arch/x86/kernel/signal.c

   1 /*
   2  *  Copyright (C) 1991, 1992  Linus Torvalds
   3  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   4  *
   5  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   6  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   7  *  2000-2002   x86-64 support by Andi Kleen
   8  */
   9
  10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  11
  12 #include <linux/sched.h>
  13 #include <linux/mm.h>
  14 #include <linux/smp.h>
  15 #include <linux/kernel.h>
  16 #include <linux/errno.h>
  17 #include <linux/wait.h>
  18 #include <linux/tracehook.h>
  19 #include <linux/unistd.h>
  20 #include <linux/stddef.h>
  21 #include <linux/personality.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/user-return-notifier.h>
  24 #include <linux/uprobes.h>
  25 #include <linux/context_tracking.h>
  26
  27 #include <asm/processor.h>
  28 #include <asm/ucontext.h>
  29 #include <asm/fpu/internal.h>
  30 #include <asm/fpu/signal.h>
  31 #include <asm/vdso.h>
  32 #include <asm/mce.h>
  33 #include <asm/sighandling.h>
  34 #include <asm/vm86.h>
  35
  36 #ifdef CONFIG_X86_64
  37 #include <asm/proto.h>
  38 #include <asm/ia32_unistd.h>
  39 #endif /* CONFIG_X86_64 */
  40
  41 #include <asm/syscall.h>
  42 #include <asm/syscalls.h>
  43
  44 #include <asm/sigframe.h>
  45 #include <asm/signal.h>
  46
  47 #define COPY(x)                 do {                    \
  48         get_user_ex(regs->x, &sc->x);                   \
  49 } while (0)
  50
  51 #define GET_SEG(seg)            ({                      \
  52         unsigned short tmp;                             \
  53         get_user_ex(tmp, &sc->seg);                     \
  54         tmp;                                            \
  55 })
  56
  57 #define COPY_SEG(seg)           do {                    \
  58         regs->seg = GET_SEG(seg);                       \
  59 } while (0)
  60
  61 #define COPY_SEG_CPL3(seg)      do {                    \
  62         regs->seg = GET_SEG(seg) | 3;                   \
  63 } while (0)
  64
  65 #ifdef CONFIG_X86_64
  66 /*
  67  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  68  * alone.  Using this generally makes no sense unless
  69  * user_64bit_mode(regs) would return true.
  70  */
  71 static void force_valid_ss(struct pt_regs *regs)
  72 {
  73         u32 ar;
  74         asm volatile ("lar %[old_ss], %[ar]\n\t"
  75                       "jz 1f\n\t"               /* If invalid: */
  76                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  77                       "1:"
  78                       : [ar] "=r" (ar)
  79                       : [old_ss] "rm" ((u16)regs->ss));
  80
  81         /*
  82          * For a valid 64-bit user context, we need DPL 3, type
  83          * read-write data or read-write exp-down data, and S and P
  84          * set.  We can't use VERW because VERW doesn't check the
  85          * P bit.
  86          */
  87         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  88         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  89             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  90                 regs->ss = __USER_DS;
  91 }
  92 #endif
  93
  94 static int restore_sigcontext(struct pt_regs *regs,
  95                               struct sigcontext __user *sc,
  96                               unsigned long uc_flags)
  97 {
  98         unsigned long buf_val;
  99         void __user *buf;
 100         unsigned int tmpflags;
 101         unsigned int err = 0;
 102
 103         /* Always make any pending restarted system calls return -EINTR */
 104         current->restart_block.fn = do_no_restart_syscall;
 105
 106         get_user_try {
 107
 108 #ifdef CONFIG_X86_32
 109                 set_user_gs(regs, GET_SEG(gs));
 110                 COPY_SEG(fs);
 111                 COPY_SEG(es);
 112                 COPY_SEG(ds);
 113 #endif /* CONFIG_X86_32 */
 114
 115                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 116                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
 117
 118 #ifdef CONFIG_X86_64
 119                 COPY(r8);
 120                 COPY(r9);
 121                 COPY(r10);
 122                 COPY(r11);
 123                 COPY(r12);
 124                 COPY(r13);
 125                 COPY(r14);
 126                 COPY(r15);
 127 #endif /* CONFIG_X86_64 */
 128
 129                 COPY_SEG_CPL3(cs);
 130                 COPY_SEG_CPL3(ss);
 131
 132 #ifdef CONFIG_X86_64
 133                 /*
 134                  * Fix up SS if needed for the benefit of old DOSEMU and
 135                  * CRIU.
