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   1 /*
   2  *  linux/arch/x86-64/kernel/process.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *
   6  *  Pentium III FXSR, SSE support
   7  *      Gareth Hughes <gareth@valinux.com>, May 2000
   8  *
   9  *  X86-64 port
  10  *      Andi Kleen.
  11  *
  12  *      CPU hotplug support - ashok.raj@intel.com
  13  *  $Id: process.c,v 1.38 2002/01/15 10:08:03 ak Exp $
  14  */
  15
  16 /*
  17  * This file handles the architecture-dependent parts of process handling..
  18  */
  19
  20 #include <stdarg.h>
  21
  22 #include <linux/cpu.h>
  23 #include <linux/errno.h>
  24 #include <linux/sched.h>
  25 #include <linux/kernel.h>
  26 #include <linux/mm.h>
  27 #include <linux/elfcore.h>
  28 #include <linux/smp.h>
  29 #include <linux/slab.h>
  30 #include <linux/user.h>
  31 #include <linux/module.h>
  32 #include <linux/a.out.h>
  33 #include <linux/interrupt.h>
  34 #include <linux/delay.h>
  35 #include <linux/ptrace.h>
  36 #include <linux/utsname.h>
  37 #include <linux/random.h>
  38 #include <linux/kprobes.h>
  39 #include <linux/notifier.h>
  40
  41 #include <asm/uaccess.h>
  42 #include <asm/pgtable.h>
  43 #include <asm/system.h>
  44 #include <asm/io.h>
  45 #include <asm/processor.h>
  46 #include <asm/i387.h>
  47 #include <asm/mmu_context.h>
  48 #include <asm/pda.h>
  49 #include <asm/prctl.h>
  50 #include <asm/kdebug.h>
  51 #include <asm/desc.h>
  52 #include <asm/proto.h>
  53 #include <asm/ia32.h>
  54 #include <asm/idle.h>
  55
  56 asmlinkage extern void ret_from_fork(void);
  57
  58 unsigned long kernel_thread_flags = CLONE_VM | CLONE_UNTRACED;
  59
  60 unsigned long boot_option_idle_override = 0;
  61 EXPORT_SYMBOL(boot_option_idle_override);
  62
  63 /*
  64  * Powermanagement idle function, if any..
  65  */
  66 void (*pm_idle)(void);
  67 static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
  68
  69 static struct notifier_block *idle_notifier;
  70 static DEFINE_SPINLOCK(idle_notifier_lock);
  71
  72 void idle_notifier_register(struct notifier_block *n)
  73 {
  74         unsigned long flags;
  75         spin_lock_irqsave(&idle_notifier_lock, flags);
  76         notifier_chain_register(&idle_notifier, n);
  77         spin_unlock_irqrestore(&idle_notifier_lock, flags);
  78 }
  79 EXPORT_SYMBOL_GPL(idle_notifier_register);
  80
  81 void idle_notifier_unregister(struct notifier_block *n)
  82 {
  83         unsigned long flags;
  84         spin_lock_irqsave(&idle_notifier_lock, flags);
  85         notifier_chain_unregister(&idle_notifier, n);
  86         spin_unlock_irqrestore(&idle_notifier_lock, flags);
  87 }
  88 EXPORT_SYMBOL(idle_notifier_unregister);
  89
  90 enum idle_state { CPU_IDLE, CPU_NOT_IDLE };
  91 static DEFINE_PER_CPU(enum idle_state, idle_state) = CPU_NOT_IDLE;
  92
  93 void enter_idle(void)
  94 {
  95         __get_cpu_var(idle_state) = CPU_IDLE;
  96         notifier_call_chain(&idle_notifier, IDLE_START, NULL);
  97 }
  98
  99 static void __exit_idle(void)
 100 {
 101         __get_cpu_var(idle_state) = CPU_NOT_IDLE;
 102         notifier_call_chain(&idle_notifier, IDLE_END, NULL);
 103 }
 104
 105 /* Called from interrupts to signify idle end */
 106 void exit_idle(void)
 107 {
 108         if (current->pid | read_pda(irqcount))
 109                 return;
 110         __exit_idle();
 111 }
 112
 113 /*
 114  * We use this if we don't have any better
 115  * idle routine..
