arch/x86/kernel/process_64.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  *  X86-64 port
   8  *      Andi Kleen.
   9  *
  10  *      CPU hotplug support - ashok.raj@intel.com
  11  */
  12
  13 /*
  14  * This file handles the architecture-dependent parts of process handling..
  15  */
  16
  17 #include <linux/stackprotector.h>
  18 #include <linux/cpu.h>
  19 #include <linux/errno.h>
  20 #include <linux/sched.h>
  21 #include <linux/fs.h>
  22 #include <linux/kernel.h>
  23 #include <linux/mm.h>
  24 #include <linux/elfcore.h>
  25 #include <linux/smp.h>
  26 #include <linux/slab.h>
  27 #include <linux/user.h>
  28 #include <linux/interrupt.h>
  29 #include <linux/delay.h>
  30 #include <linux/module.h>
  31 #include <linux/ptrace.h>
  32 #include <linux/notifier.h>
  33 #include <linux/kprobes.h>
  34 #include <linux/kdebug.h>
  35 #include <linux/tick.h>
  36 #include <linux/prctl.h>
  37 #include <linux/uaccess.h>
  38 #include <linux/io.h>
  39 #include <linux/ftrace.h>
  40
  41 #include <asm/pgtable.h>
  42 #include <asm/system.h>
  43 #include <asm/processor.h>
  44 #include <asm/i387.h>
  45 #include <asm/mmu_context.h>
  46 #include <asm/prctl.h>
  47 #include <asm/desc.h>
  48 #include <asm/proto.h>
  49 #include <asm/ia32.h>
  50 #include <asm/idle.h>
  51 #include <asm/syscalls.h>
  52 #include <asm/debugreg.h>
  53
  54 asmlinkage extern void ret_from_fork(void);
  55
  56 DEFINE_PER_CPU(unsigned long, old_rsp);
  57 static DEFINE_PER_CPU(unsigned char, is_idle);
  58
  59 static ATOMIC_NOTIFIER_HEAD(idle_notifier);
  60
  61 void idle_notifier_register(struct notifier_block *n)
  62 {
  63         atomic_notifier_chain_register(&idle_notifier, n);
  64 }
  65 EXPORT_SYMBOL_GPL(idle_notifier_register);
  66
  67 void idle_notifier_unregister(struct notifier_block *n)
  68 {
  69         atomic_notifier_chain_unregister(&idle_notifier, n);
  70 }
  71 EXPORT_SYMBOL_GPL(idle_notifier_unregister);
  72
  73 void enter_idle(void)
  74 {
  75         percpu_write(is_idle, 1);
  76         atomic_notifier_call_chain(&idle_notifier, IDLE_START, NULL);
  77 }
  78
  79 static void __exit_idle(void)
  80 {
  81         if (x86_test_and_clear_bit_percpu(0, is_idle) == 0)
  82                 return;
  83         atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);
  84 }
  85
  86 /* Called from interrupts to signify idle end */
  87 void exit_idle(void)
  88 {
  89         /* idle loop has pid 0 */
  90         if (current->pid)
  91                 return;
  92         __exit_idle();
  93 }
  94
  95 #ifndef CONFIG_SMP
  96 static inline void play_dead(void)
  97 {
  98         BUG();
  99 }
 100 #endif
 101
 102 /*
 103  * The idle thread. There's no useful work to be
 104  * done, so just try to conserve power and have a
 105  * low exit latency (ie sit in a loop waiting for
 106  * somebody to say that they'd like to reschedule)
 107  */
 108 void cpu_idle(void)
 109 {
 110         current_thread_info()->status |= TS_POLLING;
 111
 112         /*
 113          * If we're the non-boot CPU, nothing set the stack canary up
 114          * for us.  CPU0 already has it initialized but no harm in
 115          * doing it again.  This is a good place for updating it, as
 116          * we wont ever return from this function (so the invalid
 117          * canaries already on the stack wont ever trigger).
