blob: aae4f4bbbe886724c51b6be6f26a3e3f5837188f [file] [log] [blame]
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>
Len Browna0bfa132011-04-01 19:34:59 -040041#include <linux/cpuidle.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070042
Linus Torvalds1da177e2005-04-16 15:20:36 -070043#include <asm/pgtable.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044#include <asm/ldt.h>
45#include <asm/processor.h>
46#include <asm/i387.h>
Linus Torvalds1361b832012-02-21 13:19:22 -080047#include <asm/fpu-internal.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070048#include <asm/desc.h>
49#ifdef CONFIG_MATH_EMULATION
50#include <asm/math_emu.h>
51#endif
52
Linus Torvalds1da177e2005-04-16 15:20:36 -070053#include <linux/err.h>
54
Zwane Mwaikambof3705132005-06-25 14:54:50 -070055#include <asm/tlbflush.h>
56#include <asm/cpu.h>
Marc Dionne1eda8142008-09-23 22:40:02 -040057#include <asm/idle.h>
Jaswinder Singhbbc1f692008-07-21 21:34:13 +053058#include <asm/syscalls.h>
K.Prasad66cb5912009-06-01 23:44:55 +053059#include <asm/debugreg.h>
Don Zickusb227e232011-09-30 15:06:22 -040060#include <asm/nmi.h>
David Howellsf05e7982012-03-28 18:11:12 +010061#include <asm/switch_to.h>
Zwane Mwaikambof3705132005-06-25 14:54:50 -070062
Linus Torvalds1da177e2005-04-16 15:20:36 -070063asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065/*
66 * Return saved PC of a blocked thread.
67 */
68unsigned long thread_saved_pc(struct task_struct *tsk)
69{
H. Peter Anvinfaca6222008-01-30 13:31:02 +010070 return ((unsigned long *)tsk->thread.sp)[3];
Linus Torvalds1da177e2005-04-16 15:20:36 -070071}
72
Alex Nixon913da642008-09-03 14:30:23 +010073#ifndef CONFIG_SMP
74static inline void play_dead(void)
75{
76 BUG();
77}
78#endif
79
Linus Torvalds1da177e2005-04-16 15:20:36 -070080/*
81 * The idle thread. There's no useful work to be
82 * done, so just try to conserve power and have a
83 * low exit latency (ie sit in a loop waiting for
84 * somebody to say that they'd like to reschedule)
85 */
Zwane Mwaikambof3705132005-06-25 14:54:50 -070086void cpu_idle(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -070087{
Nick Piggin5bfb5d62005-11-08 21:39:01 -080088 int cpu = smp_processor_id();
Zwane Mwaikambof3705132005-06-25 14:54:50 -070089
Tejun Heo5c79d2a2009-02-11 16:31:00 +090090 /*
91 * If we're the non-boot CPU, nothing set the stack canary up
92 * for us. CPU0 already has it initialized but no harm in
93 * doing it again. This is a good place for updating it, as
94 * we wont ever return from this function (so the invalid
95 * canaries already on the stack wont ever trigger).
96 */
97 boot_init_stack_canary();
98
Andi Kleen495ab9c2006-06-26 13:59:11 +020099 current_thread_info()->status |= TS_POLLING;
Nick Piggin64c7c8f2005-11-08 21:39:04 -0800100
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 /* endless idle loop with no priority at all */
102 while (1) {
Frederic Weisbecker1268fbc2011-11-17 18:48:14 +0100103 tick_nohz_idle_enter();
104 rcu_idle_enter();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 while (!need_resched()) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106
Christoph Lameterf1d1a842007-05-12 11:15:24 -0700107 check_pgt_cache();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108 rmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109
Zwane Mwaikambof3705132005-06-25 14:54:50 -0700110 if (cpu_is_offline(cpu))
111 play_dead();
112
Don Zickusb227e232011-09-30 15:06:22 -0400113 local_touch_nmi();
Peter Zijlstra7f424a82008-04-25 17:39:01 +0200114 local_irq_disable();
Steven Rostedt6cd8a4b2008-05-12 21:20:42 +0200115 /* Don't trace irqs off for idle */
116 stop_critical_timings();
Len Browna0bfa132011-04-01 19:34:59 -0400117 if (cpuidle_idle_call())
118 pm_idle();