 136                  */
 137                 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
 138                              user_64bit_mode(regs)))
 139                         force_valid_ss(regs);
 140 #endif
 141
 142                 get_user_ex(tmpflags, &sc->flags);
 143                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 144                 regs->orig_ax = -1;             /* disable syscall checks */
 145
 146                 get_user_ex(buf_val, &sc->fpstate);
 147                 buf = (void __user *)buf_val;
 148         } get_user_catch(err);
 149
 150         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
 151
 152         force_iret();
 153
 154         return err;
 155 }
 156
 157 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 158                      struct pt_regs *regs, unsigned long mask)
 159 {
 160         int err = 0;
 161
 162         put_user_try {
 163
 164 #ifdef CONFIG_X86_32
 165                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
 166                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
 167                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
 168                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
 169 #endif /* CONFIG_X86_32 */
 170
 171                 put_user_ex(regs->di, &sc->di);
 172                 put_user_ex(regs->si, &sc->si);
 173                 put_user_ex(regs->bp, &sc->bp);
 174                 put_user_ex(regs->sp, &sc->sp);
 175                 put_user_ex(regs->bx, &sc->bx);
 176                 put_user_ex(regs->dx, &sc->dx);
 177                 put_user_ex(regs->cx, &sc->cx);
 178                 put_user_ex(regs->ax, &sc->ax);
 179 #ifdef CONFIG_X86_64
 180                 put_user_ex(regs->r8, &sc->r8);
 181                 put_user_ex(regs->r9, &sc->r9);
 182                 put_user_ex(regs->r10, &sc->r10);
 183                 put_user_ex(regs->r11, &sc->r11);
 184                 put_user_ex(regs->r12, &sc->r12);
 185                 put_user_ex(regs->r13, &sc->r13);
 186                 put_user_ex(regs->r14, &sc->r14);
 187                 put_user_ex(regs->r15, &sc->r15);
 188 #endif /* CONFIG_X86_64 */
 189
 190                 put_user_ex(current->thread.trap_nr, &sc->trapno);
 191                 put_user_ex(current->thread.error_code, &sc->err);
 192                 put_user_ex(regs->ip, &sc->ip);
 193 #ifdef CONFIG_X86_32
 194                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
 195                 put_user_ex(regs->flags, &sc->flags);
 196                 put_user_ex(regs->sp, &sc->sp_at_signal);
 197                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
 198 #else /* !CONFIG_X86_32 */
 199                 put_user_ex(regs->flags, &sc->flags);
 200                 put_user_ex(regs->cs, &sc->cs);
 201                 put_user_ex(0, &sc->gs);
 202                 put_user_ex(0, &sc->fs);
 203                 put_user_ex(regs->ss, &sc->ss);
 204 #endif /* CONFIG_X86_32 */
 205
 206                 put_user_ex(fpstate, &sc->fpstate);
 207
 208                 /* non-iBCS2 extensions.. */
 209                 put_user_ex(mask, &sc->oldmask);
 210                 put_user_ex(current->thread.cr2, &sc->cr2);
 211         } put_user_catch(err);
 212
 213         return err;
 214 }
 215
 216 /*
 217  * Set up a signal frame.
 218  */
 219
 220 /*
 221  * Determine which stack to use..
 222  */
 223 static unsigned long align_sigframe(unsigned long sp)
 224 {
 225 #ifdef CONFIG_X86_32
 226         /*
 227          * Align the stack pointer according to the i386 ABI,
 228          * i.e. so that on function entry ((sp + 4) & 15) == 0.
