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TOMOYO Linux Cross Reference
Linux/arch/tile/kernel/process.c

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  1 /*
  2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
  3  *
  4  *   This program is free software; you can redistribute it and/or
  5  *   modify it under the terms of the GNU General Public License
  6  *   as published by the Free Software Foundation, version 2.
  7  *
  8  *   This program is distributed in the hope that it will be useful, but
  9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
 10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 11  *   NON INFRINGEMENT.  See the GNU General Public License for
 12  *   more details.
 13  */
 14 
 15 #include <linux/sched.h>
 16 #include <linux/preempt.h>
 17 #include <linux/module.h>
 18 #include <linux/fs.h>
 19 #include <linux/kprobes.h>
 20 #include <linux/elfcore.h>
 21 #include <linux/tick.h>
 22 #include <linux/init.h>
 23 #include <linux/mm.h>
 24 #include <linux/compat.h>
 25 #include <linux/hardirq.h>
 26 #include <linux/syscalls.h>
 27 #include <linux/kernel.h>
 28 #include <linux/tracehook.h>
 29 #include <linux/signal.h>
 30 #include <asm/stack.h>
 31 #include <asm/switch_to.h>
 32 #include <asm/homecache.h>
 33 #include <asm/syscalls.h>
 34 #include <asm/traps.h>
 35 #include <asm/setup.h>
 36 #ifdef CONFIG_HARDWALL
 37 #include <asm/hardwall.h>
 38 #endif
 39 #include <arch/chip.h>
 40 #include <arch/abi.h>
 41 #include <arch/sim_def.h>
 42 
 43 
 44 /*
 45  * Use the (x86) "idle=poll" option to prefer low latency when leaving the
 46  * idle loop over low power while in the idle loop, e.g. if we have
 47  * one thread per core and we want to get threads out of futex waits fast.
 48  */
 49 static int no_idle_nap;
 50 static int __init idle_setup(char *str)
 51 {
 52         if (!str)
 53                 return -EINVAL;
 54 
 55         if (!strcmp(str, "poll")) {
 56                 pr_info("using polling idle threads.\n");
 57                 no_idle_nap = 1;
 58         } else if (!strcmp(str, "halt"))
 59                 no_idle_nap = 0;
 60         else
 61                 return -1;
 62 
 63         return 0;
 64 }
 65 early_param("idle", idle_setup);
 66 
 67 /*
 68  * The idle thread. There's no useful work to be
 69  * done, so just try to conserve power and have a
 70  * low exit latency (ie sit in a loop waiting for
 71  * somebody to say that they'd like to reschedule)
 72  */
 73 void cpu_idle(void)
 74 {
 75         int cpu = smp_processor_id();
 76 
 77 
 78         current_thread_info()->status |= TS_POLLING;
 79 
 80         if (no_idle_nap) {
 81                 while (1) {
 82                         while (!need_resched())
 83                                 cpu_relax();
 84                         schedule();
 85                 }
 86         }
 87 
 88         /* endless idle loop with no priority at all */
 89         while (1) {
 90                 tick_nohz_idle_enter();
 91                 rcu_idle_enter();
 92                 while (!need_resched()) {
 93                         if (cpu_is_offline(cpu))
 94                                 BUG();  /* no HOTPLUG_CPU */
 95 
 96                         local_irq_disable();
 97                         __get_cpu_var(irq_stat).idle_timestamp = jiffies;
 98                         current_thread_info()->status &= ~TS_POLLING;
 99                         /*
100                          * TS_POLLING-cleared state must be visible before we
101                          * test NEED_RESCHED:
102                          */
103                         smp_mb();
104 
105                         if (!need_resched())
106                                 _cpu_idle();
107                         else
108                                 local_irq_enable();
109                         current_thread_info()->status |= TS_POLLING;
110                 }
111                 rcu_idle_exit();
112                 tick_nohz_idle_exit();
113                 schedule_preempt_disabled();
114         }
115 }
116 
117 /*
118  * Release a thread_info structure
119  */
120 void arch_release_thread_info(struct thread_info *info)
121 {
122         struct single_step_state *step_state = info->step_state;
123 
124 #ifdef CONFIG_HARDWALL
125         /*
126          * We free a thread_info from the context of the task that has
127          * been scheduled next, so the original task is already dead.