 116  */
 117 void default_idle(void)
 118 {
 119         local_irq_enable();
 120
 121         clear_thread_flag(TIF_POLLING_NRFLAG);
 122         smp_mb__after_clear_bit();
 123         while (!need_resched()) {
 124                 local_irq_disable();
 125                 if (!need_resched())
 126                         safe_halt();
 127                 else
 128                         local_irq_enable();
 129         }
 130         set_thread_flag(TIF_POLLING_NRFLAG);
 131 }
 132
 133 /*
 134  * On SMP it's slightly faster (but much more power-consuming!)
 135  * to poll the ->need_resched flag instead of waiting for the
 136  * cross-CPU IPI to arrive. Use this option with caution.
 137  */
 138 static void poll_idle (void)
 139 {
 140         local_irq_enable();
 141
 142         asm volatile(
 143                 "2:"
 144                 "testl %0,%1;"
 145                 "rep; nop;"
 146                 "je 2b;"
 147                 : :
 148                 "i" (_TIF_NEED_RESCHED),
 149                 "m" (current_thread_info()->flags));
 150 }
 151
 152 void cpu_idle_wait(void)
 153 {
 154         unsigned int cpu, this_cpu = get_cpu();
 155         cpumask_t map;
 156
 157         set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
 158         put_cpu();
 159
 160         cpus_clear(map);
 161         for_each_online_cpu(cpu) {
 162                 per_cpu(cpu_idle_state, cpu) = 1;
 163                 cpu_set(cpu, map);
 164         }
 165
 166         __get_cpu_var(cpu_idle_state) = 0;
 167
 168         wmb();
 169         do {
 170                 ssleep(1);
 171                 for_each_online_cpu(cpu) {
 172                         if (cpu_isset(cpu, map) &&
 173                                         !per_cpu(cpu_idle_state, cpu))
 174                                 cpu_clear(cpu, map);
 175                 }
 176                 cpus_and(map, map, cpu_online_map);
 177         } while (!cpus_empty(map));
 178 }
 179 EXPORT_SYMBOL_GPL(cpu_idle_wait);
 180
 181 #ifdef CONFIG_HOTPLUG_CPU
 182 DECLARE_PER_CPU(int, cpu_state);
 183
 184 #include <asm/nmi.h>
 185 /* We halt the CPU with physical CPU hotplug */
 186 static inline void play_dead(void)
 187 {
 188         idle_task_exit();
 189         wbinvd();
 190         mb();
 191         /* Ack it */
 192         __get_cpu_var(cpu_state) = CPU_DEAD;
 193
 194         local_irq_disable();
 195         while (1)
 196                 halt();
 197 }
 198 #else
 199 static inline void play_dead(void)
 200 {
 201         BUG();
 202 }
 203 #endif /* CONFIG_HOTPLUG_CPU */
 204
 205 /*
 206  * The idle thread. There's no useful work to be
 207  * done, so just try to conserve power and have a
 208  * low exit latency (ie sit in a loop waiting for
 209  * somebody to say that they'd like to reschedule)
 210  */
 211 void cpu_idle (void)
 212 {
 213         set_thread_flag(TIF_POLLING_NRFLAG);
 214
 215         /* endless idle loop with no priority at all */
 216         while (1) {
 217                 while (!need_resched()) {
 218                         void (*idle)(void);
 219
 220                         if (__get_cpu_var(cpu_idle_state))
 221                                 __get_cpu_var(cpu_idle_state) = 0;
 222
 223                         rmb();
 224                         idle = pm_idle;
 225                         if (!idle)
 226                                 idle = default_idle;
 227                         if (cpu_is_offline(smp_processor_id()))
 228                                 play_dead();
 229                         enter_idle();
 230                         idle();
 231                         __exit_idle();
 232                 }
 233
 234                 preempt_enable_no_resched();
 235                 schedule();
 236                 preempt_disable();
 237         }
 238 }
 239
 240 /*
 241  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
 242  * which can obviate IPI to trigger checking of need_resched.
 243  * We execute MONITOR against need_resched and enter optimized wait state
 244  * through MWAIT. Whenever someone changes need_resched, we would be woken
 245  * up from MWAIT (without an IPI).