 118          */
 119         boot_init_stack_canary();
 120
 121         /* endless idle loop with no priority at all */
 122         while (1) {
 123                 tick_nohz_stop_sched_tick(1);
 124                 while (!need_resched()) {
 125
 126                         rmb();
 127
 128                         if (cpu_is_offline(smp_processor_id()))
 129                                 play_dead();
 130                         /*
 131                          * Idle routines should keep interrupts disabled
 132                          * from here on, until they go to idle.
 133                          * Otherwise, idle callbacks can misfire.
 134                          */
 135                         local_irq_disable();
 136                         enter_idle();
 137                         /* Don't trace irqs off for idle */
 138                         stop_critical_timings();
 139                         pm_idle();
 140                         start_critical_timings();
 141
 142                         /* In many cases the interrupt that ended idle
 143                            has already called exit_idle. But some idle
 144                            loops can be woken up without interrupt. */
 145                         __exit_idle();
 146                 }
 147
 148                 tick_nohz_restart_sched_tick();
 149                 preempt_enable_no_resched();
 150                 schedule();
 151                 preempt_disable();
 152         }
 153 }
 154
 155 /* Prints also some state that isn't saved in the pt_regs */
 156 void __show_regs(struct pt_regs *regs, int all)
 157 {
 158         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs;
 159         unsigned long d0, d1, d2, d3, d6, d7;
 160         unsigned int fsindex, gsindex;
 161         unsigned int ds, cs, es;
 162
 163         show_regs_common();
 164         printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip);
 165         printk_address(regs->ip, 1);
 166         printk(KERN_DEFAULT "RSP: %04lx:%016lx  EFLAGS: %08lx\n", regs->ss,
 167                         regs->sp, regs->flags);
 168         printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",
 169                regs->ax, regs->bx, regs->cx);
 170         printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n",
 171                regs->dx, regs->si, regs->di);
 172         printk(KERN_DEFAULT "RBP: %016lx R08: %016lx R09: %016lx\n",
 173                regs->bp, regs->r8, regs->r9);
 174         printk(KERN_DEFAULT "R10: %016lx R11: %016lx R12: %016lx\n",
 175                regs->r10, regs->r11, regs->r12);
 176         printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
 177                regs->r13, regs->r14, regs->r15);
 178
 179         asm("movl %%ds,%0" : "=r" (ds));
 180         asm("movl %%cs,%0" : "=r" (cs));
 181         asm("movl %%es,%0" : "=r" (es));
 182         asm("movl %%fs,%0" : "=r" (fsindex));
 183         asm("movl %%gs,%0" : "=r" (gsindex));
 184
 185         rdmsrl(MSR_FS_BASE, fs);
 186         rdmsrl(MSR_GS_BASE, gs);
 187         rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
 188
 189         if (!all)
 190                 return;
 191
 192         cr0 = read_cr0();
 193         cr2 = read_cr2();
 194         cr3 = read_cr3();
 195         cr4 = read_cr4();
 196
 197         printk(KERN_DEFAULT "FS:  %016lx(%04x) GS:%016lx(%04x) knlGS:%016lx\n",
 198                fs, fsindex, gs, gsindex, shadowgs);
 199         printk(KERN_DEFAULT "CS:  %04x DS: %04x ES: %04x CR0: %016lx\n", cs, ds,
 200                         es, cr0);
 201         printk(KERN_DEFAULT "CR2: %016lx CR3: %016lx CR4: %016lx\n", cr2, cr3,
 202                         cr4);
 203
 204         get_debugreg(d0, 0);
 205         get_debugreg(d1, 1);
 206         get_debugreg(d2, 2);
 207         printk(KERN_DEFAULT "DR0: %016lx DR1: %016lx DR2: %016lx\n", d0, d1, d2);
 208         get_debugreg(d3, 3);
 209         get_debugreg(d6, 6);
 210         get_debugreg(d7, 7);
 211         printk(KERN_DEFAULT "DR3: %016lx DR6: %016lx DR7: %016lx\n", d3, d6, d7);
 212 }
 213
 214 void release_thread(struct task_struct *dead_task)
 215 {
 216         if (dead_task->mm) {
 217                 if (dead_task->mm->context.size) {
 218                         printk("WARNING: dead process %8s still has LDT? <%p/%d>\n",
 219                                         dead_task->comm,
 220                                         dead_task->mm->context.ldt,
 221                                         dead_task->mm->context.size);
 222                         BUG();
 223                 }
 224         }
 225 }
 226
 227 static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
 228 {
 229         struct user_desc ud = {
 230                 .base_addr = addr,
 231                 .limit = 0xfffff,
 232                 .seg_32bit = 1,
 233                 .limit_in_pages = 1,
 234                 .useable = 1,
 235         };
 236         struct desc_struct *desc = t->thread.tls_array;
 237         desc += tls;
 238         fill_ldt(desc, &ud);
 239 }
 240
 241 static inline u32 read_32bit_tls(struct task_struct *t, int tls)
 242 {
 243         return get_desc_base(&t->thread.tls_array[tls]);
 244 }
 245
 246 /*
 247  * This gets called before we allocate a new thread and copy
 248  * the current task into it.
