+    push    ebp
+    mov     ebp, esp
+    push    eax
+    xor     al, al
+    out     0x00, al
+    pop     eax
+    pop     ebp
+    ret
+
 asmcli:
     cli
     ret
diff --git a/src/asm/asmio.h b/src/asm/asmio.h
@@ -5,6 +5,7 @@ extern unsigned char in_byte ( unsigned short port );
 extern void out_byte ( unsigned short port , unsigned char data );
 extern unsigned short in_word ( unsigned short port );
 extern void out_word ( unsigned short port , unsigned short data );
+extern void io_wait(void);
 extern void asmcli(void);
 extern void asmsti(void);
 
diff --git a/src/asm/asmisr.asm b/src/asm/asmisr.asm
@@ -4,7 +4,7 @@ global temp
 %macro ISR_NOERRCODE 1
 	global isr%1
 	isr%1:
-		cli				; disable hardware interrupts
+		; cli				; disable hardware interrupts
 		push byte 0		; push 0 as err code
 		push %1			; push int num
 		jmp isr_common_stub
@@ -14,7 +14,7 @@ global temp
 %macro ISR_ERRCODE 1
 	global isr%1
 	isr%1:
-		cli				; disable hardware interrupts
+		; cli				; disable hardware interrupts
 		push %1			; push int num, int errcode was already pushed by the cpu
 		jmp isr_common_stub
 %endmacro
@@ -311,5 +311,5 @@ isr_common_stub:
 	popa			; restore registers
 
 	add esp, 8		; pop int num and int err code from the stack
-	sti				; enable hardware interrupts
+	; sti				; enable hardware interrupts
 	iret			; interrupt return
diff --git a/src/asm/memory.asm b/src/asm/memory.asm
@@ -1,6 +1,7 @@
 global loadPageDirectoryAsm
 global enablePagingAsm
 global enablePaePagingAsm
+global disablePagingAsm
 loadPageDirectoryAsm:
     push    ebp
     mov     ebp, esp
@@ -18,6 +19,15 @@ enablePagingAsm:
     pop     ebp
     ret
 
+disablePagingAsm:
+    push    ebp
+    mov     ebp, esp
+    mov     eax, cr0
+    and     eax, 0xF7FFFFFFF
+    mov     cr0, eax
+    pop     ebp
+    ret
+
 enablePaePagingAsm:
     push    ebp
     mov     ebp, esp
diff --git a/src/asm/testuserapp.asm b/src/asm/testuserapp.asm
@@ -0,0 +1,8 @@
+section .usrtext
+global usermain
+usermain:
+    mov eax, msg
+    int 0x83
+    int 0x82
+    ret
+msg db 'Hello from userland!', 0xA, 0
diff --git a/src/kernel/descriptors.c b/src/kernel/descriptors.c
@@ -182,9 +182,9 @@ void idt_setup() {
 	idt_set_gate(126,(unsigned int)isr126,0x08,0x8e);
 	idt_set_gate(127,(unsigned int)isr127,0x08,0x8e);
 	idt_set_gate(128,(unsigned int)isr128,0x08,0x8e);
-	idt_set_gate(129,(unsigned int)isr129,0x08,0x8e);
+	idt_set_gate(129,(unsigned int)isr129,0x08,0x8e); 
 	idt_set_gate(130,(unsigned int)isr130,0x08,0xef); // Context switch
-	idt_set_gate(131,(unsigned int)isr131,0x08,0x8e);
+	idt_set_gate(131,(unsigned int)isr131,0x08,0xef); // Puts
 	idt_set_gate(132,(unsigned int)isr132,0x08,0x8e);
 	idt_set_gate(133,(unsigned int)isr133,0x08,0x8e);
 	idt_set_gate(134,(unsigned int)isr134,0x08,0x8e);
@@ -341,5 +341,5 @@ void write_tss(unsigned int num, unsigned short ss0, unsigned int esp0)
 // Sets the stack to use on traps
 void set_kernel_stack(unsigned int stack)
 {
-   sys_tss.esp0 = stack;
+   	sys_tss.esp0 = stack;
 } 
diff --git a/src/kernel/memory.c b/src/kernel/memory.c
@@ -1,6 +1,10 @@
 #include "memory.h"
 #include "multiboot.h"
+#include "heap.h"
 #include "../drivers/screen.h"
+#include "../asm/asmio.h"
+#include "../libs/string.h"
+extern void usermain();
 
