arch/x86/kernel/process.c

   1 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   2
   3 #include <linux/errno.h>
   4 #include <linux/kernel.h>
   5 #include <linux/mm.h>
   6 #include <linux/smp.h>
   7 #include <linux/prctl.h>
   8 #include <linux/slab.h>
   9 #include <linux/sched.h>
  10 #include <linux/init.h>
  11 #include <linux/export.h>
  12 #include <linux/pm.h>
  13 #include <linux/tick.h>
  14 #include <linux/random.h>
  15 #include <linux/user-return-notifier.h>
  16 #include <linux/dmi.h>
  17 #include <linux/utsname.h>
  18 #include <linux/stackprotector.h>
  19 #include <linux/tick.h>
  20 #include <linux/cpuidle.h>
  21 #include <trace/events/power.h>
  22 #include <linux/hw_breakpoint.h>
  23 #include <asm/cpu.h>
  24 #include <asm/apic.h>
  25 #include <asm/syscalls.h>
  26 #include <asm/uaccess.h>
  27 #include <asm/mwait.h>
  28 #include <asm/fpu/internal.h>
  29 #include <asm/debugreg.h>
  30 #include <asm/nmi.h>
  31 #include <asm/tlbflush.h>
  32 #include <asm/mce.h>
  33 #include <asm/vm86.h>
  34 #include <asm/switch_to.h>
  35
  36 /*
  37  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
  38  * no more per-task TSS's. The TSS size is kept cacheline-aligned
  39  * so they are allowed to end up in the .data..cacheline_aligned
  40  * section. Since TSS's are completely CPU-local, we want them
  41  * on exact cacheline boundaries, to eliminate cacheline ping-pong.
  42  */
  43 __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
  44         .x86_tss = {
  45                 .sp0 = TOP_OF_INIT_STACK,
  46 #ifdef CONFIG_X86_32
  47                 .ss0 = __KERNEL_DS,
  48                 .ss1 = __KERNEL_CS,
  49                 .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
  50 #endif
  51          },
  52 #ifdef CONFIG_X86_32
  53          /*
  54           * Note that the .io_bitmap member must be extra-big. This is because
  55           * the CPU will access an additional byte beyond the end of the IO
  56           * permission bitmap. The extra byte must be all 1 bits, and must
  57           * be within the limit.
  58           */
  59         .io_bitmap              = { [0 ... IO_BITMAP_LONGS] = ~0 },
  60 #endif
  61 #ifdef CONFIG_X86_32
  62         .SYSENTER_stack_canary  = STACK_END_MAGIC,
  63 #endif
  64 };
  65 EXPORT_PER_CPU_SYMBOL(cpu_tss);
  66
  67 /*
  68  * this gets called so that we can store lazy state into memory and copy the
  69  * current task into the new thread.
  70  */
  71 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
  72 {
  73         memcpy(dst, src, arch_task_struct_size);
  74 #ifdef CONFIG_VM86
  75         dst->thread.vm86 = NULL;
  76 #endif
  77
  78         return fpu__copy(&dst->thread.fpu, &src->thread.fpu);
  79 }
  80
  81 /*
  82  * Free current thread data structures etc..
  83  */
  84 void exit_thread(struct task_struct *tsk)
  85 {
  86         struct thread_struct *t = &tsk->thread;
  87         unsigned long *bp = t->io_bitmap_ptr;
  88         struct fpu *fpu = &t->fpu;
  89
  90         if (bp) {
  91                 struct tss_struct *tss = &per_cpu(cpu_tss, get_cpu());
  92
  93                 t->io_bitmap_ptr = NULL;
  94                 clear_thread_flag(TIF_IO_BITMAP);
  95                 /*
  96                  * Careful, clear this in the TSS too:
  97                  */
  98                 memset(tss->io_bitmap, 0xff, t->io_bitmap_max);
  99                 t->io_bitmap_max = 0;
 100                 put_cpu();
 101                 kfree(bp);
 102         }
 103
 104         free_vm86(t);
 105
 106         fpu__drop(fpu);
 107 }
 108
 109 void flush_thread(void)
 110 {
 111         struct task_struct *tsk = current;
 112
 113         flush_ptrace_hw_breakpoint(tsk);
 114         memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 115
 116         fpu__clear(&tsk->thread.fpu);
 117 }
 118
 119 static void hard_disable_TSC(void)
 120 {
 121         cr4_set_bits(X86_CR4_TSD);
 122 }
 123
 124 void disable_TSC(void)
 125 {
 126         preempt_disable();
 127         if (!test_and_set_thread_flag(TIF_NOTSC))
 128                 /*
 129                  * Must flip the CPU state synchronously with
 130                  * TIF_NOTSC in the current running context.
