arch/x86/kernel/process_32.c

   1 /*
   2  *  Copyright (C) 1995  Linus Torvalds
   3  *
   4  *  Pentium III FXSR, SSE support
   5  *      Gareth Hughes <gareth@valinux.com>, May 2000
   6  */
   7
   8 /*
   9  * This file handles the architecture-dependent parts of process handling..
  10  */
  11
  12 #include <stdarg.h>
  13
  14 #include <linux/cpu.h>
  15 #include <linux/errno.h>
  16 #include <linux/sched.h>
  17 #include <linux/fs.h>
  18 #include <linux/kernel.h>
  19 #include <linux/mm.h>
  20 #include <linux/elfcore.h>
  21 #include <linux/smp.h>
  22 #include <linux/stddef.h>
  23 #include <linux/slab.h>
  24 #include <linux/vmalloc.h>
  25 #include <linux/user.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/utsname.h>
  28 #include <linux/delay.h>
  29 #include <linux/reboot.h>
  30 #include <linux/init.h>
  31 #include <linux/mc146818rtc.h>
  32 #include <linux/module.h>
  33 #include <linux/kallsyms.h>
  34 #include <linux/ptrace.h>
  35 #include <linux/random.h>
  36 #include <linux/personality.h>
  37 #include <linux/tick.h>
  38 #include <linux/percpu.h>
  39 #include <linux/prctl.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/desc.h>
  49 #ifdef CONFIG_MATH_EMULATION
  50 #include <asm/math_emu.h>
  51 #endif
  52
  53 #include <linux/err.h>
  54
  55 #include <asm/tlbflush.h>
  56 #include <asm/cpu.h>
  57 #include <asm/kdebug.h>
  58
  59 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
  60
  61 static int hlt_counter;
  62
  63 unsigned long boot_option_idle_override = 0;
  64 EXPORT_SYMBOL(boot_option_idle_override);
  65
  66 DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
  67 EXPORT_PER_CPU_SYMBOL(current_task);
  68
  69 DEFINE_PER_CPU(int, cpu_number);
  70 EXPORT_PER_CPU_SYMBOL(cpu_number);
  71
  72 /*
  73  * Return saved PC of a blocked thread.
  74  */
  75 unsigned long thread_saved_pc(struct task_struct *tsk)
  76 {
  77         return ((unsigned long *)tsk->thread.sp)[3];
  78 }
  79
  80 /*
  81  * Powermanagement idle function, if any..
  82  */
  83 void (*pm_idle)(void);
  84 EXPORT_SYMBOL(pm_idle);
  85
  86 void disable_hlt(void)
  87 {
  88         hlt_counter++;
  89 }
  90
  91 EXPORT_SYMBOL(disable_hlt);
  92
  93 void enable_hlt(void)
  94 {
  95         hlt_counter--;
  96 }
  97
  98 EXPORT_SYMBOL(enable_hlt);
  99
 100 /*
 101  * We use this if we don't have any better
 102  * idle routine..
 103  */
 104 void default_idle(void)
 105 {
 106         if (!hlt_counter && boot_cpu_data.hlt_works_ok) {
 107                 current_thread_info()->status &= ~TS_POLLING;
 108                 /*
 109                  * TS_POLLING-cleared state must be visible before we
 110                  * test NEED_RESCHED:
 111                  */
 112                 smp_mb();
 113
 114                 if (!need_resched())
 115                         safe_halt();    /* enables interrupts racelessly */
 116                 else
 117                         local_irq_enable();
 118                 current_thread_info()->status |= TS_POLLING;
 119         } else {
 120                 local_irq_enable();
 121                 /* loop is done by the caller */
 122                 cpu_relax();
 123         }
 124 }
 125 #ifdef CONFIG_APM_MODULE
 126 EXPORT_SYMBOL(default_idle);
 127 #endif
 128
 129 #ifdef CONFIG_HOTPLUG_CPU
 130 #include <asm/nmi.h>
 131 /* We don't actually take CPU down, just spin without interrupts. */
 132 static inline void play_dead(void)
 133 {
 134         /* This must be done before dead CPU ack */
 135         cpu_exit_clear();
 136         wbinvd();
 137         mb();
 138         /* Ack it */
 139         __get_cpu_var(cpu_state) = CPU_DEAD;
 140
 141         /*
 142          * With physical CPU hotplug, we should halt the cpu
 143          */
 144         local_irq_disable();
 145         while (1)
 146                 halt();
 147 }
 148 #else
 149 static inline void play_dead(void)
 150 {
 151         BUG();
 152 }
 153 #endif /* CONFIG_HOTPLUG_CPU */
 154
 155 /*
 156  * The idle thread. There's no useful work to be
 157  * done, so just try to conserve power and have a