 229          */
 230         sp = ((sp + 4) & -16ul) - 4;
 231 #else /* !CONFIG_X86_32 */
 232         sp = round_down(sp, 16) - 8;
 233 #endif
 234         return sp;
 235 }
 236
 237 static void __user *
 238 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 239              void __user **fpstate)
 240 {
 241         /* Default to using normal stack */
 242         unsigned long math_size = 0;
 243         unsigned long sp = regs->sp;
 244         unsigned long buf_fx = 0;
 245         int onsigstack = on_sig_stack(sp);
 246         struct fpu *fpu = &current->thread.fpu;
 247
 248         /* redzone */
 249         if (IS_ENABLED(CONFIG_X86_64))
 250                 sp -= 128;
 251
 252         /* This is the X/Open sanctioned signal stack switching.  */
 253         if (ka->sa.sa_flags & SA_ONSTACK) {
 254                 if (sas_ss_flags(sp) == 0)
 255                         sp = current->sas_ss_sp + current->sas_ss_size;
 256         } else if (IS_ENABLED(CONFIG_X86_32) &&
 257                    !onsigstack &&
 258                    (regs->ss & 0xffff) != __USER_DS &&
 259                    !(ka->sa.sa_flags & SA_RESTORER) &&
 260                    ka->sa.sa_restorer) {
 261                 /* This is the legacy signal stack switching. */
 262                 sp = (unsigned long) ka->sa.sa_restorer;
 263         }
 264
 265         if (fpu->fpstate_active) {
 266                 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 267                                           &buf_fx, &math_size);
 268                 *fpstate = (void __user *)sp;
 269         }
 270
 271         sp = align_sigframe(sp - frame_size);
 272
 273         /*
 274          * If we are on the alternate signal stack and would overflow it, don't.
 275          * Return an always-bogus address instead so we will die with SIGSEGV.
 276          */
 277         if (onsigstack && !likely(on_sig_stack(sp)))
 278                 return (void __user *)-1L;
 279
 280         /* save i387 and extended state */
 281         if (fpu->fpstate_active &&
 282             copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
 283                 return (void __user *)-1L;
 284
 285         return (void __user *)sp;
 286 }
 287
 288 #ifdef CONFIG_X86_32
 289 static const struct {
 290         u16 poplmovl;
 291         u32 val;
 292         u16 int80;
 293 } __attribute__((packed)) retcode = {
 294         0xb858,         /* popl %eax; movl $..., %eax */
 295         __NR_sigreturn,
 296         0x80cd,         /* int $0x80 */
 297 };
 298
 299 static const struct {
 300         u8  movl;
 301         u32 val;
 302         u16 int80;
 303         u8  pad;
 304 } __attribute__((packed)) rt_retcode = {
 305         0xb8,           /* movl $..., %eax */
 306         __NR_rt_sigreturn,
 307         0x80cd,         /* int $0x80 */
 308         0
 309 };
 310
 311 static int
 312 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 313               struct pt_regs *regs)
 314 {
 315         struct sigframe __user *frame;
 316         void __user *restorer;
 317         int err = 0;
 318         void __user *fpstate = NULL;
 319
 320         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 321
 322         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 323                 return -EFAULT;
 324
 325         if (__put_user(sig, &frame->sig))
 326                 return -EFAULT;
 327
 328         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 329                 return -EFAULT;
 330
 331         if (_NSIG_WORDS > 1) {
 332                 if (__copy_to_user(&frame->extramask, &set->sig[1],
 333                                    sizeof(frame->extramask)))
 334                         return -EFAULT;
 335         }
 336
 337         if (current->mm->context.vdso)
 338                 restorer = current->mm->context.vdso +
 339                         vdso_image_32.sym___kernel_sigreturn;
 340         else
 341                 restorer = &frame->retcode;
 342         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 343                 restorer = ksig->ka.sa.sa_restorer;
 344
 345         /* Set up to return from userspace.  */
 346         err |= __put_user(restorer, &frame->pretcode);
 347
 348         /*
 349          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 350          *
 351          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 352          * reasons and because gdb uses it as a signature to notice
 353          * signal handler stack frames.
