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 <linux/stackprotector.h>
  13 #include <linux/cpu.h>
  14 #include <linux/errno.h>
  15 #include <linux/sched.h>
  16 #include <linux/fs.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/elfcore.h>
  20 #include <linux/smp.h>
  21 #include <linux/stddef.h>
  22 #include <linux/slab.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/user.h>
  25 #include <linux/interrupt.h>
  26 #include <linux/utsname.h>
  27 #include <linux/delay.h>
  28 #include <linux/reboot.h>
  29 #include <linux/init.h>
  30 #include <linux/mc146818rtc.h>
  31 #include <linux/module.h>
  32 #include <linux/kallsyms.h>
  33 #include <linux/ptrace.h>
  34 #include <linux/personality.h>
  35 #include <linux/tick.h>
  36 #include <linux/percpu.h>
  37 #include <linux/prctl.h>
  38 #include <linux/dmi.h>
  39 #include <linux/ftrace.h>
  40 #include <linux/uaccess.h>
  41 #include <linux/io.h>
  42 #include <linux/kdebug.h>
  43
  44 #include <asm/pgtable.h>
  45 #include <asm/system.h>
  46 #include <asm/ldt.h>
  47 #include <asm/processor.h>
  48 #include <asm/i387.h>
  49 #include <asm/desc.h>
  50 #ifdef CONFIG_MATH_EMULATION
  51 #include <asm/math_emu.h>
  52 #endif
  53
  54 #include <linux/err.h>
  55
  56 #include <asm/tlbflush.h>
  57 #include <asm/cpu.h>
  58 #include <asm/idle.h>
  59 #include <asm/syscalls.h>
  60 #include <asm/ds.h>
  61
  62 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
  63
  64 DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
  65 EXPORT_PER_CPU_SYMBOL(current_task);
  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.sp)[3];
  73 }
  74
  75 #ifndef CONFIG_SMP
  76 static inline void play_dead(void)
  77 {
  78         BUG();
  79 }
  80 #endif
  81
  82 /*
  83  * The idle thread. There's no useful work to be
  84  * done, so just try to conserve power and have a
  85  * low exit latency (ie sit in a loop waiting for
  86  * somebody to say that they'd like to reschedule)
  87  */
  88 void cpu_idle(void)
  89 {
  90         int cpu = smp_processor_id();
  91
  92         /*
  93          * If we're the non-boot CPU, nothing set the stack canary up
  94          * for us.  CPU0 already has it initialized but no harm in
  95          * doing it again.  This is a good place for updating it, as
  96          * we wont ever return from this function (so the invalid
  97          * canaries already on the stack wont ever trigger).
  98          */
  99         boot_init_stack_canary();
 100
 101         current_thread_info()->status |= TS_POLLING;
 102
 103         /* endless idle loop with no priority at all */
 104         while (1) {
 105                 tick_nohz_stop_sched_tick(1);
 106                 while (!need_resched()) {
 107
 108                         check_pgt_cache();
 109                         rmb();
 110
 111                         if (cpu_is_offline(cpu))
 112                                 play_dead();
 113
 114                         local_irq_disable();
 115                         /* Don't trace irqs off for idle */
 116                         stop_critical_timings();
 117                         pm_idle();
 118                         start_critical_timings();
 119                 }
 120                 tick_nohz_restart_sched_tick();
 121                 preempt_enable_no_resched();
 122                 schedule();
 123                 preempt_disable();
 124         }
 125 }
 126
 127 void __show_regs(struct pt_regs *regs, int all)
 128 {
 129         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
 130         unsigned long d0, d1, d2, d3, d6, d7;
 131         unsigned long sp;
 132         unsigned short ss, gs;
 133         const char *board;
 134
 135         if (user_mode_vm(regs)) {
 136                 sp = regs->sp;
 137                 ss = regs->ss & 0xffff;
 138                 gs = get_user_gs(regs);
 139         } else {
 140                 sp = (unsigned long) (&regs->sp);
 141                 savesegment(ss, ss);
 142                 savesegment(gs, gs);
 143         }
 144
 145         printk("\n");
 146
 147         board = dmi_get_system_info(DMI_PRODUCT_NAME);
 148         if (!board)
 149                 board = "";
 150         printk("Pid: %d, comm: %s %s (%s %.*s) %s\n",
 151                         task_pid_nr(current), current->comm,
