arch/i386/kernel/process.c

   1 /*
   2  *  linux/arch/i386/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
  10 /*
  11  * This file handles the architecture-dependent parts of process handling..
  12  */
  13
  14 #include <stdarg.h>
  15
  16 #include <linux/cpu.h>
  17 #include <linux/errno.h>
  18 #include <linux/sched.h>
  19 #include <linux/fs.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/elfcore.h>
  23 #include <linux/smp.h>
  24 #include <linux/smp_lock.h>
  25 #include <linux/stddef.h>
  26 #include <linux/slab.h>
  27 #include <linux/vmalloc.h>
  28 #include <linux/user.h>
  29 #include <linux/a.out.h>
  30 #include <linux/interrupt.h>
  31 #include <linux/config.h>
  32 #include <linux/utsname.h>
  33 #include <linux/delay.h>
  34 #include <linux/reboot.h>
  35 #include <linux/init.h>
  36 #include <linux/mc146818rtc.h>
  37 #include <linux/module.h>
  38 #include <linux/kallsyms.h>
  39 #include <linux/ptrace.h>
  40 #include <linux/random.h>
  41 #include <linux/kprobes.h>
  42
  43 #include <asm/uaccess.h>
  44 #include <asm/pgtable.h>
  45 #include <asm/system.h>
  46 #include <asm/io.h>
  47 #include <asm/ldt.h>
  48 #include <asm/processor.h>
  49 #include <asm/i387.h>
  50 #include <asm/desc.h>
  51 #ifdef CONFIG_MATH_EMULATION
  52 #include <asm/math_emu.h>
  53 #endif
  54
  55 #include <linux/err.h>
  56
  57 #include <asm/tlbflush.h>
  58 #include <asm/cpu.h>
  59
  60 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
  61
  62 static int hlt_counter;
  63
  64 unsigned long boot_option_idle_override = 0;
  65 EXPORT_SYMBOL(boot_option_idle_override);
  66
  67 /*
  68  * Return saved PC of a blocked thread.
  69  */
  70 unsigned long thread_saved_pc(struct task_struct *tsk)
  71 {
  72         return ((unsigned long *)tsk->thread.esp)[3];
  73 }
  74
  75 /*
  76  * Powermanagement idle function, if any..
  77  */
  78 void (*pm_idle)(void);
  79 EXPORT_SYMBOL(pm_idle);
  80 static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
  81
  82 void disable_hlt(void)
  83 {
  84         hlt_counter++;
  85 }
  86
  87 EXPORT_SYMBOL(disable_hlt);
  88
  89 void enable_hlt(void)
  90 {
  91         hlt_counter--;
  92 }
  93
  94 EXPORT_SYMBOL(enable_hlt);
  95
  96 /*
  97  * We use this if we don't have any better
  98  * idle routine..
  99  */
 100 void default_idle(void)
 101 {
 102         local_irq_enable();
 103
 104         if (!hlt_counter && boot_cpu_data.hlt_works_ok) {
 105                 clear_thread_flag(TIF_POLLING_NRFLAG);
 106                 smp_mb__after_clear_bit();
 107                 while (!need_resched()) {
 108                         local_irq_disable();
 109                         if (!need_resched())
 110                                 safe_halt();
 111                         else
 112                                 local_irq_enable();
 113                 }
 114                 set_thread_flag(TIF_POLLING_NRFLAG);
 115         } else {
 116                 while (!need_resched())
 117                         cpu_relax();
 118         }
 119 }
 120 #ifdef CONFIG_APM_MODULE
 121 EXPORT_SYMBOL(default_idle);
 122 #endif
 123
 124 /*
 125  * On SMP it's slightly faster (but much more power-consuming!)
 126  * to poll the ->work.need_resched flag instead of waiting for the
 127  * cross-CPU IPI to arrive. Use this option with caution.
