process_32.c revision 25e41933b58777f2d020c3b0186b430ea004ec28 
1/*
2 *  Copyright (C) 1995  Linus Torvalds
3 *
4 *  Pentium III FXSR, SSE support
5 *	Gareth Hughes <gareth@valinux.com>, May 2000
6 */
7
8/*
9 * This file handles the architecture-dependent parts of process handling..
10 */
11
12#include <linux/stackprotector.h>
13#include <linux/cpu.h>
14#include <linux/errno.h>
15#include <linux/sched.h>
16#include <linux/fs.h>
17#include <linux/kernel.h>
18#include <linux/mm.h>
19#include <linux/elfcore.h>
20#include <linux/smp.h>
21#include <linux/stddef.h>
22#include <linux/slab.h>
23#include <linux/vmalloc.h>
24#include <linux/user.h>
25#include <linux/interrupt.h>
26#include <linux/delay.h>
27#include <linux/reboot.h>
28#include <linux/init.h>
29#include <linux/mc146818rtc.h>
30#include <linux/module.h>
31#include <linux/kallsyms.h>
32#include <linux/ptrace.h>
33#include <linux/personality.h>
34#include <linux/tick.h>
35#include <linux/percpu.h>
36#include <linux/prctl.h>
37#include <linux/ftrace.h>
38#include <linux/uaccess.h>
39#include <linux/io.h>
40#include <linux/kdebug.h>
41
42#include <asm/pgtable.h>
43#include <asm/system.h>
44#include <asm/ldt.h>
45#include <asm/processor.h>
46#include <asm/i387.h>
47#include <asm/desc.h>
48#ifdef CONFIG_MATH_EMULATION
49#include <asm/math_emu.h>
50#endif
51
52#include <linux/err.h>
53
54#include <asm/tlbflush.h>
55#include <asm/cpu.h>
56#include <asm/idle.h>
57#include <asm/syscalls.h>
58#include <asm/debugreg.h>
59
60#include <trace/events/power.h>
61
62asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
63
64/*
65 * Return saved PC of a blocked thread.
66 */
67unsigned long thread_saved_pc(struct task_struct *tsk)
68{
69	return ((unsigned long *)tsk->thread.sp)[3];
70}
71
72#ifndef CONFIG_SMP
73static inline void play_dead(void)
74{
75	BUG();
76}
77#endif
78
79/*
80 * The idle thread. There's no useful work to be
81 * done, so just try to conserve power and have a
82 * low exit latency (ie sit in a loop waiting for
83 * somebody to say that they'd like to reschedule)
84 */
85void cpu_idle(void)
86{
87	int cpu = smp_processor_id();
88
89	/*
90	 * If we're the non-boot CPU, nothing set the stack canary up
91	 * for us.  CPU0 already has it initialized but no harm in
92	 * doing it again.  This is a good place for updating it, as
93	 * we wont ever return from this function (so the invalid
94	 * canaries already on the stack wont ever trigger).
95	 */
96	boot_init_stack_canary();
97
98	current_thread_info()->status |= TS_POLLING;
99
100	/* endless idle loop with no priority at all */
101	while (1) {
102		tick_nohz_stop_sched_tick(1);
103		while (!need_resched()) {
104
105			check_pgt_cache();
106			rmb();
107
108			if (cpu_is_offline(cpu))
109				play_dead();
110
111			local_irq_disable();
112			/* Don't trace irqs off for idle */
113			stop_critical_timings();
114			pm_idle();
115			start_critical_timings();
116			trace_power_end(smp_processor_id());
117			trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
118		}
119		tick_nohz_restart_sched_tick();
120		preempt_enable_no_resched();
121		schedule();
122		preempt_disable();
123	}
124}
125
126void __show_regs(struct pt_regs *regs, int all)
127{
128	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
129	unsigned long d0, d1, d2, d3, d6, d7;
130	unsigned long sp;
131	unsigned short ss, gs;
132
133	if (user_mode_vm(regs)) {
134		sp = regs->sp;
135		ss = regs->ss & 0xffff;
136		gs = get_user_gs(regs);
137	} else {
138		sp = kernel_stack_pointer(regs);
139		savesegment(ss, ss);
140		savesegment(gs, gs);
141	}
142
143	show_regs_common();
144
145	printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
146			(u16)regs->cs, regs->ip, regs->flags,
147			smp_processor_id());
148	print_symbol("EIP is at %s\n", regs->ip);
149
150	printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
151		regs->ax, regs->bx, regs->cx, regs->dx);
152	printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
153		regs->si, regs->di, regs->bp, sp);
154	printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
155	       (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
156
157	if (!all)
158		return;
159
160	cr0 = read_cr0();
161	cr2 = read_cr2();
162	cr3 = read_cr3();
163	cr4 = read_cr4_safe();
164	printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
165			cr0, cr2, cr3, cr4);
166
167	get_debugreg(d0, 0);
168	get_debugreg(d1, 1);
169	get_debugreg(d2, 2);
170	get_debugreg(d3, 3);
171	printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
172			d0, d1, d2, d3);
173
174	get_debugreg(d6, 6);
175	get_debugreg(d7, 7);
176	printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
177			d6, d7);
178}
179
180void release_thread(struct task_struct *dead_task)
181{
182	BUG_ON(dead_task->mm);
183	release_vm86_irqs(dead_task);
184}
185
186/*
187 * This gets called before we allocate a new thread and copy
188 * the current task into it.
