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/entry-common.h>
  29 #include <linux/syscalls.h>
  30
  31 #include <asm/processor.h>
  32 #include <asm/ucontext.h>
  33 #include <asm/fpu/internal.h>
  34 #include <asm/fpu/signal.h>
  35 #include <asm/vdso.h>
  36 #include <asm/mce.h>
  37 #include <asm/sighandling.h>
  38 #include <asm/vm86.h>
  39
  40 #ifdef CONFIG_X86_64
  41 #include <linux/compat.h>
  42 #include <asm/proto.h>
  43 #include <asm/ia32_unistd.h>
  44 #endif /* CONFIG_X86_64 */
  45
  46 #include <asm/syscall.h>
  47 #include <asm/sigframe.h>
  48 #include <asm/signal.h>
  49
  50 #ifdef CONFIG_X86_64
  51 /*
  52  * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
  53  * alone.  Using this generally makes no sense unless
  54  * user_64bit_mode(regs) would return true.
  55  */
  56 static void force_valid_ss(struct pt_regs *regs)
  57 {
  58         u32 ar;
  59         asm volatile ("lar %[old_ss], %[ar]\n\t"
  60                       "jz 1f\n\t"               /* If invalid: */
  61                       "xorl %[ar], %[ar]\n\t"   /* set ar = 0 */
  62                       "1:"
  63                       : [ar] "=r" (ar)
  64                       : [old_ss] "rm" ((u16)regs->ss));
  65
  66         /*
  67          * For a valid 64-bit user context, we need DPL 3, type
  68          * read-write data or read-write exp-down data, and S and P
  69          * set.  We can't use VERW because VERW doesn't check the
  70          * P bit.
  71          */
  72         ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
  73         if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
  74             ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
  75                 regs->ss = __USER_DS;
  76 }
  77 # define CONTEXT_COPY_SIZE      offsetof(struct sigcontext, reserved1)
  78 #else
  79 # define CONTEXT_COPY_SIZE      sizeof(struct sigcontext)
  80 #endif
  81
  82 static int restore_sigcontext(struct pt_regs *regs,
  83                               struct sigcontext __user *usc,
  84                               unsigned long uc_flags)
  85 {
  86         struct sigcontext sc;
  87
  88         /* Always make any pending restarted system calls return -EINTR */
  89         current->restart_block.fn = do_no_restart_syscall;
  90
  91         if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
  92                 return -EFAULT;
  93
  94 #ifdef CONFIG_X86_32
  95         set_user_gs(regs, sc.gs);
  96         regs->fs = sc.fs;
  97         regs->es = sc.es;
  98         regs->ds = sc.ds;
  99 #endif /* CONFIG_X86_32 */
 100
 101         regs->bx = sc.bx;
 102         regs->cx = sc.cx;
 103         regs->dx = sc.dx;
 104         regs->si = sc.si;
 105         regs->di = sc.di;
 106         regs->bp = sc.bp;
 107         regs->ax = sc.ax;
 108         regs->sp = sc.sp;
 109         regs->ip = sc.ip;
 110
 111 #ifdef CONFIG_X86_64
 112         regs->r8 = sc.r8;
 113         regs->r9 = sc.r9;
 114         regs->r10 = sc.r10;
 115         regs->r11 = sc.r11;
 116         regs->r12 = sc.r12;
 117         regs->r13 = sc.r13;
 118         regs->r14 = sc.r14;
 119         regs->r15 = sc.r15;
 120 #endif /* CONFIG_X86_64 */
 121
 122         /* Get CS/SS and force CPL3 */
 123         regs->cs = sc.cs | 0x03;
 124         regs->ss = sc.ss | 0x03;
 125
 126         regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
 127         /* disable syscall checks */
 128         regs->orig_ax = -1;
 129
 130 #ifdef CONFIG_X86_64
 131         /*
 132          * Fix up SS if needed for the benefit of old DOSEMU and
 133          * CRIU.