 131                  */
 132                 hard_disable_TSC();
 133         preempt_enable();
 134 }
 135
 136 static void hard_enable_TSC(void)
 137 {
 138         cr4_clear_bits(X86_CR4_TSD);
 139 }
 140
 141 static void enable_TSC(void)
 142 {
 143         preempt_disable();
 144         if (test_and_clear_thread_flag(TIF_NOTSC))
 145                 /*
 146                  * Must flip the CPU state synchronously with
 147                  * TIF_NOTSC in the current running context.
 148                  */
 149                 hard_enable_TSC();
 150         preempt_enable();
 151 }
 152
 153 int get_tsc_mode(unsigned long adr)
 154 {
 155         unsigned int val;
 156
 157         if (test_thread_flag(TIF_NOTSC))
 158                 val = PR_TSC_SIGSEGV;
 159         else
 160                 val = PR_TSC_ENABLE;
 161
 162         return put_user(val, (unsigned int __user *)adr);
 163 }
 164
 165 int set_tsc_mode(unsigned int val)
 166 {
 167         if (val == PR_TSC_SIGSEGV)
 168                 disable_TSC();
 169         else if (val == PR_TSC_ENABLE)
 170                 enable_TSC();
 171         else
 172                 return -EINVAL;
 173
 174         return 0;
 175 }
 176
 177 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 178                       struct tss_struct *tss)
 179 {
 180         struct thread_struct *prev, *next;
 181
 182         prev = &prev_p->thread;
 183         next = &next_p->thread;
 184
 185         if (test_tsk_thread_flag(prev_p, TIF_BLOCKSTEP) ^
 186             test_tsk_thread_flag(next_p, TIF_BLOCKSTEP)) {
 187                 unsigned long debugctl = get_debugctlmsr();
 188
 189                 debugctl &= ~DEBUGCTLMSR_BTF;
 190                 if (test_tsk_thread_flag(next_p, TIF_BLOCKSTEP))
 191                         debugctl |= DEBUGCTLMSR_BTF;
 192
 193                 update_debugctlmsr(debugctl);
 194         }
 195
 196         if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
 197             test_tsk_thread_flag(next_p, TIF_NOTSC)) {
 198                 /* prev and next are different */
 199                 if (test_tsk_thread_flag(next_p, TIF_NOTSC))
 200                         hard_disable_TSC();
 201                 else
 202                         hard_enable_TSC();
 203         }
 204
 205         if (test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
 206                 /*
 207                  * Copy the relevant range of the IO bitmap.
 208                  * Normally this is 128 bytes or less:
 209                  */
 210                 memcpy(tss->io_bitmap, next->io_bitmap_ptr,
 211                        max(prev->io_bitmap_max, next->io_bitmap_max));
 212         } else if (test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) {
 213                 /*
 214                  * Clear any possible leftover bits:
 215                  */
 216                 memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
 217         }
 218         propagate_user_return_notify(prev_p, next_p);
 219 }
 220
 221 /*
 222  * Idle related variables and functions
 223  */
 224 unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
 225 EXPORT_SYMBOL(boot_option_idle_override);
 226
 227 static void (*x86_idle)(void);
 228
 229 #ifndef CONFIG_SMP
 230 static inline void play_dead(void)
 231 {
 232         BUG();
 233 }
 234 #endif
 235
 236 void arch_cpu_idle_enter(void)
 237 {
 238         local_touch_nmi();
 239 }
 240
 241 void arch_cpu_idle_dead(void)
 242 {
 243         play_dead();
 244 }
 245
 246 /*
 247  * Called from the generic idle code.
 248  */
 249 void arch_cpu_idle(void)
 250 {
 251         x86_idle();
 252 }
 253
 254 /*
 255  * We use this if we don't have any better idle routine..
 256  */
 257 void __cpuidle default_idle(void)
 258 {
 259         trace_cpu_idle_rcuidle(1, smp_processor_id());
 260         safe_halt();
 261         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 262 }
 263 #ifdef CONFIG_APM_MODULE
 264 EXPORT_SYMBOL(default_idle);
 265 #endif
 266
 267 #ifdef CONFIG_XEN
 268 bool xen_set_default_idle(void)
 269 {
 270         bool ret = !!x86_idle;
 271
 272         x86_idle = default_idle;
 273
 274         return ret;
 275 }
 276 #endif
 277 void stop_this_cpu(void *dummy)
 278 {
 279         local_irq_disable();
 280         /*
 281          * Remove this CPU:
 282          */
 283         set_cpu_online(smp_processor_id(), false);
 284         disable_local_APIC();
 285         mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
 286
 287         for (;;)
 288                 halt();
 289 }
 290
 291 /*
 292  * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power
 293  * states (local apic timer and TSC stop).
