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/cpu.h>
  18 #include <linux/errno.h>
  19 #include <linux/sched.h>
  20 #include <linux/fs.h>
  21 #include <linux/kernel.h>
  22 #include <linux/mm.h>
  23 #include <linux/elfcore.h>
  24 #include <linux/smp.h>
  25 #include <linux/slab.h>
  26 #include <linux/user.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/delay.h>
  29 #include <linux/module.h>
  30 #include <linux/ptrace.h>
  31 #include <linux/notifier.h>
  32 #include <linux/kprobes.h>
  33 #include <linux/kdebug.h>
  34 #include <linux/prctl.h>
  35 #include <linux/uaccess.h>
  36 #include <linux/io.h>
  37 #include <linux/ftrace.h>
  38
  39 #include <asm/pgtable.h>
  40 #include <asm/processor.h>
  41 #include <asm/fpu/internal.h>
  42 #include <asm/mmu_context.h>
  43 #include <asm/prctl.h>
  44 #include <asm/desc.h>
  45 #include <asm/proto.h>
  46 #include <asm/ia32.h>
  47 #include <asm/idle.h>
  48 #include <asm/syscalls.h>
  49 #include <asm/debugreg.h>
  50 #include <asm/switch_to.h>
  51
  52 asmlinkage extern void ret_from_fork(void);
  53
  54 __visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
  55
  56 /* Prints also some state that isn't saved in the pt_regs */
  57 void __show_regs(struct pt_regs *regs, int all)
  58 {
  59         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L, fs, gs, shadowgs;
  60         unsigned long d0, d1, d2, d3, d6, d7;
  61         unsigned int fsindex, gsindex;
  62         unsigned int ds, cs, es;
  63
  64         printk(KERN_DEFAULT "RIP: %04lx:[<%016lx>] ", regs->cs & 0xffff, regs->ip);
  65         printk_address(regs->ip);
  66         printk(KERN_DEFAULT "RSP: %04lx:%016lx  EFLAGS: %08lx\n", regs->ss,
  67                         regs->sp, regs->flags);
  68         printk(KERN_DEFAULT "RAX: %016lx RBX: %016lx RCX: %016lx\n",
  69                regs->ax, regs->bx, regs->cx);
  70         printk(KERN_DEFAULT "RDX: %016lx RSI: %016lx RDI: %016lx\n",
  71                regs->dx, regs->si, regs->di);
  72         printk(KERN_DEFAULT "RBP: %016lx R08: %016lx R09: %016lx\n",
  73                regs->bp, regs->r8, regs->r9);
  74         printk(KERN_DEFAULT "R10: %016lx R11: %016lx R12: %016lx\n",
  75                regs->r10, regs->r11, regs->r12);
  76         printk(KERN_DEFAULT "R13: %016lx R14: %016lx R15: %016lx\n",
  77                regs->r13, regs->r14, regs->r15);
  78
  79         asm("movl %%ds,%0" : "=r" (ds));
  80         asm("movl %%cs,%0" : "=r" (cs));
  81         asm("movl %%es,%0" : "=r" (es));
  82         asm("movl %%fs,%0" : "=r" (fsindex));
  83         asm("movl %%gs,%0" : "=r" (gsindex));
  84
  85         rdmsrl(MSR_FS_BASE, fs);
  86         rdmsrl(MSR_GS_BASE, gs);
  87         rdmsrl(MSR_KERNEL_GS_BASE, shadowgs);
  88
  89         if (!all)
  90                 return;
  91
  92         cr0 = read_cr0();
  93         cr2 = read_cr2();
  94         cr3 = read_cr3();
  95         cr4 = __read_cr4();
  96
  97         printk(KERN_DEFAULT "FS:  %016lx(%04x) GS:%016lx(%04x) knlGS:%016lx\n",
  98                fs, fsindex, gs, gsindex, shadowgs);
  99         printk(KERN_DEFAULT "CS:  %04x DS: %04x ES: %04x CR0: %016lx\n", cs, ds,
 100                         es, cr0);
 101         printk(KERN_DEFAULT "CR2: %016lx CR3: %016lx CR4: %016lx\n", cr2, cr3,
 102                         cr4);
 103
 104         get_debugreg(d0, 0);
 105         get_debugreg(d1, 1);
 106         get_debugreg(d2, 2);
 107         get_debugreg(d3, 3);
 108         get_debugreg(d6, 6);
 109         get_debugreg(d7, 7);
 110
 111         /* Only print out debug registers if they are in their non-default state. */
 112         if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