 246  */
 247 static void mwait_idle(void)
 248 {
 249         local_irq_enable();
 250
 251         while (!need_resched()) {
 252                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 253                 smp_mb();
 254                 if (need_resched())
 255                         break;
 256                 __mwait(0, 0);
 257         }
 258 }
 259
 260 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 261 {
 262         static int printed;
 263         if (cpu_has(c, X86_FEATURE_MWAIT)) {
 264                 /*
 265                  * Skip, if setup has overridden idle.
 266                  * One CPU supports mwait => All CPUs supports mwait
 267                  */
 268                 if (!pm_idle) {
 269                         if (!printed) {
 270                                 printk("using mwait in idle threads.\n");
 271                                 printed = 1;
 272                         }
 273                         pm_idle = mwait_idle;
 274                 }
 275         }
 276 }
 277
 278 static int __init idle_setup (char *str)
 279 {
 280         if (!strncmp(str, "poll", 4)) {
 281                 printk("using polling idle threads.\n");
 282                 pm_idle = poll_idle;
 283         }
 284
 285         boot_option_idle_override = 1;
 286         return 1;
 287 }
 288
 289 __setup("idle=", idle_setup);
 290
 291 /* Prints also some state that isn't saved in the pt_regs */
 292 void __show_regs(struct pt_regs * regs)
 293 {
 294         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs;
 295         unsigned int fsindex,gsindex;
 296         unsigned int ds,cs,es;
 297
 298         printk("\n");
 299         print_modules();
 300         printk("Pid: %d, comm: %.20s %s %s %.*s\n",
 301                 current->pid, current->comm, print_tainted(),
 302                 system_utsname.release,
 303                 (int)strcspn(system_utsname.version, " "),
 304                 system_utsname.version);
 305         printk("RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->rip);
 306         printk_address(regs->rip);
 307         printk("\nRSP: %04lx:%016lx  EFLAGS: %08lx\n", regs->ss, regs->rsp,
 308                 regs->eflags);
 309         printk("RAX: %016lx RBX: %016lx RCX: %016lx\n",
 310                regs->rax, regs->rbx, regs->rcx);
 311         printk("RDX: %016lx RSI: %016lx RDI: %016lx\n",
 312                regs->rdx, regs->rsi, regs->rdi);
 313         printk("RBP: %016lx R08: %016lx R09: %016lx\n",
 314                regs->rbp, regs->r8, regs->r9);
 315         printk("R10: %016lx R11: %016lx R12: %016lx\n",
 316                regs->r10, regs->r11, regs->r12);
 317         printk("R13: %016lx R14: %016lx R15: %016lx\n",
 318                regs->r13, regs->r14, regs->r15);
 319
 320         asm("movl %%ds,%0" : "=r" (ds));
 321         asm("movl %%cs,%0" : "=r" (cs));
 322         asm("movl %%es,%0" : "=r" (es));
 323         asm("movl %%fs,%0" : "=r" (fsindex));
 324         asm("movl %%gs,%0" : "=r" (gsindex));
 325
 326         rdmsrl(MSR_FS_BASE, fs);
 327         rdmsrl(MSR_GS_BASE, gs);
 328         rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
 329
 330         asm("movq %%cr0, %0": "=r" (cr0));
 331         asm("movq %%cr2, %0": "=r" (cr2));
 332         asm("movq %%cr3, %0": "=r" (cr3));
 333         asm("movq %%cr4, %0": "=r" (cr4));
 334
 335         printk("FS:  %016lx(%04x) GS:%016lx(%04x) knlGS:%016lx\n",
 336                fs,fsindex,gs,gsindex,shadowgs);
 337         printk("CS:  %04x DS: %04x ES: %04x CR0: %016lx\n", cs, ds, es, cr0);
 338         printk("CR2: %016lx CR3: %016lx CR4: %016lx\n", cr2, cr3, cr4);
 339 }
 340
 341 void show_regs(struct pt_regs *regs)
 342 {
 343         printk("CPU %d:", smp_processor_id());
 344         __show_regs(regs);
 345         show_trace(&regs->rsp);
 346 }
 347
 348 /*
 349  * Free current thread data structures etc..
 350  */
 351 void exit_thread(void)
 352 {
 353         struct task_struct *me = current;
 354         struct thread_struct *t = &me->thread;
 355
 356         /*
 357          * Remove function-return probe instances associated with this task
 358          * and put them back on the free list. Do not insert an exit probe for
 359          * this function, it will be disabled by kprobe_flush_task if you do.