 134          */
 135         if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
 136                 force_valid_ss(regs);
 137 #endif
 138
 139         return fpu__restore_sig((void __user *)sc.fpstate,
 140                                IS_ENABLED(CONFIG_X86_32));
 141 }
 142
 143 static __always_inline int
 144 __unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 145                      struct pt_regs *regs, unsigned long mask)
 146 {
 147 #ifdef CONFIG_X86_32
 148         unsafe_put_user(get_user_gs(regs),
 149                                   (unsigned int __user *)&sc->gs, Efault);
 150         unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
 151         unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
 152         unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
 153 #endif /* CONFIG_X86_32 */
 154
 155         unsafe_put_user(regs->di, &sc->di, Efault);
 156         unsafe_put_user(regs->si, &sc->si, Efault);
 157         unsafe_put_user(regs->bp, &sc->bp, Efault);
 158         unsafe_put_user(regs->sp, &sc->sp, Efault);
 159         unsafe_put_user(regs->bx, &sc->bx, Efault);
 160         unsafe_put_user(regs->dx, &sc->dx, Efault);
 161         unsafe_put_user(regs->cx, &sc->cx, Efault);
 162         unsafe_put_user(regs->ax, &sc->ax, Efault);
 163 #ifdef CONFIG_X86_64
 164         unsafe_put_user(regs->r8, &sc->r8, Efault);
 165         unsafe_put_user(regs->r9, &sc->r9, Efault);
 166         unsafe_put_user(regs->r10, &sc->r10, Efault);
 167         unsafe_put_user(regs->r11, &sc->r11, Efault);
 168         unsafe_put_user(regs->r12, &sc->r12, Efault);
 169         unsafe_put_user(regs->r13, &sc->r13, Efault);
 170         unsafe_put_user(regs->r14, &sc->r14, Efault);
 171         unsafe_put_user(regs->r15, &sc->r15, Efault);
 172 #endif /* CONFIG_X86_64 */
 173
 174         unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
 175         unsafe_put_user(current->thread.error_code, &sc->err, Efault);
 176         unsafe_put_user(regs->ip, &sc->ip, Efault);
 177 #ifdef CONFIG_X86_32
 178         unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
 179         unsafe_put_user(regs->flags, &sc->flags, Efault);
 180         unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
 181         unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
 182 #else /* !CONFIG_X86_32 */
 183         unsafe_put_user(regs->flags, &sc->flags, Efault);
 184         unsafe_put_user(regs->cs, &sc->cs, Efault);
 185         unsafe_put_user(0, &sc->gs, Efault);
 186         unsafe_put_user(0, &sc->fs, Efault);
 187         unsafe_put_user(regs->ss, &sc->ss, Efault);
 188 #endif /* CONFIG_X86_32 */
 189
 190         unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);
 191
 192         /* non-iBCS2 extensions.. */
 193         unsafe_put_user(mask, &sc->oldmask, Efault);
 194         unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
 195         return 0;
 196 Efault:
 197         return -EFAULT;
 198 }
 199
 200 #define unsafe_put_sigcontext(sc, fp, regs, set, label)                 \
 201 do {                                                                    \
 202         if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0]))       \
 203                 goto label;                                             \
 204 } while(0);
 205
 206 #define unsafe_put_sigmask(set, frame, label) \
 207         unsafe_put_user(*(__u64 *)(set), \
 208                         (__u64 __user *)&(frame)->uc.uc_sigmask, \
 209                         label)
 210
 211 /*
 212  * Set up a signal frame.
 213  */
 214
 215 /*
 216  * Determine which stack to use..
 217  */
 218 static unsigned long align_sigframe(unsigned long sp)
 219 {
 220 #ifdef CONFIG_X86_32
 221         /*
 222          * Align the stack pointer according to the i386 ABI,
 223          * i.e. so that on function entry ((sp + 4) & 15) == 0.