 113             (d6 == DR6_RESERVED) && (d7 == 0x400))
 114                 return;
 115
 116         printk(KERN_DEFAULT "DR0: %016lx DR1: %016lx DR2: %016lx\n", d0, d1, d2);
 117         printk(KERN_DEFAULT "DR3: %016lx DR6: %016lx DR7: %016lx\n", d3, d6, d7);
 118
 119 }
 120
 121 void release_thread(struct task_struct *dead_task)
 122 {
 123         if (dead_task->mm) {
 124 #ifdef CONFIG_MODIFY_LDT_SYSCALL
 125                 if (dead_task->mm->context.ldt) {
 126                         pr_warn("WARNING: dead process %s still has LDT? <%p/%d>\n",
 127                                 dead_task->comm,
 128                                 dead_task->mm->context.ldt,
 129                                 dead_task->mm->context.ldt->size);
 130                         BUG();
 131                 }
 132 #endif
 133         }
 134 }
 135
 136 static inline void set_32bit_tls(struct task_struct *t, int tls, u32 addr)
 137 {
 138         struct user_desc ud = {
 139                 .base_addr = addr,
 140                 .limit = 0xfffff,
 141                 .seg_32bit = 1,
 142                 .limit_in_pages = 1,
 143                 .useable = 1,
 144         };
 145         struct desc_struct *desc = t->thread.tls_array;
 146         desc += tls;
 147         fill_ldt(desc, &ud);
 148 }
 149
 150 static inline u32 read_32bit_tls(struct task_struct *t, int tls)
 151 {
 152         return get_desc_base(&t->thread.tls_array[tls]);
 153 }
 154
 155 int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 156                 unsigned long arg, struct task_struct *p, unsigned long tls)
 157 {
 158         int err;
 159         struct pt_regs *childregs;
 160         struct task_struct *me = current;
 161
 162         p->thread.sp0 = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 163         childregs = task_pt_regs(p);
 164         p->thread.sp = (unsigned long) childregs;
 165         set_tsk_thread_flag(p, TIF_FORK);
 166         p->thread.io_bitmap_ptr = NULL;
 167
 168         savesegment(gs, p->thread.gsindex);
 169         p->thread.gs = p->thread.gsindex ? 0 : me->thread.gs;
 170         savesegment(fs, p->thread.fsindex);
 171         p->thread.fs = p->thread.fsindex ? 0 : me->thread.fs;
 172         savesegment(es, p->thread.es);
 173         savesegment(ds, p->thread.ds);
 174         memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 175
 176         if (unlikely(p->flags & PF_KTHREAD)) {
 177                 /* kernel thread */
 178                 memset(childregs, 0, sizeof(struct pt_regs));
 179                 childregs->sp = (unsigned long)childregs;
 180                 childregs->ss = __KERNEL_DS;
 181                 childregs->bx = sp; /* function */
 182                 childregs->bp = arg;
 183                 childregs->orig_ax = -1;
 184                 childregs->cs = __KERNEL_CS | get_kernel_rpl();
 185                 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
 186                 return 0;
 187         }
 188         *childregs = *current_pt_regs();
 189
 190         childregs->ax = 0;
 191         if (sp)
 192                 childregs->sp = sp;
 193
 194         err = -ENOMEM;
 195         if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
 196                 p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,
 197                                                   IO_BITMAP_BYTES, GFP_KERNEL);
 198                 if (!p->thread.io_bitmap_ptr) {
 199                         p->thread.io_bitmap_max = 0;
 200                         return -ENOMEM;
 201                 }
 202                 set_tsk_thread_flag(p, TIF_IO_BITMAP);
 203         }
 204
 205         /*
 206          * Set a new TLS for the child thread?