 294  */
 295 static void amd_e400_idle(void)
 296 {
 297         /*
 298          * We cannot use static_cpu_has_bug() here because X86_BUG_AMD_APIC_C1E
 299          * gets set after static_cpu_has() places have been converted via
 300          * alternatives.
 301          */
 302         if (!boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
 303                 default_idle();
 304                 return;
 305         }
 306
 307         tick_broadcast_enter();
 308
 309         default_idle();
 310
 311         /*
 312          * The switch back from broadcast mode needs to be called with
 313          * interrupts disabled.
 314          */
 315         local_irq_disable();
 316         tick_broadcast_exit();
 317         local_irq_enable();
 318 }
 319
 320 /*
 321  * Intel Core2 and older machines prefer MWAIT over HALT for C1.
 322  * We can't rely on cpuidle installing MWAIT, because it will not load
 323  * on systems that support only C1 -- so the boot default must be MWAIT.
 324  *
 325  * Some AMD machines are the opposite, they depend on using HALT.
 326  *
 327  * So for default C1, which is used during boot until cpuidle loads,
 328  * use MWAIT-C1 on Intel HW that has it, else use HALT.
 329  */
 330 static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
 331 {
 332         if (c->x86_vendor != X86_VENDOR_INTEL)
 333                 return 0;
 334
 335         if (!cpu_has(c, X86_FEATURE_MWAIT) || static_cpu_has_bug(X86_BUG_MONITOR))
 336                 return 0;
 337
 338         return 1;
 339 }
 340
 341 /*
 342  * MONITOR/MWAIT with no hints, used for default C1 state. This invokes MWAIT
 343  * with interrupts enabled and no flags, which is backwards compatible with the
 344  * original MWAIT implementation.
 345  */
 346 static __cpuidle void mwait_idle(void)
 347 {
 348         if (!current_set_polling_and_test()) {
 349                 trace_cpu_idle_rcuidle(1, smp_processor_id());
 350                 if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) {
 351                         mb(); /* quirk */
 352                         clflush((void *)&current_thread_info()->flags);
 353                         mb(); /* quirk */
 354                 }
 355
 356                 __monitor((void *)&current_thread_info()->flags, 0, 0);
 357                 if (!need_resched())
 358                         __sti_mwait(0, 0);
 359                 else
 360                         local_irq_enable();
 361                 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 362         } else {
 363                 local_irq_enable();
 364         }
 365         __current_clr_polling();
 366 }
 367
 368 void select_idle_routine(const struct cpuinfo_x86 *c)
 369 {
 370 #ifdef CONFIG_SMP
 371         if (boot_option_idle_override == IDLE_POLL && smp_num_siblings > 1)
 372                 pr_warn_once("WARNING: polling idle and HT enabled, performance may degrade\n");
 373 #endif
 374         if (x86_idle || boot_option_idle_override == IDLE_POLL)
 375                 return;
 376
 377         if (boot_cpu_has_bug(X86_BUG_AMD_E400)) {
 378                 pr_info("using AMD E400 aware idle routine\n");
 379                 x86_idle = amd_e400_idle;
 380         } else if (prefer_mwait_c1_over_halt(c)) {
 381                 pr_info("using mwait in idle threads\n");
 382                 x86_idle = mwait_idle;
 383         } else
 384                 x86_idle = default_idle;
 385 }
 386
 387 void amd_e400_c1e_apic_setup(void)
 388 {
 389         if (boot_cpu_has_bug(X86_BUG_AMD_APIC_C1E)) {
 390                 pr_info("Switch to broadcast mode on CPU%d\n", smp_processor_id());
 391                 local_irq_disable();
 392                 tick_broadcast_force();
 393                 local_irq_enable();
 394         }
 395 }
 396
 397 void __init arch_post_acpi_subsys_init(void)
 398 {
 399         u32 lo, hi;
 400
 401         if (!boot_cpu_has_bug(X86_BUG_AMD_E400))
 402                 return;
 403
 404         /*
 405          * AMD E400 detection needs to happen after ACPI has been enabled. If
 406          * the machine is affected K8_INTP_C1E_ACTIVE_MASK bits are set in
 407          * MSR_K8_INT_PENDING_MSG.