Steven Rostedt6cd8a4b2008-05-12 21:20:42 +0200119 start_critical_timings();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 }
Frederic Weisbecker1268fbc2011-11-17 18:48:14 +0100121 rcu_idle_exit();
122 tick_nohz_idle_exit();
Thomas Gleixnerbd2f5532011-03-21 12:33:18 +0100123 schedule_preempt_disabled();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124 }
125}
126
Pekka Enberge2ce07c2008-04-03 16:40:48 +0300127void __show_regs(struct pt_regs *regs, int all)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128{
129 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
Alan Sternbb1995d2007-07-21 17:10:42 +0200130 unsigned long d0, d1, d2, d3, d6, d7;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100131 unsigned long sp;
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200132 unsigned short ss, gs;
133
134 if (user_mode_vm(regs)) {
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100135 sp = regs->sp;
136 ss = regs->ss & 0xffff;
Tejun Heod9a89a22009-02-09 22:17:40 +0900137 gs = get_user_gs(regs);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200138 } else {
H. Peter Anvindef3c5d2009-10-12 14:09:07 -0700139 sp = kernel_stack_pointer(regs);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200140 savesegment(ss, ss);
141 savesegment(gs, gs);
142 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
Andy Isaacson814e2c82009-12-08 00:29:42 -0800144 show_regs_common();
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200145
Pekka Enbergd015a092009-12-28 10:26:59 +0200146 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
Harvey Harrison92bc2052008-02-08 12:09:56 -0800147 (u16)regs->cs, regs->ip, regs->flags,
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200148 smp_processor_id());
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100149 print_symbol("EIP is at %s\n", regs->ip);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150
Pekka Enbergd015a092009-12-28 10:26:59 +0200151 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100152 regs->ax, regs->bx, regs->cx, regs->dx);
Pekka Enbergd015a092009-12-28 10:26:59 +0200153 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100154 regs->si, regs->di, regs->bp, sp);
Pekka Enbergd015a092009-12-28 10:26:59 +0200155 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
Harvey Harrison92bc2052008-02-08 12:09:56 -0800156 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200157
158 if (!all)
159 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
Zachary Amsden4bb0d3e2005-09-03 15:56:36 -0700161 cr0 = read_cr0();
162 cr2 = read_cr2();
163 cr3 = read_cr3();
Zachary Amsdenff6e8c02006-01-06 00:11:50 -0800164 cr4 = read_cr4_safe();
Pekka Enbergd015a092009-12-28 10:26:59 +0200165 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200166 cr0, cr2, cr3, cr4);
Alan Sternbb1995d2007-07-21 17:10:42 +0200167
168 get_debugreg(d0, 0);
169 get_debugreg(d1, 1);
170 get_debugreg(d2, 2);
171 get_debugreg(d3, 3);
Pekka Enbergd015a092009-12-28 10:26:59 +0200172 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
Alan Sternbb1995d2007-07-21 17:10:42 +0200173 d0, d1, d2, d3);
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200174
Alan Sternbb1995d2007-07-21 17:10:42 +0200175 get_debugreg(d6, 6);
176 get_debugreg(d7, 7);
Pekka Enbergd015a092009-12-28 10:26:59 +0200177 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
Pavel Emelyanov9d975eb2007-10-19 20:35:03 +0200178 d6, d7);
179}
Alan Sternbb1995d2007-07-21 17:10:42 +0200180
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181void release_thread(struct task_struct *dead_task)
182{
Zachary Amsden26849272006-01-06 00:11:59 -0800183 BUG_ON(dead_task->mm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184 release_vm86_irqs(dead_task);
185}
186
187/*
188 * This gets called before we allocate a new thread and copy
189 * the current task into it.
