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 #ifdef CONFIG_X86_64
 136                 /*
 137                  * Fix up SS if needed for the benefit of old DOSEMU and
 138                  * CRIU.
 139                  */
 140                 if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) &&
 141                              user_64bit_mode(regs)))
 142                         force_valid_ss(regs);
 143 #endif
 144
 145                 get_user_ex(tmpflags, &sc->flags);
 146                 regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
 147                 regs->orig_ax = -1;             /* disable syscall checks */
 148
 149                 get_user_ex(buf_val, &sc->fpstate);
 150                 buf = (void __user *)buf_val;
 151         } get_user_catch(err);
 152
 153         err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
 154
 155         force_iret();
 156
 157         return err;
 158 }
 159
 160 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 161                      struct pt_regs *regs, unsigned long mask)
 162 {
 163         int err = 0;
 164
 165         put_user_try {
 166
 167 #ifdef CONFIG_X86_32
 168                 put_user_ex(get_user_gs(regs), (unsigned int __user *)&sc->gs);
 169                 put_user_ex(regs->fs, (unsigned int __user *)&sc->fs);
 170                 put_user_ex(regs->es, (unsigned int __user *)&sc->es);
 171                 put_user_ex(regs->ds, (unsigned int __user *)&sc->ds);
 172 #endif /* CONFIG_X86_32 */
 173
 174                 put_user_ex(regs->di, &sc->di);
 175                 put_user_ex(regs->si, &sc->si);
 176                 put_user_ex(regs->bp, &sc->bp);
 177                 put_user_ex(regs->sp, &sc->sp);
 178                 put_user_ex(regs->bx, &sc->bx);
 179                 put_user_ex(regs->dx, &sc->dx);
 180                 put_user_ex(regs->cx, &sc->cx);
 181                 put_user_ex(regs->ax, &sc->ax);
 182 #ifdef CONFIG_X86_64
 183                 put_user_ex(regs->r8, &sc->r8);
 184                 put_user_ex(regs->r9, &sc->r9);
 185                 put_user_ex(regs->r10, &sc->r10);
 186                 put_user_ex(regs->r11, &sc->r11);
 187                 put_user_ex(regs->r12, &sc->r12);
 188                 put_user_ex(regs->r13, &sc->r13);
 189                 put_user_ex(regs->r14, &sc->r14);
 190                 put_user_ex(regs->r15, &sc->r15);
 191 #endif /* CONFIG_X86_64 */
 192
 193                 put_user_ex(current->thread.trap_nr, &sc->trapno);
 194                 put_user_ex(current->thread.error_code, &sc->err);
 195                 put_user_ex(regs->ip, &sc->ip);
 196 #ifdef CONFIG_X86_32
 197                 put_user_ex(regs->cs, (unsigned int __user *)&sc->cs);
 198                 put_user_ex(regs->flags, &sc->flags);
 199                 put_user_ex(regs->sp, &sc->sp_at_signal);
 200                 put_user_ex(regs->ss, (unsigned int __user *)&sc->ss);
 201 #else /* !CONFIG_X86_32 */
 202                 put_user_ex(regs->flags, &sc->flags);
 203                 put_user_ex(regs->cs, &sc->cs);
 204                 put_user_ex(0, &sc->gs);
 205                 put_user_ex(0, &sc->fs);
 206                 put_user_ex(regs->ss, &sc->ss);
 207 #endif /* CONFIG_X86_32 */
 208
 209                 put_user_ex(fpstate, &sc->fpstate);
 210
 211                 /* non-iBCS2 extensions.. */
 212                 put_user_ex(mask, &sc->oldmask);
 213                 put_user_ex(current->thread.cr2, &sc->cr2);
 214         } put_user_catch(err);
 215
 216         return err;
 217 }
 218
 219 /*
 220  * Set up a signal frame.
 221  */
 222
 223 /*
 224  * Determine which stack to use..
 225  */
 226 static unsigned long align_sigframe(unsigned long sp)
 227 {
 228 #ifdef CONFIG_X86_32
 229         /*
 230          * Align the stack pointer according to the i386 ABI,
 231          * i.e. so that on function entry ((sp + 4) & 15) == 0.
