arch/x86/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1991, 1992  Linus Torvalds
   4  *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
   5  *
   6  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
   7  *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
   8  *  2000-2002   x86-64 support by Andi Kleen
   9  */
  10
  11 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13 #include <linux/sched.h>
  14 #include <linux/sched/task_stack.h>
  15 #include <linux/mm.h>
  16 #include <linux/smp.h>
  17 #include <linux/kernel.h>
  18 #include <linux/errno.h>
  19 #include <linux/wait.h>
  20 #include <linux/tracehook.h>
  21 #include <linux/unistd.h>
  22 #include <linux/stddef.h>
  23 #include <linux/personality.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/user-return-notifier.h>
  26 #include <linux/uprobes.h>
  27 #include <linux/context_tracking.h>
  28 #include <linux/syscalls.h>
  29
  30 #include <asm/processor.h>
  31 #include <asm/ucontext.h>
  32 #include <asm/fpu/internal.h>
  33 #include <asm/fpu/signal.h>
  34 #include <asm/vdso.h>
  35 #include <asm/mce.h>
  36 #include <asm/sighandling.h>
  37 #include <asm/vm86.h>
  38
  39 #ifdef CONFIG_X86_64
  40 #include <asm/proto.h>
  41 #include <asm/ia32_unistd.h>
  42 #endif /* CONFIG_X86_64 */
  43
  44 #include <asm/syscall.h>
  45 #include <asm/syscalls.h>
  46
  47 #include <asm/sigframe.h>
  48 #include <asm/signal.h>
  49
  50 #define COPY(x)                 do {                    \
  51         get_user_ex(regs->x, &sc->x);                   \
  52 } while (0)
  53
  54 #define GET_SEG(seg)            ({                      \
  55         unsigned short tmp;                             \
  56         get_user_ex(tmp, &sc->seg);                     \
  57         tmp;                                            \
  58 })
  59
  60 #define COPY_SEG(seg)           do {                    \
  61         regs->seg = GET_SEG(seg);                       \
  62 } while (0)
  63
  64 #define COPY_SEG_CPL3(seg)      do {                    \
  65         regs->seg = GET_SEG(seg) | 3;                   \
  66 } while (0)
  67
  68 #ifdef CONFIG_X86_64
  69 /*
  70  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  71  * alone.  Using this generally makes no sense unless
  72  * user_64bit_mode(regs) would return true.
  73  */
  74 static void force_valid_ss(struct pt_regs *regs)
  75 {
  76         u32 ar;
  77         asm volatile ("lar %[old_ss], %[ar]\n\t"
  78                       "jz 1f\n\t"               /* If invalid: */
  79                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  80                       "1:"
  81                       : [ar] "=r" (ar)
  82                       : [old_ss] "rm" ((u16)regs->ss));
  83
  84         /*
  85          * For a valid 64-bit user context, we need DPL 3, type
  86          * read-write data or read-write exp-down data, and S and P
  87          * set.  We can't use VERW because VERW doesn't check the
  88          * P bit.
  89          */
  90         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  91         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  92             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  93                 regs->ss = __USER_DS;
  94 }
  95 #endif
  96
  97 static int restore_sigcontext(struct pt_regs *regs,
  98                               struct sigcontext __user *sc,
  99                               unsigned long uc_flags)
 100 {
 101         unsigned long buf_val;
 102         void __user *buf;
 103         unsigned int tmpflags;
 104         unsigned int err = 0;
 105
 106         /* Always make any pending restarted system calls return -EINTR */
 107         current->restart_block.fn = do_no_restart_syscall;
 108
 109         get_user_try {
 110
 111 #ifdef CONFIG_X86_32
 112                 set_user_gs(regs, GET_SEG(gs));
 113                 COPY_SEG(fs);
 114                 COPY_SEG(es);
 115                 COPY_SEG(ds);
 116 #endif /* CONFIG_X86_32 */
 117
 118                 COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
 119                 COPY(dx); COPY(cx); COPY(ip); COPY(ax);
 120
 121 #ifdef CONFIG_X86_64
 122                 COPY(r8);
 123                 COPY(r9);
 124                 COPY(r10);
 125                 COPY(r11);
 126                 COPY(r12);
 127                 COPY(r13);
 128                 COPY(r14);
 129                 COPY(r15);
 130 #endif /* CONFIG_X86_64 */
 131
 132                 COPY_SEG_CPL3(cs);
 133                 COPY_SEG_CPL3(ss);
 134
 135                 get_user_ex(tmpflags, &sc->flags);
 136                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 137                 regs->orig_ax = -1;             /* disable syscall checks */
 138
 139                 get_user_ex(buf_val, &sc->fpstate);
 140                 buf = (void __user *)buf_val;
 141         } get_user_catch(err);
 142
 143 #ifdef CONFIG_X86_64
 144         /*
 145          * Fix up SS if needed for the benefit of old DOSEMU and
 146          * CRIU.
