Shell. Apparently buggy context switch.

Makefile

@@ -20,7 +20,7 @@ CFLAGS = -mcpu=$(CPU) -gstabs -I include -I arch/$(arch)/include -marm \
          -fno-builtin-printf -fno-builtin-strcpy -Wno-overlength-strings \
          -fno-builtin-exit
 ASFLAGS = -mcpu=$(CPU) -g -I include -I arch/$(arch)/include
-QEMU_FLAGS = $(ARCH_QEMU_FLAGS) -nographic
+QEMU_FLAGS = $(ARCH_QEMU_FLAGS) -nographic -d in_asm
 
 all: $(OS).bin
 

include/lib/syscall.h

@@ -16,7 +16,8 @@ enum SystemCallCode {
 	SYSCALL_GETPID,
 	SYSCALL_FORK,
 	SYSCALL_EXEC,
-	SYSCALL_YIELD
+	SYSCALL_YIELD,
+	SYSCALL_WAIT
 };
 
 int syscall0(enum SystemCallCode code);
@@ -30,5 +31,6 @@ int getpid(void);
 int fork(void);
 void exec(int id);
 void yield(void);
+void wait(int id);
 
 #endif

include/proc.h

@@ -49,6 +49,9 @@ struct Process {
 	char *user_stack;
 	char *kernel_stack;
 	int context[17];
+
+	int wait_pid;
+	int child_return_value;
 };
 
 #define ELF_MAGIC 0x464C457FU
@@ -115,6 +118,7 @@ int syscall_getpid(void);
 int syscall_fork(void);
 int syscall_exec(int id);
 int syscall_yield(void);
+int syscall_wait(int id);
 
 #endif
 #endif

kernel/init.c

@@ -18,12 +18,12 @@ void c_entry(void)
 	console_init();
 	kalloc_init(KERNEL_BASE + INITIAL_MEMORY_SIZE,
 		    KERNEL_BASE + TOTAL_MEMORY_SIZE);
-	scheduler_init();
 
 	/* start the first program */
 	{
 		struct Process *proc = proc_create();
 		proc_load_program(proc, 0);
+		scheduler_init();
 		schedule();
 	}
 }

kernel/ksyscall.c

@@ -9,7 +9,8 @@ static int (*const syscall_handler[])() = {
 	[SYSCALL_GETPID] = syscall_getpid,
 	[SYSCALL_FORK] = syscall_fork,
 	[SYSCALL_EXEC] = syscall_exec,
-	[SYSCALL_YIELD] = syscall_yield
+	[SYSCALL_YIELD] = syscall_yield,
+	[SYSCALL_WAIT] = syscall_wait
 };
 
 /* kernel side of system calls. */

kernel/proc/build.mk

@@ -8,3 +8,4 @@ OBJS += $(PROC_DIR)/syscall_getpid.o
 OBJS += $(PROC_DIR)/syscall_fork.o
 OBJS += $(PROC_DIR)/syscall_exec.o
 OBJS += $(PROC_DIR)/syscall_yield.o
+OBJS += $(PROC_DIR)/syscall_wait.o

kernel/proc/proc.c

@@ -69,6 +69,7 @@ struct Process *proc_create(void)
 	proc->heap_size = 0;
 	proc->kernel_stack = kernel_stack;
 	proc->user_stack = user_stack;
+	proc->wait_pid = -1;
 
 	return proc;
 }

kernel/proc/scheduler.c

@@ -17,7 +17,7 @@ void handle_timer(void)
 void scheduler_init(void)
 {
 	round_robin_index = 0;
-	timer_set_interval(100000);
+	timer_set_interval(10000);
 	register_interrupt_handler(0x5, handle_timer);
 }
 
@@ -36,12 +36,17 @@ void schedule(void)
 		proc = &process_table[round_robin_index];
 
 		if (proc->state == READY) {
+			//kprintf("scheduling %d\n", round_robin_index);
 			current_process = proc;
 			proc_start(proc);
 		}
 	}
 
 	/* no process? panic */
+	mon_status(0, 0);
+	kprintf("round_robin_index = %d\n", round_robin_index);
+	for (i = 0; i < PROCESS_COUNT_MAX; i++)
+		kprintf("[%d] = %d\n", i, process_table[i].state);
 	kprintf("PANIC");
 	while(1);
 }

kernel/proc/syscall_exit.c

@@ -4,13 +4,26 @@
 
 int syscall_exit(int arg1)
 {
+	int pid;
+
 	(void) arg1;
 	if (current_process == NULL)
 		return -1;
 
 	set_translation_table_base((uint32_t) V2P(kernel_vm));
 	__asm__ volatile("ldr sp, =kernel_stack_start");
 
+	for (pid = 0; pid < PROCESS_COUNT_MAX; pid++) {
+		struct Process *proc = &process_table[pid];
+
+		if (proc->state == SLEEPING &&
+		    proc->wait_pid == current_process->pid) {
+
+			proc->wait_pid = -1;
+			proc->state = READY;
+		}
+	}
+
 	proc_free(current_process);
 	current_process = NULL;
 

kernel/proc/syscall_wait.c

@@ -0,0 +1,12 @@
+#include <ksyscall.h>
+#include <proc.h>
+#include <system.h>
+
+int syscall_wait(int arg1)
+{
+	current_process->wait_pid = arg1;
+	current_process->state = SLEEPING;
+	schedule();
+
+	return 0;
+}

kernel/startup.S

@@ -9,7 +9,6 @@ entry:
 	bl copy_interrupt_table
 	bl use_high_interrupts
 	bl enable_interrupts
-	bl setup_irq_stack_pointer
 
 	bl jump_to_high_mem
 	bl c_entry
@@ -45,16 +44,6 @@ copy_interrupt_table:
 
 	mov pc, lr
 
-setup_irq_stack_pointer:
-	mrs r0, cpsr
-	bic r1, r0, #0x1F
-	orr r1, r1, #0x12  
-	msr cpsr, r1  
-	ldr sp, =irq_stack_start
-	msr cpsr, r0
-
-	mov pc, lr
-
 interrupt_table_start:
 	nop
 	subs pc, lr, #4

lib/syscall.c

@@ -69,4 +69,9 @@ void exec(int id)
 void yield(void)
 {
 	syscall0(SYSCALL_YIELD);
-}
+}
+
+void wait(int id)
+{
+	syscall1(SYSCALL_WAIT, id);
+}

user/exec_test.c

@@ -4,8 +4,8 @@
 void _start()
 {
 	if (fork() == 0) {
-		printf("starting program 0 ...\n");
-		exec(0);
+		printf("starting program 1 ...\n");
+		exec(1);
 	}
 	else {
 		printf("message from parent.\n");

user/shell.c

@@ -3,15 +3,25 @@
 
 void _start()
 {
-	int i = 0, j = 0;
-	fork();
-	fork();
-	fork();
+	char command[128];
+	int program_idx = 0;
+	int child_pid = 0;
 
 	while (1) {
-		printf("step %d at pid %d\n", i, getpid());
-		yield();
-		i++;
+		printf("$ ");
+		gets(command);
+		if (command[0] < '0' || command[0] > '9')
+			continue;
+
+		program_idx = command[0] - '0';
+		child_pid = fork();
+		printf("child_pid = %d\n", child_pid);
+		if (child_pid == 0) {
+			exec(program_idx);
+		}
+		else {
+			wait(child_pid);
+		}
 	}
 
 	exit(0);