 232          */
 233         sp = ((sp + 4) & -16ul) - 4;
 234 #else /* !CONFIG_X86_32 */
 235         sp = round_down(sp, 16) - 8;
 236 #endif
 237         return sp;
 238 }
 239
 240 static void __user *
 241 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 242              void __user **fpstate)
 243 {
 244         /* Default to using normal stack */
 245         unsigned long math_size = 0;
 246         unsigned long sp = regs->sp;
 247         unsigned long buf_fx = 0;
 248         int onsigstack = on_sig_stack(sp);
 249         struct fpu *fpu = &current->thread.fpu;
 250
 251         /* redzone */
 252         if (IS_ENABLED(CONFIG_X86_64))
 253                 sp -= 128;
 254
 255         /* This is the X/Open sanctioned signal stack switching.  */
 256         if (ka->sa.sa_flags & SA_ONSTACK) {
 257                 if (sas_ss_flags(sp) == 0)
 258                         sp = current->sas_ss_sp + current->sas_ss_size;
 259         } else if (IS_ENABLED(CONFIG_X86_32) &&
 260                    !onsigstack &&
 261                    regs->ss != __USER_DS &&
 262                    !(ka->sa.sa_flags & SA_RESTORER) &&
 263                    ka->sa.sa_restorer) {
 264                 /* This is the legacy signal stack switching. */
 265                 sp = (unsigned long) ka->sa.sa_restorer;
 266         }
 267
 268         if (fpu->initialized) {
 269                 sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 270                                           &buf_fx, &math_size);
 271                 *fpstate = (void __user *)sp;
 272         }
 273
 274         sp = align_sigframe(sp - frame_size);
 275
 276         /*
 277          * If we are on the alternate signal stack and would overflow it, don't.
 278          * Return an always-bogus address instead so we will die with SIGSEGV.
 279          */
 280         if (onsigstack && !likely(on_sig_stack(sp)))
 281                 return (void __user *)-1L;
 282
 283         /* save i387 and extended state */
 284         if (fpu->initialized &&
 285             copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
 286                 return (void __user *)-1L;
 287
 288         return (void __user *)sp;
 289 }
 290
 291 #ifdef CONFIG_X86_32
 292 static const struct {
 293         u16 poplmovl;
 294         u32 val;
 295         u16 int80;
 296 } __attribute__((packed)) retcode = {
 297         0xb858,         /* popl %eax; movl $..., %eax */
 298         __NR_sigreturn,
 299         0x80cd,         /* int $0x80 */
 300 };
 301
 302 static const struct {
 303         u8  movl;
 304         u32 val;
 305         u16 int80;
 306         u8  pad;
 307 } __attribute__((packed)) rt_retcode = {
 308         0xb8,           /* movl $..., %eax */
 309         __NR_rt_sigreturn,
 310         0x80cd,         /* int $0x80 */
 311         0
 312 };
 313
 314 static int
 315 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 316               struct pt_regs *regs)
 317 {
 318         struct sigframe __user *frame;
 319         void __user *restorer;
 320         int err = 0;
 321         void __user *fpstate = NULL;
 322
 323         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 324
 325         if (!access_ok(frame, sizeof(*frame)))
 326                 return -EFAULT;
 327
 328         if (__put_user(sig, &frame->sig))
 329                 return -EFAULT;
 330
 331         if (setup_sigcontext(&frame->sc, fpstate, regs, set->sig[0]))
 332                 return -EFAULT;
 333
 334         if (_NSIG_WORDS > 1) {
 335                 if (__copy_to_user(&frame->extramask, &set->sig[1],
 336                                    sizeof(frame->extramask)))
 337                         return -EFAULT;
 338         }
 339
 340         if (current->mm->context.vdso)
 341                 restorer = current->mm->context.vdso +
 342                         vdso_image_32.sym___kernel_sigreturn;
 343         else
 344                 restorer = &frame->retcode;
 345         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 346                 restorer = ksig->ka.sa.sa_restorer;
 347
 348         /* Set up to return from userspace.  */
 349         err |= __put_user(restorer, &frame->pretcode);
 350
 351         /*
 352          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 353          *
 354          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 355          * reasons and because gdb uses it as a signature to notice
 356          * signal handler stack frames.