189 */
190void prepare_to_copy(struct task_struct *tsk)
191{
192	unlazy_fpu(tsk);
193}
194
195int copy_thread(unsigned long clone_flags, unsigned long sp,
196	unsigned long unused,
197	struct task_struct *p, struct pt_regs *regs)
198{
199	struct pt_regs *childregs;
200	struct task_struct *tsk;
201	int err;
202
203	childregs = task_pt_regs(p);
204	*childregs = *regs;
205	childregs->ax = 0;
206	childregs->sp = sp;
207
208	p->thread.sp = (unsigned long) childregs;
209	p->thread.sp0 = (unsigned long) (childregs+1);
210
211	p->thread.ip = (unsigned long) ret_from_fork;
212
213	task_user_gs(p) = get_user_gs(regs);
214
215	p->thread.io_bitmap_ptr = NULL;
216	tsk = current;
217	err = -ENOMEM;
218
219	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
220
221	if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
222		p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
223						IO_BITMAP_BYTES, GFP_KERNEL);
224		if (!p->thread.io_bitmap_ptr) {
225			p->thread.io_bitmap_max = 0;
226			return -ENOMEM;
227		}
228		set_tsk_thread_flag(p, TIF_IO_BITMAP);
229	}
230
231	err = 0;
232
233	/*
234	 * Set a new TLS for the child thread?
235	 */
236	if (clone_flags & CLONE_SETTLS)
237		err = do_set_thread_area(p, -1,
238			(struct user_desc __user *)childregs->si, 0);
239
240	if (err && p->thread.io_bitmap_ptr) {
241		kfree(p->thread.io_bitmap_ptr);
242		p->thread.io_bitmap_max = 0;
243	}
244	return err;
245}
246
247void
248start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
249{
250	set_user_gs(regs, 0);
251	regs->fs		= 0;
252	set_fs(USER_DS);
253	regs->ds		= __USER_DS;
254	regs->es		= __USER_DS;
255	regs->ss		= __USER_DS;
256	regs->cs		= __USER_CS;
257	regs->ip		= new_ip;
258	regs->sp		= new_sp;
259	/*
260	 * Free the old FP and other extended state
261	 */
262	free_thread_xstate(current);
263}
264EXPORT_SYMBOL_GPL(start_thread);
265
266
267/*
268 *	switch_to(x,yn) should switch tasks from x to y.
269 *
270 * We fsave/fwait so that an exception goes off at the right time
271 * (as a call from the fsave or fwait in effect) rather than to
272 * the wrong process. Lazy FP saving no longer makes any sense
273 * with modern CPU's, and this simplifies a lot of things (SMP
274 * and UP become the same).
275 *
276 * NOTE! We used to use the x86 hardware context switching. The
277 * reason for not using it any more becomes apparent when you
278 * try to recover gracefully from saved state that is no longer
279 * valid (stale segment register values in particular). With the
280 * hardware task-switch, there is no way to fix up bad state in
281 * a reasonable manner.
