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