 147          */
 148         if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
 149                 force_valid_ss(regs);
 150 #endif
 151
 152         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
 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, (unsigned long __user *)&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         int ret;
 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 != __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         sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 266                                   &buf_fx, &math_size);
 267         *fpstate = (void __user *)sp;
 268
 269         sp = align_sigframe(sp - frame_size);
 270
 271         /*
 272          * If we are on the alternate signal stack and would overflow it, don't.
 273          * Return an always-bogus address instead so we will die with SIGSEGV.
 274          */
 275         if (onsigstack && !likely(on_sig_stack(sp)))
 276                 return (void __user *)-1L;
 277
 278         /* save i387 and extended state */
 279         ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
 280         if (ret < 0)
 281                 return (void __user *)-1L;
 282
 283         return (void __user *)sp;
 284 }
 285
 286 #ifdef CONFIG_X86_32
 287 static const struct {
 288         u16 poplmovl;
 289         u32 val;
 290         u16 int80;
 291 } __attribute__((packed)) retcode = {
 292         0xb858,         /* popl %eax; movl $..., %eax */
 293         __NR_sigreturn,
 294         0x80cd,         /* int $0x80 */
 295 };
 296
 297 static const struct {
 298         u8  movl;
 299         u32 val;
 300         u16 int80;
 301         u8  pad;
 302 } __attribute__((packed)) rt_retcode = {
 303         0xb8,           /* movl $..., %eax */
 304         __NR_rt_sigreturn,
 305         0x80cd,         /* int $0x80 */
 306         0
 307 };
 308
 309 static int
 310 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 311               struct pt_regs *regs)
 312 {
 313         struct sigframe __user *frame;
 314         void __user *restorer;
 315         int err = 0;
 316         void __user *fpstate = NULL;
 317
 318         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 319
 320         if (!access_ok(frame, sizeof(*frame)))
 321                 return -EFAULT;
 322
 323         if (__put_user(sig, &frame->sig))
 324                 return -EFAULT;
 325
 326         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 327                 return -EFAULT;
 328
 329         if (_NSIG_WORDS > 1) {
 330                 if (__copy_to_user(&frame->extramask, &set->sig[1],
 331                                    sizeof(frame->extramask)))
 332                         return -EFAULT;
 333         }
 334
 335         if (current->mm->context.vdso)
 336                 restorer = current->mm->context.vdso +
 337                         vdso_image_32.sym___kernel_sigreturn;
 338         else
 339                 restorer = &frame->retcode;
 340         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 341                 restorer = ksig->ka.sa.sa_restorer;
 342
 343         /* Set up to return from userspace.  */
 344         err |= __put_user(restorer, &frame->pretcode);
 345
 346         /*
 347          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 348          *
 349          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 350          * reasons and because gdb uses it as a signature to notice
 351          * signal handler stack frames.