128          * Calling deactivate here just frees up the data structures.
129          * If the task we're freeing held the last reference to a
130          * hardwall fd, it would have been released prior to this point
131          * anyway via exit_files(), and the hardwall_task.info pointers
132          * would be NULL by now.
133          */
134         hardwall_deactivate_all(info->task);
135 #endif
136 
137         if (step_state) {
138 
139                 /*
140                  * FIXME: we don't munmap step_state->buffer
141                  * because the mm_struct for this process (info->task->mm)
142                  * has already been zeroed in exit_mm().  Keeping a
143                  * reference to it here seems like a bad move, so this
144                  * means we can't munmap() the buffer, and therefore if we
145                  * ptrace multiple threads in a process, we will slowly
146                  * leak user memory.  (Note that as soon as the last
147                  * thread in a process dies, we will reclaim all user
148                  * memory including single-step buffers in the usual way.)
149                  * We should either assign a kernel VA to this buffer
150                  * somehow, or we should associate the buffer(s) with the
151                  * mm itself so we can clean them up that way.
152                  */
153                 kfree(step_state);
154         }
155 }
156 
157 static void save_arch_state(struct thread_struct *t);
158 
159 int copy_thread(unsigned long clone_flags, unsigned long sp,
160                 unsigned long stack_size,
161                 struct task_struct *p, struct pt_regs *regs)
162 {
163         struct pt_regs *childregs;
164         unsigned long ksp;
165 
166         /*
167          * When creating a new kernel thread we pass sp as zero.
168          * Assign it to a reasonable value now that we have the stack.
169          */
170         if (sp == 0 && regs->ex1 == PL_ICS_EX1(KERNEL_PL, 0))
171                 sp = KSTK_TOP(p);
172 
173         /*
174          * Do not clone step state from the parent; each thread
175          * must make its own lazily.
176          */
177         task_thread_info(p)->step_state = NULL;
178 
179         /*
180          * Start new thread in ret_from_fork so it schedules properly
181          * and then return from interrupt like the parent.
182          */
183         p->thread.pc = (unsigned long) ret_from_fork;
184 
185         /* Save user stack top pointer so we can ID the stack vm area later. */
186         p->thread.usp0 = sp;
187 
188         /* Record the pid of the process that created this one. */
189         p->thread.creator_pid = current->pid;
190 
191         /*
192          * Copy the registers onto the kernel stack so the
193          * return-from-interrupt code will reload it into registers.
194          */
195         childregs = task_pt_regs(p);
196         *childregs = *regs;
197         childregs->regs[0] = 0;         /* return value is zero */
198         childregs->sp = sp;  /* override with new user stack pointer */
199 
200         /*
201          * If CLONE_SETTLS is set, set "tp" in the new task to "r4",
202          * which is passed in as arg #5 to sys_clone().
203          */
204         if (clone_flags & CLONE_SETTLS)
205                 childregs->tp = regs->regs[4];
206 
207         /*
208          * Copy the callee-saved registers from the passed pt_regs struct
209          * into the context-switch callee-saved registers area.
210          * This way when we start the interrupt-return sequence, the
211          * callee-save registers will be correctly in registers, which
212          * is how we assume the compiler leaves them as we start doing
213          * the normal return-from-interrupt path after calling C code.
214          * Zero out the C ABI save area to mark the top of the stack.
215          */
216         ksp = (unsigned long) childregs;
217         ksp -= C_ABI_SAVE_AREA_SIZE;   /* interrupt-entry save area */
218         ((long *)ksp)[0] = ((long *)ksp)[1] = 0;
219         ksp -= CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long);
220         memcpy((void *)ksp, &regs->regs[CALLEE_SAVED_FIRST_REG],
221                CALLEE_SAVED_REGS_COUNT * sizeof(unsigned long));
222         ksp -= C_ABI_SAVE_AREA_SIZE;   /* __switch_to() save area */
223         ((long *)ksp)[0] = ((long *)ksp)[1] = 0;
224         p->thread.ksp = ksp;
225 
226 #if CHIP_HAS_TILE_DMA()
227         /*
228          * No DMA in the new thread.  We model this on the fact that
229          * fork() clears the pending signals, alarms, and aio for the child.