190 */
191void prepare_to_copy(struct task_struct *tsk)
192{
193 unlazy_fpu(tsk);
194}
195
Alexey Dobriyan6f2c55b2009-04-02 16:56:59 -0700196int copy_thread(unsigned long clone_flags, unsigned long sp,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197 unsigned long unused,
Jaswinder Singh Rajputbefa9e72009-01-04 16:18:56 +0530198 struct task_struct *p, struct pt_regs *regs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199{
Jaswinder Singh Rajputbefa9e72009-01-04 16:18:56 +0530200 struct pt_regs *childregs;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 struct task_struct *tsk;
202 int err;
203
akpm@osdl.org07b047f2006-01-12 01:05:41 -0800204 childregs = task_pt_regs(p);
Alexander Nybergf48d9662005-05-05 16:15:03 -0700205 *childregs = *regs;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100206 childregs->ax = 0;
207 childregs->sp = sp;
Alexander Nybergf48d9662005-05-05 16:15:03 -0700208
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100209 p->thread.sp = (unsigned long) childregs;
210 p->thread.sp0 = (unsigned long) (childregs+1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100212 p->thread.ip = (unsigned long) ret_from_fork;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213
Tejun Heod9a89a22009-02-09 22:17:40 +0900214 task_user_gs(p) = get_user_gs(regs);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215
Linus Torvaldscea20ca2012-02-20 10:24:09 -0800216 p->fpu_counter = 0;
K.Prasad66cb5912009-06-01 23:44:55 +0530217 p->thread.io_bitmap_ptr = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 tsk = current;
K.Prasad66cb5912009-06-01 23:44:55 +0530219 err = -ENOMEM;
Frederic Weisbecker24f1e32c2009-09-09 19:22:48 +0200220
221 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
K.Prasad66cb5912009-06-01 23:44:55 +0530222
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400223 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
Alexey Dobriyan52978be2006-09-30 23:27:21 -0700224 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
225 IO_BITMAP_BYTES, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 if (!p->thread.io_bitmap_ptr) {
227 p->thread.io_bitmap_max = 0;
228 return -ENOMEM;
229 }
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400230 set_tsk_thread_flag(p, TIF_IO_BITMAP);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 }
232
Roland McGrathefd1ca52008-01-30 13:30:46 +0100233 err = 0;
234
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235 /*
236 * Set a new TLS for the child thread?
237 */
Roland McGrathefd1ca52008-01-30 13:30:46 +0100238 if (clone_flags & CLONE_SETTLS)
239 err = do_set_thread_area(p, -1,
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100240 (struct user_desc __user *)childregs->si, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 if (err && p->thread.io_bitmap_ptr) {
243 kfree(p->thread.io_bitmap_ptr);
244 p->thread.io_bitmap_max = 0;
245 }
246 return err;
247}
248
Ingo Molnar513ad842008-02-21 05:18:40 +0100249void
250start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
251{
Tejun Heod9a89a22009-02-09 22:17:40 +0900252 set_user_gs(regs, 0);
Ingo Molnar513ad842008-02-21 05:18:40 +0100253 regs->fs = 0;
Ingo Molnar513ad842008-02-21 05:18:40 +0100254 regs->ds = __USER_DS;
255 regs->es = __USER_DS;
256 regs->ss = __USER_DS;
257 regs->cs = __USER_CS;
258 regs->ip = new_ip;
259 regs->sp = new_sp;
Suresh Siddhaaa283f42008-03-10 15:28:05 -0700260 /*
261 * Free the old FP and other extended state
262 */
263 free_thread_xstate(current);
Ingo Molnar513ad842008-02-21 05:18:40 +0100264}
265EXPORT_SYMBOL_GPL(start_thread);
266
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267
268/*
Kamalesh Babulalea70ef32011-04-28 14:32:08 +0530269 * switch_to(x,y) should switch tasks from x to y.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270 *
271 * We fsave/fwait so that an exception goes off at the right time
272 * (as a call from the fsave or fwait in effect) rather than to
273 * the wrong process. Lazy FP saving no longer makes any sense
274 * with modern CPU's, and this simplifies a lot of things (SMP
275 * and UP become the same).
276 *
277 * NOTE! We used to use the x86 hardware context switching. The
278 * reason for not using it any more becomes apparent when you
279 * try to recover gracefully from saved state that is no longer
280 * valid (stale segment register values in particular). With the
281 * hardware task-switch, there is no way to fix up bad state in
282 * a reasonable manner.
283 *
284 * The fact that Intel documents the hardware task-switching to
285 * be slow is a fairly red herring - this code is not noticeably
286 * faster. However, there _is_ some room for improvement here,
287 * so the performance issues may eventually be a valid point.
288 * More important, however, is the fact that this allows us much
289 * more flexibility.
290 *
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100291 * The return value (in %ax) will be the "prev" task after
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 * the task-switch, and shows up in ret_from_fork in entry.S,
293 * for example.