 207          */
 208         if (clone_flags & CLONE_SETTLS) {
 209 #ifdef CONFIG_IA32_EMULATION
 210                 if (is_ia32_task())
 211                         err = do_set_thread_area(p, -1,
 212                                 (struct user_desc __user *)tls, 0);
 213                 else
 214 #endif
 215                         err = do_arch_prctl(p, ARCH_SET_FS, tls);
 216                 if (err)
 217                         goto out;
 218         }
 219         err = 0;
 220 out:
 221         if (err && p->thread.io_bitmap_ptr) {
 222                 kfree(p->thread.io_bitmap_ptr);
 223                 p->thread.io_bitmap_max = 0;
 224         }
 225
 226         return err;
 227 }
 228
 229 static void
 230 start_thread_common(struct pt_regs *regs, unsigned long new_ip,
 231                     unsigned long new_sp,
 232                     unsigned int _cs, unsigned int _ss, unsigned int _ds)
 233 {
 234         loadsegment(fs, 0);
 235         loadsegment(es, _ds);
 236         loadsegment(ds, _ds);
 237         load_gs_index(0);
 238         regs->ip                = new_ip;
 239         regs->sp                = new_sp;
 240         regs->cs                = _cs;
 241         regs->ss                = _ss;
 242         regs->flags             = X86_EFLAGS_IF;
 243         force_iret();
 244 }
 245
 246 void
 247 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 248 {
 249         start_thread_common(regs, new_ip, new_sp,
 250                             __USER_CS, __USER_DS, 0);
 251 }
 252
 253 #ifdef CONFIG_COMPAT
 254 void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp)
 255 {
 256         start_thread_common(regs, new_ip, new_sp,
 257                             test_thread_flag(TIF_X32)
 258                             ? __USER_CS : __USER32_CS,
 259                             __USER_DS, __USER_DS);
 260 }
 261 #endif
 262
 263 /*
 264  *      switch_to(x,y) should switch tasks from x to y.
 265  *
 266  * This could still be optimized:
 267  * - fold all the options into a flag word and test it with a single test.
 268  * - could test fs/gs bitsliced
 269  *
 270  * Kprobes not supported here. Set the probe on schedule instead.
 271  * Function graph tracer not supported too.
 272  */
 273 __visible __notrace_funcgraph struct task_struct *
 274 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 275 {
 276         struct thread_struct *prev = &prev_p->thread;
 277         struct thread_struct *next = &next_p->thread;
 278         struct fpu *prev_fpu = &prev->fpu;
 279         struct fpu *next_fpu = &next->fpu;
 280         int cpu = smp_processor_id();
 281         struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
 282         unsigned fsindex, gsindex;
 283         fpu_switch_t fpu_switch;
 284
 285         fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu);
 286
 287         /* We must save %fs and %gs before load_TLS() because
 288          * %fs and %gs may be cleared by load_TLS().
 289          *
 290          * (e.g. xen_load_tls())
 291          */
 292         savesegment(fs, fsindex);
 293         savesegment(gs, gsindex);
 294
 295         /*
 296          * Load TLS before restoring any segments so that segment loads
 297          * reference the correct GDT entries.
 298          */
 299         load_TLS(next, cpu);
 300
 301         /*
 302          * Leave lazy mode, flushing any hypercalls made here.  This
 303          * must be done after loading TLS entries in the GDT but before
 304          * loading segments that might reference them, and and it must
 305          * be done before fpu__restore(), so the TS bit is up to
 306          * date.