 128  */
 129 static void poll_idle (void)
 130 {
 131         local_irq_enable();
 132
 133         asm volatile(
 134                 "2:"
 135                 "testl %0, %1;"
 136                 "rep; nop;"
 137                 "je 2b;"
 138                 : : "i"(_TIF_NEED_RESCHED), "m" (current_thread_info()->flags));
 139 }
 140
 141 #ifdef CONFIG_HOTPLUG_CPU
 142 #include <asm/nmi.h>
 143 /* We don't actually take CPU down, just spin without interrupts. */
 144 static inline void play_dead(void)
 145 {
 146         /* This must be done before dead CPU ack */
 147         cpu_exit_clear();
 148         wbinvd();
 149         mb();
 150         /* Ack it */
 151         __get_cpu_var(cpu_state) = CPU_DEAD;
 152
 153         /*
 154          * With physical CPU hotplug, we should halt the cpu
 155          */
 156         local_irq_disable();
 157         while (1)
 158                 halt();
 159 }
 160 #else
 161 static inline void play_dead(void)
 162 {
 163         BUG();
 164 }
 165 #endif /* CONFIG_HOTPLUG_CPU */
 166
 167 /*
 168  * The idle thread. There's no useful work to be
 169  * done, so just try to conserve power and have a
 170  * low exit latency (ie sit in a loop waiting for
 171  * somebody to say that they'd like to reschedule)
 172  */
 173 void cpu_idle(void)
 174 {
 175         int cpu = smp_processor_id();
 176
 177         set_thread_flag(TIF_POLLING_NRFLAG);
 178
 179         /* endless idle loop with no priority at all */
 180         while (1) {
 181                 while (!need_resched()) {
 182                         void (*idle)(void);
 183
 184                         if (__get_cpu_var(cpu_idle_state))
 185                                 __get_cpu_var(cpu_idle_state) = 0;
 186
 187                         rmb();
 188                         idle = pm_idle;
 189
 190                         if (!idle)
 191                                 idle = default_idle;
 192
 193                         if (cpu_is_offline(cpu))
 194                                 play_dead();
 195
 196                         __get_cpu_var(irq_stat).idle_timestamp = jiffies;
 197                         idle();
 198                 }
 199                 preempt_enable_no_resched();
 200                 schedule();
 201                 preempt_disable();
 202         }
 203 }
 204
 205 void cpu_idle_wait(void)
 206 {
 207         unsigned int cpu, this_cpu = get_cpu();
 208         cpumask_t map;
 209
 210         set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
 211         put_cpu();
 212
 213         cpus_clear(map);
 214         for_each_online_cpu(cpu) {
 215                 per_cpu(cpu_idle_state, cpu) = 1;
 216                 cpu_set(cpu, map);
 217         }
 218
 219         __get_cpu_var(cpu_idle_state) = 0;
 220
 221         wmb();
 222         do {
 223                 ssleep(1);
 224                 for_each_online_cpu(cpu) {
 225                         if (cpu_isset(cpu, map) && !per_cpu(cpu_idle_state, cpu))
 226                                 cpu_clear(cpu, map);
 227                 }
 228                 cpus_and(map, map, cpu_online_map);
 229         } while (!cpus_empty(map));
 230 }
 231 EXPORT_SYMBOL_GPL(cpu_idle_wait);
 232
 233 /*
 234  * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
 235  * which can obviate IPI to trigger checking of need_resched.
 236  * We execute MONITOR against need_resched and enter optimized wait state
 237  * through MWAIT. Whenever someone changes need_resched, we would be woken
 238  * up from MWAIT (without an IPI).
 239  */
 240 static void mwait_idle(void)
 241 {
 242         local_irq_enable();
 243
 244         while (!need_resched()) {
 245                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 246                 smp_mb();
 247                 if (need_resched())
 248                         break;
 249                 __mwait(0, 0);
 250         }
 251 }
 252
 253 void __devinit select_idle_routine(const struct cpuinfo_x86 *c)
 254 {
 255         if (cpu_has(c, X86_FEATURE_MWAIT)) {
 256                 printk("monitor/mwait feature present.\n");
 257                 /*
 258                  * Skip, if setup has overridden idle.
