add file operations, clean up syscall and execute

fsdir/Programs/src/syscall.h

 #include "types.h"
 
-extern int32_t sys_write(int32_t fd, const void* buf, int32_t len);
\ No newline at end of file
+extern int32_t sys_write(int32_t fd, const void* buf, int32_t len);
+extern int32_t sys_exec(uint8_t* name);
\ No newline at end of file

kernel/Devices/keyboard.c

@@ -76,7 +76,6 @@ uint32_t keyboard_handle_irq()
 				last_key = normal_map[scancode];
 			}
 			flag = 1;
-			printf("%c", last_key);
 		}
 	} else {
 		scancode &= ~0x80;

kernel/Devices/terminal.c

+#include <types.h>
+#include <lib.h>
+
+#include "terminal.h"
+
+int32_t terminal_read(int32_t fd, void* buf, int32_t nbytes){
+	return -1;
+}
+
+int32_t terminal_write(int32_t fd, const void* buf, int32_t nbytes)
+{
+	int i;
+	for (i = 0; i < nbytes; i++) {
+		putc(*(uint8_t*)(buf + i));
+	}
+	return 0;
+}
+
+int32_t terminal_open(const uint8_t* filename)
+{
+	return -1;
+}
+
+int32_t terminal_close(int32_t fd)
+{
+	return -1;
+}

kernel/Syscalls/execute.c

 #include <types.h>
 #include <lib.h>
 #include <x86_desc.h>
-#include <Devices/Storage/ext2.h>
 #include <paging.h>
+#include <Devices/Storage/ext2.h>
+#include <Devices/terminal.h>
 
 #include "execute.h"
 
@@ -11,6 +12,10 @@
 // TEMPORARY!!!
 static uint32_t pid = 0;
 
+static fops_t stdin_ops = {terminal_open, terminal_close, terminal_read, NULL};
+static fops_t stdout_ops = {terminal_open, terminal_close, NULL, terminal_write};
+
+
 void get_ret_addr()
 {
 	uint32_t ret_eip;
@@ -46,9 +51,6 @@ pcb_t* get_pcb_ptr()
 
 int32_t _sys_exec(uint8_t* name)
 {
-	printf("In _sys_exec\n");
-
-
 	union {
 		uint16_t data16[512];
 		uint8_t data8[1024];
@@ -80,21 +82,15 @@ int32_t _sys_exec(uint8_t* name)
 	pcb->pid = pid;
 	pcb->parent_pid = get_pcb_ptr()->pid;
 
+	pcb->file_desc_array[0].file_ops = &stdin_ops;
+	pcb->file_desc_array[1].file_ops = &stdout_ops;
+
 
 	/* increment pid and run process; decrement it after termination */
 	pid++;
 
 	uint32_t status;
 
-	printf("Some code for you: %x\n", header->e_entry);
-	int i;
-	for (i = 0; i < 16; i++) {
-		printf("%x ", *((uint8_t*)(header->e_entry) + i));
-	}
-	printf("\n");
-
-	printf("gonna execute now, wish me luck! %x\n", header->e_entry);
-
 	/* push use data segment, user stack pointer,
 	* flags, user code segment, entry point, then iret */
 	asm volatile("           \n\
@@ -122,8 +118,33 @@ int32_t _sys_exec(uint8_t* name)
 	return status;
 }
 
-int32_t _sys_exit()
+int32_t _sys_exit(uint32_t status)
 {
-	printf("in _sys_exit\n");
+	pcb_t* pcb = get_pcb_ptr();
+
+	/* restart the shell if the user quits the last layer */
+	if (!pcb->execute_return) {
+		if (pcb->pid == 0) {
+			pid = 0;            // this feels like a hack...
+			_sys_exec((uint8_t*)"stop");
+		}
+	}
+
+	// unmap the current process memory before going back to the execute that called it
+	// remap original program memory
+	map_large(EXEC_BASE_ADDR, (_8MB + (get_pcb_ptr()->parent_pid)*_4MB));
+
+	tss.esp0 = pcb->parent_esp;
+
+	/* give the control back */
+	asm volatile("              \
+	mov %0, %%ebp           \n\
+	mov %1, %%esp           \n\
+	push %%ebx              \n\
+	jmp *%%eax"
+	: 
+	:"m"(pcb->parent_ebp), "m"(pcb->parent_esp), "b"(status), "a"(pcb->execute_return)
+	);
+
 	return -1;
 }

kernel/Syscalls/execute.h

@@ -66,15 +66,36 @@ typedef struct elf_header{
         uint16_t e_shstrndx;
 } elf_header_t;
 
