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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * 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
Tejun Heo5c79d2a2009-02-11 16:31:00 +090012#include <linux/stackprotector.h>
Zwane Mwaikambof3705132005-06-25 14:54:50 -070013#include <linux/cpu.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#include <linux/stddef.h>
22#include <linux/slab.h>
23#include <linux/vmalloc.h>
24#include <linux/user.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070025#include <linux/interrupt.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#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>
Andi Kleenc16b63e2006-09-26 10:52:28 +020033#include <linux/personality.h>
Ingo Molnar74167342007-02-16 01:28:07 -080034#include <linux/tick.h>
Jeremy Fitzhardinge7c3576d2007-05-02 19:27:16 +020035#include <linux/percpu.h>
Erik Bosman529e25f2008-04-14 00:24:18 +020036#include <linux/prctl.h>
Frederic Weisbecker8b96f012008-12-06 03:40:00 +010037#include <linux/ftrace.h>
Jaswinder Singh Rajputbefa9e72009-01-04 16:18:56 +053038#include <linux/uaccess.h>
39#include <linux/io.h>
40#include <linux/kdebug.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070041
Linus Torvalds1da177e2005-04-16 15:20:36 -070042#include <asm/pgtable.h>
43#include <asm/system.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044#include <asm/ldt.h>
45#include <asm/processor.h>
46#include <asm/i387.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070047#include <asm/desc.h>
48#ifdef CONFIG_MATH_EMULATION
49#include <asm/math_emu.h>
50#endif
51
Linus Torvalds1da177e2005-04-16 15:20:36 -070052#include <linux/err.h>
53
Zwane Mwaikambof3705132005-06-25 14:54:50 -070054#include <asm/tlbflush.h>
55#include <asm/cpu.h>
Marc Dionne1eda8142008-09-23 22:40:02 -040056#include <asm/idle.h>
Jaswinder Singhbbc1f692008-07-21 21:34:13 +053057#include <asm/syscalls.h>
K.Prasad66cb5912009-06-01 23:44:55 +053058#include <asm/debugreg.h>
Zwane Mwaikambof3705132005-06-25 14:54:50 -070059
Linus Torvalds1da177e2005-04-16 15:20:36 -070060asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
61
Linus Torvalds1da177e2005-04-16 15:20:36 -070062/*
63 * Return saved PC of a blocked thread.
64 */
65unsigned long thread_saved_pc(struct task_struct *tsk)
66{
H. Peter Anvinfaca6222008-01-30 13:31:02 +010067 return ((unsigned long *)tsk->thread.sp)[3];
Linus Torvalds1da177e2005-04-16 15:20:36 -070068}
69
Alex Nixon913da642008-09-03 14:30:23 +010070#ifndef CONFIG_SMP
71static inline void play_dead(void)
72{
73 BUG();
74}
75#endif
76
Linus Torvalds1da177e2005-04-16 15:20:36 -070077/*
78 * The idle thread. There's no useful work to be
79 * done, so just try to conserve power and have a
80 * low exit latency (ie sit in a loop waiting for
81 * somebody to say that they'd like to reschedule)
82 */
Zwane Mwaikambof3705132005-06-25 14:54:50 -070083void cpu_idle(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -070084{
Nick Piggin5bfb5d62005-11-08 21:39:01 -080085 int cpu = smp_processor_id();
Zwane Mwaikambof3705132005-06-25 14:54:50 -070086
Tejun Heo5c79d2a2009-02-11 16:31:00 +090087 /*
88 * If we're the non-boot CPU, nothing set the stack canary up
89 * for us. CPU0 already has it initialized but no harm in
90 * doing it again. This is a good place for updating it, as
91 * we wont ever return from this function (so the invalid
92 * canaries already on the stack wont ever trigger).