230          */
231         memset(&p->thread.tile_dma_state, 0, sizeof(struct tile_dma_state));
232         memset(&p->thread.dma_async_tlb, 0, sizeof(struct async_tlb));
233 #endif
234 
235 #if CHIP_HAS_SN_PROC()
236         /* Likewise, the new thread is not running static processor code. */
237         p->thread.sn_proc_running = 0;
238         memset(&p->thread.sn_async_tlb, 0, sizeof(struct async_tlb));
239 #endif
240 
241 #if CHIP_HAS_PROC_STATUS_SPR()
242         /* New thread has its miscellaneous processor state bits clear. */
243         p->thread.proc_status = 0;
244 #endif
245 
246 #ifdef CONFIG_HARDWALL
247         /* New thread does not own any networks. */
248         memset(&p->thread.hardwall[0], 0,
249                sizeof(struct hardwall_task) * HARDWALL_TYPES);
250 #endif
251 
252 
253         /*
254          * Start the new thread with the current architecture state
255          * (user interrupt masks, etc.).
256          */
257         save_arch_state(&p->thread);
258 
259         return 0;
260 }
261 
262 /*
263  * Return "current" if it looks plausible, or else a pointer to a dummy.
264  * This can be helpful if we are just trying to emit a clean panic.
265  */
266 struct task_struct *validate_current(void)
267 {
268         static struct task_struct corrupt = { .comm = "<corrupt>" };
269         struct task_struct *tsk = current;
270         if (unlikely((unsigned long)tsk < PAGE_OFFSET ||
271                      (high_memory && (void *)tsk > high_memory) ||
272                      ((unsigned long)tsk & (__alignof__(*tsk) - 1)) != 0)) {
273                 pr_err("Corrupt 'current' %p (sp %#lx)\n", tsk, stack_pointer);
274                 tsk = &corrupt;
275         }
276         return tsk;
277 }
278 
279 /* Take and return the pointer to the previous task, for schedule_tail(). */
280 struct task_struct *sim_notify_fork(struct task_struct *prev)
281 {
282         struct task_struct *tsk = current;
283         __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK_PARENT |
284                      (tsk->thread.creator_pid << _SIM_CONTROL_OPERATOR_BITS));
285         __insn_mtspr(SPR_SIM_CONTROL, SIM_CONTROL_OS_FORK |
286                      (tsk->pid << _SIM_CONTROL_OPERATOR_BITS));
287         return prev;
288 }
289 
290 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
291 {
292         struct pt_regs *ptregs = task_pt_regs(tsk);
293         elf_core_copy_regs(regs, ptregs);
294         return 1;
295 }
296 
297 #if CHIP_HAS_TILE_DMA()
298 
299 /* Allow user processes to access the DMA SPRs */
300 void grant_dma_mpls(void)
301 {
302 #if CONFIG_KERNEL_PL == 2
303         __insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
304         __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
305 #else
306         __insn_mtspr(SPR_MPL_DMA_CPL_SET_0, 1);
307         __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_0, 1);
308 #endif
309 }
310 
311 /* Forbid user processes from accessing the DMA SPRs */
312 void restrict_dma_mpls(void)
313 {
314 #if CONFIG_KERNEL_PL == 2
315         __insn_mtspr(SPR_MPL_DMA_CPL_SET_2, 1);
316         __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_2, 1);
317 #else
318         __insn_mtspr(SPR_MPL_DMA_CPL_SET_1, 1);
319         __insn_mtspr(SPR_MPL_DMA_NOTIFY_SET_1, 1);
320 #endif
321 }
322 
323 /* Pause the DMA engine, then save off its state registers. */
324 static void save_tile_dma_state(struct tile_dma_state *dma)
325 {
326         unsigned long state = __insn_mfspr(SPR_DMA_USER_STATUS);
327         unsigned long post_suspend_state;
328 
329         /* If we're running, suspend the engine. */
330         if ((state & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK)
331                 __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__SUSPEND_MASK);
332 
333         /*
334          * Wait for the engine to idle, then save regs.  Note that we
335          * want to record the "running" bit from before suspension,
336          * and the "done" bit from after, so that we can properly
337          * distinguish a case where the user suspended the engine from
338          * the case where the kernel suspended as part of the context
339          * swap.