 307          */
 308         arch_end_context_switch(next_p);
 309
 310         /* Switch DS and ES.
 311          *
 312          * Reading them only returns the selectors, but writing them (if
 313          * nonzero) loads the full descriptor from the GDT or LDT.  The
 314          * LDT for next is loaded in switch_mm, and the GDT is loaded
 315          * above.
 316          *
 317          * We therefore need to write new values to the segment
 318          * registers on every context switch unless both the new and old
 319          * values are zero.
 320          *
 321          * Note that we don't need to do anything for CS and SS, as
 322          * those are saved and restored as part of pt_regs.
 323          */
 324         savesegment(es, prev->es);
 325         if (unlikely(next->es | prev->es))
 326                 loadsegment(es, next->es);
 327
 328         savesegment(ds, prev->ds);
 329         if (unlikely(next->ds | prev->ds))
 330                 loadsegment(ds, next->ds);
 331
 332         /*
 333          * Switch FS and GS.
 334          *
 335          * These are even more complicated than FS and GS: they have
 336          * 64-bit bases are that controlled by arch_prctl.  Those bases
 337          * only differ from the values in the GDT or LDT if the selector
 338          * is 0.
 339          *
 340          * Loading the segment register resets the hidden base part of
 341          * the register to 0 or the value from the GDT / LDT.  If the
 342          * next base address zero, writing 0 to the segment register is
 343          * much faster than using wrmsr to explicitly zero the base.
 344          *
 345          * The thread_struct.fs and thread_struct.gs values are 0
 346          * if the fs and gs bases respectively are not overridden
 347          * from the values implied by fsindex and gsindex.  They
 348          * are nonzero, and store the nonzero base addresses, if
 349          * the bases are overridden.
 350          *
 351          * (fs != 0 && fsindex != 0) || (gs != 0 && gsindex != 0) should
 352          * be impossible.
 353          *
 354          * Therefore we need to reload the segment registers if either
 355          * the old or new selector is nonzero, and we need to override
 356          * the base address if next thread expects it to be overridden.
 357          *
 358          * This code is unnecessarily slow in the case where the old and
 359          * new indexes are zero and the new base is nonzero -- it will
 360          * unnecessarily write 0 to the selector before writing the new
 361          * base address.
 362          *
 363          * Note: This all depends on arch_prctl being the only way that
 364          * user code can override the segment base.  Once wrfsbase and
 365          * wrgsbase are enabled, most of this code will need to change.
 366          */
 367         if (unlikely(fsindex | next->fsindex | prev->fs)) {
 368                 loadsegment(fs, next->fsindex);
 369
 370                 /*
 371                  * If user code wrote a nonzero value to FS, then it also
 372                  * cleared the overridden base address.
 373                  *
 374                  * XXX: if user code wrote 0 to FS and cleared the base
 375                  * address itself, we won't notice and we'll incorrectly
 376                  * restore the prior base address next time we reschdule
 377                  * the process.
 378                  */
 379                 if (fsindex)
 380                         prev->fs = 0;
 381         }
 382         if (next->fs)
 383                 wrmsrl(MSR_FS_BASE, next->fs);
 384         prev->fsindex = fsindex;
 385
 386         if (unlikely(gsindex | next->gsindex | prev->gs)) {
 387                 load_gs_index(next->gsindex);
 388
 389                 /* This works (and fails) the same way as fsindex above. */
 390                 if (gsindex)
 391                         prev->gs = 0;
 392         }
 393         if (next->gs)
 394                 wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
 395         prev->gsindex = gsindex;
 396
 397         switch_fpu_finish(next_fpu, fpu_switch);
 398
 399         /*
 400          * Switch the PDA and FPU contexts.
 401          */
 402         this_cpu_write(current_task, next_p);
 403
 404         /*
 405          * If it were not for PREEMPT_ACTIVE we could guarantee that the
 406          * preempt_count of all tasks was equal here and this would not be
 407          * needed.