294 */
Frederic Weisbecker8b96f012008-12-06 03:40:00 +0100295__notrace_funcgraph struct task_struct *
296__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297{
298 struct thread_struct *prev = &prev_p->thread,
299 *next = &next_p->thread;
300 int cpu = smp_processor_id();
301 struct tss_struct *tss = &per_cpu(init_tss, cpu);
Linus Torvalds34ddc812012-02-18 12:56:35 -0800302 fpu_switch_t fpu;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303
304 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
305
Linus Torvalds7e168382012-02-19 13:27:00 -0800306 fpu = switch_fpu_prepare(prev_p, next_p, cpu);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307
308 /*
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700309 * Reload esp0.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 */
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100311 load_sp0(tss, next);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700312
313 /*
Jeremy Fitzhardinge464d1a72007-02-13 13:26:20 +0100314 * Save away %gs. No need to save %fs, as it was saved on the
Jeremy Fitzhardingef95d47c2006-12-07 02:14:02 +0100315 * stack on entry. No need to save %es and %ds, as those are
316 * always kernel segments while inside the kernel. Doing this
317 * before setting the new TLS descriptors avoids the situation
318 * where we temporarily have non-reloadable segments in %fs
319 * and %gs. This could be an issue if the NMI handler ever
320 * used %fs or %gs (it does not today), or if the kernel is
321 * running inside of a hypervisor layer.
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700322 */
Tejun Heoccbeed32009-02-09 22:17:40 +0900323 lazy_save_gs(prev->gs);
Zachary Amsdene7a2ff52005-09-03 15:56:39 -0700324
325 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326 * Load the per-thread Thread-Local Storage descriptor.
327 */
328 load_TLS(next, cpu);
329
330 /*
Zachary Amsden8b151142007-02-13 13:26:21 +0100331 * Restore IOPL if needed. In normal use, the flags restore
332 * in the switch assembly will handle this. But if the kernel
333 * is running virtualized at a non-zero CPL, the popf will
334 * not restore flags, so it must be done in a separate step.
335 */
336 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
337 set_iopl_mask(next->iopl);
338
339 /*
Stephane Eranianb3cf2572006-07-09 21:12:39 -0400340 * Now maybe handle debug registers and/or IO bitmaps
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 */
Andrea Arcangelicf99aba2007-07-15 23:41:33 -0700342 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
343 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
344 __switch_to_xtra(prev_p, next_p, tss);
Andrea Arcangeliffaa8bd2005-06-27 14:36:36 -0700345
Zachary Amsden9226d122007-02-13 13:26:21 +0100346 /*
347 * Leave lazy mode, flushing any hypercalls made here.
348 * This must be done before restoring TLS segments so
349 * the GDT and LDT are properly updated, and must be
350 * done before math_state_restore, so the TS bit is up
351 * to date.
352 */
Jeremy Fitzhardinge224101e2009-02-18 11:18:57 -0800353 arch_end_context_switch(next_p);
Zachary Amsden9226d122007-02-13 13:26:21 +0100354
Zachary Amsden9226d122007-02-13 13:26:21 +0100355 /*
356 * Restore %gs if needed (which is common)
357 */
358 if (prev->gs | next->gs)
Tejun Heoccbeed32009-02-09 22:17:40 +0900359 lazy_load_gs(next->gs);
Zachary Amsden9226d122007-02-13 13:26:21 +0100360
Linus Torvalds34ddc812012-02-18 12:56:35 -0800361 switch_fpu_finish(next_p, fpu);
362
Ingo Molnar6dbde352009-01-15 22:15:53 +0900363 percpu_write(current_task, next_p);
Zachary Amsden9226d122007-02-13 13:26:21 +0100364
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 return prev_p;
366}
367
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368#define top_esp (THREAD_SIZE - sizeof(unsigned long))
369#define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
370
371unsigned long get_wchan(struct task_struct *p)
372{
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100373 unsigned long bp, sp, ip;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 unsigned long stack_page;
375 int count = 0;
376 if (!p || p == current || p->state == TASK_RUNNING)
377 return 0;
Al Viro65e0fdf2006-01-12 01:05:41 -0800378 stack_page = (unsigned long)task_stack_page(p);
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100379 sp = p->thread.sp;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100380 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 return 0;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100382 /* include/asm-i386/system.h:switch_to() pushes bp last. */
383 bp = *(unsigned long *) sp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 do {
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100385 if (bp < stack_page || bp > top_ebp+stack_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 return 0;
H. Peter Anvin65ea5b02008-01-30 13:30:56 +0100387 ip = *(unsigned long *) (bp+4);
388 if (!in_sched_functions(ip))
389 return ip;
390 bp = *(unsigned long *) bp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391 } while (count++ < 16);
392 return 0;
393}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700394