 158  * low exit latency (ie sit in a loop waiting for
 159  * somebody to say that they'd like to reschedule)
 160  */
 161 void cpu_idle(void)
 162 {
 163         int cpu = smp_processor_id();
 164
 165         current_thread_info()->status |= TS_POLLING;
 166
 167         /* endless idle loop with no priority at all */
 168         while (1) {
 169                 tick_nohz_stop_sched_tick();
 170                 while (!need_resched()) {
 171                         void (*idle)(void);
 172
 173                         check_pgt_cache();
 174                         rmb();
 175                         idle = pm_idle;
 176
 177                         if (rcu_pending(cpu))
 178                                 rcu_check_callbacks(cpu, 0);
 179
 180                         if (!idle)
 181                                 idle = default_idle;
 182
 183                         if (cpu_is_offline(cpu))
 184                                 play_dead();
 185
 186                         local_irq_disable();
 187                         __get_cpu_var(irq_stat).idle_timestamp = jiffies;
 188                         /* Don't trace irqs off for idle */
 189                         stop_critical_timings();
 190                         idle();
 191                         start_critical_timings();
 192                 }
 193                 tick_nohz_restart_sched_tick();
 194                 preempt_enable_no_resched();
 195                 schedule();
 196                 preempt_disable();
 197         }
 198 }
 199
 200 void __show_registers(struct pt_regs *regs, int all)
 201 {
 202         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
 203         unsigned long d0, d1, d2, d3, d6, d7;
 204         unsigned long sp;
 205         unsigned short ss, gs;
 206
 207         if (user_mode_vm(regs)) {
 208                 sp = regs->sp;
 209                 ss = regs->ss & 0xffff;
 210                 savesegment(gs, gs);
 211         } else {
 212                 sp = (unsigned long) (&regs->sp);
 213                 savesegment(ss, ss);
 214                 savesegment(gs, gs);
 215         }
 216
 217         printk("\n");
 218         printk("Pid: %d, comm: %s %s (%s %.*s)\n",
 219                         task_pid_nr(current), current->comm,
 220                         print_tainted(), init_utsname()->release,
 221                         (int)strcspn(init_utsname()->version, " "),
 222                         init_utsname()->version);
 223
 224         printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
 225                         (u16)regs->cs, regs->ip, regs->flags,
 226                         smp_processor_id());
 227         print_symbol("EIP is at %s\n", regs->ip);
 228
 229         printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
 230                 regs->ax, regs->bx, regs->cx, regs->dx);
 231         printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
 232                 regs->si, regs->di, regs->bp, sp);
 233         printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
 234                (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
 235
 236         if (!all)
 237                 return;
 238
 239         cr0 = read_cr0();
 240         cr2 = read_cr2();
 241         cr3 = read_cr3();
 242         cr4 = read_cr4_safe();
 243         printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
 244                         cr0, cr2, cr3, cr4);
 245
 246         get_debugreg(d0, 0);
 247         get_debugreg(d1, 1);
 248         get_debugreg(d2, 2);
 249         get_debugreg(d3, 3);
 250         printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
 251                         d0, d1, d2, d3);
 252
 253         get_debugreg(d6, 6);
 254         get_debugreg(d7, 7);
 255         printk("DR6: %08lx DR7: %08lx\n",
 256                         d6, d7);
 257 }
 258
 259 void show_regs(struct pt_regs *regs)
 260 {
 261         __show_registers(regs, 1);
 262         show_trace(NULL, regs, &regs->sp, regs->bp);
 263 }
 264
 265 /*
 266  * This gets run with %bx containing the
 267  * function to call, and %dx containing
 268  * the "args".