 259                  * One CPU supports mwait => All CPUs supports mwait
 260                  */
 261                 if (!pm_idle) {
 262                         printk("using mwait in idle threads.\n");
 263                         pm_idle = mwait_idle;
 264                 }
 265         }
 266 }
 267
 268 static int __init idle_setup (char *str)
 269 {
 270         if (!strncmp(str, "poll", 4)) {
 271                 printk("using polling idle threads.\n");
 272                 pm_idle = poll_idle;
 273 #ifdef CONFIG_X86_SMP
 274                 if (smp_num_siblings > 1)
 275                         printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
 276 #endif
 277         } else if (!strncmp(str, "halt", 4)) {
 278                 printk("using halt in idle threads.\n");
 279                 pm_idle = default_idle;
 280         }
 281
 282         boot_option_idle_override = 1;
 283         return 1;
 284 }
 285
 286 __setup("idle=", idle_setup);
 287
 288 void show_regs(struct pt_regs * regs)
 289 {
 290         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
 291
 292         printk("\n");
 293         printk("Pid: %d, comm: %20s\n", current->pid, current->comm);
 294         printk("EIP: %04x:[<%08lx>] CPU: %d\n",0xffff & regs->xcs,regs->eip, smp_processor_id());
 295         print_symbol("EIP is at %s\n", regs->eip);
 296
 297         if (user_mode(regs))
 298                 printk(" ESP: %04x:%08lx",0xffff & regs->xss,regs->esp);
 299         printk(" EFLAGS: %08lx    %s  (%s)\n",
 300                regs->eflags, print_tainted(), system_utsname.release);
 301         printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
 302                 regs->eax,regs->ebx,regs->ecx,regs->edx);
 303         printk("ESI: %08lx EDI: %08lx EBP: %08lx",
 304                 regs->esi, regs->edi, regs->ebp);
 305         printk(" DS: %04x ES: %04x\n",
 306                 0xffff & regs->xds,0xffff & regs->xes);
 307
 308         cr0 = read_cr0();
 309         cr2 = read_cr2();
 310         cr3 = read_cr3();
 311         cr4 = read_cr4_safe();
 312         printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
 313         show_trace(NULL, &regs->esp);
 314 }
 315
 316 /*
 317  * This gets run with %ebx containing the
 318  * function to call, and %edx containing
 319  * the "args".
 320  */
 321 extern void kernel_thread_helper(void);
 322 __asm__(".section .text\n"
 323         ".align 4\n"
 324         "kernel_thread_helper:\n\t"
 325         "movl %edx,%eax\n\t"
 326         "pushl %edx\n\t"
 327         "call *%ebx\n\t"
 328         "pushl %eax\n\t"
 329         "call do_exit\n"
 330         ".previous");
 331
 332 /*
 333  * Create a kernel thread
 334  */
 335 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 336 {
 337         struct pt_regs regs;
 338
 339         memset(&regs, 0, sizeof(regs));
 340
 341         regs.ebx = (unsigned long) fn;
 342         regs.edx = (unsigned long) arg;
 343
 344         regs.xds = __USER_DS;
 345         regs.xes = __USER_DS;
 346         regs.orig_eax = -1;
 347         regs.eip = (unsigned long) kernel_thread_helper;
 348         regs.xcs = __KERNEL_CS;
 349         regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
 350
 351         /* Ok, create the new process.. */
 352         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 353 }
 354 EXPORT_SYMBOL(kernel_thread);
 355
 356 /*
 357  * Free current thread data structures etc..
 358  */
 359 void exit_thread(void)
 360 {
 361         struct task_struct *tsk = current;
 362         struct thread_struct *t = &tsk->thread;
 363
 364         /*
 365          * Remove function-return probe instances associated with this task
 366          * and put them back on the free list. Do not insert an exit probe for
 367          * this function, it will be disabled by kprobe_flush_task if you do.
