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 #include <linux/cpuidle.h>
42
43 #include <asm/pgtable.h>
44 #include <asm/system.h>
45 #include <asm/ldt.h>
46 #include <asm/processor.h>
47 #include <asm/i387.h>
48 #include <asm/desc.h>
49 #ifdef CONFIG_MATH_EMULATION
50 #include <asm/math_emu.h>
51 #endif
52
53 #include <linux/err.h>
54
55 #include <asm/tlbflush.h>
56 #include <asm/cpu.h>
57 #include <asm/idle.h>
58 #include <asm/syscalls.h>
59 #include <asm/debugreg.h>
60 #include <asm/nmi.h>
61
62 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
63
64 /*
65 * Return saved PC of a blocked thread.
66 */
thread_saved_pc(struct task_struct * tsk)67 unsigned long thread_saved_pc(struct task_struct *tsk)
68 {
69 return ((unsigned long *)tsk->thread.sp)[3];
70 }
71
72 #ifndef CONFIG_SMP
play_dead(void)73 static 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 */
cpu_idle(void)85 void 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_idle_enter();
103 rcu_idle_enter();
104 while (!need_resched()) {
105
106 check_pgt_cache();
107 rmb();
108
109 if (cpu_is_offline(cpu))
110 play_dead();
111
112 local_touch_nmi();
113 local_irq_disable();
114 /* Don't trace irqs off for idle */
115 stop_critical_timings();
116 if (cpuidle_idle_call())
117 pm_idle();
118 start_critical_timings();
119 }
120 rcu_idle_exit();
121 tick_nohz_idle_exit();
122 preempt_enable_no_resched();
123 schedule();
124 preempt_disable();
125 }
126 }
127
__show_regs(struct pt_regs * regs,int all)128 void __show_regs(struct pt_regs *regs, int all)
129 {
130 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
131 unsigned long d0, d1, d2, d3, d6, d7;
132 unsigned long sp;
133 unsigned short ss, gs;
134
135 if (user_mode_vm(regs)) {
136 sp = regs->sp;
137 ss = regs->ss & 0xffff;
138 gs = get_user_gs(regs);
139 } else {
140 sp = kernel_stack_pointer(regs);
141 savesegment(ss, ss);
142 savesegment(gs, gs);
143 }
144
145 show_regs_common();
146
147 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
148 (u16)regs->cs, regs->ip, regs->flags,
149 smp_processor_id());
150 print_symbol("EIP is at %s\n", regs->ip);
151
152 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
153 regs->ax, regs->bx, regs->cx, regs->dx);
154 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
155 regs->si, regs->di, regs->bp, sp);
156 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
157 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
158
159 if (!all)
160 return;
161
162 cr0 = read_cr0();
163 cr2 = read_cr2();
164 cr3 = read_cr3();
165 cr4 = read_cr4_safe();
166 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
167 cr0, cr2, cr3, cr4);
168
169 get_debugreg(d0, 0);
170 get_debugreg(d1, 1);
171 get_debugreg(d2, 2);
172 get_debugreg(d3, 3);
173 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
174 d0, d1, d2, d3);
175
176 get_debugreg(d6, 6);
177 get_debugreg(d7, 7);
178 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
179 d6, d7);
180 }
181
release_thread(struct task_struct * dead_task)182 void release_thread(struct task_struct *dead_task)
183 {
184 BUG_ON(dead_task->mm);
185 release_vm86_irqs(dead_task);
186 }
187
188 /*
189 * This gets called before we allocate a new thread and copy
190 * the current task into it.
191 */
prepare_to_copy(struct task_struct * tsk)192 void prepare_to_copy(struct task_struct *tsk)
193 {
194 unlazy_fpu(tsk);
195 }
196
copy_thread(unsigned long clone_flags,unsigned long sp,unsigned long unused,struct task_struct * p,struct pt_regs * regs)197 int copy_thread(unsigned long clone_flags, unsigned long sp,
198 unsigned long unused,
199 struct task_struct *p, struct pt_regs *regs)
200 {
201 struct pt_regs *childregs;
202 struct task_struct *tsk;
203 int err;
204
205 childregs = task_pt_regs(p);
206 *childregs = *regs;
207 childregs->ax = 0;
208 childregs->sp = sp;
209
210 p->thread.sp = (unsigned long) childregs;
211 p->thread.sp0 = (unsigned long) (childregs+1);
212
213 p->thread.ip = (unsigned long) ret_from_fork;
214
215 task_user_gs(p) = get_user_gs(regs);
216
217 p->fpu_counter = 0;
218 p->thread.io_bitmap_ptr = NULL;
219 tsk = current;
220 err = -ENOMEM;
221
222 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
223
224 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
225 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
226 IO_BITMAP_BYTES, GFP_KERNEL);
227 if (!p->thread.io_bitmap_ptr) {
228 p->thread.io_bitmap_max = 0;
229 return -ENOMEM;
230 }
231 set_tsk_thread_flag(p, TIF_IO_BITMAP);
232 }
233
234 err = 0;
235
236 /*
237 * Set a new TLS for the child thread?