 249  */
 250 void prepare_to_copy(struct task_struct *tsk)
 251 {
 252         unlazy_fpu(tsk);
 253 }
 254
 255 int copy_thread(unsigned long clone_flags, unsigned long sp,
 256                 unsigned long unused,
 257         struct task_struct *p, struct pt_regs *regs)
 258 {
 259         int err;
 260         struct pt_regs *childregs;
 261         struct task_struct *me = current;
 262
 263         childregs = ((struct pt_regs *)
 264                         (THREAD_SIZE + task_stack_page(p))) - 1;
 265         *childregs = *regs;
 266
 267         childregs->ax = 0;
 268         if (user_mode(regs))
 269                 childregs->sp = sp;
 270         else
 271                 childregs->sp = (unsigned long)childregs;
 272
 273         p->thread.sp = (unsigned long) childregs;
 274         p->thread.sp0 = (unsigned long) (childregs+1);
 275         p->thread.usersp = me->thread.usersp;
 276
 277         set_tsk_thread_flag(p, TIF_FORK);
 278
 279         p->thread.io_bitmap_ptr = NULL;
 280
 281         savesegment(gs, p->thread.gsindex);
 282         p->thread.gs = p->thread.gsindex ? 0 : me->thread.gs;
 283         savesegment(fs, p->thread.fsindex);
 284         p->thread.fs = p->thread.fsindex ? 0 : me->thread.fs;
 285         savesegment(es, p->thread.es);
 286         savesegment(ds, p->thread.ds);
 287
 288         err = -ENOMEM;
 289         memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 290
 291         if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
 292                 p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 293                 if (!p->thread.io_bitmap_ptr) {
 294                         p->thread.io_bitmap_max = 0;
 295                         return -ENOMEM;
 296                 }
 297                 memcpy(p->thread.io_bitmap_ptr, me->thread.io_bitmap_ptr,
 298                                 IO_BITMAP_BYTES);
 299                 set_tsk_thread_flag(p, TIF_IO_BITMAP);
 300         }
 301
 302         /*
 303          * Set a new TLS for the child thread?