 352          */
 353         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 354
 355         if (err)
 356                 return -EFAULT;
 357
 358         /* Set up registers for signal handler */
 359         regs->sp = (unsigned long)frame;
 360         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 361         regs->ax = (unsigned long)sig;
 362         regs->dx = 0;
 363         regs->cx = 0;
 364
 365         regs->ds = __USER_DS;
 366         regs->es = __USER_DS;
 367         regs->ss = __USER_DS;
 368         regs->cs = __USER_CS;
 369
 370         return 0;
 371 }
 372
 373 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 374                             sigset_t *set, struct pt_regs *regs)
 375 {
 376         struct rt_sigframe __user *frame;
 377         void __user *restorer;
 378         int err = 0;
 379         void __user *fpstate = NULL;
 380
 381         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 382
 383         if (!access_ok(frame, sizeof(*frame)))
 384                 return -EFAULT;
 385
 386         put_user_try {
 387                 put_user_ex(sig, &frame->sig);
 388                 put_user_ex(&frame->info, &frame->pinfo);
 389                 put_user_ex(&frame->uc, &frame->puc);
 390
 391                 /* Create the ucontext.  */
 392                 if (static_cpu_has(X86_FEATURE_XSAVE))
 393                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 394                 else
 395                         put_user_ex(0, &frame->uc.uc_flags);
 396                 put_user_ex(0, &frame->uc.uc_link);
 397                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 398
 399                 /* Set up to return from userspace.  */
 400                 restorer = current->mm->context.vdso +
 401                         vdso_image_32.sym___kernel_rt_sigreturn;
 402                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 403                         restorer = ksig->ka.sa.sa_restorer;
 404                 put_user_ex(restorer, &frame->pretcode);
 405
 406                 /*
 407                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 408                  *
 409                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 410                  * reasons and because gdb uses it as a signature to notice
 411                  * signal handler stack frames.
 412                  */
 413                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 414         } put_user_catch(err);
 415
 416         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 417         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 418                                 regs, set->sig[0]);
 419         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 420
 421         if (err)
 422                 return -EFAULT;
 423
 424         /* Set up registers for signal handler */
 425         regs->sp = (unsigned long)frame;
 426         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 427         regs->ax = (unsigned long)sig;
 428         regs->dx = (unsigned long)&frame->info;
 429         regs->cx = (unsigned long)&frame->uc;
 430
 431         regs->ds = __USER_DS;
 432         regs->es = __USER_DS;
 433         regs->ss = __USER_DS;
 434         regs->cs = __USER_CS;
 435
 436         return 0;
 437 }
 438 #else /* !CONFIG_X86_32 */
 439 static unsigned long frame_uc_flags(struct pt_regs *regs)
 440 {
 441         unsigned long flags;
 442
 443         if (boot_cpu_has(X86_FEATURE_XSAVE))
 444                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 445         else
 446                 flags = UC_SIGCONTEXT_SS;
 447
 448         if (likely(user_64bit_mode(regs)))
 449                 flags |= UC_STRICT_RESTORE_SS;
 450
 451         return flags;
 452 }
 453
 454 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 455                             sigset_t *set, struct pt_regs *regs)
 456 {
 457         struct rt_sigframe __user *frame;
 458         void __user *fp = NULL;
 459         unsigned long uc_flags;
 460         int err = 0;
 461
 462         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 463
 464         if (!access_ok(frame, sizeof(*frame)))
 465                 return -EFAULT;
 466
 467         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 468                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 469                         return -EFAULT;
 470         }
 471
 472         uc_flags = frame_uc_flags(regs);
 473
 474         put_user_try {
 475                 /* Create the ucontext.  */
 476                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 477                 put_user_ex(0, &frame->uc.uc_link);
 478                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 479
 480                 /* Set up to return from userspace.  If provided, use a stub
 481                    already in userspace.  */
 482                 /* x86-64 should always use SA_RESTORER. */
 483                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 484                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 485                 } else {
 486                         /* could use a vstub here */
 487                         err |= -EFAULT;
 488                 }
 489         } put_user_catch(err);
 490
 491         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 492         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 493
 494         if (err)
 495                 return -EFAULT;
 496
 497         /* Set up registers for signal handler */
 498         regs->di = sig;
 499         /* In case the signal handler was declared without prototypes */
 500         regs->ax = 0;
 501
 502         /* This also works for non SA_SIGINFO handlers because they expect the
 503            next argument after the signal number on the stack. */
 504         regs->si = (unsigned long)&frame->info;
 505         regs->dx = (unsigned long)&frame->uc;
 506         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 507
 508         regs->sp = (unsigned long)frame;
 509
 510         /*
 511          * Set up the CS and SS registers to run signal handlers in
 512          * 64-bit mode, even if the handler happens to be interrupting
 513          * 32-bit or 16-bit code.