238 */
239 if (clone_flags & CLONE_SETTLS)
240 err = do_set_thread_area(p, -1,
241 (struct user_desc __user *)childregs->si, 0);
242
243 if (err && p->thread.io_bitmap_ptr) {
244 kfree(p->thread.io_bitmap_ptr);
245 p->thread.io_bitmap_max = 0;
246 }
247 return err;
248 }
249
250 void
start_thread(struct pt_regs * regs,unsigned long new_ip,unsigned long new_sp)251 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
252 {
253 set_user_gs(regs, 0);
254 regs->fs = 0;
255 regs->ds = __USER_DS;
256 regs->es = __USER_DS;
257 regs->ss = __USER_DS;
258 regs->cs = __USER_CS;
259 regs->ip = new_ip;
260 regs->sp = new_sp;
261 /*
262 * Free the old FP and other extended state
263 */
264 free_thread_xstate(current);
265 }
266 EXPORT_SYMBOL_GPL(start_thread);
267
268
269 /*
270 * switch_to(x,y) should switch tasks from x to y.
271 *
272 * We fsave/fwait so that an exception goes off at the right time
273 * (as a call from the fsave or fwait in effect) rather than to
274 * the wrong process. Lazy FP saving no longer makes any sense
275 * with modern CPU's, and this simplifies a lot of things (SMP
276 * and UP become the same).
277 *
278 * NOTE! We used to use the x86 hardware context switching. The
279 * reason for not using it any more becomes apparent when you
280 * try to recover gracefully from saved state that is no longer
281 * valid (stale segment register values in particular). With the
282 * hardware task-switch, there is no way to fix up bad state in
283 * a reasonable manner.
284 *
285 * The fact that Intel documents the hardware task-switching to
286 * be slow is a fairly red herring - this code is not noticeably
287 * faster. However, there _is_ some room for improvement here,
288 * so the performance issues may eventually be a valid point.
289 * More important, however, is the fact that this allows us much
290 * more flexibility.
291 *
292 * The return value (in %ax) will be the "prev" task after
293 * the task-switch, and shows up in ret_from_fork in entry.S,
294 * for example.
295 */
296 __notrace_funcgraph struct task_struct *
__switch_to(struct task_struct * prev_p,struct task_struct * next_p)297 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
298 {
299 struct thread_struct *prev = &prev_p->thread,
300 *next = &next_p->thread;
301 int cpu = smp_processor_id();
302 struct tss_struct *tss = &per_cpu(init_tss, cpu);
303 fpu_switch_t fpu;
304
305 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
306
307 fpu = switch_fpu_prepare(prev_p, next_p, cpu);
308
309 /*
310 * Reload esp0.
311 */
312 load_sp0(tss, next);
313
314 /*
315 * Save away %gs. No need to save %fs, as it was saved on the
316 * stack on entry. No need to save %es and %ds, as those are
317 * always kernel segments while inside the kernel. Doing this
318 * before setting the new TLS descriptors avoids the situation
319 * where we temporarily have non-reloadable segments in %fs
320 * and %gs. This could be an issue if the NMI handler ever
321 * used %fs or %gs (it does not today), or if the kernel is
322 * running inside of a hypervisor layer.
323 */
324 lazy_save_gs(prev->gs);
325
326 /*
327 * Load the per-thread Thread-Local Storage descriptor.
328 */
329 load_TLS(next, cpu);
330
331 /*
332 * Restore IOPL if needed. In normal use, the flags restore
333 * in the switch assembly will handle this. But if the kernel
334 * is running virtualized at a non-zero CPL, the popf will
335 * not restore flags, so it must be done in a separate step.
336 */
337 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
338 set_iopl_mask(next->iopl);
339
340 /*
341 * Now maybe handle debug registers and/or IO bitmaps
342 */
343 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
344 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
345 __switch_to_xtra(prev_p, next_p, tss);
346
347 /*
348 * Leave lazy mode, flushing any hypercalls made here.
349 * This must be done before restoring TLS segments so
350 * the GDT and LDT are properly updated, and must be
351 * done before math_state_restore, so the TS bit is up
352 * to date.
353 */
354 arch_end_context_switch(next_p);
355
356 /*
357 * Restore %gs if needed (which is common)
358 */
359 if (prev->gs | next->gs)
360 lazy_load_gs(next->gs);
361
362 switch_fpu_finish(next_p, fpu);
363
364 percpu_write(current_task, next_p);
365
366 return prev_p;
367 }
368
369 #define top_esp (THREAD_SIZE - sizeof(unsigned long))
370 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
371
get_wchan(struct task_struct * p)372 unsigned long get_wchan(struct task_struct *p)
373 {
374 unsigned long bp, sp, ip;
375 unsigned long stack_page;
376 int count = 0;
377 if (!p || p == current || p->state == TASK_RUNNING)
378 return 0;
379 stack_page = (unsigned long)task_stack_page(p);
380 sp = p->thread.sp;
381 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
382 return 0;
383 /* include/asm-i386/system.h:switch_to() pushes bp last. */
384 bp = *(unsigned long *) sp;
385 do {
386 if (bp < stack_page || bp > top_ebp+stack_page)
387 return 0;
388 ip = *(unsigned long *) (bp+4);
389 if (!in_sched_functions(ip))
390 return ip;
391 bp = *(unsigned long *) bp;
392 } while (count++ < 16);
393 return 0;
394 }
395
396