 357          */
 358         err |= __put_user(*((u64 *)&retcode), (u64 *)frame->retcode);
 359
 360         if (err)
 361                 return -EFAULT;
 362
 363         /* Set up registers for signal handler */
 364         regs->sp = (unsigned long)frame;
 365         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 366         regs->ax = (unsigned long)sig;
 367         regs->dx = 0;
 368         regs->cx = 0;
 369
 370         regs->ds = __USER_DS;
 371         regs->es = __USER_DS;
 372         regs->ss = __USER_DS;
 373         regs->cs = __USER_CS;
 374
 375         return 0;
 376 }
 377
 378 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 379                             sigset_t *set, struct pt_regs *regs)
 380 {
 381         struct rt_sigframe __user *frame;
 382         void __user *restorer;
 383         int err = 0;
 384         void __user *fpstate = NULL;
 385
 386         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 387
 388         if (!access_ok(frame, sizeof(*frame)))
 389                 return -EFAULT;
 390
 391         put_user_try {
 392                 put_user_ex(sig, &frame->sig);
 393                 put_user_ex(&frame->info, &frame->pinfo);
 394                 put_user_ex(&frame->uc, &frame->puc);
 395
 396                 /* Create the ucontext.  */
 397                 if (boot_cpu_has(X86_FEATURE_XSAVE))
 398                         put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
 399                 else
 400                         put_user_ex(0, &frame->uc.uc_flags);
 401                 put_user_ex(0, &frame->uc.uc_link);
 402                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 403
 404                 /* Set up to return from userspace.  */
 405                 restorer = current->mm->context.vdso +
 406                         vdso_image_32.sym___kernel_rt_sigreturn;
 407                 if (ksig->ka.sa.sa_flags & SA_RESTORER)
 408                         restorer = ksig->ka.sa.sa_restorer;
 409                 put_user_ex(restorer, &frame->pretcode);
 410
 411                 /*
 412                  * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 413                  *
 414                  * WE DO NOT USE IT ANY MORE! It's only left here for historical
 415                  * reasons and because gdb uses it as a signature to notice
 416                  * signal handler stack frames.
 417                  */
 418                 put_user_ex(*((u64 *)&rt_retcode), (u64 *)frame->retcode);
 419         } put_user_catch(err);
 420
 421         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 422         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 423                                 regs, set->sig[0]);
 424         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 425
 426         if (err)
 427                 return -EFAULT;
 428
 429         /* Set up registers for signal handler */
 430         regs->sp = (unsigned long)frame;
 431         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 432         regs->ax = (unsigned long)sig;
 433         regs->dx = (unsigned long)&frame->info;
 434         regs->cx = (unsigned long)&frame->uc;
 435
 436         regs->ds = __USER_DS;
 437         regs->es = __USER_DS;
 438         regs->ss = __USER_DS;
 439         regs->cs = __USER_CS;
 440
 441         return 0;
 442 }
 443 #else /* !CONFIG_X86_32 */
 444 static unsigned long frame_uc_flags(struct pt_regs *regs)
 445 {
 446         unsigned long flags;
 447
 448         if (boot_cpu_has(X86_FEATURE_XSAVE))
 449                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 450         else
 451                 flags = UC_SIGCONTEXT_SS;
 452
 453         if (likely(user_64bit_mode(regs)))
 454                 flags |= UC_STRICT_RESTORE_SS;
 455
 456         return flags;
 457 }
 458
 459 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 460                             sigset_t *set, struct pt_regs *regs)
 461 {
 462         struct rt_sigframe __user *frame;
 463         void __user *fp = NULL;
 464         int err = 0;
 465
 466         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 467
 468         if (!access_ok(frame, sizeof(*frame)))
 469                 return -EFAULT;
 470
 471         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 472                 if (copy_siginfo_to_user(&frame->info, &ksig->info))
 473                         return -EFAULT;
 474         }
 475
 476         put_user_try {
 477                 /* Create the ucontext.  */
 478                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 479                 put_user_ex(0, &frame->uc.uc_link);
 480                 save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 481
 482                 /* Set up to return from userspace.  If provided, use a stub
 483                    already in userspace.  */
 484                 /* x86-64 should always use SA_RESTORER. */
 485                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 486                         put_user_ex(ksig->ka.sa.sa_restorer, &frame->pretcode);
 487                 } else {
 488                         /* could use a vstub here */
 489                         err |= -EFAULT;
 490                 }
 491         } put_user_catch(err);
 492
 493         err |= setup_sigcontext(&frame->uc.uc_mcontext, fp, regs, set->sig[0]);
 494         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 495
 496         if (err)
 497                 return -EFAULT;
 498
 499         /* Set up registers for signal handler */
 500         regs->di = sig;
 501         /* In case the signal handler was declared without prototypes */
 502         regs->ax = 0;
 503
 504         /* This also works for non SA_SIGINFO handlers because they expect the
 505            next argument after the signal number on the stack. */
 506         regs->si = (unsigned long)&frame->info;
 507         regs->dx = (unsigned long)&frame->uc;
 508         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 509
 510         regs->sp = (unsigned long)frame;
 511
 512         /*
 513          * Set up the CS and SS registers to run signal handlers in
 514          * 64-bit mode, even if the handler happens to be interrupting
 515          * 32-bit or 16-bit code.