 224          */
 225         sp = ((sp + 4) & -16ul) - 4;
 226 #else /* !CONFIG_X86_32 */
 227         sp = round_down(sp, 16) - 8;
 228 #endif
 229         return sp;
 230 }
 231
 232 static void __user *
 233 get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 234              void __user **fpstate)
 235 {
 236         /* Default to using normal stack */
 237         unsigned long math_size = 0;
 238         unsigned long sp = regs->sp;
 239         unsigned long buf_fx = 0;
 240         int onsigstack = on_sig_stack(sp);
 241         int ret;
 242
 243         /* redzone */
 244         if (IS_ENABLED(CONFIG_X86_64))
 245                 sp -= 128;
 246
 247         /* This is the X/Open sanctioned signal stack switching.  */
 248         if (ka->sa.sa_flags & SA_ONSTACK) {
 249                 if (sas_ss_flags(sp) == 0)
 250                         sp = current->sas_ss_sp + current->sas_ss_size;
 251         } else if (IS_ENABLED(CONFIG_X86_32) &&
 252                    !onsigstack &&
 253                    regs->ss != __USER_DS &&
 254                    !(ka->sa.sa_flags & SA_RESTORER) &&
 255                    ka->sa.sa_restorer) {
 256                 /* This is the legacy signal stack switching. */
 257                 sp = (unsigned long) ka->sa.sa_restorer;
 258         }
 259
 260         sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
 261                                   &buf_fx, &math_size);
 262         *fpstate = (void __user *)sp;
 263
 264         sp = align_sigframe(sp - frame_size);
 265
 266         /*
 267          * If we are on the alternate signal stack and would overflow it, don't.
 268          * Return an always-bogus address instead so we will die with SIGSEGV.
 269          */
 270         if (onsigstack && !likely(on_sig_stack(sp)))
 271                 return (void __user *)-1L;
 272
 273         /* save i387 and extended state */
 274         ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
 275         if (ret < 0)
 276                 return (void __user *)-1L;
 277
 278         return (void __user *)sp;
 279 }
 280
 281 #ifdef CONFIG_X86_32
 282 static const struct {
 283         u16 poplmovl;
 284         u32 val;
 285         u16 int80;
 286 } __attribute__((packed)) retcode = {
 287         0xb858,         /* popl %eax; movl $..., %eax */
 288         __NR_sigreturn,
 289         0x80cd,         /* int $0x80 */
 290 };
 291
 292 static const struct {
 293         u8  movl;
 294         u32 val;
 295         u16 int80;
 296         u8  pad;
 297 } __attribute__((packed)) rt_retcode = {
 298         0xb8,           /* movl $..., %eax */
 299         __NR_rt_sigreturn,
 300         0x80cd,         /* int $0x80 */
 301         0
 302 };
 303
 304 static int
 305 __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
 306               struct pt_regs *regs)
 307 {
 308         struct sigframe __user *frame;
 309         void __user *restorer;
 310         void __user *fp = NULL;
 311
 312         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
 313
 314         if (!user_access_begin(frame, sizeof(*frame)))
 315                 return -EFAULT;
 316
 317         unsafe_put_user(sig, &frame->sig, Efault);
 318         unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault);
 319         unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
 320         if (current->mm->context.vdso)
 321                 restorer = current->mm->context.vdso +
 322                         vdso_image_32.sym___kernel_sigreturn;
 323         else
 324                 restorer = &frame->retcode;
 325         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 326                 restorer = ksig->ka.sa.sa_restorer;
 327
 328         /* Set up to return from userspace.  */
 329         unsafe_put_user(restorer, &frame->pretcode, Efault);
 330
 331         /*
 332          * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
 333          *
 334          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 335          * reasons and because gdb uses it as a signature to notice
 336          * signal handler stack frames.
 337          */
 338         unsafe_put_user(*((u64 *)&retcode), (u64 *)frame->retcode, Efault);
 339         user_access_end();
 340
 341         /* Set up registers for signal handler */
 342         regs->sp = (unsigned long)frame;
 343         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 344         regs->ax = (unsigned long)sig;
 345         regs->dx = 0;
 346         regs->cx = 0;
 347
 348         regs->ds = __USER_DS;
 349         regs->es = __USER_DS;
 350         regs->ss = __USER_DS;
 351         regs->cs = __USER_CS;
 352
 353         return 0;
 354
 355 Efault:
 356         user_access_end();
 357         return -EFAULT;
 358 }
 359
 360 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 361                             sigset_t *set, struct pt_regs *regs)
 362 {
 363         struct rt_sigframe __user *frame;
 364         void __user *restorer;
 365         void __user *fp = NULL;
 366
 367         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
 368
 369         if (!user_access_begin(frame, sizeof(*frame)))
 370                 return -EFAULT;
 371
 372         unsafe_put_user(sig, &frame->sig, Efault);
 373         unsafe_put_user(&frame->info, &frame->pinfo, Efault);
 374         unsafe_put_user(&frame->uc, &frame->puc, Efault);
 375
 376         /* Create the ucontext.  */
 377         if (static_cpu_has(X86_FEATURE_XSAVE))
 378                 unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
 379         else
 380                 unsafe_put_user(0, &frame->uc.uc_flags, Efault);
 381         unsafe_put_user(0, &frame->uc.uc_link, Efault);
 382         unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
 383
 384         /* Set up to return from userspace.  */
 385         restorer = current->mm->context.vdso +
 386                 vdso_image_32.sym___kernel_rt_sigreturn;
 387         if (ksig->ka.sa.sa_flags & SA_RESTORER)
 388                 restorer = ksig->ka.sa.sa_restorer;
 389         unsafe_put_user(restorer, &frame->pretcode, Efault);
 390
 391         /*
 392          * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
 393          *
 394          * WE DO NOT USE IT ANY MORE! It's only left here for historical
 395          * reasons and because gdb uses it as a signature to notice
 396          * signal handler stack frames.