 152                         print_tainted(), init_utsname()->release,
 153                         (int)strcspn(init_utsname()->version, " "),
 154                         init_utsname()->version, board);
 155
 156         printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
 157                         (u16)regs->cs, regs->ip, regs->flags,
 158                         smp_processor_id());
 159         print_symbol("EIP is at %s\n", regs->ip);
 160
 161         printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
 162                 regs->ax, regs->bx, regs->cx, regs->dx);
 163         printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
 164                 regs->si, regs->di, regs->bp, sp);
 165         printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
 166                (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
 167
 168         if (!all)
 169                 return;
 170
 171         cr0 = read_cr0();
 172         cr2 = read_cr2();
 173         cr3 = read_cr3();
 174         cr4 = read_cr4_safe();
 175         printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
 176                         cr0, cr2, cr3, cr4);
 177
 178         get_debugreg(d0, 0);
 179         get_debugreg(d1, 1);
 180         get_debugreg(d2, 2);
 181         get_debugreg(d3, 3);
 182         printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
 183                         d0, d1, d2, d3);
 184
 185         get_debugreg(d6, 6);
 186         get_debugreg(d7, 7);
 187         printk("DR6: %08lx DR7: %08lx\n",
 188                         d6, d7);
 189 }
 190
 191 void show_regs(struct pt_regs *regs)
 192 {
 193         __show_regs(regs, 1);
 194         show_trace(NULL, regs, &regs->sp, regs->bp);
 195 }
 196
 197 /*
 198  * This gets run with %bx containing the
 199  * function to call, and %dx containing
 200  * the "args".
 201  */
 202 extern void kernel_thread_helper(void);
 203
 204 /*
 205  * Create a kernel thread
 206  */
 207 int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 208 {
 209         struct pt_regs regs;
 210
 211         memset(&regs, 0, sizeof(regs));
 212
 213         regs.bx = (unsigned long) fn;
 214         regs.dx = (unsigned long) arg;
 215
 216         regs.ds = __USER_DS;
 217         regs.es = __USER_DS;
 218         regs.fs = __KERNEL_PERCPU;
 219         regs.gs = __KERNEL_STACK_CANARY;
 220         regs.orig_ax = -1;
 221         regs.ip = (unsigned long) kernel_thread_helper;
 222         regs.cs = __KERNEL_CS | get_kernel_rpl();
 223         regs.flags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
 224
 225         /* Ok, create the new process.. */
 226         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 227 }
 228 EXPORT_SYMBOL(kernel_thread);
 229
 230 void release_thread(struct task_struct *dead_task)
 231 {
 232         BUG_ON(dead_task->mm);
 233         release_vm86_irqs(dead_task);
 234 }
 235
 236 /*
 237  * This gets called before we allocate a new thread and copy
 238  * the current task into it.
 239  */
 240 void prepare_to_copy(struct task_struct *tsk)
 241 {
 242         unlazy_fpu(tsk);
 243 }
 244
 245 int copy_thread(unsigned long clone_flags, unsigned long sp,
 246         unsigned long unused,
 247         struct task_struct *p, struct pt_regs *regs)
 248 {
 249         struct pt_regs *childregs;
 250         struct task_struct *tsk;
 251         int err;
 252
 253         childregs = task_pt_regs(p);
 254         *childregs = *regs;
 255         childregs->ax = 0;
 256         childregs->sp = sp;
 257
 258         p->thread.sp = (unsigned long) childregs;
 259         p->thread.sp0 = (unsigned long) (childregs+1);
 260
 261         p->thread.ip = (unsigned long) ret_from_fork;
 262
 263         task_user_gs(p) = get_user_gs(regs);
 264
 265         tsk = current;
 266         if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
 267                 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
 268                                                 IO_BITMAP_BYTES, GFP_KERNEL);
 269                 if (!p->thread.io_bitmap_ptr) {
 270                         p->thread.io_bitmap_max = 0;
 271                         return -ENOMEM;
 272                 }
 273                 set_tsk_thread_flag(p, TIF_IO_BITMAP);
 274         }
 275
 276         err = 0;
 277
 278         /*
 279          * Set a new TLS for the child thread?