 368          */
 369         kprobe_flush_task(tsk);
 370
 371         /* The process may have allocated an io port bitmap... nuke it. */
 372         if (unlikely(NULL != t->io_bitmap_ptr)) {
 373                 int cpu = get_cpu();
 374                 struct tss_struct *tss = &per_cpu(init_tss, cpu);
 375
 376                 kfree(t->io_bitmap_ptr);
 377                 t->io_bitmap_ptr = NULL;
 378                 /*
 379                  * Careful, clear this in the TSS too:
 380                  */
 381                 memset(tss->io_bitmap, 0xff, tss->io_bitmap_max);
 382                 t->io_bitmap_max = 0;
 383                 tss->io_bitmap_owner = NULL;
 384                 tss->io_bitmap_max = 0;
 385                 tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
 386                 put_cpu();
 387         }
 388 }
 389
 390 void flush_thread(void)
 391 {
 392         struct task_struct *tsk = current;
 393
 394         memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
 395         memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 396         /*
 397          * Forget coprocessor state..
 398          */
 399         clear_fpu(tsk);
 400         clear_used_math();
 401 }
 402
 403 void release_thread(struct task_struct *dead_task)
 404 {
 405         if (dead_task->mm) {
 406                 // temporary debugging check
 407                 if (dead_task->mm->context.size) {
 408                         printk("WARNING: dead process %8s still has LDT? <%p/%d>\n",
 409                                         dead_task->comm,
 410                                         dead_task->mm->context.ldt,
 411                                         dead_task->mm->context.size);
 412                         BUG();
 413                 }
 414         }
 415
 416         release_vm86_irqs(dead_task);
 417 }
 418
 419 /*
 420  * This gets called before we allocate a new thread and copy
 421  * the current task into it.
 422  */
 423 void prepare_to_copy(struct task_struct *tsk)
 424 {
 425         unlazy_fpu(tsk);
 426 }
 427
 428 int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
 429         unsigned long unused,
 430         struct task_struct * p, struct pt_regs * regs)
 431 {
 432         struct pt_regs * childregs;
 433         struct task_struct *tsk;
 434         int err;
 435
 436         childregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) p->thread_info)) - 1;
 437         /*
 438          * The below -8 is to reserve 8 bytes on top of the ring0 stack.
 439          * This is necessary to guarantee that the entire "struct pt_regs"
 440          * is accessable even if the CPU haven't stored the SS/ESP registers
 441          * on the stack (interrupt gate does not save these registers
 442          * when switching to the same priv ring).
 443          * Therefore beware: accessing the xss/esp fields of the
 444          * "struct pt_regs" is possible, but they may contain the
 445          * completely wrong values.
 446          */
 447         childregs = (struct pt_regs *) ((unsigned long) childregs - 8);
 448         *childregs = *regs;
 449         childregs->eax = 0;
 450         childregs->esp = esp;
 451
 452         p->thread.esp = (unsigned long) childregs;
 453         p->thread.esp0 = (unsigned long) (childregs+1);
 454
 455         p->thread.eip = (unsigned long) ret_from_fork;
 456
 457         savesegment(fs,p->thread.fs);
 458         savesegment(gs,p->thread.gs);
 459
 460         tsk = current;
 461         if (unlikely(NULL != tsk->thread.io_bitmap_ptr)) {
 462                 p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 463                 if (!p->thread.io_bitmap_ptr) {
 464                         p->thread.io_bitmap_max = 0;
 465                         return -ENOMEM;
 466                 }
 467                 memcpy(p->thread.io_bitmap_ptr, tsk->thread.io_bitmap_ptr,
 468                         IO_BITMAP_BYTES);
 469         }
 470
 471         /*
 472          * Set a new TLS for the child thread?
 473          */
 474         if (clone_flags & CLONE_SETTLS) {
 475                 struct desc_struct *desc;
 476                 struct user_desc info;
 477                 int idx;
 478
 479                 err = -EFAULT;
 480                 if (copy_from_user(&info, (void __user *)childregs->esi, sizeof(info)))
 481                         goto out;
 482                 err = -EINVAL;
 483                 if (LDT_empty(&info))
 484                         goto out;
 485
 486                 idx = info.entry_number;
 487                 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 488                         goto out;
 489
 490                 desc = p->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 491                 desc->a = LDT_entry_a(&info);
 492                 desc->b = LDT_entry_b(&info);
 493         }
 494
 495         err = 0;
 496  out:
 497         if (err && p->thread.io_bitmap_ptr) {
 498                 kfree(p->thread.io_bitmap_ptr);
 499                 p->thread.io_bitmap_max = 0;
 500         }
 501         return err;
 502 }
 503
 504 /*
 505  * fill in the user structure for a core dump..