 514          *
 515          * SS is subtle.  In 64-bit mode, we don't need any particular
 516          * SS descriptor, but we do need SS to be valid.  It's possible
 517          * that the old SS is entirely bogus -- this can happen if the
 518          * signal we're trying to deliver is #GP or #SS caused by a bad
 519          * SS value.  We also have a compatbility issue here: DOSEMU
 520          * relies on the contents of the SS register indicating the
 521          * SS value at the time of the signal, even though that code in
 522          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 523          * avoids relying on sigreturn to restore SS; instead it uses
 524          * a trampoline.)  So we do our best: if the old SS was valid,
 525          * we keep it.  Otherwise we replace it.
 526          */
 527         regs->cs = __USER_CS;
 528
 529         if (unlikely(regs->ss != __USER_DS))
 530                 force_valid_ss(regs);
 531
 532         return 0;
 533 }
 534 #endif /* CONFIG_X86_32 */
 535
 536 static int x32_setup_rt_frame(struct ksignal *ksig,
 537                               compat_sigset_t *set,
 538                               struct pt_regs *regs)
 539 {
 540 #ifdef CONFIG_X86_X32_ABI
 541         struct rt_sigframe_x32 __user *frame;
 542         unsigned long uc_flags;
 543         void __user *restorer;
 544         int err = 0;
 545         void __user *fpstate = NULL;
 546
 547         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 548
 549         if (!access_ok(frame, sizeof(*frame)))
 550                 return -EFAULT;
 551
 552         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 553                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 554                         return -EFAULT;
 555         }
 556
 557         uc_flags = frame_uc_flags(regs);
 558
 559         put_user_try {
 560                 /* Create the ucontext.  */
 561                 put_user_ex(uc_flags, &frame->uc.uc_flags);
 562                 put_user_ex(0, &frame->uc.uc_link);
 563                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 564                 put_user_ex(0, &frame->uc.uc__pad0);
 565
 566                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 567                         restorer = ksig->ka.sa.sa_restorer;
 568                 } else {
 569                         /* could use a vstub here */
 570                         restorer = NULL;
 571                         err |= -EFAULT;
 572                 }
 573                 put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
 574         } put_user_catch(err);
 575
 576         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 577                                 regs, set->sig[0]);
 578         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 579
 580         if (err)
 581                 return -EFAULT;
 582
 583         /* Set up registers for signal handler */
 584         regs->sp = (unsigned long) frame;
 585         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 586
 587         /* We use the x32 calling convention here... */
 588         regs->di = ksig->sig;
 589         regs->si = (unsigned long) &frame->info;
 590         regs->dx = (unsigned long) &frame->uc;
 591
 592         loadsegment(ds, __USER_DS);
 593         loadsegment(es, __USER_DS);
 594
 595         regs->cs = __USER_CS;
 596         regs->ss = __USER_DS;
 597 #endif  /* CONFIG_X86_X32_ABI */
 598
 599         return 0;
 600 }
 601
 602 /*
 603  * Do a signal return; undo the signal stack.
 604  */
 605 #ifdef CONFIG_X86_32
 606 SYSCALL_DEFINE0(sigreturn)
 607 {
 608         struct pt_regs *regs = current_pt_regs();
 609         struct sigframe __user *frame;
 610         sigset_t set;
 611
 612         frame = (struct sigframe __user *)(regs->sp - 8);
 613
 614         if (!access_ok(frame, sizeof(*frame)))
 615                 goto badframe;
 616         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
 617                 && __copy_from_user(&set.sig[1], &frame->extramask,
 618                                     sizeof(frame->extramask))))
 619                 goto badframe;
 620
 621         set_current_blocked(&set);
 622
 623         /*
 624          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 625          * Save a few cycles by skipping the __get_user.