340          */
341         do {
342                 post_suspend_state = __insn_mfspr(SPR_DMA_USER_STATUS);
343         } while (post_suspend_state & SPR_DMA_STATUS__BUSY_MASK);
344 
345         dma->src = __insn_mfspr(SPR_DMA_SRC_ADDR);
346         dma->src_chunk = __insn_mfspr(SPR_DMA_SRC_CHUNK_ADDR);
347         dma->dest = __insn_mfspr(SPR_DMA_DST_ADDR);
348         dma->dest_chunk = __insn_mfspr(SPR_DMA_DST_CHUNK_ADDR);
349         dma->strides = __insn_mfspr(SPR_DMA_STRIDE);
350         dma->chunk_size = __insn_mfspr(SPR_DMA_CHUNK_SIZE);
351         dma->byte = __insn_mfspr(SPR_DMA_BYTE);
352         dma->status = (state & SPR_DMA_STATUS__RUNNING_MASK) |
353                 (post_suspend_state & SPR_DMA_STATUS__DONE_MASK);
354 }
355 
356 /* Restart a DMA that was running before we were context-switched out. */
357 static void restore_tile_dma_state(struct thread_struct *t)
358 {
359         const struct tile_dma_state *dma = &t->tile_dma_state;
360 
361         /*
362          * The only way to restore the done bit is to run a zero
363          * length transaction.
364          */
365         if ((dma->status & SPR_DMA_STATUS__DONE_MASK) &&
366             !(__insn_mfspr(SPR_DMA_USER_STATUS) & SPR_DMA_STATUS__DONE_MASK)) {
367                 __insn_mtspr(SPR_DMA_BYTE, 0);
368                 __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
369                 while (__insn_mfspr(SPR_DMA_USER_STATUS) &
370                        SPR_DMA_STATUS__BUSY_MASK)
371                         ;
372         }
373 
374         __insn_mtspr(SPR_DMA_SRC_ADDR, dma->src);
375         __insn_mtspr(SPR_DMA_SRC_CHUNK_ADDR, dma->src_chunk);
376         __insn_mtspr(SPR_DMA_DST_ADDR, dma->dest);
377         __insn_mtspr(SPR_DMA_DST_CHUNK_ADDR, dma->dest_chunk);
378         __insn_mtspr(SPR_DMA_STRIDE, dma->strides);
379         __insn_mtspr(SPR_DMA_CHUNK_SIZE, dma->chunk_size);
380         __insn_mtspr(SPR_DMA_BYTE, dma->byte);
381 
382         /*
383          * Restart the engine if we were running and not done.
384          * Clear a pending async DMA fault that we were waiting on return
385          * to user space to execute, since we expect the DMA engine
386          * to regenerate those faults for us now.  Note that we don't
387          * try to clear the TIF_ASYNC_TLB flag, since it's relatively
388          * harmless if set, and it covers both DMA and the SN processor.