 360          */
 361         kprobe_flush_task(me);
 362
 363         if (me->thread.io_bitmap_ptr) {
 364                 struct tss_struct *tss = &per_cpu(init_tss, get_cpu());
 365
 366                 kfree(t->io_bitmap_ptr);
 367                 t->io_bitmap_ptr = NULL;
 368                 /*
 369                  * Careful, clear this in the TSS too:
 370                  */
 371                 memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
 372                 t->io_bitmap_max = 0;
 373                 put_cpu();
 374         }
 375 }
 376
 377 void flush_thread(void)
 378 {
 379         struct task_struct *tsk = current;
 380         struct thread_info *t = current_thread_info();
 381
 382         if (t->flags & _TIF_ABI_PENDING)
 383                 t->flags ^= (_TIF_ABI_PENDING | _TIF_IA32);
 384
 385         tsk->thread.debugreg0 = 0;
 386         tsk->thread.debugreg1 = 0;
 387         tsk->thread.debugreg2 = 0;
 388         tsk->thread.debugreg3 = 0;
 389         tsk->thread.debugreg6 = 0;
 390         tsk->thread.debugreg7 = 0;
 391         memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 392         /*
 393          * Forget coprocessor state..
 394          */
 395         clear_fpu(tsk);
 396         clear_used_math();
 397 }
 398
 399 void release_thread(struct task_struct *dead_task)
 400 {
 401         if (dead_task->mm) {
 402                 if (dead_task->mm->context.size) {
 403                         printk("WARNING: dead process %8s still has LDT? <%p/%d>\n",
 404                                         dead_task->comm,
 405                                         dead_task->mm->context.ldt,
 406                                         dead_task->mm->context.size);
 407                         BUG();
 408                 }
 409         }
 410 }
 411
 412 static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
 413 {
 414         struct user_desc ud = {
 415                 .base_addr = addr,
 416                 .limit = 0xfffff,
 417                 .seg_32bit = 1,
 418                 .limit_in_pages = 1,
 419                 .useable = 1,
 420         };
 421         struct n_desc_struct *desc = (void *)t->thread.tls_array;
 422         desc += tls;
 423         desc->a = LDT_entry_a(&ud);
 424         desc->b = LDT_entry_b(&ud);
 425 }
 426
 427 static inline u32 read_32bit_tls(struct task_struct *t, int tls)
 428 {
 429         struct desc_struct *desc = (void *)t->thread.tls_array;
 430         desc += tls;
 431         return desc->base0 |
 432                 (((u32)desc->base1) << 16) |
 433                 (((u32)desc->base2) << 24);
 434 }
 435
 436 /*
 437  * This gets called before we allocate a new thread and copy
 438  * the current task into it.
 439  */
 440 void prepare_to_copy(struct task_struct *tsk)
 441 {
 442         unlazy_fpu(tsk);
 443 }
 444
 445 int copy_thread(int nr, unsigned long clone_flags, unsigned long rsp,
 446                 unsigned long unused,
 447         struct task_struct * p, struct pt_regs * regs)
 448 {
 449         int err;
 450         struct pt_regs * childregs;
 451         struct task_struct *me = current;
 452
 453         childregs = ((struct pt_regs *)
 454                         (THREAD_SIZE + task_stack_page(p))) - 1;
 455         *childregs = *regs;
 456
 457         childregs->rax = 0;
 458         childregs->rsp = rsp;
 459         if (rsp == ~0UL)
 460                 childregs->rsp = (unsigned long)childregs;
 461
 462         p->thread.rsp = (unsigned long) childregs;
 463         p->thread.rsp0 = (unsigned long) (childregs+1);
 464         p->thread.userrsp = me->thread.userrsp;
 465
 466         set_tsk_thread_flag(p, TIF_FORK);
 467
 468         p->thread.fs = me->thread.fs;
 469         p->thread.gs = me->thread.gs;
 470
 471         asm("mov %%gs,%0" : "=m" (p->thread.gsindex));
 472         asm("mov %%fs,%0" : "=m" (p->thread.fsindex));
 473         asm("mov %%es,%0" : "=m" (p->thread.es));
 474         asm("mov %%ds,%0" : "=m" (p->thread.ds));
 475
 476         if (unlikely(me->thread.io_bitmap_ptr != NULL)) {
 477                 p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 478                 if (!p->thread.io_bitmap_ptr) {
 479                         p->thread.io_bitmap_max = 0;
 480                         return -ENOMEM;
 481                 }
 482                 memcpy(p->thread.io_bitmap_ptr, me->thread.io_bitmap_ptr,
 483                                 IO_BITMAP_BYTES);
 484         }
 485
 486         /*
 487          * Set a new TLS for the child thread?