 354          */
 355         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 356
 357         if (err)
 358                 return -EFAULT;
 359
 360         /* Set up registers for signal handler */
 361         regs->sp = (unsigned long)frame;
 362         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 363         regs->ax = (unsigned long)sig;
 364         regs->dx = 0;
 365         regs->cx = 0;
 366
 367         regs->ds = __USER_DS;
 368         regs->es = __USER_DS;
 369         regs->ss = __USER_DS;
 370         regs->cs = __USER_CS;
 371
 372         return 0;
 373 }
 374
 375 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 376                             sigset_t *set, struct pt_regs *regs)
 377 {
 378         struct rt_sigframe __user *frame;
 379         void __user *restorer;
 380         int err = 0;
 381         void __user *fpstate = NULL;
 382
 383         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 384
 385         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 386                 return -EFAULT;
 387
 388         put_user_try {
 389                 put_user_ex(sig, &frame->sig);
 390                 put_user_ex(&frame->info, &frame->pinfo);
 391                 put_user_ex(&frame->uc, &frame->puc);
 392
 393                 /* Create the ucontext.  */
 394                 if (boot_cpu_has(X86_FEATURE_XSAVE))
 395                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 396                 else
 397                         put_user_ex(0, &frame->uc.uc_flags);
 398                 put_user_ex(0, &frame->uc.uc_link);
 399                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 400
 401                 /* Set up to return from userspace.  */
 402                 restorer = current->mm->context.vdso +
 403                         vdso_image_32.sym___kernel_rt_sigreturn;
 404                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 405                         restorer = ksig->ka.sa.sa_restorer;
 406                 put_user_ex(restorer, &frame->pretcode);
 407
 408                 /*
 409                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 410                  *
 411                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 412                  * reasons and because gdb uses it as a signature to notice
 413                  * signal handler stack frames.
 414                  */
 415                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 416         } put_user_catch(err);
 417
 418         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 419         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 420                                 regs, set->sig[0]);
 421         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 422
 423         if (err)
 424                 return -EFAULT;
 425
 426         /* Set up registers for signal handler */
 427         regs->sp = (unsigned long)frame;
 428         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 429         regs->ax = (unsigned long)sig;
 430         regs->dx = (unsigned long)&frame->info;
 431         regs->cx = (unsigned long)&frame->uc;
 432
 433         regs->ds = __USER_DS;
 434         regs->es = __USER_DS;
 435         regs->ss = __USER_DS;
 436         regs->cs = __USER_CS;
 437
 438         return 0;
 439 }
 440 #else /* !CONFIG_X86_32 */
 441 static unsigned long frame_uc_flags(struct pt_regs *regs)
 442 {
 443         unsigned long flags;
 444
 445         if (boot_cpu_has(X86_FEATURE_XSAVE))
 446                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 447         else
 448                 flags = UC_SIGCONTEXT_SS;
 449
 450         if (likely(user_64bit_mode(regs)))
 451                 flags |= UC_STRICT_RESTORE_SS;
 452
 453         return flags;
 454 }
 455
 456 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 457                             sigset_t *set, struct pt_regs *regs)
 458 {
 459         struct rt_sigframe __user *frame;
 460         void __user *fp = NULL;
 461         int err = 0;
 462
 463         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 464
 465         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 466                 return -EFAULT;
 467
 468         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 469                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 470                         return -EFAULT;
 471         }
 472
 473         put_user_try {
 474                 /* Create the ucontext.  */
 475                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 476                 put_user_ex(0, &frame->uc.uc_link);
 477                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 478
 479                 /* Set up to return from userspace.  If provided, use a stub
 480                    already in userspace.  */
 481                 /* x86-64 should always use SA_RESTORER. */
 482                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 483                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 484                 } else {
 485                         /* could use a vstub here */
 486                         err |= -EFAULT;
 487                 }
 488         } put_user_catch(err);
 489
 490         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 491         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 492
 493         if (err)
 494                 return -EFAULT;
 495
 496         /* Set up registers for signal handler */
 497         regs->di = sig;
 498         /* In case the signal handler was declared without prototypes */
 499         regs->ax = 0;
 500
 501         /* This also works for non SA_SIGINFO handlers because they expect the
 502            next argument after the signal number on the stack. */
 503         regs->si = (unsigned long)&frame->info;
 504         regs->dx = (unsigned long)&frame->uc;
 505         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 506
 507         regs->sp = (unsigned long)frame;
 508
 509         /*
 510          * Set up the CS and SS registers to run signal handlers in
 511          * 64-bit mode, even if the handler happens to be interrupting
 512          * 32-bit or 16-bit code.