93 */
94 boot_init_stack_canary();
95
Andi Kleen495ab9c2006-06-26 13:59:11 +020096 current_thread_info()->status |= TS_POLLING;
Nick Piggin64c7c8f2005-11-08 21:39:04 -080097
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 /* endless idle loop with no priority at all */
99 while (1) {
Thomas Gleixnerb8f8c3c2008-07-18 17:27:28 +0200100 tick_nohz_stop_sched_tick(1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 while (!need_resched()) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102
Christoph Lameterf1d1a842007-05-12 11:15:24 -0700103 check_pgt_cache();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 rmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105
Zwane Mwaikambof3705132005-06-25 14:54:50 -0700106 if (cpu_is_offline(cpu))
107 play_dead();
108
Peter Zijlstra7f424a82008-04-25 17:39:01 +0200109 local_irq_disable();
Steven Rostedt6cd8a4b2008-05-12 21:20:42 +0200110 /* Don't trace irqs off for idle */
111 stop_critical_timings();
Thomas Gleixner6ddd2a22008-06-09 16:59:53 +0200112 pm_idle();
Steven Rostedt6cd8a4b2008-05-12 21:20:42 +0200113 start_critical_timings();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 }
Ingo Molnar74167342007-02-16 01:28:07 -0800115 tick_nohz_restart_sched_tick();
Nick Piggin5bfb5d62005-11-08 21:39:01 -0800116 preempt_enable_no_resched();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117 schedule();
Nick Piggin5bfb5d62005-11-08 21:39:01 -0800118 preempt_disable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 }
120}
121
Pekka Enberge2ce07c2008-04-03 16:40:48 +0300122void __show_regs(struct pt_regs *regs, int all)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123{
124 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
Alan Sternbb1995d2007-07-21 17:10:42 +0200125 unsigned long d0, d1, d2, d3, d6, d7;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100126 unsigned long sp;
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200127 unsigned short ss, gs;
128
129 if (user_mode_vm(regs)) {
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100130 sp = regs->sp;
131 ss = regs->ss & 0xffff;
Tejun Heod9a89a22009-02-09 22:17:40 +0900132 gs = get_user_gs(regs);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200133 } else {
H. Peter Anvindef3c5d2009-10-12 14:09:07 -0700134 sp = kernel_stack_pointer(regs);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200135 savesegment(ss, ss);
136 savesegment(gs, gs);
137 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138
Andy Isaacson814e2c82009-12-08 00:29:42 -0800139 show_regs_common();
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200140
Pekka Enbergd015a092009-12-28 10:26:59 +0200141 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
Harvey Harrison92bc2052008-02-08 12:09:56 -0800142 (u16)regs->cs, regs->ip, regs->flags,
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200143 smp_processor_id());
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100144 print_symbol("EIP is at %s\n", regs->ip);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145
Pekka Enbergd015a092009-12-28 10:26:59 +0200146 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100147 regs->ax, regs->bx, regs->cx, regs->dx);
Pekka Enbergd015a092009-12-28 10:26:59 +0200148 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100149 regs->si, regs->di, regs->bp, sp);
Pekka Enbergd015a092009-12-28 10:26:59 +0200150 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
Harvey Harrison92bc2052008-02-08 12:09:56 -0800151 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200152
153 if (!all)
154 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155
Zachary Amsden4bb0d3e2005-09-03 15:56:36 -0700156 cr0 = read_cr0();
157 cr2 = read_cr2();
158 cr3 = read_cr3();
Zachary Amsdenff6e8c02006-01-06 00:11:50 -0800159 cr4 = read_cr4_safe();
Pekka Enbergd015a092009-12-28 10:26:59 +0200160 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200161 cr0, cr2, cr3, cr4);
Alan Sternbb1995d2007-07-21 17:10:42 +0200162
163 get_debugreg(d0, 0);
164 get_debugreg(d1, 1);
165 get_debugreg(d2, 2);
166 get_debugreg(d3, 3);
Pekka Enbergd015a092009-12-28 10:26:59 +0200167 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
Alan Sternbb1995d2007-07-21 17:10:42 +0200168 d0, d1, d2, d3);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200169
Alan Sternbb1995d2007-07-21 17:10:42 +0200170 get_debugreg(d6, 6);
171 get_debugreg(d7, 7);
Pekka Enbergd015a092009-12-28 10:26:59 +0200172 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200173 d6, d7);
174}
Alan Sternbb1995d2007-07-21 17:10:42 +0200175
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176void release_thread(struct task_struct *dead_task)
177{
Zachary Amsden26849272006-01-06 00:11:59 -0800178 BUG_ON(dead_task->mm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179 release_vm86_irqs(dead_task);
180}
181
182/*
183 * This gets called before we allocate a new thread and copy
184 * the current task into it.