 280          */
 281         if (clone_flags & CLONE_SETTLS)
 282                 err = do_set_thread_area(p, -1,
 283                         (struct user_desc __user *)childregs->si, 0);
 284
 285         if (err && p->thread.io_bitmap_ptr) {
 286                 kfree(p->thread.io_bitmap_ptr);
 287                 p->thread.io_bitmap_max = 0;
 288         }
 289
 290         clear_tsk_thread_flag(p, TIF_DS_AREA_MSR);
 291         p->thread.ds_ctx = NULL;
 292
 293         clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
 294         p->thread.debugctlmsr = 0;
 295
 296         return err;
 297 }
 298
 299 void
 300 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 301 {
 302         set_user_gs(regs, 0);
 303         regs->fs                = 0;
 304         set_fs(USER_DS);
 305         regs->ds                = __USER_DS;
 306         regs->es                = __USER_DS;
 307         regs->ss                = __USER_DS;
 308         regs->cs                = __USER_CS;
 309         regs->ip                = new_ip;
 310         regs->sp                = new_sp;
 311         /*
 312          * Free the old FP and other extended state
 313          */
 314         free_thread_xstate(current);
 315 }
 316 EXPORT_SYMBOL_GPL(start_thread);
 317
 318
 319 /*
 320  *      switch_to(x,yn) should switch tasks from x to y.
 321  *
 322  * We fsave/fwait so that an exception goes off at the right time
 323  * (as a call from the fsave or fwait in effect) rather than to
 324  * the wrong process. Lazy FP saving no longer makes any sense
 325  * with modern CPU's, and this simplifies a lot of things (SMP
 326  * and UP become the same).
 327  *
 328  * NOTE! We used to use the x86 hardware context switching. The
 329  * reason for not using it any more becomes apparent when you
 330  * try to recover gracefully from saved state that is no longer
 331  * valid (stale segment register values in particular). With the
 332  * hardware task-switch, there is no way to fix up bad state in
 333  * a reasonable manner.
 334  *
 335  * The fact that Intel documents the hardware task-switching to
 336  * be slow is a fairly red herring - this code is not noticeably
 337  * faster. However, there _is_ some room for improvement here,
 338  * so the performance issues may eventually be a valid point.
 339  * More important, however, is the fact that this allows us much
 340  * more flexibility.
 341  *
 342  * The return value (in %ax) will be the "prev" task after
 343  * the task-switch, and shows up in ret_from_fork in entry.S,
 344  * for example.
 345  */
 346 __notrace_funcgraph struct task_struct *
 347 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 348 {
 349         struct thread_struct *prev = &prev_p->thread,
 350                                  *next = &next_p->thread;
 351         int cpu = smp_processor_id();
 352         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 353
 354         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 355
 356         __unlazy_fpu(prev_p);
 357
 358
 359         /* we're going to use this soon, after a few expensive things */
 360         if (next_p->fpu_counter > 5)
 361                 prefetch(next->xstate);
 362
 363         /*
 364          * Reload esp0.
 365          */
 366         load_sp0(tss, next);
 367
 368         /*
 369          * Save away %gs. No need to save %fs, as it was saved on the
 370          * stack on entry.  No need to save %es and %ds, as those are
 371          * always kernel segments while inside the kernel.  Doing this
 372          * before setting the new TLS descriptors avoids the situation
 373          * where we temporarily have non-reloadable segments in %fs
 374          * and %gs.  This could be an issue if the NMI handler ever
 375          * used %fs or %gs (it does not today), or if the kernel is
 376          * running inside of a hypervisor layer.
