process.c

优龙2410linux2.6.8内核源代码

/*
 *  linux/arch/i386/kernel/process.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *	Gareth Hughes <[e-mail]>, May 2000
 */

/*
 * This file handles the architecture-dependent parts of process handling..
 */

#include <stdarg.h>

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/interrupt.h>
#include <linux/config.h>
#include <linux/version.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/ptrace.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/irq.h>
#include <asm/desc.h>
#ifdef CONFIG_MATH_EMULATION
#include <asm/math_emu.h>
#endif

#include <linux/irq.h>
#include <linux/err.h>

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");

int hlt_counter;

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
	return ((unsigned long *)tsk->thread.esp)[3];
}

/*
 * Powermanagement idle function, if any..
 */
void (*pm_idle)(void);

void disable_hlt(void)
{
	hlt_counter++;
}

EXPORT_SYMBOL(disable_hlt);

void enable_hlt(void)
{
	hlt_counter--;
}

EXPORT_SYMBOL(enable_hlt);

/*
 * We use this if we don't have any better
 * idle routine..
 */
void default_idle(void)
{
	if (!hlt_counter && current_cpu_data.hlt_works_ok) {
		local_irq_disable();
		if (!need_resched())
			safe_halt();
		else
			local_irq_enable();
	}
}

/*
 * On SMP it's slightly faster (but much more power-consuming!)
 * to poll the ->work.need_resched flag instead of waiting for the
 * cross-CPU IPI to arrive. Use this option with caution.
 */
static void poll_idle (void)
{
	int oldval;

	local_irq_enable();

	/*
	 * Deal with another CPU just having chosen a thread to
	 * run here:
	 */
	oldval = test_and_clear_thread_flag(TIF_NEED_RESCHED);

	if (!oldval) {
		set_thread_flag(TIF_POLLING_NRFLAG);
		asm volatile(
			"2:"
			"testl %0, %1;"
			"rep; nop;"
			"je 2b;"
			: : "i"(_TIF_NEED_RESCHED), "m" (current_thread_info()->flags));

		clear_thread_flag(TIF_POLLING_NRFLAG);
	} else {
		set_need_resched();
	}
}

/*
 * The idle thread. There's no useful work to be
 * done, so just try to conserve power and have a
 * low exit latency (ie sit in a loop waiting for
 * somebody to say that they'd like to reschedule)
 */
void cpu_idle (void)
{
	/* endless idle loop with no priority at all */
	while (1) {
		while (!need_resched()) {
			void (*idle)(void) = pm_idle;

			if (!idle)
				idle = default_idle;

			irq_stat[smp_processor_id()].idle_timestamp = jiffies;
			idle();
		}
		schedule();
	}
}

/*
 * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
 * which can obviate IPI to trigger checking of need_resched.
 * We execute MONITOR against need_resched and enter optimized wait state
 * through MWAIT. Whenever someone changes need_resched, we would be woken
 * up from MWAIT (without an IPI).
 */
static void mwait_idle(void)
{
	local_irq_enable();

	if (!need_resched()) {
		set_thread_flag(TIF_POLLING_NRFLAG);
		do {
			__monitor((void *)&current_thread_info()->flags, 0, 0);
			if (need_resched())
				break;
			__mwait(0, 0);
		} while (!need_resched());
		clear_thread_flag(TIF_POLLING_NRFLAG);
	}
}

void __init select_idle_routine(const struct cpuinfo_x86 *c)
{
	if (cpu_has(c, X86_FEATURE_MWAIT)) {
		printk("monitor/mwait feature present.\n");
		/*
		 * Skip, if setup has overridden idle.
		 * Also, take care of system with asymmetric CPUs.
		 * Use, mwait_idle only if all cpus support it.
		 * If not, we fallback to default_idle()
		 */
		if (!pm_idle) {
			printk("using mwait in idle threads.\n");
			pm_idle = mwait_idle;
		}
		return;
	}
	pm_idle = default_idle;
	return;
}

static int __init idle_setup (char *str)
{
	if (!strncmp(str, "poll", 4)) {
		printk("using polling idle threads.\n");
		pm_idle = poll_idle;
#ifdef CONFIG_X86_SMP
		if (smp_num_siblings > 1)
			printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
#endif
	} else if (!strncmp(str, "halt", 4)) {
		printk("using halt in idle threads.\n");
		pm_idle = default_idle;
	}

	return 1;
}

__setup("idle=", idle_setup);

void show_regs(struct pt_regs * regs)
{
	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;

	printk("\n");
	printk("Pid: %d, comm: %20s\n", current->pid, current->comm);
	printk("EIP: %04x:[<%08lx>] CPU: %d\n",0xffff & regs->xcs,regs->eip, smp_processor_id());
	print_symbol("EIP is at %s\n", regs->eip);

	if (regs->xcs & 3)
		printk(" ESP: %04x:%08lx",0xffff & regs->xss,regs->esp);
	printk(" EFLAGS: %08lx    %s  (%s)\n",regs->eflags, print_tainted(),UTS_RELEASE);
	printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
		regs->eax,regs->ebx,regs->ecx,regs->edx);
	printk("ESI: %08lx EDI: %08lx EBP: %08lx",
		regs->esi, regs->edi, regs->ebp);
	printk(" DS: %04x ES: %04x\n",
		0xffff & regs->xds,0xffff & regs->xes);

