Add few system calls like read, waitpid, exit

* First shell implementation, requires waitpid, read and exit
system calls
* User entry point changed to _start, that also call `exit` on
return from application
* User input is stored in circular buffer, and `read` is blocked
on this buffer, interrupt handler wakes up thread
* Added forktest user app

Signed-off-by: Mahavir Jain <[email protected]>

Makefile

@@ -7,7 +7,7 @@ OBJCOPY := objcopy
 AR := ar
 
 # Tiny OS version
-VERSION := 0.1
+VERSION := 0.2
 
 # Verbose build pass verbose=1
 ifeq ($(verbose),1)
@@ -32,14 +32,40 @@ app_src_dir := app
 
 app_obj_dir := $(objdir)/$(app_src_dir)
 
-c_srcs := $(foreach dir, $(kernel_src_dir), $(wildcard $(dir)/*.c))
-asm_srcs := $(foreach dir, $(boot_src_dir), $(wildcard $(dir)/*.s))
+c_srcs := kernel/cpio_parser.c \
+	  kernel/gdt.c \
+	  kernel/idt.c \
+	  kernel/isr.c \
+	  kernel/keyboard.c \
+	  kernel/main.c \
+	  kernel/mem.c \
+	  kernel/sync.c \
+	  kernel/syscall.c \
+	  kernel/task.c \
+	  kernel/timer.c \
+	  kernel/vm.c \
+	  kernel/wait_queue.c \
+	  drivers/vga.c \
+	  stdlib/stdlib.c \
+	  stdlib/printk.c \
+
+asm_srcs := boot/boot.s \
+	    boot/helper.s \
+	    boot/isr.s \
+	    boot/swtch.s \
+	    boot/sync.s \
+
 c_objs := $(c_srcs:%.c=$(objdir)/%.o)
 asm_objs := $(asm_srcs:%.s=$(objdir)/%.o)
 
-app_lib_objs := $(objdir)/$(boot_src_dir)/syscall.o \
-		$(objdir)/stdlib/stdlib.o \
-		$(objdir)/stdlib/printf.o \
+app_lib_srcs := stdlib/crt.c \
+		stdlib/stdlib.c \
+		stdlib/printf.c \
+
+app_asm_srcs := boot/syscall.s \
+
+app_lib_objs := $(app_lib_srcs:%.c=$(objdir)/%.o)
+app_asm_objs := $(app_asm_srcs:%.s=$(objdir)/%.o)
 
 app_lib := $(objdir)/lib_helper.a
 
@@ -51,7 +77,7 @@ LDSCRIPT = -T ldscript/linker.ld
 APP_LDSCRIPT = -T app/linker.ld
 LDFLAGS = -nostdlib -Wl,--build-id=none
 APP_CFLAGS := -g -O2 -m32 -static -fno-pic -Wall -Wextra -ffreestanding -I app/
-APP_LDFLAGS := -nostdlib -Ttext 0x100000 -e main -Wl,--build-id=none
+APP_LDFLAGS := -nostdlib -Ttext 0x100000 -Wl,--build-id=none
 ASFLAGS = -f elf
 
 define make-repo
@@ -63,13 +89,17 @@ endef
 
 all: pre-build $(kernel) $(os_image)
 
-ramfs.obj: $(app_lib) $(app_obj_dir)/init $(app_obj_dir)/shell
+ramfs.obj: $(app_lib) $(app_obj_dir)/init $(app_obj_dir)/shell $(app_obj_dir)/forktest
 	$(V)cd $(app_obj_dir) && find . | cpio -o -H newc > ../ramfs.cpio
 	$(V)cd $(objdir) && $(OBJCOPY) -I binary -O elf32-i386 -B i386 ramfs.cpio $@
 
-$(app_lib): $(app_lib_objs)
+$(app_lib): $(app_lib_objs) $(app_asm_objs)
 	$(V)$(AR) cru $@ $^
 