 269  */
 270 extern void kernel_thread_helper(void);
 271
 272 /*
 273  * Create a kernel thread
 274  */
 275 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 276 {
 277         struct pt_regs regs;
 278
 279         memset(&regs, 0, sizeof(regs));
 280
 281         regs.bx = (unsigned long) fn;
 282         regs.dx = (unsigned long) arg;
 283
 284         regs.ds = __USER_DS;
 285         regs.es = __USER_DS;
 286         regs.fs = __KERNEL_PERCPU;
 287         regs.orig_ax = -1;
 288         regs.ip = (unsigned long) kernel_thread_helper;
 289         regs.cs = __KERNEL_CS | get_kernel_rpl();
 290         regs.flags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
 291
 292         /* Ok, create the new process.. */
 293         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 294 }
 295 EXPORT_SYMBOL(kernel_thread);
 296
 297 /*
 298  * Free current thread data structures etc..
 299  */
 300 void exit_thread(void)
 301 {
 302         /* The process may have allocated an io port bitmap... nuke it. */
 303         if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
 304                 struct task_struct *tsk = current;
 305                 struct thread_struct *t = &tsk->thread;
 306                 int cpu = get_cpu();
 307                 struct tss_struct *tss = &per_cpu(init_tss, cpu);
 308
 309                 kfree(t->io_bitmap_ptr);
 310                 t->io_bitmap_ptr = NULL;
 311                 clear_thread_flag(TIF_IO_BITMAP);
 312                 /*
 313                  * Careful, clear this in the TSS too:
 314                  */
 315                 memset(tss->io_bitmap, 0xff, tss->io_bitmap_max);
 316                 t->io_bitmap_max = 0;
 317                 tss->io_bitmap_owner = NULL;
 318                 tss->io_bitmap_max = 0;
 319                 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
 320                 put_cpu();
 321         }
 322 }
 323
 324 void flush_thread(void)
 325 {
 326         struct task_struct *tsk = current;
 327
 328         tsk->thread.debugreg0 = 0;
 329         tsk->thread.debugreg1 = 0;
 330         tsk->thread.debugreg2 = 0;
 331         tsk->thread.debugreg3 = 0;
 332         tsk->thread.debugreg6 = 0;
 333         tsk->thread.debugreg7 = 0;
 334         memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 335         clear_tsk_thread_flag(tsk, TIF_DEBUG);
 336         /*
 337          * Forget coprocessor state..
 338          */
 339         clear_fpu(tsk);
 340         clear_used_math();
 341 }
 342
 343 void release_thread(struct task_struct *dead_task)
 344 {
 345         BUG_ON(dead_task->mm);
 346         release_vm86_irqs(dead_task);
 347 }
 348
 349 /*
 350  * This gets called before we allocate a new thread and copy
 351  * the current task into it.
 352  */
 353 void prepare_to_copy(struct task_struct *tsk)
 354 {
 355         unlazy_fpu(tsk);
 356 }
 357
 358 int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
 359         unsigned long unused,
 360         struct task_struct * p, struct pt_regs * regs)
 361 {
 362         struct pt_regs * childregs;
 363         struct task_struct *tsk;
 364         int err;
 365
 366         childregs = task_pt_regs(p);
 367         *childregs = *regs;
 368         childregs->ax = 0;
 369         childregs->sp = sp;
 370
 371         p->thread.sp = (unsigned long) childregs;
 372         p->thread.sp0 = (unsigned long) (childregs+1);
 373
 374         p->thread.ip = (unsigned long) ret_from_fork;
 375
 376         savesegment(gs, p->thread.gs);
 377
 378         tsk = current;
 379         if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
 380                 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
 381                                                 IO_BITMAP_BYTES, GFP_KERNEL);
 382                 if (!p->thread.io_bitmap_ptr) {
 383                         p->thread.io_bitmap_max = 0;
 384                         return -ENOMEM;
 385                 }
 386                 set_tsk_thread_flag(p, TIF_IO_BITMAP);
 387         }
 388
 389         err = 0;
 390
 391         /*
 392          * Set a new TLS for the child thread?