 516          *
 517          * SS is subtle.  In 64-bit mode, we don't need any particular
 518          * SS descriptor, but we do need SS to be valid.  It's possible
 519          * that the old SS is entirely bogus -- this can happen if the
 520          * signal we're trying to deliver is #GP or #SS caused by a bad
 521          * SS value.  We also have a compatbility issue here: DOSEMU
 522          * relies on the contents of the SS register indicating the
 523          * SS value at the time of the signal, even though that code in
 524          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 525          * avoids relying on sigreturn to restore SS; instead it uses
 526          * a trampoline.)  So we do our best: if the old SS was valid,
 527          * we keep it.  Otherwise we replace it.
 528          */
 529         regs->cs = __USER_CS;
 530
 531         if (unlikely(regs->ss != __USER_DS))
 532                 force_valid_ss(regs);
 533
 534         return 0;
 535 }
 536 #endif /* CONFIG_X86_32 */
 537
 538 static int x32_setup_rt_frame(struct ksignal *ksig,
 539                               compat_sigset_t *set,
 540                               struct pt_regs *regs)
 541 {
 542 #ifdef CONFIG_X86_X32_ABI
 543         struct rt_sigframe_x32 __user *frame;
 544         void __user *restorer;
 545         int err = 0;
 546         void __user *fpstate = NULL;
 547
 548         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);
 549
 550         if (!access_ok(frame, sizeof(*frame)))
 551                 return -EFAULT;
 552
 553         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 554                 if (__copy_siginfo_to_user32(&frame->info, &ksig->info, true))
 555                         return -EFAULT;
 556         }
 557
 558         put_user_try {
 559                 /* Create the ucontext.  */
 560                 put_user_ex(frame_uc_flags(regs), &frame->uc.uc_flags);
 561                 put_user_ex(0, &frame->uc.uc_link);
 562                 compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
 563                 put_user_ex(0, &frame->uc.uc__pad0);
 564
 565                 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 566                         restorer = ksig->ka.sa.sa_restorer;
 567                 } else {
 568                         /* could use a vstub here */
 569                         restorer = NULL;
 570                         err |= -EFAULT;
 571                 }
 572                 put_user_ex(restorer, &frame->pretcode);
 573         } put_user_catch(err);
 574
 575         err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
 576                                 regs, set->sig[0]);
 577         err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
 578
 579         if (err)
 580                 return -EFAULT;
 581
 582         /* Set up registers for signal handler */
 583         regs->sp = (unsigned long) frame;
 584         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 585
 586         /* We use the x32 calling convention here... */
 587         regs->di = ksig->sig;
 588         regs->si = (unsigned long) &frame->info;
 589         regs->dx = (unsigned long) &frame->uc;
 590
 591         loadsegment(ds, __USER_DS);
 592         loadsegment(es, __USER_DS);
 593
 594         regs->cs = __USER_CS;
 595         regs->ss = __USER_DS;
 596 #endif  /* CONFIG_X86_X32_ABI */
 597
 598         return 0;
 599 }
 600
 601 /*
 602  * Do a signal return; undo the signal stack.
 603  */
 604 #ifdef CONFIG_X86_32
 605 SYSCALL_DEFINE0(sigreturn)
 606 {
 607         struct pt_regs *regs = current_pt_regs();
 608         struct sigframe __user *frame;
 609         sigset_t set;
 610
 611         frame = (struct sigframe __user *)(regs->sp - 8);
 612
 613         if (!access_ok(frame, sizeof(*frame)))
 614                 goto badframe;
 615         if (__get_user(set.sig[0], &frame->sc.oldmask) || (_NSIG_WORDS > 1
 616                 && __copy_from_user(&set.sig[1], &frame->extramask,
 617                                     sizeof(frame->extramask))))
 618                 goto badframe;
 619
 620         set_current_blocked(&set);
 621
 622         /*
 623          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 624          * Save a few cycles by skipping the __get_user.