389          */
390         if ((dma->status & DMA_STATUS_MASK) == SPR_DMA_STATUS__RUNNING_MASK) {
391                 t->dma_async_tlb.fault_num = 0;
392                 __insn_mtspr(SPR_DMA_CTR, SPR_DMA_CTR__REQUEST_MASK);
393         }
394 }
395 
396 #endif
397 
398 static void save_arch_state(struct thread_struct *t)
399 {
400 #if CHIP_HAS_SPLIT_INTR_MASK()
401         t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0_0) |
402                 ((u64)__insn_mfspr(SPR_INTERRUPT_MASK_0_1) << 32);
403 #else
404         t->interrupt_mask = __insn_mfspr(SPR_INTERRUPT_MASK_0);
405 #endif
406         t->ex_context[0] = __insn_mfspr(SPR_EX_CONTEXT_0_0);
407         t->ex_context[1] = __insn_mfspr(SPR_EX_CONTEXT_0_1);
408         t->system_save[0] = __insn_mfspr(SPR_SYSTEM_SAVE_0_0);
409         t->system_save[1] = __insn_mfspr(SPR_SYSTEM_SAVE_0_1);
410         t->system_save[2] = __insn_mfspr(SPR_SYSTEM_SAVE_0_2);
411         t->system_save[3] = __insn_mfspr(SPR_SYSTEM_SAVE_0_3);
412         t->intctrl_0 = __insn_mfspr(SPR_INTCTRL_0_STATUS);
413 #if CHIP_HAS_PROC_STATUS_SPR()
414         t->proc_status = __insn_mfspr(SPR_PROC_STATUS);
415 #endif
416 #if !CHIP_HAS_FIXED_INTVEC_BASE()
417         t->interrupt_vector_base = __insn_mfspr(SPR_INTERRUPT_VECTOR_BASE_0);
418 #endif
419 #if CHIP_HAS_TILE_RTF_HWM()
420         t->tile_rtf_hwm = __insn_mfspr(SPR_TILE_RTF_HWM);
421 #endif
422 #if CHIP_HAS_DSTREAM_PF()
423         t->dstream_pf = __insn_mfspr(SPR_DSTREAM_PF);
424 #endif
425 }
426 
427 static void restore_arch_state(const struct thread_struct *t)
428 {
429 #if CHIP_HAS_SPLIT_INTR_MASK()
430         __insn_mtspr(SPR_INTERRUPT_MASK_0_0, (u32) t->interrupt_mask);
431         __insn_mtspr(SPR_INTERRUPT_MASK_0_1, t->interrupt_mask >> 32);
432 #else
433         __insn_mtspr(SPR_INTERRUPT_MASK_0, t->interrupt_mask);
434 #endif
435         __insn_mtspr(SPR_EX_CONTEXT_0_0, t->ex_context[0]);
436         __insn_mtspr(SPR_EX_CONTEXT_0_1, t->ex_context[1]);
437         __insn_mtspr(SPR_SYSTEM_SAVE_0_0, t->system_save[0]);
438         __insn_mtspr(SPR_SYSTEM_SAVE_0_1, t->system_save[1]);
439         __insn_mtspr(SPR_SYSTEM_SAVE_0_2, t->system_save[2]);
440         __insn_mtspr(SPR_SYSTEM_SAVE_0_3, t->system_save[3]);
441         __insn_mtspr(SPR_INTCTRL_0_STATUS, t->intctrl_0);
442 #if CHIP_HAS_PROC_STATUS_SPR()
443         __insn_mtspr(SPR_PROC_STATUS, t->proc_status);
444 #endif
445 #if !CHIP_HAS_FIXED_INTVEC_BASE()
446         __insn_mtspr(SPR_INTERRUPT_VECTOR_BASE_0, t->interrupt_vector_base);
447 #endif
448 #if CHIP_HAS_TILE_RTF_HWM()
449         __insn_mtspr(SPR_TILE_RTF_HWM, t->tile_rtf_hwm);
450 #endif
451 #if CHIP_HAS_DSTREAM_PF()
452         __insn_mtspr(SPR_DSTREAM_PF, t->dstream_pf);
453 #endif
454 }
455 
456 
457 void _prepare_arch_switch(struct task_struct *next)
458 {
459 #if CHIP_HAS_SN_PROC()
460         int snctl;
461 #endif
462 #if CHIP_HAS_TILE_DMA()
463         struct tile_dma_state *dma = &current->thread.tile_dma_state;
464         if (dma->enabled)
465                 save_tile_dma_state(dma);
466 #endif
467 #if CHIP_HAS_SN_PROC()
468         /*
469          * Suspend the static network processor if it was running.
470          * We do not suspend the fabric itself, just like we don't
471          * try to suspend the UDN.
472          */
473         snctl = __insn_mfspr(SPR_SNCTL);
474         current->thread.sn_proc_running =
475                 (snctl & SPR_SNCTL__FRZPROC_MASK) == 0;
476         if (current->thread.sn_proc_running)
477                 __insn_mtspr(SPR_SNCTL, snctl | SPR_SNCTL__FRZPROC_MASK);
478 #endif
479 }
480 
481 
482 struct task_struct *__sched _switch_to(struct task_struct *prev,
483                                        struct task_struct *next)
484 {
485         /* DMA state is already saved; save off other arch state. */
486         save_arch_state(&prev->thread);
487 
488 #if CHIP_HAS_TILE_DMA()
489         /*
490          * Restore DMA in new task if desired.