	__asm__("movl %%cr0, %0": "=r" (cr0));
	__asm__("movl %%cr2, %0": "=r" (cr2));
	__asm__("movl %%cr3, %0": "=r" (cr3));
	/* This could fault if %cr4 does not exist */
	__asm__("1: movl %%cr4, %0		\n"
		"2:				\n"
		".section __ex_table,\"a\"	\n"
		".long 1b,2b			\n"
		".previous			\n"
		: "=r" (cr4): "0" (0));
	printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
	show_trace(NULL, &regs->esp);
}

/*
 * This gets run with %ebx containing the
 * function to call, and %edx containing
 * the "args".
 */
extern void kernel_thread_helper(void);
__asm__(".section .text\n"
	".align 4\n"
	"kernel_thread_helper:\n\t"
	"movl %edx,%eax\n\t"
	"pushl %edx\n\t"
	"call *%ebx\n\t"
	"pushl %eax\n\t"
	"call do_exit\n"
	".previous");

/*
 * Create a kernel thread
 */
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
	struct pt_regs regs;

	memset(&regs, 0, sizeof(regs));

	regs.ebx = (unsigned long) fn;
	regs.edx = (unsigned long) arg;

	regs.xds = __USER_DS;
	regs.xes = __USER_DS;
	regs.orig_eax = -1;
	regs.eip = (unsigned long) kernel_thread_helper;
	regs.xcs = __KERNEL_CS;
	regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;

	/* Ok, create the new process.. */
	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
}

/*
 * Free current thread data structures etc..
 */
void exit_thread(void)
{
	struct task_struct *tsk = current;

	/* The process may have allocated an io port bitmap... nuke it. */
	if (unlikely(NULL != tsk->thread.io_bitmap_ptr)) {
		int cpu = get_cpu();
		struct tss_struct *tss = init_tss + cpu;
		kfree(tsk->thread.io_bitmap_ptr);
		tsk->thread.io_bitmap_ptr = NULL;
		tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
		put_cpu();
	}
}

void flush_thread(void)
{
	struct task_struct *tsk = current;

	memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));	
	/*
	 * Forget coprocessor state..
	 */
	clear_fpu(tsk);
	tsk->used_math = 0;
}

void release_thread(struct task_struct *dead_task)
{
	if (dead_task->mm) {
		// temporary debugging check
		if (dead_task->mm->context.size) {
			printk("WARNING: dead process %8s still has LDT? <%p/%d>\n",
					dead_task->comm,
					dead_task->mm->context.ldt,
					dead_task->mm->context.size);
			BUG();
		}
	}

	release_x86_irqs(dead_task);
}

/*
 * This gets called before we allocate a new thread and copy
 * the current task into it.
 */
void prepare_to_copy(struct task_struct *tsk)
{
	unlazy_fpu(tsk);
}

int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
	unsigned long unused,
	struct task_struct * p, struct pt_regs * regs)
{
	struct pt_regs * childregs;
	struct task_struct *tsk;
	int err;

	childregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) p->thread_info)) - 1;
	*childregs = *regs;
	childregs->eax = 0;
	childregs->esp = esp;
	p->set_child_tid = p->clear_child_tid = NULL;

	p->thread.esp = (unsigned long) childregs;
	p->thread.esp0 = (unsigned long) (childregs+1);

	p->thread.eip = (unsigned long) ret_from_fork;

	savesegment(fs,p->thread.fs);
	savesegment(gs,p->thread.gs);

	tsk = current;
	if (unlikely(NULL != tsk->thread.io_bitmap_ptr)) {
		p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
		if (!p->thread.io_bitmap_ptr)
			return -ENOMEM;
		memcpy(p->thread.io_bitmap_ptr, tsk->thread.io_bitmap_ptr,
			IO_BITMAP_BYTES);
	}

	/*
	 * Set a new TLS for the child thread?
	 */
	if (clone_flags & CLONE_SETTLS) {
		struct desc_struct *desc;
		struct user_desc info;
		int idx;

		err = -EFAULT;
		if (copy_from_user(&info, (void __user *)childregs->esi, sizeof(info)))
			goto out;
		err = -EINVAL;
		if (LDT_empty(&info))