 506  */
 507 void dump_thread(struct pt_regs * regs, struct user * dump)
 508 {
 509         int i;
 510
 511 /* changed the size calculations - should hopefully work better. lbt */
 512         dump->magic = CMAGIC;
 513         dump->start_code = 0;
 514         dump->start_stack = regs->esp & ~(PAGE_SIZE - 1);
 515         dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
 516         dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
 517         dump->u_dsize -= dump->u_tsize;
 518         dump->u_ssize = 0;
 519         for (i = 0; i < 8; i++)
 520                 dump->u_debugreg[i] = current->thread.debugreg[i];
 521
 522         if (dump->start_stack < TASK_SIZE)
 523                 dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
 524
 525         dump->regs.ebx = regs->ebx;
 526         dump->regs.ecx = regs->ecx;
 527         dump->regs.edx = regs->edx;
 528         dump->regs.esi = regs->esi;
 529         dump->regs.edi = regs->edi;
 530         dump->regs.ebp = regs->ebp;
 531         dump->regs.eax = regs->eax;
 532         dump->regs.ds = regs->xds;
 533         dump->regs.es = regs->xes;
 534         savesegment(fs,dump->regs.fs);
 535         savesegment(gs,dump->regs.gs);
 536         dump->regs.orig_eax = regs->orig_eax;
 537         dump->regs.eip = regs->eip;
 538         dump->regs.cs = regs->xcs;
 539         dump->regs.eflags = regs->eflags;
 540         dump->regs.esp = regs->esp;
 541         dump->regs.ss = regs->xss;
 542
 543         dump->u_fpvalid = dump_fpu (regs, &dump->i387);
 544 }
 545 EXPORT_SYMBOL(dump_thread);
 546
 547 /*
 548  * Capture the user space registers if the task is not running (in user space)
 549  */
 550 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 551 {
 552         struct pt_regs ptregs;
 553
 554         ptregs = *(struct pt_regs *)
 555                 ((unsigned long)tsk->thread_info +
 556                 /* see comments in copy_thread() about -8 */
 557                 THREAD_SIZE - sizeof(ptregs) - 8);
 558         ptregs.xcs &= 0xffff;
 559         ptregs.xds &= 0xffff;
 560         ptregs.xes &= 0xffff;
 561         ptregs.xss &= 0xffff;
 562
 563         elf_core_copy_regs(regs, &ptregs);
 564
 565         return 1;
 566 }
 567
 568 static inline void
 569 handle_io_bitmap(struct thread_struct *next, struct tss_struct *tss)
 570 {
 571         if (!next->io_bitmap_ptr) {
 572                 /*
 573                  * Disable the bitmap via an invalid offset. We still cache
 574                  * the previous bitmap owner and the IO bitmap contents:
 575                  */
 576                 tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
 577                 return;
 578         }
 579         if (likely(next == tss->io_bitmap_owner)) {
 580                 /*
 581                  * Previous owner of the bitmap (hence the bitmap content)
 582                  * matches the next task, we dont have to do anything but
 583                  * to set a valid offset in the TSS:
 584                  */
 585                 tss->io_bitmap_base = IO_BITMAP_OFFSET;
 586                 return;
 587         }
 588         /*
 589          * Lazy TSS's I/O bitmap copy. We set an invalid offset here
 590          * and we let the task to get a GPF in case an I/O instruction
 591          * is performed.  The handler of the GPF will verify that the
 592          * faulting task has a valid I/O bitmap and, it true, does the
 593          * real copy and restart the instruction.  This will save us
 594          * redundant copies when the currently switched task does not
 595          * perform any I/O during its timeslice.