 408          */
 409         rdmsr(MSR_K8_INT_PENDING_MSG, lo, hi);
 410         if (!(lo & K8_INTP_C1E_ACTIVE_MASK))
 411                 return;
 412
 413         boot_cpu_set_bug(X86_BUG_AMD_APIC_C1E);
 414
 415         if (!boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
 416                 mark_tsc_unstable("TSC halt in AMD C1E");
 417         pr_info("System has AMD C1E enabled\n");
 418 }
 419
 420 static int __init idle_setup(char *str)
 421 {
 422         if (!str)
 423                 return -EINVAL;
 424
 425         if (!strcmp(str, "poll")) {
 426                 pr_info("using polling idle threads\n");
 427                 boot_option_idle_override = IDLE_POLL;
 428                 cpu_idle_poll_ctrl(true);
 429         } else if (!strcmp(str, "halt")) {
 430                 /*
 431                  * When the boot option of idle=halt is added, halt is
 432                  * forced to be used for CPU idle. In such case CPU C2/C3
 433                  * won't be used again.
 434                  * To continue to load the CPU idle driver, don't touch
 435                  * the boot_option_idle_override.
 436                  */
 437                 x86_idle = default_idle;
 438                 boot_option_idle_override = IDLE_HALT;
 439         } else if (!strcmp(str, "nomwait")) {
 440                 /*
 441                  * If the boot option of "idle=nomwait" is added,
 442                  * it means that mwait will be disabled for CPU C2/C3
 443                  * states. In such case it won't touch the variable
 444                  * of boot_option_idle_override.
 445                  */
 446                 boot_option_idle_override = IDLE_NOMWAIT;
 447         } else
 448                 return -1;
 449
 450         return 0;
 451 }
 452 early_param("idle", idle_setup);
 453
 454 unsigned long arch_align_stack(unsigned long sp)
 455 {
 456         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 457                 sp -= get_random_int() % 8192;
 458         return sp & ~0xf;
 459 }
 460
 461 unsigned long arch_randomize_brk(struct mm_struct *mm)
 462 {
 463         return randomize_page(mm->brk, 0x02000000);
 464 }
 465
 466 /*
 467  * Return saved PC of a blocked thread.
 468  * What is this good for? it will be always the scheduler or ret_from_fork.
 469  */
 470 unsigned long thread_saved_pc(struct task_struct *tsk)
 471 {
 472         struct inactive_task_frame *frame =
 473                 (struct inactive_task_frame *) READ_ONCE(tsk->thread.sp);
 474         return READ_ONCE_NOCHECK(frame->ret_addr);
 475 }
 476
 477 /*
 478  * Called from fs/proc with a reference on @p to find the function
 479  * which called into schedule(). This needs to be done carefully
 480  * because the task might wake up and we might look at a stack
 481  * changing under us.
 482  */
 483 unsigned long get_wchan(struct task_struct *p)
 484 {
 485         unsigned long start, bottom, top, sp, fp, ip, ret = 0;
 486         int count = 0;
 487
 488         if (!p || p == current || p->state == TASK_RUNNING)
 489                 return 0;
 490
 491         if (!try_get_task_stack(p))
 492                 return 0;
 493
 494         start = (unsigned long)task_stack_page(p);
 495         if (!start)
 496                 goto out;
 497
 498         /*
 499          * Layout of the stack page:
 500          *
 501          * ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
 502          * PADDING
 503          * ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
 504          * stack
 505          * ----------- bottom = start
 506          *
 507          * The tasks stack pointer points at the location where the
 508          * framepointer is stored. The data on the stack is:
 509          * ... IP FP ... IP FP
 510          *
 511          * We need to read FP and IP, so we need to adjust the upper
 512          * bound by another unsigned long.
 513          */
 514         top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
 515         top -= 2 * sizeof(unsigned long);
 516         bottom = start;
 517
 518         sp = READ_ONCE(p->thread.sp);
 519         if (sp < bottom || sp > top)
 520                 goto out;
 521
 522         fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
 523         do {
 524                 if (fp < bottom || fp > top)
 525                         goto out;
 526                 ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
 527                 if (!in_sched_functions(ip)) {
 528                         ret = ip;
 529                         goto out;
 530                 }
 531                 fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
 532         } while (count++ < 16 && p->state != TASK_RUNNING);
 533
 534 out:
 535         put_task_stack(p);
 536         return ret;
 537 }