 625          */
 626         if (restore_sigcontext(regs, &frame->sc, 0))
 627                 goto badframe;
 628         return regs->ax;
 629
 630 badframe:
 631         signal_fault(regs, frame, "sigreturn");
 632
 633         return 0;
 634 }
 635 #endif /* CONFIG_X86_32 */
 636
 637 SYSCALL_DEFINE0(rt_sigreturn)
 638 {
 639         struct pt_regs *regs = current_pt_regs();
 640         struct rt_sigframe __user *frame;
 641         sigset_t set;
 642         unsigned long uc_flags;
 643
 644         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 645         if (!access_ok(frame, sizeof(*frame)))
 646                 goto badframe;
 647         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 648                 goto badframe;
 649         if (__get_user(uc_flags, &frame->uc.uc_flags))
 650                 goto badframe;
 651
 652         set_current_blocked(&set);
 653
 654         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 655                 goto badframe;
 656
 657         if (restore_altstack(&frame->uc.uc_stack))
 658                 goto badframe;
 659
 660         return regs->ax;
 661
 662 badframe:
 663         signal_fault(regs, frame, "rt_sigreturn");
 664         return 0;
 665 }
 666
 667 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 668 {
 669         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 670                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 671 }
 672
 673 static inline int is_ia32_frame(struct ksignal *ksig)
 674 {
 675         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 676 }
 677
 678 static inline int is_x32_frame(struct ksignal *ksig)
 679 {
 680         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 681                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 682 }
 683
 684 static int
 685 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 686 {
 687         int usig = ksig->sig;
 688         sigset_t *set = sigmask_to_save();
 689         compat_sigset_t *cset = (compat_sigset_t *) set;
 690
 691         /*
 692          * Increment event counter and perform fixup for the pre-signal
 693          * frame.
 694          */
 695         rseq_signal_deliver(ksig, regs);
 696
 697         /* Set up the stack frame */
 698         if (is_ia32_frame(ksig)) {
 699                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 700                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 701                 else
 702                         return ia32_setup_frame(usig, ksig, cset, regs);
 703         } else if (is_x32_frame(ksig)) {
 704                 return x32_setup_rt_frame(ksig, cset, regs);
 705         } else {
 706                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 707         }
 708 }
 709
 710 static void
 711 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 712 {
 713         bool stepping, failed;
 714         struct fpu *fpu = &current->thread.fpu;
 715
 716         if (v8086_mode(regs))
 717                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 718
 719         /* Are we from a system call? */
 720         if (syscall_get_nr(current, regs) >= 0) {
 721                 /* If so, check system call restarting.. */
 722                 switch (syscall_get_error(current, regs)) {
 723                 case -ERESTART_RESTARTBLOCK:
 724                 case -ERESTARTNOHAND:
 725                         regs->ax = -EINTR;
 726                         break;
 727
 728                 case -ERESTARTSYS:
 729                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 730                                 regs->ax = -EINTR;
 731                                 break;
 732                         }
 733                 /* fallthrough */
 734                 case -ERESTARTNOINTR:
 735                         regs->ax = regs->orig_ax;
 736                         regs->ip -= 2;
 737                         break;
 738                 }
 739         }
 740
 741         /*
 742          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 743          * so that register information in the sigcontext is correct and
 744          * then notify the tracer before entering the signal handler.
 745          */
 746         stepping = test_thread_flag(TIF_SINGLESTEP);
 747         if (stepping)
 748                 user_disable_single_step(current);
 749
 750         failed = (setup_rt_frame(ksig, regs) < 0);
 751         if (!failed) {
 752                 /*
 753                  * Clear the direction flag as per the ABI for function entry.
 754                  *
 755                  * Clear RF when entering the signal handler, because
 756                  * it might disable possible debug exception from the
 757                  * signal handler.
 758                  *
 759                  * Clear TF for the case when it wasn't set by debugger to
 760                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 761                  */
 762                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 763                 /*
 764                  * Ensure the signal handler starts with the new fpu state.