+$(app_obj_dir)/forktest: $(app_src_dir)/forktest.c
+	@echo "  APP   $<"
+	$(V)$(CC) $(APP_CFLAGS) $(APP_LDFLAGS) $< $(app_lib) -o $@
+
 $(app_obj_dir)/init: $(app_src_dir)/init.c
 	@echo "  APP   $<"
 	$(V)$(CC) $(APP_CFLAGS) $(APP_LDFLAGS) $< $(app_lib) -o $@

app/forktest.c

@@ -0,0 +1,34 @@
+#include <tinyos.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+#define N 32
+
+void forktest(void)
+{
+	int n, pid;
+
+	printf("fork test\n");
+
+	for (n=0; n<N; n++) {
+		pid = fork();
+		if(pid < 0) {
+			break;
+		}
+		if(pid == 0) {
+			exit(0);
+		}
+	} 
+
+	if (n == N) {
+		printf("fork claimed to work N times!\n", N);
+	}
+}
+
+int main(void)
+{
+	forktest();
+	waitpid(-1, NULL, 0);
+	return 0;
+}

app/init.c

@@ -1,8 +1,6 @@
 #include <tinyos.h>
 #include <unistd.h>
-
-char a[] = "Hello World Parent!\n";
-char b[] = "Hello World Child!\n";
+#include <sys/wait.h>
 
 int main(void)
 {
@@ -12,12 +10,8 @@ int main(void)
 	if (ret == 0) {
 		execve("shell", &argv, NULL);
 	} else {
-		for (;;) {
-			printf("%s", a);
-			volatile int a = 1 << 23;
-			while (a--)
-				;
-		}
+		waitpid(-1, NULL, 0);
+		printf("Bye! Init exiting\n");
 	}
 	return 0;
 }

app/shell.c

@@ -1,11 +1,39 @@
 #include <tinyos.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <string.h>
 
-int a = 0xa5a5;
 int main()
 {
-	if (a == 0xa5a5)
-		printf("I am shell\n");
-	else
-		printf("I lost you\n");
-	for(;;);
+	int ret;
+	int c;
+	char buf[32];
+	int index = 0;
+
+	printf("\nStarting sh\n");
+	printf("Type `help` for commands\n");
+	printf("# ");
+	for (;;) {
+		ret = read(0, &c, 1);
+		if (!ret)
+			continue;
+		buf[index++] = c;
+		if (c == '\n') {
+			buf[--index] = '\0';
+			ret = fork();
+			if (ret == 0) {
+				if (!strcmp(buf, "help"))
+					printf("Available commands 'forktest'\n");
+				else
+					execve(buf, (char **) &ret, NULL);
+				return -1;
+			} else {
+				waitpid(-1, NULL, 0);
+				index = 0;
+				printf("# ");
+			}
+		}
+	}
+	printf("Bye! Shell exiting\n");
+	return 0;
 }

boot/syscall.s

@@ -17,7 +17,19 @@ execve:
 	ret
 
 [GLOBAL read]
-sleep:
+read:
 	mov eax, 3
 	int 64
 	ret
+
+[GLOBAL exit]
+exit:
+	mov eax, 4
+	int 64
+	ret
+
+[GLOBAL waitpid]
+waitpid:
+	mov eax, 5
+	int 64
+	ret

include/kernel/keyboard.h

@@ -2,4 +2,6 @@
 #define __KEYBOARD_H__
 
 void init_keyboard();
+int sys_read();
+
 #endif /* __KEYBOARD_H__ */

include/kernel/task.h

@@ -8,6 +8,7 @@ enum task_state {
 	TASK_RUNNING = 2,
 	TASK_READY = 3,
 	TASK_SLEEPING = 4,
+	TASK_EXITED = 5,
 };
 
 /* Callee saved register context */
@@ -47,6 +48,8 @@ void tiny_schedule(void);
 int create_init_task(void);
 int sys_fork(void);
 int sys_exec(void);
+int sys_exit(void);
+int sys_waitpid(void);
 void swtch(struct context **old, struct context *new);
 void yield();
 void sched();

kernel/keyboard.c

@@ -2,6 +2,10 @@
 #include <helper.h>
 #include <keyboard.h>
 #include <vga.h>
+#include <sync.h>
+#include <mem.h>
+#include <syscall.h>
+#include <string.h>
 
 /* KBDUS means US Keyboard Layout. This is a scancode table
  *  used to layout a standard US keyboard. I have left some
@@ -48,6 +52,26 @@ unsigned char kbdus[128] =
 	0,	/* All other keys are undefined */
 };
 