 596          */
 597         tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
 598 }
 599
 600 /*
 601  * This function selects if the context switch from prev to next
 602  * has to tweak the TSC disable bit in the cr4.
 603  */
 604 static inline void disable_tsc(struct task_struct *prev_p,
 605                                struct task_struct *next_p)
 606 {
 607         struct thread_info *prev, *next;
 608
 609         /*
 610          * gcc should eliminate the ->thread_info dereference if
 611          * has_secure_computing returns 0 at compile time (SECCOMP=n).
 612          */
 613         prev = prev_p->thread_info;
 614         next = next_p->thread_info;
 615
 616         if (has_secure_computing(prev) || has_secure_computing(next)) {
 617                 /* slow path here */
 618                 if (has_secure_computing(prev) &&
 619                     !has_secure_computing(next)) {
 620                         write_cr4(read_cr4() & ~X86_CR4_TSD);
 621                 } else if (!has_secure_computing(prev) &&
 622                            has_secure_computing(next))
 623                         write_cr4(read_cr4() | X86_CR4_TSD);
 624         }
 625 }
 626
 627 /*
 628  *      switch_to(x,yn) should switch tasks from x to y.
 629  *
 630  * We fsave/fwait so that an exception goes off at the right time
 631  * (as a call from the fsave or fwait in effect) rather than to
 632  * the wrong process. Lazy FP saving no longer makes any sense
 633  * with modern CPU's, and this simplifies a lot of things (SMP
 634  * and UP become the same).
 635  *
 636  * NOTE! We used to use the x86 hardware context switching. The
 637  * reason for not using it any more becomes apparent when you
 638  * try to recover gracefully from saved state that is no longer
 639  * valid (stale segment register values in particular). With the
 640  * hardware task-switch, there is no way to fix up bad state in
 641  * a reasonable manner.
 642  *
 643  * The fact that Intel documents the hardware task-switching to
 644  * be slow is a fairly red herring - this code is not noticeably
 645  * faster. However, there _is_ some room for improvement here,
 646  * so the performance issues may eventually be a valid point.
 647  * More important, however, is the fact that this allows us much
 648  * more flexibility.
 649  *
 650  * The return value (in %eax) will be the "prev" task after
 651  * the task-switch, and shows up in ret_from_fork in entry.S,
 652  * for example.
 653  */
 654 struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 655 {
 656         struct thread_struct *prev = &prev_p->thread,
 657                                  *next = &next_p->thread;
 658         int cpu = smp_processor_id();
 659         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 660
 661         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 662
 663         __unlazy_fpu(prev_p);
 664
 665         /*
 666          * Reload esp0.
 667          */
 668         load_esp0(tss, next);
 669
 670         /*
 671          * Save away %fs and %gs. No need to save %es and %ds, as
 672          * those are always kernel segments while inside the kernel.
 673          * Doing this before setting the new TLS descriptors avoids
 674          * the situation where we temporarily have non-reloadable
 675          * segments in %fs and %gs.  This could be an issue if the
 676          * NMI handler ever used %fs or %gs (it does not today), or
 677          * if the kernel is running inside of a hypervisor layer.
 678          */
 679         savesegment(fs, prev->fs);
 680         savesegment(gs, prev->gs);
 681
 682         /*
 683          * Load the per-thread Thread-Local Storage descriptor.
 684          */
 685         load_TLS(next, cpu);
 686
 687         /*
 688          * Restore %fs and %gs if needed.
 689          *
 690          * Glibc normally makes %fs be zero, and %gs is one of
 691          * the TLS segments.
 692          */
 693         if (unlikely(prev->fs | next->fs))
 694                 loadsegment(fs, next->fs);
 695
 696         if (prev->gs | next->gs)
 697                 loadsegment(gs, next->gs);
 698
 699         /*
 700          * Restore IOPL if needed.