 513          *
 514          * SS is subtle.  In 64-bit mode, we don't need any particular
 515          * SS descriptor, but we do need SS to be valid.  It's possible
 516          * that the old SS is entirely bogus -- this can happen if the
 517          * signal we're trying to deliver is #GP or #SS caused by a bad
 518          * SS value.  We also have a compatbility issue here: DOSEMU
 519          * relies on the contents of the SS register indicating the
 520          * SS value at the time of the signal, even though that code in
 521          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 522          * avoids relying on sigreturn to restore SS; instead it uses
 523          * a trampoline.)  So we do our best: if the old SS was valid,
 524          * we keep it.  Otherwise we replace it.
 525          */
 526         regs->cs = __USER_CS;
 527
 528         if (unlikely(regs->ss != __USER_DS))
 529                 force_valid_ss(regs);
 530
 531         return 0;
 532 }
 533 #endif /* CONFIG_X86_32 */
 534
 535 static int x32_setup_rt_frame(struct ksignal *ksig,
 536                               compat_sigset_t *set,
 537                               struct pt_regs *regs)
 538 {
 539 #ifdef CONFIG_X86_X32_ABI
 540         struct rt_sigframe_x32 __user *frame;
 541         void __user *restorer;
 542         int err = 0;
 543         void __user *fpstate = NULL;
 544
 545         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 546
 547         if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
 548                 return -EFAULT;
 549
 550         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 551                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 552                         return -EFAULT;
 553         }
 554
 555         put_user_try {
 556                 /* Create the ucontext.  */
 557                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 558                 put_user_ex(0, &frame->uc.uc_link);
 559                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 560                 put_user_ex(0, &frame->uc.uc__pad0);
 561
 562                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 563                         restorer = ksig->ka.sa.sa_restorer;
 564                 } else {
 565                         /* could use a vstub here */
 566                         restorer = NULL;
 567                         err |= -EFAULT;
 568                 }
 569                 put_user_ex(restorer, &frame->pretcode);
 570         } put_user_catch(err);
 571
 572         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 573                                 regs, set->sig[0]);
 574         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 575
 576         if (err)
 577                 return -EFAULT;
 578
 579         /* Set up registers for signal handler */
 580         regs->sp = (unsigned long) frame;
 581         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 582
 583         /* We use the x32 calling convention here... */
 584         regs->di = ksig->sig;
 585         regs->si = (unsigned long) &frame->info;
 586         regs->dx = (unsigned long) &frame->uc;
 587
 588         loadsegment(ds, __USER_DS);
 589         loadsegment(es, __USER_DS);
 590
 591         regs->cs = __USER_CS;
 592         regs->ss = __USER_DS;
 593 #endif  /* CONFIG_X86_X32_ABI */
 594
 595         return 0;
 596 }
 597
 598 /*
 599  * Do a signal return; undo the signal stack.
 600  */
 601 #ifdef CONFIG_X86_32
 602 asmlinkage unsigned long sys_sigreturn(void)
 603 {
 604         struct pt_regs *regs = current_pt_regs();
 605         struct sigframe __user *frame;
 606         sigset_t set;
 607
 608         frame = (struct sigframe __user *)(regs->sp - 8);
 609
 610         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 611                 goto badframe;
 612         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
 613                 && __copy_from_user(&set.sig[1], &frame->extramask,
 614                                     sizeof(frame->extramask))))
 615                 goto badframe;
 616
 617         set_current_blocked(&set);
 618
 619         /*
 620          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 621          * Save a few cycles by skipping the __get_user.