 393          */
 394         if (clone_flags & CLONE_SETTLS)
 395                 err = do_set_thread_area(p, -1,
 396                         (struct user_desc __user *)childregs->si, 0);
 397
 398         if (err && p->thread.io_bitmap_ptr) {
 399                 kfree(p->thread.io_bitmap_ptr);
 400                 p->thread.io_bitmap_max = 0;
 401         }
 402         return err;
 403 }
 404
 405 void
 406 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 407 {
 408         __asm__("movl %0, %%gs" :: "r"(0));
 409         regs->fs                = 0;
 410         set_fs(USER_DS);
 411         regs->ds                = __USER_DS;
 412         regs->es                = __USER_DS;
 413         regs->ss                = __USER_DS;
 414         regs->cs                = __USER_CS;
 415         regs->ip                = new_ip;
 416         regs->sp                = new_sp;
 417         /*
 418          * Free the old FP and other extended state
 419          */
 420         free_thread_xstate(current);
 421 }
 422 EXPORT_SYMBOL_GPL(start_thread);
 423
 424 static void hard_disable_TSC(void)
 425 {
 426         write_cr4(read_cr4() | X86_CR4_TSD);
 427 }
 428
 429 void disable_TSC(void)
 430 {
 431         preempt_disable();
 432         if (!test_and_set_thread_flag(TIF_NOTSC))
 433                 /*
 434                  * Must flip the CPU state synchronously with
 435                  * TIF_NOTSC in the current running context.
 436                  */
 437                 hard_disable_TSC();
 438         preempt_enable();
 439 }
 440
 441 static void hard_enable_TSC(void)
 442 {
 443         write_cr4(read_cr4() & ~X86_CR4_TSD);
 444 }
 445
 446 static void enable_TSC(void)
 447 {
 448         preempt_disable();
 449         if (test_and_clear_thread_flag(TIF_NOTSC))
 450                 /*
 451                  * Must flip the CPU state synchronously with
 452                  * TIF_NOTSC in the current running context.
 453                  */
 454                 hard_enable_TSC();
 455         preempt_enable();
 456 }
 457
 458 int get_tsc_mode(unsigned long adr)
 459 {
 460         unsigned int val;
 461
 462         if (test_thread_flag(TIF_NOTSC))
 463                 val = PR_TSC_SIGSEGV;
 464         else
 465                 val = PR_TSC_ENABLE;
 466
 467         return put_user(val, (unsigned int __user *)adr);
 468 }
 469
 470 int set_tsc_mode(unsigned int val)
 471 {
 472         if (val == PR_TSC_SIGSEGV)
 473                 disable_TSC();
 474         else if (val == PR_TSC_ENABLE)
 475                 enable_TSC();
 476         else
 477                 return -EINVAL;
 478
 479         return 0;
 480 }
 481
 482 static noinline void
 483 __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 484                  struct tss_struct *tss)
 485 {
 486         struct thread_struct *prev, *next;
 487         unsigned long debugctl;
 488
 489         prev = &prev_p->thread;
 490         next = &next_p->thread;
 491
 492         debugctl = prev->debugctlmsr;
 493         if (next->ds_area_msr != prev->ds_area_msr) {
 494                 /* we clear debugctl to make sure DS
 495                  * is not in use when we change it */
 496                 debugctl = 0;
 497                 update_debugctlmsr(0);
 498                 wrmsr(MSR_IA32_DS_AREA, next->ds_area_msr, 0);
 499         }
 500
 501         if (next->debugctlmsr != debugctl)
 502                 update_debugctlmsr(next->debugctlmsr);
 503
 504         if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
 505                 set_debugreg(next->debugreg0, 0);
 506                 set_debugreg(next->debugreg1, 1);
 507                 set_debugreg(next->debugreg2, 2);
 508                 set_debugreg(next->debugreg3, 3);
 509                 /* no 4 and 5 */
 510                 set_debugreg(next->debugreg6, 6);
 511                 set_debugreg(next->debugreg7, 7);
 512         }
 513
 514         if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
 515             test_tsk_thread_flag(next_p, TIF_NOTSC)) {
 516                 /* prev and next are different */
 517                 if (test_tsk_thread_flag(next_p, TIF_NOTSC))
 518                         hard_disable_TSC();
 519                 else
 520                         hard_enable_TSC();
 521         }
 522
 523 #ifdef X86_BTS
 524         if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
 525                 ptrace_bts_take_timestamp(prev_p, BTS_TASK_DEPARTS);
 526
 527         if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
 528                 ptrace_bts_take_timestamp(next_p, BTS_TASK_ARRIVES);
 529 #endif
 530
 531
 532         if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
 533                 /*
 534                  * Disable the bitmap via an invalid offset. We still cache
 535                  * the previous bitmap owner and the IO bitmap contents:
 536                  */
 537                 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
 538                 return;
 539         }
 540
 541         if (likely(next == tss->io_bitmap_owner)) {
 542                 /*
 543                  * Previous owner of the bitmap (hence the bitmap content)
 544                  * matches the next task, we dont have to do anything but
 545                  * to set a valid offset in the TSS:
 546                  */
 547                 tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
 548                 return;
 549         }
 550         /*
 551          * Lazy TSS's I/O bitmap copy. We set an invalid offset here
 552          * and we let the task to get a GPF in case an I/O instruction
 553          * is performed.  The handler of the GPF will verify that the
 554          * faulting task has a valid I/O bitmap and, it true, does the
 555          * real copy and restart the instruction.  This will save us
 556          * redundant copies when the currently switched task does not
 557          * perform any I/O during its timeslice.