 765                  */
 766                 if (fpu->initialized)
 767                         fpu__clear(fpu);
 768         }
 769         signal_setup_done(failed, ksig, stepping);
 770 }
 771
 772 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 773 {
 774         /*
 775          * This function is fundamentally broken as currently
 776          * implemented.
 777          *
 778          * The idea is that we want to trigger a call to the
 779          * restart_block() syscall and that we want in_ia32_syscall(),
 780          * in_x32_syscall(), etc. to match whatever they were in the
 781          * syscall being restarted.  We assume that the syscall
 782          * instruction at (regs->ip - 2) matches whatever syscall
 783          * instruction we used to enter in the first place.
 784          *
 785          * The problem is that we can get here when ptrace pokes
 786          * syscall-like values into regs even if we're not in a syscall
 787          * at all.
 788          *
 789          * For now, we maintain historical behavior and guess based on
 790          * stored state.  We could do better by saving the actual
 791          * syscall arch in restart_block or (with caveats on x32) by
 792          * checking if regs->ip points to 'int $0x80'.  The current
 793          * behavior is incorrect if a tracer has a different bitness
 794          * than the tracee.
 795          */
 796 #ifdef CONFIG_IA32_EMULATION
 797         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 798                 return __NR_ia32_restart_syscall;
 799 #endif
 800 #ifdef CONFIG_X86_X32_ABI
 801         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 802 #else
 803         return __NR_restart_syscall;
 804 #endif
 805 }
 806
 807 /*
 808  * Note that 'init' is a special process: it doesn't get signals it doesn't
 809  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 810  * mistake.
 811  */
 812 void do_signal(struct pt_regs *regs)
 813 {
 814         struct ksignal ksig;
 815
 816         if (get_signal(&ksig)) {
 817                 /* Whee! Actually deliver the signal.  */
 818                 handle_signal(&ksig, regs);
 819                 return;
 820         }
 821
 822         /* Did we come from a system call? */
 823         if (syscall_get_nr(current, regs) >= 0) {
 824                 /* Restart the system call - no handlers present */
 825                 switch (syscall_get_error(current, regs)) {
 826                 case -ERESTARTNOHAND:
 827                 case -ERESTARTSYS:
 828                 case -ERESTARTNOINTR:
 829                         regs->ax = regs->orig_ax;
 830                         regs->ip -= 2;
 831                         break;
 832
 833                 case -ERESTART_RESTARTBLOCK:
 834                         regs->ax = get_nr_restart_syscall(regs);
 835                         regs->ip -= 2;
 836                         break;
 837                 }
 838         }
 839
 840         /*
 841          * If there's no signal to deliver, we just put the saved sigmask
 842          * back.
 843          */
 844         restore_saved_sigmask();
 845 }
 846
 847 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 848 {
 849         struct task_struct *me = current;
 850
 851         if (show_unhandled_signals && printk_ratelimit()) {
 852                 printk("%s"
 853                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 854                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 855                        me->comm, me->pid, where, frame,
 856                        regs->ip, regs->sp, regs->orig_ax);
 857                 print_vma_addr(KERN_CONT " in ", regs->ip);
 858                 pr_cont("\n");
 859         }
 860
 861         force_sig(SIGSEGV, me);
 862 }
 863
 864 #ifdef CONFIG_X86_X32_ABI
 865 asmlinkage long sys32_x32_rt_sigreturn(void)
 866 {
 867         struct pt_regs *regs = current_pt_regs();
 868         struct rt_sigframe_x32 __user *frame;
 869         sigset_t set;
 870         unsigned long uc_flags;
 871
 872         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 873
 874         if (!access_ok(frame, sizeof(*frame)))
 875                 goto badframe;
 876         if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
 877                 goto badframe;
 878         if (__get_user(uc_flags, &frame->uc.uc_flags))
 879                 goto badframe;
 880
 881         set_current_blocked(&set);
 882
 883         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 884                 goto badframe;
 885
 886         if (compat_restore_altstack(&frame->uc.uc_stack))
 887                 goto badframe;
 888
 889         return regs->ax;
 890
 891 badframe:
 892         signal_fault(regs, frame, "x32 rt_sigreturn");
 893         return 0;
 894 }
 895 #endif