 408          */
 409         task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
 410         this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
 411
 412         /* Reload esp0 and ss1.  This changes current_thread_info(). */
 413         load_sp0(tss, next);
 414
 415         /*
 416          * Now maybe reload the debug registers and handle I/O bitmaps
 417          */
 418         if (unlikely(task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT ||
 419                      task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
 420                 __switch_to_xtra(prev_p, next_p, tss);
 421
 422         if (static_cpu_has_bug(X86_BUG_SYSRET_SS_ATTRS)) {
 423                 /*
 424                  * AMD CPUs have a misfeature: SYSRET sets the SS selector but
 425                  * does not update the cached descriptor.  As a result, if we
 426                  * do SYSRET while SS is NULL, we'll end up in user mode with
 427                  * SS apparently equal to __USER_DS but actually unusable.
 428                  *
 429                  * The straightforward workaround would be to fix it up just
 430                  * before SYSRET, but that would slow down the system call
 431                  * fast paths.  Instead, we ensure that SS is never NULL in
 432                  * system call context.  We do this by replacing NULL SS
 433                  * selectors at every context switch.  SYSCALL sets up a valid
 434                  * SS, so the only way to get NULL is to re-enter the kernel
 435                  * from CPL 3 through an interrupt.  Since that can't happen
 436                  * in the same task as a running syscall, we are guaranteed to
 437                  * context switch between every interrupt vector entry and a
 438                  * subsequent SYSRET.
 439                  *
 440                  * We read SS first because SS reads are much faster than
 441                  * writes.  Out of caution, we force SS to __KERNEL_DS even if
 442                  * it previously had a different non-NULL value.
 443                  */
 444                 unsigned short ss_sel;
 445                 savesegment(ss, ss_sel);
 446                 if (ss_sel != __KERNEL_DS)
 447                         loadsegment(ss, __KERNEL_DS);
 448         }
 449
 450         return prev_p;
 451 }
 452
 453 void set_personality_64bit(void)
 454 {
 455         /* inherit personality from parent */
 456
 457         /* Make sure to be in 64bit mode */
 458         clear_thread_flag(TIF_IA32);
 459         clear_thread_flag(TIF_ADDR32);
 460         clear_thread_flag(TIF_X32);
 461
 462         /* Ensure the corresponding mm is not marked. */
 463         if (current->mm)
 464                 current->mm->context.ia32_compat = 0;
 465
 466         /* TBD: overwrites user setup. Should have two bits.
 467            But 64bit processes have always behaved this way,
 468            so it's not too bad. The main problem is just that
 469            32bit childs are affected again. */
 470         current->personality &= ~READ_IMPLIES_EXEC;
 471 }
 472
 473 void set_personality_ia32(bool x32)
 474 {
 475         /* inherit personality from parent */
 476
 477         /* Make sure to be in 32bit mode */
 478         set_thread_flag(TIF_ADDR32);
 479
 480         /* Mark the associated mm as containing 32-bit tasks. */
 481         if (x32) {
 482                 clear_thread_flag(TIF_IA32);
 483                 set_thread_flag(TIF_X32);
 484                 if (current->mm)
 485                         current->mm->context.ia32_compat = TIF_X32;
 486                 current->personality &= ~READ_IMPLIES_EXEC;
 487                 /* is_compat_task() uses the presence of the x32
 488                    syscall bit flag to determine compat status */
 489                 current_thread_info()->status &= ~TS_COMPAT;
 490         } else {
 491                 set_thread_flag(TIF_IA32);
 492                 clear_thread_flag(TIF_X32);
 493                 if (current->mm)
 494                         current->mm->context.ia32_compat = TIF_IA32;
 495                 current->personality |= force_personality32;
 496                 /* Prepare the first "return" to user space */
 497                 current_thread_info()->status |= TS_COMPAT;
 498         }
 499 }