 626          */
 627         if (restore_sigcontext(regs, &frame->sc, 0))
 628                 goto badframe;
 629         return regs->ax;
 630
 631 badframe:
 632         signal_fault(regs, frame, "sigreturn");
 633
 634         return 0;
 635 }
 636 #endif /* CONFIG_X86_32 */
 637
 638 SYSCALL_DEFINE0(rt_sigreturn)
 639 {
 640         struct pt_regs *regs = current_pt_regs();
 641         struct rt_sigframe __user *frame;
 642         sigset_t set;
 643         unsigned long uc_flags;
 644
 645         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 646         if (!access_ok(frame, sizeof(*frame)))
 647                 goto badframe;
 648         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 649                 goto badframe;
 650         if (__get_user(uc_flags, &frame->uc.uc_flags))
 651                 goto badframe;
 652
 653         set_current_blocked(&set);
 654
 655         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 656                 goto badframe;
 657
 658         if (restore_altstack(&frame->uc.uc_stack))
 659                 goto badframe;
 660
 661         return regs->ax;
 662
 663 badframe:
 664         signal_fault(regs, frame, "rt_sigreturn");
 665         return 0;
 666 }
 667
 668 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 669 {
 670         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 671                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 672 }
 673
 674 static inline int is_ia32_frame(struct ksignal *ksig)
 675 {
 676         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 677 }
 678
 679 static inline int is_x32_frame(struct ksignal *ksig)
 680 {
 681         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 682                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 683 }
 684
 685 static int
 686 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 687 {
 688         int usig = ksig->sig;
 689         sigset_t *set = sigmask_to_save();
 690         compat_sigset_t *cset = (compat_sigset_t *) set;
 691
 692         /* Perform fixup for the pre-signal frame. */
 693         rseq_signal_deliver(ksig, regs);
 694
 695         /* Set up the stack frame */
 696         if (is_ia32_frame(ksig)) {
 697                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 698                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 699                 else
 700                         return ia32_setup_frame(usig, ksig, cset, regs);
 701         } else if (is_x32_frame(ksig)) {
 702                 return x32_setup_rt_frame(ksig, cset, regs);
 703         } else {
 704                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 705         }
 706 }
 707
 708 static void
 709 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 710 {
 711         bool stepping, failed;
 712         struct fpu *fpu = &current->thread.fpu;
 713
 714         if (v8086_mode(regs))
 715                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 716
 717         /* Are we from a system call? */
 718         if (syscall_get_nr(current, regs) >= 0) {
 719                 /* If so, check system call restarting.. */
 720                 switch (syscall_get_error(current, regs)) {
 721                 case -ERESTART_RESTARTBLOCK:
 722                 case -ERESTARTNOHAND:
 723                         regs->ax = -EINTR;
 724                         break;
 725
 726                 case -ERESTARTSYS:
 727                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 728                                 regs->ax = -EINTR;
 729                                 break;
 730                         }
 731                 /* fallthrough */
 732                 case -ERESTARTNOINTR:
 733                         regs->ax = regs->orig_ax;
 734                         regs->ip -= 2;
 735                         break;
 736                 }
 737         }
 738
 739         /*
 740          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 741          * so that register information in the sigcontext is correct and
 742          * then notify the tracer before entering the signal handler.
 743          */
 744         stepping = test_thread_flag(TIF_SINGLESTEP);
 745         if (stepping)
 746                 user_disable_single_step(current);
 747
 748         failed = (setup_rt_frame(ksig, regs) < 0);
 749         if (!failed) {
 750                 /*
 751                  * Clear the direction flag as per the ABI for function entry.
 752                  *
 753                  * Clear RF when entering the signal handler, because
 754                  * it might disable possible debug exception from the
 755                  * signal handler.
 756                  *
 757                  * Clear TF for the case when it wasn't set by debugger to
 758                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 759                  */
 760                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 761                 /*
 762                  * Ensure the signal handler starts with the new fpu state.