491          * Note that it is only safe to restart here since interrupts
492          * are disabled, so we can't take any DMATLB miss or access
493          * interrupts before we have finished switching stacks.
494          */
495         if (next->thread.tile_dma_state.enabled) {
496                 restore_tile_dma_state(&next->thread);
497                 grant_dma_mpls();
498         } else {
499                 restrict_dma_mpls();
500         }
501 #endif
502 
503         /* Restore other arch state. */
504         restore_arch_state(&next->thread);
505 
506 #if CHIP_HAS_SN_PROC()
507         /*
508          * Restart static network processor in the new process
509          * if it was running before.
510          */
511         if (next->thread.sn_proc_running) {
512                 int snctl = __insn_mfspr(SPR_SNCTL);
513                 __insn_mtspr(SPR_SNCTL, snctl & ~SPR_SNCTL__FRZPROC_MASK);
514         }
515 #endif
516 
517 #ifdef CONFIG_HARDWALL
518         /* Enable or disable access to the network registers appropriately. */
519         hardwall_switch_tasks(prev, next);
520 #endif
521 
522         /*
523          * Switch kernel SP, PC, and callee-saved registers.
524          * In the context of the new task, return the old task pointer
525          * (i.e. the task that actually called __switch_to).
526          * Pass the value to use for SYSTEM_SAVE_K_0 when we reset our sp.
527          */
528         return __switch_to(prev, next, next_current_ksp0(next));
529 }
530 
531 /*
532  * This routine is called on return from interrupt if any of the
533  * TIF_WORK_MASK flags are set in thread_info->flags.  It is
534  * entered with interrupts disabled so we don't miss an event
535  * that modified the thread_info flags.  If any flag is set, we
536  * handle it and return, and the calling assembly code will
537  * re-disable interrupts, reload the thread flags, and call back
538  * if more flags need to be handled.
539  *
540  * We return whether we need to check the thread_info flags again
541  * or not.  Note that we don't clear TIF_SINGLESTEP here, so it's
542  * important that it be tested last, and then claim that we don't
543  * need to recheck the flags.
544  */
545 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
546 {
547         /* If we enter in kernel mode, do nothing and exit the caller loop. */
548         if (!user_mode(regs))
549                 return 0;
550 
551         /* Enable interrupts; they are disabled again on return to caller. */
552         local_irq_enable();
553 
554         if (thread_info_flags & _TIF_NEED_RESCHED) {
555                 schedule();
556                 return 1;
557         }
558 #if CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
559         if (thread_info_flags & _TIF_ASYNC_TLB) {
560                 do_async_page_fault(regs);
561                 return 1;
562         }
563 #endif
564         if (thread_info_flags & _TIF_SIGPENDING) {
565                 do_signal(regs);
566                 return 1;
567         }
568         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
569                 clear_thread_flag(TIF_NOTIFY_RESUME);
570                 tracehook_notify_resume(regs);
571                 return 1;
572         }
573         if (thread_info_flags & _TIF_SINGLESTEP) {
574                 single_step_once(regs);
575                 return 0;
576         }
577         panic("work_pending: bad flags %#x\n", thread_info_flags);
578 }
579 
580 /* Note there is an implicit fifth argument if (clone_flags & CLONE_SETTLS). */
581 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
582                 void __user *, parent_tidptr, void __user *, child_tidptr,
583                 struct pt_regs *, regs)
584 {
585         if (!newsp)
586                 newsp = regs->sp;
587         return do_fork(clone_flags, newsp, regs, 0,
588                        parent_tidptr, child_tidptr);
589 }
590 
591 /*
592  * sys_execve() executes a new program.