 558          */
 559         tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
 560 }
 561
 562 /*
 563  *      switch_to(x,yn) should switch tasks from x to y.
 564  *
 565  * We fsave/fwait so that an exception goes off at the right time
 566  * (as a call from the fsave or fwait in effect) rather than to
 567  * the wrong process. Lazy FP saving no longer makes any sense
 568  * with modern CPU's, and this simplifies a lot of things (SMP
 569  * and UP become the same).
 570  *
 571  * NOTE! We used to use the x86 hardware context switching. The
 572  * reason for not using it any more becomes apparent when you
 573  * try to recover gracefully from saved state that is no longer
 574  * valid (stale segment register values in particular). With the
 575  * hardware task-switch, there is no way to fix up bad state in
 576  * a reasonable manner.
 577  *
 578  * The fact that Intel documents the hardware task-switching to
 579  * be slow is a fairly red herring - this code is not noticeably
 580  * faster. However, there _is_ some room for improvement here,
 581  * so the performance issues may eventually be a valid point.
 582  * More important, however, is the fact that this allows us much
 583  * more flexibility.
 584  *
 585  * The return value (in %ax) will be the "prev" task after
 586  * the task-switch, and shows up in ret_from_fork in entry.S,
 587  * for example.
 588  */
 589 struct task_struct * __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 590 {
 591         struct thread_struct *prev = &prev_p->thread,
 592                                  *next = &next_p->thread;
 593         int cpu = smp_processor_id();
 594         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 595
 596         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 597
 598         __unlazy_fpu(prev_p);
 599
 600
 601         /* we're going to use this soon, after a few expensive things */
 602         if (next_p->fpu_counter > 5)
 603                 prefetch(next->xstate);
 604
 605         /*
 606          * Reload esp0.
 607          */
 608         load_sp0(tss, next);
 609
 610         /*
 611          * Save away %gs. No need to save %fs, as it was saved on the
 612          * stack on entry.  No need to save %es and %ds, as those are
 613          * always kernel segments while inside the kernel.  Doing this
 614          * before setting the new TLS descriptors avoids the situation
 615          * where we temporarily have non-reloadable segments in %fs
 616          * and %gs.  This could be an issue if the NMI handler ever
 617          * used %fs or %gs (it does not today), or if the kernel is
 618          * running inside of a hypervisor layer.
 619          */
 620         savesegment(gs, prev->gs);
 621
 622         /*
 623          * Load the per-thread Thread-Local Storage descriptor.
 624          */
 625         load_TLS(next, cpu);
 626
 627         /*
 628          * Restore IOPL if needed.  In normal use, the flags restore
 629          * in the switch assembly will handle this.  But if the kernel
 630          * is running virtualized at a non-zero CPL, the popf will
 631          * not restore flags, so it must be done in a separate step.
 632          */
 633         if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
 634                 set_iopl_mask(next->iopl);
 635
 636         /*
 637          * Now maybe handle debug registers and/or IO bitmaps
 638          */
 639         if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
 640                      task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
 641                 __switch_to_xtra(prev_p, next_p, tss);
 642
 643         /*
 644          * Leave lazy mode, flushing any hypercalls made here.