 488          */
 489         if (clone_flags & CLONE_SETTLS) {
 490 #ifdef CONFIG_IA32_EMULATION
 491                 if (test_thread_flag(TIF_IA32))
 492                         err = ia32_child_tls(p, childregs);
 493                 else
 494 #endif
 495                         err = do_arch_prctl(p, ARCH_SET_FS, childregs->r8);
 496                 if (err)
 497                         goto out;
 498         }
 499         err = 0;
 500 out:
 501         if (err && p->thread.io_bitmap_ptr) {
 502                 kfree(p->thread.io_bitmap_ptr);
 503                 p->thread.io_bitmap_max = 0;
 504         }
 505         return err;
 506 }
 507
 508 /*
 509  * This special macro can be used to load a debugging register
 510  */
 511 #define loaddebug(thread,r) set_debug(thread->debugreg ## r, r)
 512
 513 /*
 514  *      switch_to(x,y) should switch tasks from x to y.
 515  *
 516  * This could still be optimized:
 517  * - fold all the options into a flag word and test it with a single test.
 518  * - could test fs/gs bitsliced
 519  *
 520  * Kprobes not supported here. Set the probe on schedule instead.
 521  */
 522 __kprobes struct task_struct *
 523 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 524 {
 525         struct thread_struct *prev = &prev_p->thread,
 526                                  *next = &next_p->thread;
 527         int cpu = smp_processor_id();
 528         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 529
 530         unlazy_fpu(prev_p);
 531
 532         /*
 533          * Reload esp0, LDT and the page table pointer:
 534          */
 535         tss->rsp0 = next->rsp0;
 536
 537         /*
 538          * Switch DS and ES.
 539          * This won't pick up thread selector changes, but I guess that is ok.
 540          */
 541         asm volatile("mov %%es,%0" : "=m" (prev->es));
 542         if (unlikely(next->es | prev->es))
 543                 loadsegment(es, next->es);
 544
 545         asm volatile ("mov %%ds,%0" : "=m" (prev->ds));
 546         if (unlikely(next->ds | prev->ds))
 547                 loadsegment(ds, next->ds);
 548
 549         load_TLS(next, cpu);
 550
 551         /*
 552          * Switch FS and GS.
 553          */
 554         {
 555                 unsigned fsindex;
 556                 asm volatile("movl %%fs,%0" : "=r" (fsindex));
 557                 /* segment register != 0 always requires a reload.
 558                    also reload when it has changed.
 559                    when prev process used 64bit base always reload
 560                    to avoid an information leak. */
 561                 if (unlikely(fsindex | next->fsindex | prev->fs)) {
 562                         loadsegment(fs, next->fsindex);
 563                         /* check if the user used a selector != 0
 564                          * if yes clear 64bit base, since overloaded base
 565                          * is always mapped to the Null selector
 566                          */
 567                         if (fsindex)
 568                         prev->fs = 0;
 569                 }
 570                 /* when next process has a 64bit base use it */
 571                 if (next->fs)
 572                         wrmsrl(MSR_FS_BASE, next->fs);
 573                 prev->fsindex = fsindex;
 574         }
 575         {
 576                 unsigned gsindex;
 577                 asm volatile("movl %%gs,%0" : "=r" (gsindex));
 578                 if (unlikely(gsindex | next->gsindex | prev->gs)) {
 579                         load_gs_index(next->gsindex);
 580                         if (gsindex)
 581                         prev->gs = 0;
 582                 }
 583                 if (next->gs)
 584                         wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
 585                 prev->gsindex = gsindex;
 586         }
 587
 588         /*
 589          * Switch the PDA context.