 701          */
 702         if (unlikely(prev->iopl != next->iopl))
 703                 set_iopl_mask(next->iopl);
 704
 705         /*
 706          * Now maybe reload the debug registers
 707          */
 708         if (unlikely(next->debugreg[7])) {
 709                 set_debugreg(next->debugreg[0], 0);
 710                 set_debugreg(next->debugreg[1], 1);
 711                 set_debugreg(next->debugreg[2], 2);
 712                 set_debugreg(next->debugreg[3], 3);
 713                 /* no 4 and 5 */
 714                 set_debugreg(next->debugreg[6], 6);
 715                 set_debugreg(next->debugreg[7], 7);
 716         }
 717
 718         if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr))
 719                 handle_io_bitmap(next, tss);
 720
 721         disable_tsc(prev_p, next_p);
 722
 723         return prev_p;
 724 }
 725
 726 asmlinkage int sys_fork(struct pt_regs regs)
 727 {
 728         return do_fork(SIGCHLD, regs.esp, &regs, 0, NULL, NULL);
 729 }
 730
 731 asmlinkage int sys_clone(struct pt_regs regs)
 732 {
 733         unsigned long clone_flags;
 734         unsigned long newsp;
 735         int __user *parent_tidptr, *child_tidptr;
 736
 737         clone_flags = regs.ebx;
 738         newsp = regs.ecx;
 739         parent_tidptr = (int __user *)regs.edx;
 740         child_tidptr = (int __user *)regs.edi;
 741         if (!newsp)
 742                 newsp = regs.esp;
 743         return do_fork(clone_flags, newsp, &regs, 0, parent_tidptr, child_tidptr);
 744 }
 745
 746 /*
 747  * This is trivial, and on the face of it looks like it
 748  * could equally well be done in user mode.
 749  *
 750  * Not so, for quite unobvious reasons - register pressure.
 751  * In user mode vfork() cannot have a stack frame, and if
 752  * done by calling the "clone()" system call directly, you
 753  * do not have enough call-clobbered registers to hold all
 754  * the information you need.
 755  */
 756 asmlinkage int sys_vfork(struct pt_regs regs)
 757 {
 758         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, &regs, 0, NULL, NULL);
 759 }
 760
 761 /*
 762  * sys_execve() executes a new program.
 763  */
 764 asmlinkage int sys_execve(struct pt_regs regs)
 765 {
 766         int error;
 767         char * filename;
 768
 769         filename = getname((char __user *) regs.ebx);
 770         error = PTR_ERR(filename);
 771         if (IS_ERR(filename))
 772                 goto out;
 773         error = do_execve(filename,
 774                         (char __user * __user *) regs.ecx,
 775                         (char __user * __user *) regs.edx,
 776                         &regs);
 777         if (error == 0) {
 778                 task_lock(current);
 779                 current->ptrace &= ~PT_DTRACE;
 780                 task_unlock(current);
 781                 /* Make sure we don't return using sysenter.. */
 782                 set_thread_flag(TIF_IRET);
 783         }
 784         putname(filename);
 785 out:
 786         return error;
 787 }
 788
 789 #define top_esp                (THREAD_SIZE - sizeof(unsigned long))
 790 #define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
 791
 792 unsigned long get_wchan(struct task_struct *p)
 793 {
 794         unsigned long ebp, esp, eip;
 795         unsigned long stack_page;
 796         int count = 0;
 797         if (!p || p == current || p->state == TASK_RUNNING)
 798                 return 0;
 799         stack_page = (unsigned long)p->thread_info;
 800         esp = p->thread.esp;
 801         if (!stack_page || esp < stack_page || esp > top_esp+stack_page)
 802                 return 0;
 803         /* include/asm-i386/system.h:switch_to() pushes ebp last. */
 804         ebp = *(unsigned long *) esp;
 805         do {
 806                 if (ebp < stack_page || ebp > top_ebp+stack_page)
 807                         return 0;
 808                 eip = *(unsigned long *) (ebp+4);
 809                 if (!in_sched_functions(eip))
 810                         return eip;
 811                 ebp = *(unsigned long *) ebp;
 812         } while (count++ < 16);
 813         return 0;
 814 }
 815 EXPORT_SYMBOL(get_wchan);
 816
 817 /*
 818  * sys_alloc_thread_area: get a yet unused TLS descriptor index.