+#define MAX_SIZE 32
+
+#define WRAP(x) \
+	((x + 1) & (MAX_SIZE - 1))
+
+#define CIRC_BUF_EMPTY(x) \
+	(x->rindex == x->windex)
+
+#define CIRC_BUF_FULL(x) \
+	(x->rindex == WRAP(x->windex + 1))
+
+struct circ_buf {
+	struct spinlock lock;
+	char buf[MAX_SIZE];
+	int rindex;
+	int windex;
+};
+
+static struct circ_buf *circ_buf;
+
 /* Handles the keyboard interrupt */
 void keyboard_handler(registers_t *r)
 {
@@ -59,31 +83,47 @@ void keyboard_handler(registers_t *r)
 
 	/* If the top bit of the byte we read from the keyboard is
 	 *  set, that means that a key has just been released */
-	if (scancode & 0x80)
-	{
-		/* You can use this one to see if the user released the
-		 *  shift, alt, or control keys... */
-	}
-	else
-	{
+	if (scancode & 0x80) {
+		/* Special keyboard chars */
+	} else {
 		/* Here, a key was just pressed. Please note that if you
 		 *  hold a key down, you will get repeated key press
 		 *  interrupts. */
-
-		/* Just to show you how this works, we simply translate
-		 *  the keyboard scancode into an ASCII value, and then
-		 *  display it to the screen. You can get creative and
-		 *  use some flags to see if a shift is pressed and use a
-		 *  different layout, or you can add another 128 entries
-		 *  to the above layout to correspond to 'shift' being
-		 *  held. If shift is held using the larger lookup table,
-		 *  you would add 128 to the scancode when you look for it */
 		sys_write_char(kbdus[scancode]);
+		if (!CIRC_BUF_FULL(circ_buf)) {
+			circ_buf->buf[circ_buf->windex] = kbdus[scancode];
+			circ_buf->windex = WRAP(circ_buf->windex);
+			wakeup(&circ_buf->lock);
+		}
 	}
 }
 
 void init_keyboard()
 {
+	circ_buf = kcalloc(sizeof(struct circ_buf));
+	if (!circ_buf) {
+		printk("malloc failed\n");
+		return;
+	}
 	/* Installs 'keyboard_handler' to IRQ1 */
 	irq_install_handler(IRQ1, keyboard_handler);
 }
+
+int sys_read()
+{
+	char *buf;
+	int len;
+	int read_bytes = 0;
+
+	argstr(1, &buf);
+	argint(2, &len);
+
+	if (CIRC_BUF_EMPTY(circ_buf))
+		sleep(circ_buf, &circ_buf->lock);
+
+	while (!CIRC_BUF_EMPTY(circ_buf) && (read_bytes < len)) {
+		buf[read_bytes++]  = circ_buf->buf[circ_buf->rindex];
+		circ_buf->rindex = WRAP(circ_buf->rindex);
+	}
+	return read_bytes;
+}

kernel/syscall.c

@@ -2,14 +2,17 @@
 #include <vga.h>
 #include <helper.h>
 #include <task.h>
+#include <keyboard.h>
 
 static registers_t *irqf;
 
 static void *sys_handlers[] = {
 	sys_write,
 	sys_fork,
 	sys_exec,
-	//sys_read,
+	sys_read,
+	sys_exit,
+	sys_waitpid,
 };
 
 int argint(int n, int *p)

kernel/task.c

@@ -267,8 +267,27 @@ int sys_exec()
 	return 0;
 }
 
+int sys_exit()
+{
+	/* FIXME: Resources should be freed from IDLE task context */
+	current_task->state = TASK_EXITED;
+	task_wakeup(current_task->parent);
+	sched();
+	return 0;
+}
+
+int sys_waitpid()
+{
+	task_sleep(current_task);
+	sched();
+	return 0;
+}
+
 void task_sleep(void *resource)
 {
+	if (!resource)
+		return;
+
 	cli();
 	current_task->wait_resource = resource;
 	current_task->state = TASK_SLEEPING;
@@ -277,6 +296,9 @@ void task_sleep(void *resource)
 
 void task_wakeup(void *resource)
 {
+	if (!resource)
+		return;
+
 	cli();
 	list_head_t *node;
 	list_for_each(node, task_list) {