 645          * This must be done before restoring TLS segments so
 646          * the GDT and LDT are properly updated, and must be
 647          * done before math_state_restore, so the TS bit is up
 648          * to date.
 649          */
 650         arch_leave_lazy_cpu_mode();
 651
 652         /* If the task has used fpu the last 5 timeslices, just do a full
 653          * restore of the math state immediately to avoid the trap; the
 654          * chances of needing FPU soon are obviously high now
 655          */
 656         if (next_p->fpu_counter > 5)
 657                 math_state_restore();
 658
 659         /*
 660          * Restore %gs if needed (which is common)
 661          */
 662         if (prev->gs | next->gs)
 663                 loadsegment(gs, next->gs);
 664
 665         x86_write_percpu(current_task, next_p);
 666
 667         return prev_p;
 668 }
 669
 670 asmlinkage int sys_fork(struct pt_regs regs)
 671 {
 672         return do_fork(SIGCHLD, regs.sp, &regs, 0, NULL, NULL);
 673 }
 674
 675 asmlinkage int sys_clone(struct pt_regs regs)
 676 {
 677         unsigned long clone_flags;
 678         unsigned long newsp;
 679         int __user *parent_tidptr, *child_tidptr;
 680
 681         clone_flags = regs.bx;
 682         newsp = regs.cx;
 683         parent_tidptr = (int __user *)regs.dx;
 684         child_tidptr = (int __user *)regs.di;
 685         if (!newsp)
 686                 newsp = regs.sp;
 687         return do_fork(clone_flags, newsp, &regs, 0, parent_tidptr, child_tidptr);
 688 }
 689
 690 /*
 691  * This is trivial, and on the face of it looks like it
 692  * could equally well be done in user mode.
 693  *
 694  * Not so, for quite unobvious reasons - register pressure.
 695  * In user mode vfork() cannot have a stack frame, and if
 696  * done by calling the "clone()" system call directly, you
 697  * do not have enough call-clobbered registers to hold all
 698  * the information you need.
 699  */
 700 asmlinkage int sys_vfork(struct pt_regs regs)
 701 {
 702         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.sp, &regs, 0, NULL, NULL);
 703 }
 704
 705 /*
 706  * sys_execve() executes a new program.
 707  */
 708 asmlinkage int sys_execve(struct pt_regs regs)
 709 {
 710         int error;
 711         char * filename;
 712
 713         filename = getname((char __user *) regs.bx);
 714         error = PTR_ERR(filename);
 715         if (IS_ERR(filename))
 716                 goto out;
 717         error = do_execve(filename,
 718                         (char __user * __user *) regs.cx,
 719                         (char __user * __user *) regs.dx,
 720                         &regs);
 721         if (error == 0) {
 722                 /* Make sure we don't return using sysenter.. */
 723                 set_thread_flag(TIF_IRET);
 724         }
 725         putname(filename);
 726 out:
 727         return error;
 728 }
 729
 730 #define top_esp                (THREAD_SIZE - sizeof(unsigned long))
 731 #define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
 732
 733 unsigned long get_wchan(struct task_struct *p)
 734 {
 735         unsigned long bp, sp, ip;
 736         unsigned long stack_page;
 737         int count = 0;
 738         if (!p || p == current || p->state == TASK_RUNNING)
 739                 return 0;
 740         stack_page = (unsigned long)task_stack_page(p);
 741         sp = p->thread.sp;
 742         if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
 743                 return 0;
 744         /* include/asm-i386/system.h:switch_to() pushes bp last. */
 745         bp = *(unsigned long *) sp;
 746         do {
 747                 if (bp < stack_page || bp > top_ebp+stack_page)
 748                         return 0;
 749                 ip = *(unsigned long *) (bp+4);
 750                 if (!in_sched_functions(ip))
 751                         return ip;
 752                 bp = *(unsigned long *) bp;
 753         } while (count++ < 16);
 754         return 0;
 755 }
 756
 757 unsigned long arch_align_stack(unsigned long sp)
 758 {
 759         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 760                 sp -= get_random_int() % 8192;
 761         return sp & ~0xf;
 762 }
 763
 764 unsigned long arch_randomize_brk(struct mm_struct *mm)
 765 {
 766         unsigned long range_end = mm->brk + 0x02000000;
 767         return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
 768 }