 304          */
 305         if (clone_flags & CLONE_SETTLS) {
 306 #ifdef CONFIG_IA32_EMULATION
 307                 if (test_thread_flag(TIF_IA32))
 308                         err = do_set_thread_area(p, -1,
 309                                 (struct user_desc __user *)childregs->si, 0);
 310                 else
 311 #endif
 312                         err = do_arch_prctl(p, ARCH_SET_FS, childregs->r8);
 313                 if (err)
 314                         goto out;
 315         }
 316         err = 0;
 317 out:
 318         if (err && p->thread.io_bitmap_ptr) {
 319                 kfree(p->thread.io_bitmap_ptr);
 320                 p->thread.io_bitmap_max = 0;
 321         }
 322
 323         return err;
 324 }
 325
 326 static void
 327 start_thread_common(struct pt_regs *regs, unsigned long new_ip,
 328                     unsigned long new_sp,
 329                     unsigned int _cs, unsigned int _ss, unsigned int _ds)
 330 {
 331         loadsegment(fs, 0);
 332         loadsegment(es, _ds);
 333         loadsegment(ds, _ds);
 334         load_gs_index(0);
 335         regs->ip                = new_ip;
 336         regs->sp                = new_sp;
 337         percpu_write(old_rsp, new_sp);
 338         regs->cs                = _cs;
 339         regs->ss                = _ss;
 340         regs->flags             = X86_EFLAGS_IF;
 341         set_fs(USER_DS);
 342         /*
 343          * Free the old FP and other extended state
 344          */
 345         free_thread_xstate(current);
 346 }
 347
 348 void
 349 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 350 {
 351         start_thread_common(regs, new_ip, new_sp,
 352                             __USER_CS, __USER_DS, 0);
 353 }
 354
 355 #ifdef CONFIG_IA32_EMULATION
 356 void start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp)
 357 {
 358         start_thread_common(regs, new_ip, new_sp,
 359                             __USER32_CS, __USER32_DS, __USER32_DS);
 360 }
 361 #endif
 362
 363 /*
 364  *      switch_to(x,y) should switch tasks from x to y.
 365  *
 366  * This could still be optimized:
 367  * - fold all the options into a flag word and test it with a single test.
 368  * - could test fs/gs bitsliced
 369  *
 370  * Kprobes not supported here. Set the probe on schedule instead.
 371  * Function graph tracer not supported too.
 372  */
 373 __notrace_funcgraph struct task_struct *
 374 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 375 {
 376         struct thread_struct *prev = &prev_p->thread;
 377         struct thread_struct *next = &next_p->thread;
 378         int cpu = smp_processor_id();
 379         struct tss_struct *tss = &per_cpu(init_tss, cpu);
 380         unsigned fsindex, gsindex;
 381         bool preload_fpu;
 382
 383         /*
 384          * If the task has used fpu the last 5 timeslices, just do a full
 385          * restore of the math state immediately to avoid the trap; the
 386          * chances of needing FPU soon are obviously high now
 387          */
 388         preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
 389
 390         /* we're going to use this soon, after a few expensive things */
 391         if (preload_fpu)
 392                 prefetch(next->fpu.state);
 393
 394         /*
 395          * Reload esp0, LDT and the page table pointer:
 396          */
 397         load_sp0(tss, next);
 398
 399         /*
 400          * Switch DS and ES.
 401          * This won't pick up thread selector changes, but I guess that is ok.
 402          */
 403         savesegment(es, prev->es);
 404         if (unlikely(next->es | prev->es))
 405                 loadsegment(es, next->es);
 406
 407         savesegment(ds, prev->ds);
 408         if (unlikely(next->ds | prev->ds))
 409                 loadsegment(ds, next->ds);
 410
 411
 412         /* We must save %fs and %gs before load_TLS() because
 413          * %fs and %gs may be cleared by load_TLS().
 414          *
 415          * (e.g. xen_load_tls())
 416          */
 417         savesegment(fs, fsindex);
 418         savesegment(gs, gsindex);
 419
 420         load_TLS(next, cpu);
 421
 422         /* Must be after DS reload */
 423         __unlazy_fpu(prev_p);
 424
 425         /* Make sure cpu is ready for new context */
 426         if (preload_fpu)
 427                 clts();
 428
 429         /*
 430          * Leave lazy mode, flushing any hypercalls made here.
 431          * This must be done before restoring TLS segments so
 432          * the GDT and LDT are properly updated, and must be
 433          * done before math_state_restore, so the TS bit is up
 434          * to date.
 435          */
 436         arch_end_context_switch(next_p);
 437
 438         /*
 439          * Switch FS and GS.