 500 EXPORT_SYMBOL_GPL(set_personality_ia32);
 501
 502 long do_arch_prctl(struct task_struct *task, int code, unsigned long addr)
 503 {
 504         int ret = 0;
 505         int doit = task == current;
 506         int cpu;
 507
 508         switch (code) {
 509         case ARCH_SET_GS:
 510                 if (addr >= TASK_SIZE_OF(task))
 511                         return -EPERM;
 512                 cpu = get_cpu();
 513                 /* handle small bases via the GDT because that's faster to
 514                    switch. */
 515                 if (addr <= 0xffffffff) {
 516                         set_32bit_tls(task, GS_TLS, addr);
 517                         if (doit) {
 518                                 load_TLS(&task->thread, cpu);
 519                                 load_gs_index(GS_TLS_SEL);
 520                         }
 521                         task->thread.gsindex = GS_TLS_SEL;
 522                         task->thread.gs = 0;
 523                 } else {
 524                         task->thread.gsindex = 0;
 525                         task->thread.gs = addr;
 526                         if (doit) {
 527                                 load_gs_index(0);
 528                                 ret = wrmsrl_safe(MSR_KERNEL_GS_BASE, addr);
 529                         }
 530                 }
 531                 put_cpu();
 532                 break;
 533         case ARCH_SET_FS:
 534                 /* Not strictly needed for fs, but do it for symmetry
 535                    with gs */
 536                 if (addr >= TASK_SIZE_OF(task))
 537                         return -EPERM;
 538                 cpu = get_cpu();
 539                 /* handle small bases via the GDT because that's faster to
 540                    switch. */
 541                 if (addr <= 0xffffffff) {
 542                         set_32bit_tls(task, FS_TLS, addr);
 543                         if (doit) {
 544                                 load_TLS(&task->thread, cpu);
 545                                 loadsegment(fs, FS_TLS_SEL);
 546                         }
 547                         task->thread.fsindex = FS_TLS_SEL;
 548                         task->thread.fs = 0;
 549                 } else {
 550                         task->thread.fsindex = 0;
 551                         task->thread.fs = addr;
 552                         if (doit) {
 553                                 /* set the selector to 0 to not confuse
 554                                    __switch_to */
 555                                 loadsegment(fs, 0);
 556                                 ret = wrmsrl_safe(MSR_FS_BASE, addr);
 557                         }
 558                 }
 559                 put_cpu();
 560                 break;
 561         case ARCH_GET_FS: {
 562                 unsigned long base;
 563                 if (task->thread.fsindex == FS_TLS_SEL)
 564                         base = read_32bit_tls(task, FS_TLS);
 565                 else if (doit)
 566                         rdmsrl(MSR_FS_BASE, base);
 567                 else
 568                         base = task->thread.fs;
 569                 ret = put_user(base, (unsigned long __user *)addr);
 570                 break;
 571         }
 572         case ARCH_GET_GS: {
 573                 unsigned long base;
 574                 unsigned gsindex;
 575                 if (task->thread.gsindex == GS_TLS_SEL)
 576                         base = read_32bit_tls(task, GS_TLS);
 577                 else if (doit) {
 578                         savesegment(gs, gsindex);
 579                         if (gsindex)
 580                                 rdmsrl(MSR_KERNEL_GS_BASE, base);
 581                         else
 582                                 base = task->thread.gs;
 583                 } else
 584                         base = task->thread.gs;
 585                 ret = put_user(base, (unsigned long __user *)addr);
 586                 break;
 587         }
 588
 589         default:
 590                 ret = -EINVAL;
 591                 break;
 592         }
 593
 594         return ret;
 595 }
 596
 597 long sys_arch_prctl(int code, unsigned long addr)
 598 {
 599         return do_arch_prctl(current, code, addr);
 600 }
 601
 602 unsigned long KSTK_ESP(struct task_struct *task)
 603 {
 604         return task_pt_regs(task)->sp;
 605 }