 819  */
 820 static int get_free_idx(void)
 821 {
 822         struct thread_struct *t = &current->thread;
 823         int idx;
 824
 825         for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
 826                 if (desc_empty(t->tls_array + idx))
 827                         return idx + GDT_ENTRY_TLS_MIN;
 828         return -ESRCH;
 829 }
 830
 831 /*
 832  * Set a given TLS descriptor:
 833  */
 834 asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
 835 {
 836         struct thread_struct *t = &current->thread;
 837         struct user_desc info;
 838         struct desc_struct *desc;
 839         int cpu, idx;
 840
 841         if (copy_from_user(&info, u_info, sizeof(info)))
 842                 return -EFAULT;
 843         idx = info.entry_number;
 844
 845         /*
 846          * index -1 means the kernel should try to find and
 847          * allocate an empty descriptor:
 848          */
 849         if (idx == -1) {
 850                 idx = get_free_idx();
 851                 if (idx < 0)
 852                         return idx;
 853                 if (put_user(idx, &u_info->entry_number))
 854                         return -EFAULT;
 855         }
 856
 857         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 858                 return -EINVAL;
 859
 860         desc = t->tls_array + idx - GDT_ENTRY_TLS_MIN;
 861
 862         /*
 863          * We must not get preempted while modifying the TLS.
 864          */
 865         cpu = get_cpu();
 866
 867         if (LDT_empty(&info)) {
 868                 desc->a = 0;
 869                 desc->b = 0;
 870         } else {
 871                 desc->a = LDT_entry_a(&info);
 872                 desc->b = LDT_entry_b(&info);
 873         }
 874         load_TLS(t, cpu);
 875
 876         put_cpu();
 877
 878         return 0;
 879 }
 880
 881 /*
 882  * Get the current Thread-Local Storage area:
 883  */
 884
 885 #define GET_BASE(desc) ( \
 886         (((desc)->a >> 16) & 0x0000ffff) | \
 887         (((desc)->b << 16) & 0x00ff0000) | \
 888         ( (desc)->b        & 0xff000000)   )
 889
 890 #define GET_LIMIT(desc) ( \
 891         ((desc)->a & 0x0ffff) | \
 892          ((desc)->b & 0xf0000) )
 893
 894 #define GET_32BIT(desc)         (((desc)->b >> 22) & 1)
 895 #define GET_CONTENTS(desc)      (((desc)->b >> 10) & 3)
 896 #define GET_WRITABLE(desc)      (((desc)->b >>  9) & 1)
 897 #define GET_LIMIT_PAGES(desc)   (((desc)->b >> 23) & 1)
 898 #define GET_PRESENT(desc)       (((desc)->b >> 15) & 1)
 899 #define GET_USEABLE(desc)       (((desc)->b >> 20) & 1)
 900
 901 asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
 902 {
 903         struct user_desc info;
 904         struct desc_struct *desc;
 905         int idx;
 906
 907         if (get_user(idx, &u_info->entry_number))
 908                 return -EFAULT;
 909         if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
 910                 return -EINVAL;
 911
 912         memset(&info, 0, sizeof(info));
 913
 914         desc = current->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
 915
 916         info.entry_number = idx;
 917         info.base_addr = GET_BASE(desc);
 918         info.limit = GET_LIMIT(desc);
 919         info.seg_32bit = GET_32BIT(desc);
 920         info.contents = GET_CONTENTS(desc);
 921         info.read_exec_only = !GET_WRITABLE(desc);
 922         info.limit_in_pages = GET_LIMIT_PAGES(desc);
 923         info.seg_not_present = !GET_PRESENT(desc);
 924         info.useable = GET_USEABLE(desc);
 925
 926         if (copy_to_user(u_info, &info, sizeof(info)))
 927                 return -EFAULT;
 928         return 0;
 929 }
 930
 931 unsigned long arch_align_stack(unsigned long sp)
 932 {
 933         if (randomize_va_space)
 934                 sp -= get_random_int() % 8192;
 935         return sp & ~0xf;
 936 }