593  */
594 SYSCALL_DEFINE4(execve, const char __user *, path,
595                 const char __user *const __user *, argv,
596                 const char __user *const __user *, envp,
597                 struct pt_regs *, regs)
598 {
599         long error;
600         struct filename *filename;
601 
602         filename = getname(path);
603         error = PTR_ERR(filename);
604         if (IS_ERR(filename))
605                 goto out;
606         error = do_execve(filename->name, argv, envp, regs);
607         putname(filename);
608         if (error == 0)
609                 single_step_execve();
610 out:
611         return error;
612 }
613 
614 #ifdef CONFIG_COMPAT
615 long compat_sys_execve(const char __user *path,
616                        compat_uptr_t __user *argv,
617                        compat_uptr_t __user *envp,
618                        struct pt_regs *regs)
619 {
620         long error;
621         struct filename *filename;
622 
623         filename = getname(path);
624         error = PTR_ERR(filename);
625         if (IS_ERR(filename))
626                 goto out;
627         error = compat_do_execve(filename->name, argv, envp, regs);
628         putname(filename);
629         if (error == 0)
630                 single_step_execve();
631 out:
632         return error;
633 }
634 #endif
635 
636 unsigned long get_wchan(struct task_struct *p)
637 {
638         struct KBacktraceIterator kbt;
639 
640         if (!p || p == current || p->state == TASK_RUNNING)
641                 return 0;
642 
643         for (KBacktraceIterator_init(&kbt, p, NULL);
644              !KBacktraceIterator_end(&kbt);
645              KBacktraceIterator_next(&kbt)) {
646                 if (!in_sched_functions(kbt.it.pc))
647                         return kbt.it.pc;
648         }
649 
650         return 0;
651 }
652 
653 /*
654  * We pass in lr as zero (cleared in kernel_thread) and the caller
655  * part of the backtrace ABI on the stack also zeroed (in copy_thread)
656  * so that backtraces will stop with this function.
657  * Note that we don't use r0, since copy_thread() clears it.
658  */
659 static void start_kernel_thread(int dummy, int (*fn)(int), int arg)
660 {
661         do_exit(fn(arg));
662 }
663 
664 /*
665  * Create a kernel thread
666  */
667 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
668 {
669         struct pt_regs regs;
670 
671         memset(&regs, 0, sizeof(regs));
672         regs.ex1 = PL_ICS_EX1(KERNEL_PL, 0);  /* run at kernel PL, no ICS */
673         regs.pc = (long) start_kernel_thread;
674         regs.flags = PT_FLAGS_CALLER_SAVES;   /* need to restore r1 and r2 */
675         regs.regs[1] = (long) fn;             /* function pointer */
676         regs.regs[2] = (long) arg;            /* parameter register */
677 
678         /* Ok, create the new process.. */
679         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs,
680                        0, NULL, NULL);
681 }
682 EXPORT_SYMBOL(kernel_thread);
683 
684 /* Flush thread state. */
685 void flush_thread(void)
686 {
687         /* Nothing */
688 }
689 
690 /*
691  * Free current thread data structures etc..
692  */
693 void exit_thread(void)
694 {
695         /* Nothing */
696 }
697 
698 void show_regs(struct pt_regs *regs)
699 {
700         struct task_struct *tsk = validate_current();
701         int i;
702 
703         pr_err("\n");
704         pr_err(" Pid: %d, comm: %20s, CPU: %d\n",
705                tsk->pid, tsk->comm, smp_processor_id());
706 #ifdef __tilegx__
707         for (i = 0; i < 51; i += 3)
708                 pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
709                        i, regs->regs[i], i+1, regs->regs[i+1],
710                        i+2, regs->regs[i+2]);
711         pr_err(" r51: "REGFMT" r52: "REGFMT" tp : "REGFMT"\n",
712                regs->regs[51], regs->regs[52], regs->tp);
713         pr_err(" sp : "REGFMT" lr : "REGFMT"\n", regs->sp, regs->lr);
714 #else
715         for (i = 0; i < 52; i += 4)
716                 pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT
717                        " r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
718                        i, regs->regs[i], i+1, regs->regs[i+1],
719                        i+2, regs->regs[i+2], i+3, regs->regs[i+3]);
720         pr_err(" r52: "REGFMT" tp : "REGFMT" sp : "REGFMT" lr : "REGFMT"\n",
721                regs->regs[52], regs->tp, regs->sp, regs->lr);
722 #endif
723         pr_err(" pc : "REGFMT" ex1: %ld     faultnum: %ld\n",
724                regs->pc, regs->ex1, regs->faultnum);
725 
726         dump_stack_regs(regs);
727 }
728 

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