process.c

一个2.4.21版本的嵌入式linux内核

	extern void ret_from_fork(void);
	unsigned long sp = (unsigned long)p + sizeof(union task_union);
	unsigned long childframe;

	/* Copy registers */
	sp -= sizeof(struct pt_regs);
	childregs = (struct pt_regs *) sp;
	*childregs = *regs;
	if ((childregs->msr & MSR_PR) == 0) {
		/* for kernel thread, set `current' and stackptr in new task */
		childregs->gpr[1] = sp + sizeof(struct pt_regs);
		childregs->gpr[2] = (unsigned long) p;
		p->thread.regs = NULL;	/* no user register state */
	} else
		p->thread.regs = childregs;
	childregs->gpr[3] = 0;  /* Result from fork() */
	sp -= STACK_FRAME_OVERHEAD;
	childframe = sp;

	/*
	 * The way this works is that at some point in the future
	 * some task will call _switch to switch to the new task.
	 * That will pop off the stack frame created below and start
	 * the new task running at ret_from_fork.  The new task will
	 * do some house keeping and then return from the fork or clone
	 * system call, using the stack frame created above.
	 */
	sp -= sizeof(struct pt_regs);
	kregs = (struct pt_regs *) sp;
	sp -= STACK_FRAME_OVERHEAD;
	p->thread.ksp = sp;
	kregs->nip = (unsigned long)ret_from_fork;

	/*
	 * copy fpu info - assume lazy fpu switch now always
	 *  -- Cort
	 */
	if (regs->msr & MSR_FP) {
		giveup_fpu(current);
		childregs->msr &= ~(MSR_FP | MSR_FE0 | MSR_FE1);
	}
	memcpy(&p->thread.fpr, &current->thread.fpr, sizeof(p->thread.fpr));
	p->thread.fpscr = current->thread.fpscr;

#ifdef CONFIG_ALTIVEC
	/*
	 * copy altiVec info - assume lazy altiVec switch
	 * - kumar
	 */
	if (regs->msr & MSR_VEC)
		giveup_altivec(current);
	memcpy(&p->thread.vr, &current->thread.vr, sizeof(p->thread.vr));
	p->thread.vscr = current->thread.vscr;
	childregs->msr &= ~MSR_VEC;
#endif /* CONFIG_ALTIVEC */

	p->thread.last_syscall = -1;

	return 0;
}

/*
 * Set up a thread for executing a new program
 */
void start_thread(struct pt_regs *regs, unsigned long nip, unsigned long sp)
{
	set_fs(USER_DS);
	memset(regs->gpr, 0, sizeof(regs->gpr));
	memset(&regs->ctr, 0, 5 * sizeof(regs->ctr));
	regs->nip = nip;
	regs->gpr[1] = sp;
	regs->msr = MSR_USER;
	if (last_task_used_math == current)
		last_task_used_math = 0;
	if (last_task_used_altivec == current)
		last_task_used_altivec = 0;
	memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
	current->thread.fpscr = 0;
#ifdef CONFIG_ALTIVEC
	memset(current->thread.vr, 0, sizeof(current->thread.vr));
	memset(&current->thread.vscr, 0, sizeof(current->thread.vscr));
	current->thread.vrsave = 0;
#endif /* CONFIG_ALTIVEC */
}

/*
 * Support for the PR_GET/SET_FPEXC prctl() calls.
 */
static inline unsigned int __unpack_fe01(unsigned int msr_bits)
{
	return ((msr_bits & MSR_FE0) >> 10) | ((msr_bits & MSR_FE1) >> 8);
}

static inline unsigned int __pack_fe01(unsigned int fpmode)
{
	return ((fpmode << 10) & MSR_FE0) | ((fpmode << 8) & MSR_FE1);
}

int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
{
	struct pt_regs *regs = tsk->thread.regs;

	if (val > PR_FP_EXC_PRECISE)
		return -EINVAL;
	tsk->thread.fpexc_mode = __pack_fe01(val);
	if (regs != NULL && (regs->msr & MSR_FP) != 0)
		regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
			| tsk->thread.fpexc_mode;
	return 0;
}

int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
{
	unsigned int val;

	val = __unpack_fe01(tsk->thread.fpexc_mode);
	return put_user(val, (unsigned int *) adr);
}

int sys_clone(int p1, int p2, int p3, int p4, int p5, int p6,
	      struct pt_regs *regs)
{
	return do_fork(p1, p2, regs, 0);
}

int sys_fork(int p1, int p2, int p3, int p4, int p5, int p6,
	     struct pt_regs *regs)
{
	return do_fork(SIGCHLD, regs->gpr[1], regs, 0);
}

int sys_vfork(int p1, int p2, int p3, int p4, int p5, int p6,
	      struct pt_regs *regs)
{
	return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1], regs, 0);
}