 440          *
 441          * Segment register != 0 always requires a reload.  Also
 442          * reload when it has changed.  When prev process used 64bit
 443          * base always reload to avoid an information leak.
 444          */
 445         if (unlikely(fsindex | next->fsindex | prev->fs)) {
 446                 loadsegment(fs, next->fsindex);
 447                 /*
 448                  * Check if the user used a selector != 0; if yes
 449                  *  clear 64bit base, since overloaded base is always
 450                  *  mapped to the Null selector
 451                  */
 452                 if (fsindex)
 453                         prev->fs = 0;
 454         }
 455         /* when next process has a 64bit base use it */
 456         if (next->fs)
 457                 wrmsrl(MSR_FS_BASE, next->fs);
 458         prev->fsindex = fsindex;
 459
 460         if (unlikely(gsindex | next->gsindex | prev->gs)) {
 461                 load_gs_index(next->gsindex);
 462                 if (gsindex)
 463                         prev->gs = 0;
 464         }
 465         if (next->gs)
 466                 wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
 467         prev->gsindex = gsindex;
 468
 469         /*
 470          * Switch the PDA and FPU contexts.
 471          */
 472         prev->usersp = percpu_read(old_rsp);
 473         percpu_write(old_rsp, next->usersp);
 474         percpu_write(current_task, next_p);
 475
 476         percpu_write(kernel_stack,
 477                   (unsigned long)task_stack_page(next_p) +
 478                   THREAD_SIZE - KERNEL_STACK_OFFSET);
 479
 480         /*
 481          * Now maybe reload the debug registers and handle I/O bitmaps
 482          */
 483         if (unlikely(task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT ||
 484                      task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
 485                 __switch_to_xtra(prev_p, next_p, tss);
 486
 487         /*
 488          * Preload the FPU context, now that we've determined that the
 489          * task is likely to be using it.
 490          */
 491         if (preload_fpu)
 492                 __math_state_restore();
 493
 494         return prev_p;
 495 }
 496
 497 void set_personality_64bit(void)
 498 {
 499         /* inherit personality from parent */
 500
 501         /* Make sure to be in 64bit mode */
 502         clear_thread_flag(TIF_IA32);
 503
 504         /* Ensure the corresponding mm is not marked. */
 505         if (current->mm)
 506                 current->mm->context.ia32_compat = 0;
 507
 508         /* TBD: overwrites user setup. Should have two bits.
 509            But 64bit processes have always behaved this way,
 510            so it's not too bad. The main problem is just that
 511            32bit childs are affected again. */
 512         current->personality &= ~READ_IMPLIES_EXEC;
 513 }
 514
 515 void set_personality_ia32(void)
 516 {
 517         /* inherit personality from parent */
 518
 519         /* Make sure to be in 32bit mode */
 520         set_thread_flag(TIF_IA32);
 521         current->personality |= force_personality32;
 522
 523         /* Mark the associated mm as containing 32-bit tasks. */
 524         if (current->mm)
 525                 current->mm->context.ia32_compat = 1;
 526
 527         /* Prepare the first "return" to user space */
 528         current_thread_info()->status |= TS_COMPAT;
 529 }
 530
 531 unsigned long get_wchan(struct task_struct *p)
 532 {
 533         unsigned long stack;
 534         u64 fp, ip;
 535         int count = 0;
 536
 537         if (!p || p == current || p->state == TASK_RUNNING)
 538                 return 0;
 539         stack = (unsigned long)task_stack_page(p);
 540         if (p->thread.sp < stack || p->thread.sp >= stack+THREAD_SIZE)
 541                 return 0;
 542         fp = *(u64 *)(p->thread.sp);
 543         do {
 544                 if (fp < (unsigned long)stack ||
 545                     fp >= (unsigned long)stack+THREAD_SIZE)
 546                         return 0;
 547                 ip = *(u64 *)(fp+8);
 548                 if (!in_sched_functions(ip))
 549                         return ip;
 550                 fp = *(u64 *)fp;
 551         } while (count++ < 16);
 552         return 0;
 553 }
 554
 555 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 556 {