185 */
186void prepare_to_copy(struct task_struct *tsk)
187{
188 unlazy_fpu(tsk);
189}
190
Alexey Dobriyan6f2c55b2009-04-02 16:56:59 -0700191int copy_thread(unsigned long clone_flags, unsigned long sp,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 unsigned long unused,
Jaswinder Singh Rajputbefa9e72009-01-04 16:18:56 +0530193 struct task_struct *p, struct pt_regs *regs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
Jaswinder Singh Rajputbefa9e72009-01-04 16:18:56 +0530195 struct pt_regs *childregs;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 struct task_struct *tsk;
197 int err;
198
akpm@osdl.org07b047f2006-01-12 01:05:41 -0800199 childregs = task_pt_regs(p);
Alexander Nybergf48d9662005-05-05 16:15:03 -0700200 *childregs = *regs;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100201 childregs->ax = 0;
202 childregs->sp = sp;
Alexander Nybergf48d9662005-05-05 16:15:03 -0700203
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100204 p->thread.sp = (unsigned long) childregs;
205 p->thread.sp0 = (unsigned long) (childregs+1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100207 p->thread.ip = (unsigned long) ret_from_fork;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208
Tejun Heod9a89a22009-02-09 22:17:40 +0900209 task_user_gs(p) = get_user_gs(regs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210
K.Prasad66cb5912009-06-01 23:44:55 +0530211 p->thread.io_bitmap_ptr = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 tsk = current;
K.Prasad66cb5912009-06-01 23:44:55 +0530213 err = -ENOMEM;
Frederic Weisbecker24f1e32c2009-09-09 19:22:48 +0200214
215 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
K.Prasad66cb5912009-06-01 23:44:55 +0530216
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400217 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
Alexey Dobriyan52978be2006-09-30 23:27:21 -0700218 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
219 IO_BITMAP_BYTES, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 if (!p->thread.io_bitmap_ptr) {
221 p->thread.io_bitmap_max = 0;
222 return -ENOMEM;
223 }
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400224 set_tsk_thread_flag(p, TIF_IO_BITMAP);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 }
226
Roland McGrathefd1ca52008-01-30 13:30:46 +0100227 err = 0;
228
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 /*
230 * Set a new TLS for the child thread?
231 */
Roland McGrathefd1ca52008-01-30 13:30:46 +0100232 if (clone_flags & CLONE_SETTLS)
233 err = do_set_thread_area(p, -1,
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100234 (struct user_desc __user *)childregs->si, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236 if (err && p->thread.io_bitmap_ptr) {
237 kfree(p->thread.io_bitmap_ptr);
238 p->thread.io_bitmap_max = 0;
239 }
240 return err;
241}
242
Ingo Molnar513ad842008-02-21 05:18:40 +0100243void
244start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
245{
Tejun Heod9a89a22009-02-09 22:17:40 +0900246 set_user_gs(regs, 0);
Ingo Molnar513ad842008-02-21 05:18:40 +0100247 regs->fs = 0;
248 set_fs(USER_DS);
249 regs->ds = __USER_DS;
250 regs->es = __USER_DS;
251 regs->ss = __USER_DS;
252 regs->cs = __USER_CS;
253 regs->ip = new_ip;
254 regs->sp = new_sp;
Suresh Siddhaaa283f42008-03-10 15:28:05 -0700255 /*
256 * Free the old FP and other extended state
257 */
258 free_thread_xstate(current);
Ingo Molnar513ad842008-02-21 05:18:40 +0100259}
260EXPORT_SYMBOL_GPL(start_thread);
261
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262
263/*
264 * switch_to(x,yn) should switch tasks from x to y.
265 *
266 * We fsave/fwait so that an exception goes off at the right time
267 * (as a call from the fsave or fwait in effect) rather than to
268 * the wrong process. Lazy FP saving no longer makes any sense
269 * with modern CPU's, and this simplifies a lot of things (SMP
270 * and UP become the same).
271 *
272 * NOTE! We used to use the x86 hardware context switching. The
273 * reason for not using it any more becomes apparent when you
274 * try to recover gracefully from saved state that is no longer
275 * valid (stale segment register values in particular). With the
276 * hardware task-switch, there is no way to fix up bad state in
277 * a reasonable manner.
278 *
279 * The fact that Intel documents the hardware task-switching to
280 * be slow is a fairly red herring - this code is not noticeably
281 * faster. However, there _is_ some room for improvement here,
282 * so the performance issues may eventually be a valid point.
283 * More important, however, is the fact that this allows us much
284 * more flexibility.
285 *
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100286 * The return value (in %ax) will be the "prev" task after
Linus Torvalds1da177e2005-04-16 15:20:36 -0700287 * the task-switch, and shows up in ret_from_fork in entry.S,
288 * for example.