int sys_execve(unsigned long a0, unsigned long a1, unsigned long a2,
	       unsigned long a3, unsigned long a4, unsigned long a5,
	       struct pt_regs *regs)
{
	int error;
	char * filename;

	filename = getname((char *) a0);
	error = PTR_ERR(filename);
	if (IS_ERR(filename))
		goto out;
	if (regs->msr & MSR_FP)
		giveup_fpu(current);
#ifdef CONFIG_ALTIVEC
	if (regs->msr & MSR_VEC)
		giveup_altivec(current);
#endif /* CONFIG_ALTIVEC */ 
	error = do_execve(filename, (char **) a1, (char **) a2, regs);
	if (error == 0)
		current->ptrace &= ~PT_DTRACE;
	putname(filename);
out:
	return error;
}

void
print_backtrace(unsigned long *sp)
{
	int cnt = 0;
	unsigned long i;

	if (sp == NULL)
		asm("mr %0,1" : "=r" (sp));
	printk("Call backtrace: ");
	while (sp) {
		if (__get_user( i, &sp[1] ))
			break;
		if (cnt++ % 7 == 0)
			printk("\n");
		printk("%08lX ", i);
		if (cnt > 32) break;
		if (__get_user(sp, (unsigned long **)sp))
			break;
	}
	printk("\n");
}

void show_trace_task(struct task_struct *tsk)
{
	unsigned long stack_top = (unsigned long) tsk + THREAD_SIZE;
	unsigned long sp, prev_sp;
	int count = 0;

	if (tsk == NULL)
		return;
	sp = (unsigned long) &tsk->thread.ksp;
	do {
		prev_sp = sp;
		sp = *(unsigned long *)sp;
		if (sp <= prev_sp || sp >= stack_top || (sp & 3) != 0)
			break;
		if (count > 0)
			printk("[%08lx] ", *(unsigned long *)(sp + 4));
	} while (++count < 16);
	if (count > 1)
		printk("\n");
}

#if 0
/*
 * Low level print for debugging - Cort
 */
int __init ll_printk(const char *fmt, ...)
{
        va_list args;
	char buf[256];
        int i;

        va_start(args, fmt);
        i=vsprintf(buf,fmt,args);
	ll_puts(buf);
        va_end(args);
        return i;
}

int lines = 24, cols = 80;
int orig_x = 0, orig_y = 0;

void puthex(unsigned long val)
{
	unsigned char buf[10];
	int i;
	for (i = 7;  i >= 0;  i--)
	{
		buf[i] = "0123456789ABCDEF"[val & 0x0F];
		val >>= 4;
	}
	buf[8] = '\0';
	prom_print(buf);
}

void __init ll_puts(const char *s)
{
	int x,y;
	char *vidmem = (char *)/*(_ISA_MEM_BASE + 0xB8000) */0xD00B8000;
	char c;
	extern int mem_init_done;

	if ( mem_init_done ) /* assume this means we can printk */
	{
		printk(s);
		return;
	}

#if 0	
	if ( have_of )
	{
		prom_print(s);
		return;
	}
#endif

	/*
	 * can't ll_puts on chrp without openfirmware yet.
	 * vidmem just needs to be setup for it.
	 * -- Cort
	 */
	if ( _machine != _MACH_prep )
		return;
	x = orig_x;
	y = orig_y;

	while ( ( c = *s++ ) != '\0' ) {
		if ( c == '\n' ) {
			x = 0;
			if ( ++y >= lines ) {
				/*scroll();*/
				/*y--;*/
				y = 0;
			}
		} else {
			vidmem [ ( x + cols * y ) * 2 ] = c; 
			if ( ++x >= cols ) {
				x = 0;
				if ( ++y >= lines ) {
					/*scroll();*/
					/*y--;*/
					y = 0;
				}
			}
		}
	}

	orig_x = x;
	orig_y = y;
}
#endif

/*
 * These bracket the sleeping functions..
 */
extern void scheduling_functions_start_here(void);
extern void scheduling_functions_end_here(void);
#define first_sched    ((unsigned long) scheduling_functions_start_here)
#define last_sched     ((unsigned long) scheduling_functions_end_here)

unsigned long get_wchan(struct task_struct *p)
{
	unsigned long ip, sp;
	unsigned long stack_page = (unsigned long) p;
	int count = 0;
	if (!p || p == current || p->state == TASK_RUNNING)
		return 0;
	sp = p->thread.ksp;
	do {
		sp = *(unsigned long *)sp;
		if (sp < stack_page || sp >= stack_page + 8188)
			return 0;
		if (count > 0) {
			ip = *(unsigned long *)(sp + 4);
			if (ip < first_sched || ip >= last_sched)
				return ip;
		}
	} while (count++ < 16);
	return 0;
}