 590          */
 591         prev->userrsp = read_pda(oldrsp);
 592         write_pda(oldrsp, next->userrsp);
 593         write_pda(pcurrent, next_p);
 594         write_pda(kernelstack,
 595                   task_stack_page(next_p) + THREAD_SIZE - PDA_STACKOFFSET);
 596
 597         /*
 598          * Now maybe reload the debug registers
 599          */
 600         if (unlikely(next->debugreg7)) {
 601                 loaddebug(next, 0);
 602                 loaddebug(next, 1);
 603                 loaddebug(next, 2);
 604                 loaddebug(next, 3);
 605                 /* no 4 and 5 */
 606                 loaddebug(next, 6);
 607                 loaddebug(next, 7);
 608         }
 609
 610
 611         /*
 612          * Handle the IO bitmap
 613          */
 614         if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr)) {
 615                 if (next->io_bitmap_ptr)
 616                         /*
 617                          * Copy the relevant range of the IO bitmap.
 618                          * Normally this is 128 bytes or less:
 619                          */
 620                         memcpy(tss->io_bitmap, next->io_bitmap_ptr,
 621                                 max(prev->io_bitmap_max, next->io_bitmap_max));
 622                 else {
 623                         /*
 624                          * Clear any possible leftover bits:
 625                          */
 626                         memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
 627                 }
 628         }
 629
 630         return prev_p;
 631 }
 632
 633 /*
 634  * sys_execve() executes a new program.
 635  */
 636 asmlinkage
 637 long sys_execve(char __user *name, char __user * __user *argv,
 638                 char __user * __user *envp, struct pt_regs regs)
 639 {
 640         long error;
 641         char * filename;
 642
 643         filename = getname(name);
 644         error = PTR_ERR(filename);
 645         if (IS_ERR(filename))
 646                 return error;
 647         error = do_execve(filename, argv, envp, &regs);
 648         if (error == 0) {
 649                 task_lock(current);
 650                 current->ptrace &= ~PT_DTRACE;
 651                 task_unlock(current);
 652         }
 653         putname(filename);
 654         return error;
 655 }
 656
 657 void set_personality_64bit(void)
 658 {
 659         /* inherit personality from parent */
 660
 661         /* Make sure to be in 64bit mode */
 662         clear_thread_flag(TIF_IA32);
 663
 664         /* TBD: overwrites user setup. Should have two bits.
 665            But 64bit processes have always behaved this way,
 666            so it's not too bad. The main problem is just that
 667            32bit childs are affected again. */
 668         current->personality &= ~READ_IMPLIES_EXEC;
 669 }
 670
 671 asmlinkage long sys_fork(struct pt_regs *regs)
 672 {
 673         return do_fork(SIGCHLD, regs->rsp, regs, 0, NULL, NULL);
 674 }
 675
 676 asmlinkage long
 677 sys_clone(unsigned long clone_flags, unsigned long newsp,
 678           void __user *parent_tid, void __user *child_tid, struct pt_regs *regs)
 679 {
 680         if (!newsp)
 681                 newsp = regs->rsp;
 682         return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 683 }
 684
 685 /*
 686  * This is trivial, and on the face of it looks like it
 687  * could equally well be done in user mode.
 688  *
 689  * Not so, for quite unobvious reasons - register pressure.
 690  * In user mode vfork() cannot have a stack frame, and if
 691  * done by calling the "clone()" system call directly, you
 692  * do not have enough call-clobbered registers to hold all
 693  * the information you need.