282 *
283 * The fact that Intel documents the hardware task-switching to
284 * be slow is a fairly red herring - this code is not noticeably
285 * faster. However, there _is_ some room for improvement here,
286 * so the performance issues may eventually be a valid point.
287 * More important, however, is the fact that this allows us much
288 * more flexibility.
289 *
290 * The return value (in %ax) will be the "prev" task after
291 * the task-switch, and shows up in ret_from_fork in entry.S,
292 * for example.
293 */
294__notrace_funcgraph struct task_struct *
295__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
296{
297	struct thread_struct *prev = &prev_p->thread,
298				 *next = &next_p->thread;
299	int cpu = smp_processor_id();
300	struct tss_struct *tss = &per_cpu(init_tss, cpu);
301	bool preload_fpu;
302
303	/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
304
305	/*
306	 * If the task has used fpu the last 5 timeslices, just do a full
307	 * restore of the math state immediately to avoid the trap; the
308	 * chances of needing FPU soon are obviously high now
309	 */
310	preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
311
312	__unlazy_fpu(prev_p);
313
314	/* we're going to use this soon, after a few expensive things */
315	if (preload_fpu)
316		prefetch(next->fpu.state);
317
318	/*
319	 * Reload esp0.
320	 */
321	load_sp0(tss, next);
322
323	/*
324	 * Save away %gs. No need to save %fs, as it was saved on the
325	 * stack on entry.  No need to save %es and %ds, as those are
326	 * always kernel segments while inside the kernel.  Doing this
327	 * before setting the new TLS descriptors avoids the situation
328	 * where we temporarily have non-reloadable segments in %fs
329	 * and %gs.  This could be an issue if the NMI handler ever
330	 * used %fs or %gs (it does not today), or if the kernel is
331	 * running inside of a hypervisor layer.
332	 */
333	lazy_save_gs(prev->gs);
334
335	/*
336	 * Load the per-thread Thread-Local Storage descriptor.
337	 */
338	load_TLS(next, cpu);
339
340	/*
341	 * Restore IOPL if needed.  In normal use, the flags restore
342	 * in the switch assembly will handle this.  But if the kernel
343	 * is running virtualized at a non-zero CPL, the popf will
344	 * not restore flags, so it must be done in a separate step.
345	 */
346	if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
347		set_iopl_mask(next->iopl);
348
349	/*
350	 * Now maybe handle debug registers and/or IO bitmaps
351	 */
352	if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
353		     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
354		__switch_to_xtra(prev_p, next_p, tss);
355
356	/* If we're going to preload the fpu context, make sure clts
357	   is run while we're batching the cpu state updates. */
358	if (preload_fpu)
359		clts();
360
361	/*
362	 * Leave lazy mode, flushing any hypercalls made here.
363	 * This must be done before restoring TLS segments so
364	 * the GDT and LDT are properly updated, and must be
365	 * done before math_state_restore, so the TS bit is up
366	 * to date.
367	 */
368	arch_end_context_switch(next_p);
369
370	if (preload_fpu)
371		__math_state_restore();
372
373	/*
374	 * Restore %gs if needed (which is common)
375	 */
376	if (prev->gs | next->gs)
377		lazy_load_gs(next->gs);
378
379	percpu_write(current_task, next_p);
380
381	return prev_p;
382}
383
384#define top_esp                (THREAD_SIZE - sizeof(unsigned long))
385#define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
386
387unsigned long get_wchan(struct task_struct *p)
388{
389	unsigned long bp, sp, ip;
390	unsigned long stack_page;
391	int count = 0;
392	if (!p || p == current || p->state == TASK_RUNNING)
393		return 0;
394	stack_page = (unsigned long)task_stack_page(p);
395	sp = p->thread.sp;
396	if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
397		return 0;
398	/* include/asm-i386/system.h:switch_to() pushes bp last. */
399	bp = *(unsigned long *) sp;
400	do {
401		if (bp < stack_page || bp > top_ebp+stack_page)
402			return 0;
403		ip = *(unsigned long *) (bp+4);
404		if (!in_sched_functions(ip))
405			return ip;
406		bp = *(unsigned long *) bp;
407	} while (count++ < 16);
408	return 0;
409}
410
411