 page_directory_pointer_table_entry_t page_dir_ptr_tab[4] __attribute__((aligned(0x20)));
 page_directory_table_entry_t page_dir[512] __attribute__((aligned(0x1000)));
@@ -12,28 +16,37 @@ unsigned int pre_frame_map[20];
 
 void init_memory(multiboot_info_t * mymbd) {
     mbd = mymbd;
-    startframe = 0x300000;
+    startframe = 0x400000;
     // Map a 2 mb single page using an entry in the page directory table (0-0x200000)
     page_dir_ptr_tab[0].present = 1;
     page_dir_ptr_tab[0].page_directory_table_address = (unsigned int)&page_dir>>12;
     page_dir[0].present = 1;
     page_dir[0].ro_rw = 1;
     page_dir[0].size = 1;
-    page_dir[0].page_table_address =0;
+    page_dir[0].page_table_address = 0;
     page_dir[0].kernel_user = 1;
-    // Map 512 4kb pages (0x200000-0x400000)
-    page_dir[1].present = 1;
-    page_dir[1].ro_rw = 1;
-    page_dir[1].page_table_address = (unsigned int)&page_tab>>12;
-    unsigned int i, address = 0;
-    for(i = 0; i < 512; i++)
-    {
-        page_tab[i].present = 1;
-        page_tab[i].ro_rw = 1;
-        page_tab[i].physical_page_address = address>>12;
-        page_tab[i].kernel_user = 1;
-        address = address + 0x1000;
-    }
+    // page_dir[1].present = 1;
+    // page_dir[1].ro_rw = 1;
+    // page_dir[1].size = 1;
+    // page_dir[1].page_table_address = 0x200000>>12;
+    // page_dir[1].kernel_user = 1;
+    ////////////////////////////////////////////////////////////////////////////
+    // An unsuccessful attempt at making a Higher Half Kernel
+    // unsigned int i, address = 0xB0000000;
+    // puts("\n");
+    // for(i = 388; i < 475; i++){
+    //     screen_print_int(address>>12, 16);
+    //     puts(" ");
+    //     page_dir[i].present = 1;
+    //     page_dir[i].ro_rw = 1;
+    //     page_dir[i].size = 1;
+    //     page_dir[i].page_table_address = (unsigned int)address>>12;
+    //     screen_print_int(page_dir[i].page_table_address, 16);
+    //     puts("\n");
+    //     getc();
+    //     page_dir[i].kernel_user = 0;
+    //     address = (unsigned int)((unsigned int)address + (unsigned int)0x200000);
+    // }
     puts("Enabaling PAE paging...\n");
     enablePaePagingAsm(); 
     loadPageDirectoryAsm((unsigned int *)&page_dir_ptr_tab);
@@ -113,4 +126,49 @@ void kfree_frame(unsigned int page_frame_addr)
     page_frame_addr = (unsigned int)(page_frame_addr - startframe); 
     // Divide by 4kb to get the index of the page frame in frame_map
     frame_map[((unsigned int)page_frame_addr)/0x1000] = 0;
+}
+
+// Create a page directory pointer table for a userland process
+unsigned int create_pdpt() {
+    unsigned int task_pdpt, task_dt, task_tab;
+    // Get a page frame for each pdpt, dt, pt because their address 
+    // must be 0x1000 (4096) byte aligned.
+    task_pdpt = kalloc_frame();
+    task_dt = kalloc_frame();
+    task_tab = kalloc_frame();
+    // We are entering a critical section
+    asmcli();
+    // Temporarily disable paging so we can write to the physical
+    // addresses of paging tables without problems
+    disablePagingAsm();
+    // Create the pointers
+    page_directory_pointer_table_entry_t * temp_pdpt;
+    temp_pdpt = (page_directory_pointer_table_entry_t *)task_pdpt;
+    page_directory_table_entry_t * temp_dt;
+    temp_dt = (page_directory_table_entry_t *)task_dt;
+    page_table_entry_t * temp_tab;
+    temp_tab = (page_table_entry_t *)task_tab;
+    temp_pdpt[0].page_directory_table_address = (unsigned int)temp_dt>>12;
+    temp_pdpt[0].present = 1;
+    // Map the kernel space
+    temp_dt[0].present = 1;
+    temp_dt[0].ro_rw = 1;
+    temp_dt[0].size = 1;
+    temp_dt[0].page_table_address = 0;
+    temp_dt[0].kernel_user = 0; 
+    // Map user space (0x300000-0x301000)
+    temp_dt[1].present = 1;
+    temp_dt[1].page_table_address = (unsigned int)temp_tab>>12;
+    temp_dt[1].kernel_user = 1;
+    temp_tab[256].present = 1;
+    temp_tab[256].ro_rw = 1;
+    temp_tab[256].physical_page_address = 0x300000>>12;
+    temp_tab[256].kernel_user = 1;
+    // Re-enable interrupts and paging
+    /* Temporary loading of the user task to the appropriate location
+     * in memory. will be removed. */
+    memcpy(0x300000, &usermain, 0x1000); // temp
+    enablePagingAsm();
+    asmsti();
+    return task_pdpt;
 }
diff --git a/src/kernel/memory.h b/src/kernel/memory.h
@@ -60,8 +60,10 @@ typedef struct page_table_entry page_table_entry_t;
 extern void loadPageDirectoryAsm(unsigned int * ptr);
 extern void enablePagingAsm(void);
 extern void enablePaePagingAsm(void);
+extern void disablePagingAsm(void);
 void init_memory(multiboot_info_t * mbd);
 void dump_mmap(void);
 unsigned int kalloc_frame();
 void kfree_frame(unsigned int page_frame_addr);
+unsigned int create_pdpt();
 #endif
diff --git a/src/kernel/syscall.c b/src/kernel/syscall.c
@@ -1,19 +1,26 @@
 #include "syscall.h"
 #include "task.h"
 #include "isr.h"
+#include "../drivers/screen.h"
 
