/* *  Copyright (C) 1995  Linus Torvalds * *  Pentium III FXSR, SSE support *	Gareth Hughes <gareth@valinux.com>, May 2000 */ /* * This file handles the architecture-dependent parts of process handling.. */ #include <linux/stackprotector.h>#include <linux/cpu.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/stddef.h>#include <linux/slab.h>#include <linux/vmalloc.h>#include <linux/user.h>#include <linux/interrupt.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 <linux/personality.h>#include <linux/tick.h>#include <linux/percpu.h>#include <linux/prctl.h>#include <linux/ftrace.h>#include <linux/uaccess.h>#include <linux/io.h>#include <linux/kdebug.h>#include <linux/cpuidle.h> #include <asm/pgtable.h>#include <asm/system.h>#include <asm/ldt.h>#include <asm/processor.h>#include <asm/i387.h>#include <asm/desc.h>#ifdef CONFIG_MATH_EMULATION#include <asm/math_emu.h>#endif #include <linux/err.h> #include <asm/tlbflush.h>#include <asm/cpu.h>#include <asm/idle.h>#include <asm/syscalls.h>#include <asm/debugreg.h>#include <asm/nmi.h> asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); /* * Return saved PC of a blocked thread. */unsigned long thread_saved_pc(struct task_struct *tsk){	return ((unsigned long *)tsk->thread.sp)[3];} #ifndef CONFIG_SMPstatic inline void play_dead(void){	BUG();}#endif /* * 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){	int cpu = smp_processor_id(); 	/*	 * If we're the non-boot CPU, nothing set the stack canary up	 * for us.  CPU0 already has it initialized but no harm in	 * doing it again.  This is a good place for updating it, as	 * we wont ever return from this function (so the invalid	 * canaries already on the stack wont ever trigger).	 */	boot_init_stack_canary(); 	current_thread_info()->status |= TS_POLLING; 	/* endless idle loop with no priority at all */	while (1) {		tick_nohz_stop_sched_tick(1);		while (!need_resched()) { 			check_pgt_cache();			rmb(); 			if (cpu_is_offline(cpu))				play_dead(); 			local_touch_nmi();			local_irq_disable();			/* Don't trace irqs off for idle */			stop_critical_timings();			if (cpuidle_idle_call())				pm_idle();			start_critical_timings();		}		tick_nohz_restart_sched_tick();		preempt_enable_no_resched();		schedule();		preempt_disable();	}} void __show_regs(struct pt_regs *regs, int all){	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;	unsigned long d0, d1, d2, d3, d6, d7;	unsigned long sp;	unsigned short ss, gs; 	if (user_mode_vm(regs)) {		sp = regs->sp;		ss = regs->ss & 0xffff;		gs = get_user_gs(regs);	} else {		sp = kernel_stack_pointer(regs);		savesegment(ss, ss);		savesegment(gs, gs);	} 	show_regs_common(); 	printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",			(u16)regs->cs, regs->ip, regs->flags,			smp_processor_id());	print_symbol("EIP is at %s\n", regs->ip); 	printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",		regs->ax, regs->bx, regs->cx, regs->dx);	printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",		regs->si, regs->di, regs->bp, sp);	printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",	       (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 	if (!all)		return; 	cr0 = read_cr0();	cr2 = read_cr2();	cr3 = read_cr3();	cr4 = read_cr4_safe();	printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",			cr0, cr2, cr3, cr4); 	get_debugreg(d0, 0);	get_debugreg(d1, 1);	get_debugreg(d2, 2);	get_debugreg(d3, 3);	printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",			d0, d1, d2, d3); 	get_debugreg(d6, 6);	get_debugreg(d7, 7);	printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",			d6, d7);} void release_thread(struct task_struct *dead_task){	BUG_ON(dead_task->mm);	release_vm86_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(unsigned long clone_flags, unsigned long sp,	unsigned long unused,	struct task_struct *p, struct pt_regs *regs){	struct pt_regs *childregs;	struct task_struct *tsk;	int err; 	childregs = task_pt_regs(p);	*childregs = *regs;	childregs->ax = 0;	childregs->sp = sp; 	p->thread.sp = (unsigned long) childregs;	p->thread.sp0 = (unsigned long) (childregs+1); 	p->thread.ip = (unsigned long) ret_from_fork; 	task_user_gs(p) = get_user_gs(regs); 	p->thread.io_bitmap_ptr = NULL;	tsk = current;	err = -ENOMEM; 	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 	if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {		p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,						IO_BITMAP_BYTES, GFP_KERNEL);		if (!p->thread.io_bitmap_ptr) {			p->thread.io_bitmap_max = 0;			return -ENOMEM;		}		set_tsk_thread_flag(p, TIF_IO_BITMAP);	} 	err = 0; 	/*	 * Set a new TLS for the child thread?	 */	if (clone_flags & CLONE_SETTLS)		err = do_set_thread_area(p, -1,			(struct user_desc __user *)childregs->si, 0); 	if (err && p->thread.io_bitmap_ptr) {		kfree(p->thread.io_bitmap_ptr);		p->thread.io_bitmap_max = 0;	}	return err;} voidstart_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp){	set_user_gs(regs, 0);	regs->fs		= 0;	regs->ds		= __USER_DS;	regs->es		= __USER_DS;	regs->ss		= __USER_DS;	regs->cs		= __USER_CS;	regs->ip		= new_ip;	regs->sp		= new_sp;	/*	 * Free the old FP and other extended state	 */	free_thread_xstate(current);}EXPORT_SYMBOL_GPL(start_thread);  /* *	switch_to(x,y) should switch tasks from x to y. * * We fsave/fwait so that an exception goes off at the right time * (as a call from the fsave or fwait in effect) rather than to * the wrong process. Lazy FP saving no longer makes any sense * with modern CPU's, and this simplifies a lot of things (SMP * and UP become the same). * * NOTE! We used to use the x86 hardware context switching. The * reason for not using it any more becomes apparent when you * try to recover gracefully from saved state that is no longer * valid (stale segment register values in particular). With the * hardware task-switch, there is no way to fix up bad state in * a reasonable manner. * * The fact that Intel documents the hardware task-switching to * be slow is a fairly red herring - this code is not noticeably * faster. However, there _is_ some room for improvement here, * so the performance issues may eventually be a valid point. * More important, however, is the fact that this allows us much * more flexibility. * * The return value (in %ax) will be the "prev" task after * the task-switch, and shows up in ret_from_fork in entry.S, * for example. */__notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev_p, struct task_struct *next_p){	struct thread_struct *prev = &prev_p->thread,				 *next = &next_p->thread;	int cpu = smp_processor_id();	struct tss_struct *tss = &per_cpu(init_tss, cpu);	bool preload_fpu; 	/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 	/*	 * If the task has used fpu the last 5 timeslices, just do a full	 * restore of the math state immediately to avoid the trap; the	 * chances of needing FPU soon are obviously high now	 */	preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5; 	__unlazy_fpu(prev_p); 	/* we're going to use this soon, after a few expensive things */	if (preload_fpu)		prefetch(next->fpu.state); 	/*	 * Reload esp0.	 */	load_sp0(tss, next); 	/*	 * Save away %gs. No need to save %fs, as it was saved on the	 * stack on entry.  No need to save %es and %ds, as those are	 * always kernel segments while inside the kernel.  Doing this	 * before setting the new TLS descriptors avoids the situation	 * where we temporarily have non-reloadable segments in %fs	 * and %gs.  This could be an issue if the NMI handler ever	 * used %fs or %gs (it does not today), or if the kernel is	 * running inside of a hypervisor layer.	 */	lazy_save_gs(prev->gs); 	/*	 * Load the per-thread Thread-Local Storage descriptor.	 */	load_TLS(next, cpu); 	/*	 * Restore IOPL if needed.  In normal use, the flags restore	 * in the switch assembly will handle this.  But if the kernel	 * is running virtualized at a non-zero CPL, the popf will	 * not restore flags, so it must be done in a separate step.	 */	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))		set_iopl_mask(next->iopl); 	/*	 * Now maybe handle debug registers and/or IO bitmaps	 */	if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||		     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))		__switch_to_xtra(prev_p, next_p, tss); 	/* If we're going to preload the fpu context, make sure clts	   is run while we're batching the cpu state updates. */	if (preload_fpu)		clts(); 	/*	 * Leave lazy mode, flushing any hypercalls made here.	 * This must be done before restoring TLS segments so	 * the GDT and LDT are properly updated, and must be	 * done before math_state_restore, so the TS bit is up	 * to date.	 */	arch_end_context_switch(next_p); 	if (preload_fpu)		__math_state_restore(); 	/*	 * Restore %gs if needed (which is common)	 */	if (prev->gs | next->gs)		lazy_load_gs(next->gs); 	percpu_write(current_task, next_p); 	return prev_p;} #define top_esp                (THREAD_SIZE - sizeof(unsigned long))#define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long)) unsigned long get_wchan(struct task_struct *p){	unsigned long bp, sp, ip;	unsigned long stack_page;	int count = 0;	if (!p || p == current || p->state == TASK_RUNNING)		return 0;	stack_page = (unsigned long)task_stack_page(p);	sp = p->thread.sp;	if (!stack_page || sp < stack_page || sp > top_esp+stack_page)		return 0;	/* include/asm-i386/system.h:switch_to() pushes bp last. */	bp = *(unsigned long *) sp;	do {		if (bp < stack_page || bp > top_ebp+stack_page)			return 0;		ip = *(unsigned long *) (bp+4);		if (!in_sched_functions(ip))			return ip;		bp = *(unsigned long *) bp;	} while (count++ < 16);	return 0;}