 763                  */
 764                 fpu__clear(fpu);
 765         }
 766         signal_setup_done(failed, ksig, stepping);
 767 }
 768
 769 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 770 {
 771         /*
 772          * This function is fundamentally broken as currently
 773          * implemented.
 774          *
 775          * The idea is that we want to trigger a call to the
 776          * restart_block() syscall and that we want in_ia32_syscall(),
 777          * in_x32_syscall(), etc. to match whatever they were in the
 778          * syscall being restarted.  We assume that the syscall
 779          * instruction at (regs->ip - 2) matches whatever syscall
 780          * instruction we used to enter in the first place.
 781          *
 782          * The problem is that we can get here when ptrace pokes
 783          * syscall-like values into regs even if we're not in a syscall
 784          * at all.
 785          *
 786          * For now, we maintain historical behavior and guess based on
 787          * stored state.  We could do better by saving the actual
 788          * syscall arch in restart_block or (with caveats on x32) by
 789          * checking if regs->ip points to 'int $0x80'.  The current
 790          * behavior is incorrect if a tracer has a different bitness
 791          * than the tracee.
 792          */
 793 #ifdef CONFIG_IA32_EMULATION
 794         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 795                 return __NR_ia32_restart_syscall;
 796 #endif
 797 #ifdef CONFIG_X86_X32_ABI
 798         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 799 #else
 800         return __NR_restart_syscall;
 801 #endif
 802 }
 803
 804 /*
 805  * Note that 'init' is a special process: it doesn't get signals it doesn't
 806  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 807  * mistake.
 808  */
 809 void do_signal(struct pt_regs *regs)
 810 {
 811         struct ksignal ksig;
 812
 813         if (get_signal(&ksig)) {
 814                 /* Whee! Actually deliver the signal.  */
 815                 handle_signal(&ksig, regs);
 816                 return;
 817         }
 818
 819         /* Did we come from a system call? */
 820         if (syscall_get_nr(current, regs) >= 0) {
 821                 /* Restart the system call - no handlers present */
 822                 switch (syscall_get_error(current, regs)) {
 823                 case -ERESTARTNOHAND:
 824                 case -ERESTARTSYS:
 825                 case -ERESTARTNOINTR:
 826                         regs->ax = regs->orig_ax;
 827                         regs->ip -= 2;
 828                         break;
 829
 830                 case -ERESTART_RESTARTBLOCK:
 831                         regs->ax = get_nr_restart_syscall(regs);
 832                         regs->ip -= 2;
 833                         break;
 834                 }
 835         }
 836
 837         /*
 838          * If there's no signal to deliver, we just put the saved sigmask
 839          * back.
 840          */
 841         restore_saved_sigmask();
 842 }
 843
 844 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 845 {
 846         struct task_struct *me = current;
 847
 848         if (show_unhandled_signals && printk_ratelimit()) {
 849                 printk("%s"
 850                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 851                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 852                        me->comm, me->pid, where, frame,
 853                        regs->ip, regs->sp, regs->orig_ax);
 854                 print_vma_addr(KERN_CONT " in ", regs->ip);
 855                 pr_cont("\n");
 856         }
 857
 858         force_sig(SIGSEGV);
 859 }
 860
 861 #ifdef CONFIG_X86_X32_ABI
 862 asmlinkage long sys32_x32_rt_sigreturn(void)
 863 {
 864         struct pt_regs *regs = current_pt_regs();
 865         struct rt_sigframe_x32 __user *frame;
 866         sigset_t set;
 867         unsigned long uc_flags;
 868
 869         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 870
 871         if (!access_ok(frame, sizeof(*frame)))
 872                 goto badframe;
 873         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 874                 goto badframe;
 875         if (__get_user(uc_flags, &frame->uc.uc_flags))
 876                 goto badframe;
 877
 878         set_current_blocked(&set);
 879
 880         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 881                 goto badframe;
 882
 883         if (compat_restore_altstack(&frame->uc.uc_stack))
 884                 goto badframe;
 885
 886         return regs->ax;
 887
 888 badframe:
 889         signal_fault(regs, frame, "x32 rt_sigreturn");
 890         return 0;
 891 }
 892 #endif