 void initialise_syscalls() {
     ;
 }
 
 void handle_syscall(registers_t * regs) {
     switch(regs->int_no) {
-        case 0x81:
+        case 0x80: // Interrupt test                    KMODE
+            puts("Recieved interrupt: 0x80. Interrupts seem to be functioning properly.\n");
+            break;
+        case 0x81: // Init tasking                      KMODE
 			init_tasking(regs);
 			break;
-		case 0x82:
-			roundRobinNext(regs);
+		case 0x82: // Context Switch                    USERLAND
+			roundRobinNext(regs); 
 			break;
+        case 0x83: // puts                              USERLAND
+            puts((char *)regs->eax);
+            break;
         default:
             return;
     }
diff --git a/src/kernel/task.c b/src/kernel/task.c
@@ -24,12 +24,13 @@ void init_tasking(registers_t * regs) {
     mainTask.next = &otherTask;
     set_kernel_stack((unsigned int)regs->kesp);
     // Create the other task
-    create_task(&otherTask, other_main, mainTask.regs.eflags, (unsigned int*)mainTask.regs.cr3);
+    unsigned int t_pdpt = (unsigned int)create_pdpt();
+    create_task(&otherTask, 0x300000, mainTask.regs.eflags, t_pdpt);
     otherTask.next = &mainTask;
     runningTask = &mainTask;
 }
  
-void create_task(task_t *task, void (*main)(), unsigned int flags, unsigned int *pagedir) {
+void create_task(task_t *task, void (*main)(), unsigned int flags, unsigned int pagedir) {
     task->regs.eax = 0;
     task->regs.ebx = 0;
     task->regs.ecx = 0;
@@ -42,7 +43,7 @@ void create_task(task_t *task, void (*main)(), unsigned int flags, unsigned int
     task->regs.eflags = flags;
     task->regs.eip = (unsigned int) main;
     task->regs.cr3 = (unsigned int) pagedir;
-    task->regs.useresp = (unsigned int) 0x130000; // Proccess' tack
+    task->regs.useresp = (unsigned int) 0x300100; // Proccess' stack
     task->regs.kesp = (unsigned int)mainTask.regs.kesp; // ISR's stack
     task->next = 0;
 }
diff --git a/src/kernel/task.h b/src/kernel/task.h
@@ -12,9 +12,9 @@ struct task {
 
 typedef struct task task_t;
  
-void create_task(task_t*, void(*)(), unsigned int, unsigned int*);
+void create_task(task_t*, void(*)(), unsigned int, unsigned int);
 void roundRobinNext(registers_t * regs);
-
+extern void usermain(void);
 
 
 #endif
diff --git a/src/linker.ld b/src/linker.ld
@@ -31,4 +31,7 @@ SECTIONS
     }
 
     end = .; _end = .; __end = .;
+
+    . = 0x300000;
+    .text : { *(.usrtext) }
 }