289 */
Frederic Weisbecker8b96f012008-12-06 03:40:00 +0100290__notrace_funcgraph struct task_struct *
291__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292{
293 struct thread_struct *prev = &prev_p->thread,
294 *next = &next_p->thread;
295 int cpu = smp_processor_id();
296 struct tss_struct *tss = &per_cpu(init_tss, cpu);
Jeremy Fitzhardinge2fcddce2009-04-24 00:45:26 -0700297 bool preload_fpu;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298
299 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
300
Jeremy Fitzhardinge2fcddce2009-04-24 00:45:26 -0700301 /*
302 * If the task has used fpu the last 5 timeslices, just do a full
303 * restore of the math state immediately to avoid the trap; the
304 * chances of needing FPU soon are obviously high now
305 */
306 preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
307
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 __unlazy_fpu(prev_p);
309
Chuck Ebbertacc20762006-12-07 02:14:01 +0100310 /* we're going to use this soon, after a few expensive things */
Jeremy Fitzhardinge2fcddce2009-04-24 00:45:26 -0700311 if (preload_fpu)
Avi Kivity86603282010-05-06 11:45:46 +0300312 prefetch(next->fpu.state);
Chuck Ebbertacc20762006-12-07 02:14:01 +0100313
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 /*
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700315 * Reload esp0.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316 */
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100317 load_sp0(tss, next);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
319 /*
Jeremy Fitzhardinge464d1a72007-02-13 13:26:20 +0100320 * Save away %gs. No need to save %fs, as it was saved on the
Jeremy Fitzhardingef95d47c2006-12-07 02:14:02 +0100321 * stack on entry. No need to save %es and %ds, as those are
322 * always kernel segments while inside the kernel. Doing this
323 * before setting the new TLS descriptors avoids the situation
324 * where we temporarily have non-reloadable segments in %fs
325 * and %gs. This could be an issue if the NMI handler ever
326 * used %fs or %gs (it does not today), or if the kernel is
327 * running inside of a hypervisor layer.
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700328 */
Tejun Heoccbeed32009-02-09 22:17:40 +0900329 lazy_save_gs(prev->gs);
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700330
331 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 * Load the per-thread Thread-Local Storage descriptor.
333 */
334 load_TLS(next, cpu);
335
336 /*
Zachary Amsden8b151142007-02-13 13:26:21 +0100337 * Restore IOPL if needed. In normal use, the flags restore
338 * in the switch assembly will handle this. But if the kernel
339 * is running virtualized at a non-zero CPL, the popf will
340 * not restore flags, so it must be done in a separate step.
341 */
342 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
343 set_iopl_mask(next->iopl);
344
345 /*
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400346 * Now maybe handle debug registers and/or IO bitmaps
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 */
Andrea Arcangelicf99aba2007-07-15 23:41:33 -0700348 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
349 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
350 __switch_to_xtra(prev_p, next_p, tss);
Andrea Arcangeliffaa8bd2005-06-27 14:36:36 -0700351
Jeremy Fitzhardinge2fcddce2009-04-24 00:45:26 -0700352 /* If we're going to preload the fpu context, make sure clts
353 is run while we're batching the cpu state updates. */
354 if (preload_fpu)
355 clts();
356
Zachary Amsden9226d122007-02-13 13:26:21 +0100357 /*
358 * Leave lazy mode, flushing any hypercalls made here.
359 * This must be done before restoring TLS segments so
360 * the GDT and LDT are properly updated, and must be
361 * done before math_state_restore, so the TS bit is up
362 * to date.
363 */
Jeremy Fitzhardinge224101e2009-02-18 11:18:57 -0800364 arch_end_context_switch(next_p);
Zachary Amsden9226d122007-02-13 13:26:21 +0100365
Jeremy Fitzhardinge2fcddce2009-04-24 00:45:26 -0700366 if (preload_fpu)
367 __math_state_restore();
Chuck Ebbertacc20762006-12-07 02:14:01 +0100368
Zachary Amsden9226d122007-02-13 13:26:21 +0100369 /*
370 * Restore %gs if needed (which is common)
371 */
372 if (prev->gs | next->gs)
Tejun Heoccbeed32009-02-09 22:17:40 +0900373 lazy_load_gs(next->gs);
Zachary Amsden9226d122007-02-13 13:26:21 +0100374
Ingo Molnar6dbde352009-01-15 22:15:53 +0900375 percpu_write(current_task, next_p);
Zachary Amsden9226d122007-02-13 13:26:21 +0100376
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377 return prev_p;
378}
379
Linus Torvalds1da177e2005-04-16 15:20:36 -0700380#define top_esp (THREAD_SIZE - sizeof(unsigned long))
381#define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
382
383unsigned long get_wchan(struct task_struct *p)
384{
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100385 unsigned long bp, sp, ip;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 unsigned long stack_page;
387 int count = 0;
388 if (!p || p == current || p->state == TASK_RUNNING)
389 return 0;
Al Viro65e0fdf2006-01-12 01:05:41 -0800390 stack_page = (unsigned long)task_stack_page(p);
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100391 sp = p->thread.sp;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100392 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 return 0;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100394 /* include/asm-i386/system.h:switch_to() pushes bp last. */
395 bp = *(unsigned long *) sp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 do {
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100397 if (bp < stack_page || bp > top_ebp+stack_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700398 return 0;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100399 ip = *(unsigned long *) (bp+4);
400 if (!in_sched_functions(ip))
401 return ip;
402 bp = *(unsigned long *) bp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 } while (count++ < 16);
404 return 0;
405}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406