 557         int ret = 0;
 558         int doit = task == current;
 559         int cpu;
 560
 561         switch (code) {
 562         case ARCH_SET_GS:
 563                 if (addr >= TASK_SIZE_OF(task))
 564                         return -EPERM;
 565                 cpu = get_cpu();
 566                 /* handle small bases via the GDT because that's faster to
 567                    switch. */
 568                 if (addr <= 0xffffffff) {
 569                         set_32bit_tls(task, GS_TLS, addr);
 570                         if (doit) {
 571                                 load_TLS(&task->thread, cpu);
 572                                 load_gs_index(GS_TLS_SEL);
 573                         }
 574                         task->thread.gsindex = GS_TLS_SEL;
 575                         task->thread.gs = 0;
 576                 } else {
 577                         task->thread.gsindex = 0;
 578                         task->thread.gs = addr;
 579                         if (doit) {
 580                                 load_gs_index(0);
 581                                 ret = checking_wrmsrl(MSR_KERNEL_GS_BASE, addr);
 582                         }
 583                 }
 584                 put_cpu();
 585                 break;
 586         case ARCH_SET_FS:
 587                 /* Not strictly needed for fs, but do it for symmetry
 588                    with gs */
 589                 if (addr >= TASK_SIZE_OF(task))
 590                         return -EPERM;
 591                 cpu = get_cpu();
 592                 /* handle small bases via the GDT because that's faster to
 593                    switch. */
 594                 if (addr <= 0xffffffff) {
 595                         set_32bit_tls(task, FS_TLS, addr);
 596                         if (doit) {
 597                                 load_TLS(&task->thread, cpu);
 598                                 loadsegment(fs, FS_TLS_SEL);
 599                         }
 600                         task->thread.fsindex = FS_TLS_SEL;
 601                         task->thread.fs = 0;
 602                 } else {
 603                         task->thread.fsindex = 0;
 604                         task->thread.fs = addr;
 605                         if (doit) {
 606                                 /* set the selector to 0 to not confuse
 607                                    __switch_to */
 608                                 loadsegment(fs, 0);
 609                                 ret = checking_wrmsrl(MSR_FS_BASE, addr);
 610                         }
 611                 }
 612                 put_cpu();
 613                 break;
 614         case ARCH_GET_FS: {
 615                 unsigned long base;
 616                 if (task->thread.fsindex == FS_TLS_SEL)
 617                         base = read_32bit_tls(task, FS_TLS);
 618                 else if (doit)
 619                         rdmsrl(MSR_FS_BASE, base);
 620                 else
 621                         base = task->thread.fs;
 622                 ret = put_user(base, (unsigned long __user *)addr);
 623                 break;
 624         }
 625         case ARCH_GET_GS: {
 626                 unsigned long base;
 627                 unsigned gsindex;
 628                 if (task->thread.gsindex == GS_TLS_SEL)
 629                         base = read_32bit_tls(task, GS_TLS);
 630                 else if (doit) {
 631                         savesegment(gs, gsindex);
 632                         if (gsindex)
 633                                 rdmsrl(MSR_KERNEL_GS_BASE, base);
 634                         else
 635                                 base = task->thread.gs;
 636                 } else
 637                         base = task->thread.gs;
 638                 ret = put_user(base, (unsigned long __user *)addr);
 639                 break;
 640         }
 641
 642         default:
 643                 ret = -EINVAL;
 644                 break;
 645         }
 646
 647         return ret;
 648 }
 649
 650 long sys_arch_prctl(int code, unsigned long addr)
 651 {
 652         return do_arch_prctl(current, code, addr);
 653 }
 654
 655 unsigned long KSTK_ESP(struct task_struct *task)
 656 {
 657         return (test_tsk_thread_flag(task, TIF_IA32)) ?
 658                         (task_pt_regs(task)->sp) : ((task)->thread.usersp);
 659 }