 397          */
 398         unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault);
 399         unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
 400         unsafe_put_sigmask(set, frame, Efault);
 401         user_access_end();
 402
 403         if (copy_siginfo_to_user(&frame->info, &ksig->info))
 404                 return -EFAULT;
 405
 406         /* Set up registers for signal handler */
 407         regs->sp = (unsigned long)frame;
 408         regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
 409         regs->ax = (unsigned long)sig;
 410         regs->dx = (unsigned long)&frame->info;
 411         regs->cx = (unsigned long)&frame->uc;
 412
 413         regs->ds = __USER_DS;
 414         regs->es = __USER_DS;
 415         regs->ss = __USER_DS;
 416         regs->cs = __USER_CS;
 417
 418         return 0;
 419 Efault:
 420         user_access_end();
 421         return -EFAULT;
 422 }
 423 #else /* !CONFIG_X86_32 */
 424 static unsigned long frame_uc_flags(struct pt_regs *regs)
 425 {
 426         unsigned long flags;
 427
 428         if (boot_cpu_has(X86_FEATURE_XSAVE))
 429                 flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
 430         else
 431                 flags = UC_SIGCONTEXT_SS;
 432
 433         if (likely(user_64bit_mode(regs)))
 434                 flags |= UC_STRICT_RESTORE_SS;
 435
 436         return flags;
 437 }
 438
 439 static int __setup_rt_frame(int sig, struct ksignal *ksig,
 440                             sigset_t *set, struct pt_regs *regs)
 441 {
 442         struct rt_sigframe __user *frame;
 443         void __user *fp = NULL;
 444         unsigned long uc_flags;
 445
 446         /* x86-64 should always use SA_RESTORER. */
 447         if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
 448                 return -EFAULT;
 449
 450         frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
 451         uc_flags = frame_uc_flags(regs);
 452
 453         if (!user_access_begin(frame, sizeof(*frame)))
 454                 return -EFAULT;
 455
 456         /* Create the ucontext.  */
 457         unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
 458         unsafe_put_user(0, &frame->uc.uc_link, Efault);
 459         unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
 460
 461         /* Set up to return from userspace.  If provided, use a stub
 462            already in userspace.  */
 463         unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
 464         unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
 465         unsafe_put_sigmask(set, frame, Efault);
 466         user_access_end();
 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         /* Set up registers for signal handler */
 474         regs->di = sig;
 475         /* In case the signal handler was declared without prototypes */
 476         regs->ax = 0;
 477
 478         /* This also works for non SA_SIGINFO handlers because they expect the
 479            next argument after the signal number on the stack. */
 480         regs->si = (unsigned long)&frame->info;
 481         regs->dx = (unsigned long)&frame->uc;
 482         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 483
 484         regs->sp = (unsigned long)frame;
 485
 486         /*
 487          * Set up the CS and SS registers to run signal handlers in
 488          * 64-bit mode, even if the handler happens to be interrupting
 489          * 32-bit or 16-bit code.