+/* file operations struct */
+typedef struct fops_t {
+	int32_t (*open)(const uint8_t* filename);
+	int32_t (*close)(int32_t fd);
+	int32_t (*read)(int32_t fd, void* buf, int32_t nbytes);
+	int32_t (*write)(int32_t fd, const void* buf, int32_t nbytes);
+} fops_t;
+
+/* file descriptors struct */
+typedef struct file_desc_t {
+	fops_t* file_ops;
+	uint32_t inode;
+	uint32_t file_pos;
+	uint32_t flags;
+} file_desc_t;
+
 typedef struct pcb {
-	uint32_t pid;
-	uint32_t parent_pid;
-	uint32_t parent_ebp;
-	uint32_t parent_esp;
+	file_desc_t file_desc_array[8];
+	int32_t is_vidmapped;
+	uint8_t args[128];
 	uint32_t execute_return;
+	int32_t pid;
+	int32_t parent_pid;
+	uint32_t parent_esp;
+	uint32_t parent_ebp;
 } pcb_t;
 
 int32_t _sys_exec(uint8_t* name);
-int32_t _sys_exit();
+int32_t _sys_exit(uint32_t status);
+
+pcb_t* get_pcb_ptr();
 
 #endif
\ No newline at end of file

kernel/Syscalls/syscalls.c

@@ -4,20 +4,18 @@
 #include "syscalls.h"
 #include "execute.h"
 
-int32_t sys_read(int32_t fd, const void* buf, int32_t len)
+int32_t sys_read(int32_t fd, void* buf, int32_t len)
 {
-	printf("sysread\n");
-	return -1;
+	pcb_t* pcb = get_pcb_ptr();
+	pcb->file_desc_array[fd].file_ops->read(fd, buf, len);
+	return 0;
 }
 
 int32_t sys_write(int32_t fd, const void* buf, int32_t len)
 {
-	printf("syswrite\n");
-	int i;
-	for (i = 0; i < len; i++) {
-		putc(*((uint8_t*)buf + i));
-	}
-	return -1;
+	pcb_t* pcb = get_pcb_ptr();
+	pcb->file_desc_array[fd].file_ops->write(fd, buf, len);
+	return 0;
 }
 
 int32_t sys_open(uint8_t* name)
@@ -35,6 +33,6 @@ int32_t sys_exec(uint8_t* name)
 	return _sys_exec(name);
 }
 
-int32_t sys_exit() {
-	return _sys_exit();
+int32_t sys_exit(uint32_t status) {
+	return _sys_exit(status);
 }
\ No newline at end of file

kernel/Syscalls/syscalls.h

@@ -11,11 +11,11 @@
 #define SYS_EXEC 5
 #define SYS_EXIT 6
 
-int32_t sys_read(int32_t fd, const void* buf, int32_t len);
+int32_t sys_read(int32_t fd, void* buf, int32_t len);
 int32_t sys_write(int32_t fd, const void* buf, int32_t len);
 int32_t sys_open(uint8_t* name);
 int32_t sys_close(int32_t fd);
 int32_t sys_exec(uint8_t* name);
-int32_t sys_exit();
+int32_t sys_exit(uint32_t status);
 
 #endif

kernel/kernel.c

@@ -117,7 +117,7 @@ void entry(unsigned long magic, unsigned long addr) {
 	ata_read_sectors(ATA_MASTER, 0, 1, mbr.data);
 	ext2_init(mbr.partitions[0].lba_start);
 
-	int32_t error = sys_exec((uint8_t*)"/Programs/bin/hello");
+	int32_t error = sys_exec((uint8_t*)"/Programs/bin/exectest");
 	if (error) {
 		printf("Error executing file: %d\n", error);
 	}