 694  */
 695 asmlinkage long sys_vfork(struct pt_regs *regs)
 696 {
 697         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->rsp, regs, 0,
 698                     NULL, NULL);
 699 }
 700
 701 unsigned long get_wchan(struct task_struct *p)
 702 {
 703         unsigned long stack;
 704         u64 fp,rip;
 705         int count = 0;
 706
 707         if (!p || p == current || p->state==TASK_RUNNING)
 708                 return 0;
 709         stack = (unsigned long)task_stack_page(p);
 710         if (p->thread.rsp < stack || p->thread.rsp > stack+THREAD_SIZE)
 711                 return 0;
 712         fp = *(u64 *)(p->thread.rsp);
 713         do {
 714                 if (fp < (unsigned long)stack ||
 715                     fp > (unsigned long)stack+THREAD_SIZE)
 716                         return 0;
 717                 rip = *(u64 *)(fp+8);
 718                 if (!in_sched_functions(rip))
 719                         return rip;
 720                 fp = *(u64 *)fp;
 721         } while (count++ < 16);
 722         return 0;
 723 }
 724
 725 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 726 {
 727         int ret = 0;
 728         int doit = task == current;
 729         int cpu;
 730
 731         switch (code) {
 732         case ARCH_SET_GS:
 733                 if (addr >= TASK_SIZE_OF(task))
 734                         return -EPERM;
 735                 cpu = get_cpu();
 736                 /* handle small bases via the GDT because that's faster to
 737                    switch. */
 738                 if (addr <= 0xffffffff) {
 739                         set_32bit_tls(task, GS_TLS, addr);
 740                         if (doit) {
 741                                 load_TLS(&task->thread, cpu);
 742                                 load_gs_index(GS_TLS_SEL);
 743                         }
 744                         task->thread.gsindex = GS_TLS_SEL;
 745                         task->thread.gs = 0;
 746                 } else {
 747                         task->thread.gsindex = 0;
 748                         task->thread.gs = addr;
 749                         if (doit) {
 750                                 load_gs_index(0);
 751                                 ret = checking_wrmsrl(MSR_KERNEL_GS_BASE, addr);
 752                         }
 753                 }
 754                 put_cpu();
 755                 break;
 756         case ARCH_SET_FS:
 757                 /* Not strictly needed for fs, but do it for symmetry
 758                    with gs */
 759                 if (addr >= TASK_SIZE_OF(task))
 760                         return -EPERM;
 761                 cpu = get_cpu();
 762                 /* handle small bases via the GDT because that's faster to
 763                    switch. */
 764                 if (addr <= 0xffffffff) {
 765                         set_32bit_tls(task, FS_TLS, addr);
 766                         if (doit) {
 767                                 load_TLS(&task->thread, cpu);
 768                                 asm volatile("movl %0,%%fs" :: "r"(FS_TLS_SEL));
 769                         }
 770                         task->thread.fsindex = FS_TLS_SEL;
 771                         task->thread.fs = 0;
 772                 } else {
 773                         task->thread.fsindex = 0;
 774                         task->thread.fs = addr;
 775                         if (doit) {
 776                                 /* set the selector to 0 to not confuse
 777                                    __switch_to */
 778                                 asm volatile("movl %0,%%fs" :: "r" (0));
 779                                 ret = checking_wrmsrl(MSR_FS_BASE, addr);
 780                         }
 781                 }
 782                 put_cpu();
 783                 break;
 784         case ARCH_GET_FS: {
 785                 unsigned long base;
 786                 if (task->thread.fsindex == FS_TLS_SEL)
 787                         base = read_32bit_tls(task, FS_TLS);
 788                 else if (doit)
 789                         rdmsrl(MSR_FS_BASE, base);
 790                 else
 791                         base = task->thread.fs;
 792                 ret = put_user(base, (unsigned long __user *)addr);
 793                 break;
 794         }
 795         case ARCH_GET_GS: {
 796                 unsigned long base;
 797                 if (task->thread.gsindex == GS_TLS_SEL)
 798                         base = read_32bit_tls(task, GS_TLS);
 799                 else if (doit)
 800                         rdmsrl(MSR_KERNEL_GS_BASE, base);
 801                 else
 802                         base = task->thread.gs;
 803                 ret = put_user(base, (unsigned long __user *)addr);
 804                 break;
 805         }
 806
 807         default:
 808                 ret = -EINVAL;
 809                 break;
 810         }
 811
 812         return ret;
 813 }
 814
 815 long sys_arch_prctl(int code, unsigned long addr)
 816 {
 817         return do_arch_prctl(current, code, addr);
 818 }
 819
 820 /*
 821  * Capture the user space registers if the task is not running (in user space)
 822  */
 823 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 824 {
 825         struct pt_regs *pp, ptregs;
 826
 827         pp = task_pt_regs(tsk);
 828
 829         ptregs = *pp;
 830         ptregs.cs &= 0xffff;
 831         ptregs.ss &= 0xffff;
 832
 833         elf_core_copy_regs(regs, &ptregs);
 834
 835         return 1;
 836 }
 837
 838 unsigned long arch_align_stack(unsigned long sp)
 839 {
 840         if (randomize_va_space)
 841                 sp -= get_random_int() % 8192;
 842         return sp & ~0xf;
 843 }