 622          */
 623         if (restore_sigcontext(regs, &frame->sc, 0))
 624                 goto badframe;
 625         return regs->ax;
 626
 627 badframe:
 628         signal_fault(regs, frame, "sigreturn");
 629
 630         return 0;
 631 }
 632 #endif /* CONFIG_X86_32 */
 633
 634 asmlinkage long sys_rt_sigreturn(void)
 635 {
 636         struct pt_regs *regs = current_pt_regs();
 637         struct rt_sigframe __user *frame;
 638         sigset_t set;
 639         unsigned long uc_flags;
 640
 641         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 642         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 643                 goto badframe;
 644         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 645                 goto badframe;
 646         if (__get_user(uc_flags, &frame->uc.uc_flags))
 647                 goto badframe;
 648
 649         set_current_blocked(&set);
 650
 651         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 652                 goto badframe;
 653
 654         if (restore_altstack(&frame->uc.uc_stack))
 655                 goto badframe;
 656
 657         return regs->ax;
 658
 659 badframe:
 660         signal_fault(regs, frame, "rt_sigreturn");
 661         return 0;
 662 }
 663
 664 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 665 {
 666         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 667                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 668 }
 669
 670 static inline int is_ia32_frame(struct ksignal *ksig)
 671 {
 672         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 673 }
 674
 675 static inline int is_x32_frame(struct ksignal *ksig)
 676 {
 677         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 678                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 679 }
 680
 681 static int
 682 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 683 {
 684         int usig = ksig->sig;
 685         sigset_t *set = sigmask_to_save();
 686         compat_sigset_t *cset = (compat_sigset_t *) set;
 687
 688         /* Set up the stack frame */
 689         if (is_ia32_frame(ksig)) {
 690                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 691                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 692                 else
 693                         return ia32_setup_frame(usig, ksig, cset, regs);
 694         } else if (is_x32_frame(ksig)) {
 695                 return x32_setup_rt_frame(ksig, cset, regs);
 696         } else {
 697                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 698         }
 699 }
 700
 701 static void
 702 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 703 {
 704         bool stepping, failed;
 705         struct fpu *fpu = &current->thread.fpu;
 706
 707         if (v8086_mode(regs))
 708                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 709
 710         /* Are we from a system call? */
 711         if (syscall_get_nr(current, regs) >= 0) {
 712                 /* If so, check system call restarting.. */
 713                 switch (syscall_get_error(current, regs)) {
 714                 case -ERESTART_RESTARTBLOCK:
 715                 case -ERESTARTNOHAND:
 716                         regs->ax = -EINTR;
 717                         break;
 718
 719                 case -ERESTARTSYS:
 720                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 721                                 regs->ax = -EINTR;
 722                                 break;
 723                         }
 724                 /* fallthrough */
 725                 case -ERESTARTNOINTR:
 726                         regs->ax = regs->orig_ax;
 727                         regs->ip -= 2;
 728                         break;
 729                 }
 730         }
 731
 732         /*
 733          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 734          * so that register information in the sigcontext is correct and
 735          * then notify the tracer before entering the signal handler.
 736          */
 737         stepping = test_thread_flag(TIF_SINGLESTEP);
 738         if (stepping)
 739                 user_disable_single_step(current);
 740
 741         failed = (setup_rt_frame(ksig, regs) < 0);
 742         if (!failed) {
 743                 /*
 744                  * Clear the direction flag as per the ABI for function entry.
 745                  *
 746                  * Clear RF when entering the signal handler, because
 747                  * it might disable possible debug exception from the
 748                  * signal handler.
 749                  *
 750                  * Clear TF for the case when it wasn't set by debugger to
 751                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 752                  */
 753                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 754                 /*
 755                  * Ensure the signal handler starts with the new fpu state.
 756                  */
 757                 if (fpu->fpstate_active)
 758                         fpu__clear(fpu);
 759         }
 760         signal_setup_done(failed, ksig, stepping);
 761 }
 762
 763 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 764 {
 765         /*
 766          * This function is fundamentally broken as currently
 767          * implemented.