 377          */
 378         lazy_save_gs(prev->gs);
 379
 380         /*
 381          * Load the per-thread Thread-Local Storage descriptor.
 382          */
 383         load_TLS(next, cpu);
 384
 385         /*
 386          * Restore IOPL if needed.  In normal use, the flags restore
 387          * in the switch assembly will handle this.  But if the kernel
 388          * is running virtualized at a non-zero CPL, the popf will
 389          * not restore flags, so it must be done in a separate step.
 390          */
 391         if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
 392                 set_iopl_mask(next->iopl);
 393
 394         /*
 395          * Now maybe handle debug registers and/or IO bitmaps
 396          */
 397         if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
 398                      task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
 399                 __switch_to_xtra(prev_p, next_p, tss);
 400
 401         /*
 402          * Leave lazy mode, flushing any hypercalls made here.
 403          * This must be done before restoring TLS segments so
 404          * the GDT and LDT are properly updated, and must be
 405          * done before math_state_restore, so the TS bit is up
 406          * to date.
 407          */
 408         arch_end_context_switch(next_p);
 409
 410         /* If the task has used fpu the last 5 timeslices, just do a full
 411          * restore of the math state immediately to avoid the trap; the
 412          * chances of needing FPU soon are obviously high now
 413          *
 414          * tsk_used_math() checks prevent calling math_state_restore(),
 415          * which can sleep in the case of !tsk_used_math()
 416          */
 417         if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
 418                 math_state_restore();
 419
 420         /*
 421          * Restore %gs if needed (which is common)
 422          */
 423         if (prev->gs | next->gs)
 424                 lazy_load_gs(next->gs);
 425
 426         percpu_write(current_task, next_p);
 427
 428         return prev_p;
 429 }
 430
 431 int sys_clone(struct pt_regs *regs)
 432 {
 433         unsigned long clone_flags;
 434         unsigned long newsp;
 435         int __user *parent_tidptr, *child_tidptr;
 436
 437         clone_flags = regs->bx;
 438         newsp = regs->cx;
 439         parent_tidptr = (int __user *)regs->dx;
 440         child_tidptr = (int __user *)regs->di;
 441         if (!newsp)
 442                 newsp = regs->sp;
 443         return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
 444 }
 445
 446 /*
 447  * sys_execve() executes a new program.
 448  */
 449 int sys_execve(struct pt_regs *regs)
 450 {
 451         int error;
 452         char *filename;
 453
 454         filename = getname((char __user *) regs->bx);
 455         error = PTR_ERR(filename);
 456         if (IS_ERR(filename))
 457                 goto out;
 458         error = do_execve(filename,
 459                         (char __user * __user *) regs->cx,
 460                         (char __user * __user *) regs->dx,
 461                         regs);
 462         if (error == 0) {
 463                 /* Make sure we don't return using sysenter.. */
 464                 set_thread_flag(TIF_IRET);
 465         }
 466         putname(filename);
 467 out:
 468         return error;
 469 }
 470
 471 #define top_esp                (THREAD_SIZE - sizeof(unsigned long))
 472 #define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
 473
 474 unsigned long get_wchan(struct task_struct *p)
 475 {
 476         unsigned long bp, sp, ip;
 477         unsigned long stack_page;
 478         int count = 0;
 479         if (!p || p == current || p->state == TASK_RUNNING)
 480                 return 0;
 481         stack_page = (unsigned long)task_stack_page(p);
 482         sp = p->thread.sp;
 483         if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
 484                 return 0;
 485         /* include/asm-i386/system.h:switch_to() pushes bp last. */
 486         bp = *(unsigned long *) sp;
 487         do {
 488                 if (bp < stack_page || bp > top_ebp+stack_page)
 489                         return 0;
 490                 ip = *(unsigned long *) (bp+4);
 491                 if (!in_sched_functions(ip))
 492                         return ip;
 493                 bp = *(unsigned long *) bp;
 494         } while (count++ < 16);
 495         return 0;
 496 }
 497