 768          *
 769          * The idea is that we want to trigger a call to the
 770          * restart_block() syscall and that we want in_ia32_syscall(),
 771          * in_x32_syscall(), etc. to match whatever they were in the
 772          * syscall being restarted.  We assume that the syscall
 773          * instruction at (regs->ip - 2) matches whatever syscall
 774          * instruction we used to enter in the first place.
 775          *
 776          * The problem is that we can get here when ptrace pokes
 777          * syscall-like values into regs even if we're not in a syscall
 778          * at all.
 779          *
 780          * For now, we maintain historical behavior and guess based on
 781          * stored state.  We could do better by saving the actual
 782          * syscall arch in restart_block or (with caveats on x32) by
 783          * checking if regs->ip points to 'int $0x80'.  The current
 784          * behavior is incorrect if a tracer has a different bitness
 785          * than the tracee.
 786          */
 787 #ifdef CONFIG_IA32_EMULATION
 788         if (current->thread.status & (TS_COMPAT|TS_I386_REGS_POKED))
 789                 return __NR_ia32_restart_syscall;
 790 #endif
 791 #ifdef CONFIG_X86_X32_ABI
 792         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 793 #else
 794         return __NR_restart_syscall;
 795 #endif
 796 }
 797
 798 /*
 799  * Note that 'init' is a special process: it doesn't get signals it doesn't
 800  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 801  * mistake.
 802  */
 803 void do_signal(struct pt_regs *regs)
 804 {
 805         struct ksignal ksig;
 806
 807         if (get_signal(&ksig)) {
 808                 /* Whee! Actually deliver the signal.  */
 809                 handle_signal(&ksig, regs);
 810                 return;
 811         }
 812
 813         /* Did we come from a system call? */
 814         if (syscall_get_nr(current, regs) >= 0) {
 815                 /* Restart the system call - no handlers present */
 816                 switch (syscall_get_error(current, regs)) {
 817                 case -ERESTARTNOHAND:
 818                 case -ERESTARTSYS:
 819                 case -ERESTARTNOINTR:
 820                         regs->ax = regs->orig_ax;
 821                         regs->ip -= 2;
 822                         break;
 823
 824                 case -ERESTART_RESTARTBLOCK:
 825                         regs->ax = get_nr_restart_syscall(regs);
 826                         regs->ip -= 2;
 827                         break;
 828                 }
 829         }
 830
 831         /*
 832          * If there's no signal to deliver, we just put the saved sigmask
 833          * back.
 834          */
 835         restore_saved_sigmask();
 836 }
 837
 838 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 839 {
 840         struct task_struct *me = current;
 841
 842         if (show_unhandled_signals && printk_ratelimit()) {
 843                 printk("%s"
 844                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 845                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 846                        me->comm, me->pid, where, frame,
 847                        regs->ip, regs->sp, regs->orig_ax);
 848                 print_vma_addr(" in ", regs->ip);
 849                 pr_cont("\n");
 850         }
 851
 852         force_sig(SIGSEGV, me);
 853 }
 854
 855 #ifdef CONFIG_X86_X32_ABI
 856 asmlinkage long sys32_x32_rt_sigreturn(void)
 857 {
 858         struct pt_regs *regs = current_pt_regs();
 859         struct rt_sigframe_x32 __user *frame;
 860         sigset_t set;
 861         unsigned long uc_flags;
 862
 863         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 864
 865         if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
 866                 goto badframe;
 867         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 868                 goto badframe;
 869         if (__get_user(uc_flags, &frame->uc.uc_flags))
 870                 goto badframe;
 871
 872         set_current_blocked(&set);
 873
 874         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 875                 goto badframe;
 876
 877         if (compat_restore_altstack(&frame->uc.uc_stack))
 878                 goto badframe;
 879
 880         return regs->ax;
 881
 882 badframe:
 883         signal_fault(regs, frame, "x32 rt_sigreturn");
 884         return 0;
 885 }
 886 #endif