 490          *
 491          * SS is subtle.  In 64-bit mode, we don't need any particular
 492          * SS descriptor, but we do need SS to be valid.  It's possible
 493          * that the old SS is entirely bogus -- this can happen if the
 494          * signal we're trying to deliver is #GP or #SS caused by a bad
 495          * SS value.  We also have a compatbility issue here: DOSEMU
 496          * relies on the contents of the SS register indicating the
 497          * SS value at the time of the signal, even though that code in
 498          * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
 499          * avoids relying on sigreturn to restore SS; instead it uses
 500          * a trampoline.)  So we do our best: if the old SS was valid,
 501          * we keep it.  Otherwise we replace it.
 502          */
 503         regs->cs = __USER_CS;
 504
 505         if (unlikely(regs->ss != __USER_DS))
 506                 force_valid_ss(regs);
 507
 508         return 0;
 509
 510 Efault:
 511         user_access_end();
 512         return -EFAULT;
 513 }
 514 #endif /* CONFIG_X86_32 */
 515
 516 #ifdef CONFIG_X86_X32_ABI
 517 static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
 518                 const struct kernel_siginfo *from)
 519 {
 520         struct compat_siginfo new;
 521
 522         copy_siginfo_to_external32(&new, from);
 523         if (from->si_signo == SIGCHLD) {
 524                 new._sifields._sigchld_x32._utime = from->si_utime;
 525                 new._sifields._sigchld_x32._stime = from->si_stime;
 526         }
 527         if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
 528                 return -EFAULT;
 529         return 0;
 530 }
 531
 532 int copy_siginfo_to_user32(struct compat_siginfo __user *to,
 533                            const struct kernel_siginfo *from)
 534 {
 535         if (in_x32_syscall())
 536                 return x32_copy_siginfo_to_user(to, from);
 537         return __copy_siginfo_to_user32(to, from);
 538 }
 539 #endif /* CONFIG_X86_X32_ABI */
 540
 541 static int x32_setup_rt_frame(struct ksignal *ksig,
 542                               compat_sigset_t *set,
 543                               struct pt_regs *regs)
 544 {
 545 #ifdef CONFIG_X86_X32_ABI
 546         struct rt_sigframe_x32 __user *frame;
 547         unsigned long uc_flags;
 548         void __user *restorer;
 549         void __user *fp = NULL;
 550
 551         if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
 552                 return -EFAULT;
 553
 554         frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);
 555
 556         uc_flags = frame_uc_flags(regs);
 557
 558         if (!user_access_begin(frame, sizeof(*frame)))
 559                 return -EFAULT;
 560
 561         /* Create the ucontext.  */
 562         unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
 563         unsafe_put_user(0, &frame->uc.uc_link, Efault);
 564         unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
 565         unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
 566         restorer = ksig->ka.sa.sa_restorer;
 567         unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
 568         unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
 569         unsafe_put_sigmask(set, frame, Efault);
 570         user_access_end();
 571
 572         if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 573                 if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
 574                         return -EFAULT;
 575         }
 576
 577         /* Set up registers for signal handler */
 578         regs->sp = (unsigned long) frame;
 579         regs->ip = (unsigned long) ksig->ka.sa.sa_handler;
 580
 581         /* We use the x32 calling convention here... */
 582         regs->di = ksig->sig;
 583         regs->si = (unsigned long) &frame->info;
 584         regs->dx = (unsigned long) &frame->uc;
 585
 586         loadsegment(ds, __USER_DS);
 587         loadsegment(es, __USER_DS);
 588
 589         regs->cs = __USER_CS;
 590         regs->ss = __USER_DS;
 591 #endif  /* CONFIG_X86_X32_ABI */
 592
 593         return 0;
 594 #ifdef CONFIG_X86_X32_ABI
 595 Efault:
 596         user_access_end();
 597         return -EFAULT;
 598 #endif
 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) ||
 616             __get_user(set.sig[1], &frame->extramask[0]))
 617                 goto badframe;
 618
 619         set_current_blocked(&set);
 620
 621         /*
 622          * x86_32 has no uc_flags bits relevant to restore_sigcontext.
 623          * Save a few cycles by skipping the __get_user.
 624          */
 625         if (restore_sigcontext(regs, &frame->sc, 0))
 626                 goto badframe;
 627         return regs->ax;
 628
 629 badframe:
 630         signal_fault(regs, frame, "sigreturn");
 631
 632         return 0;
 633 }
 634 #endif /* CONFIG_X86_32 */
 635
 636 SYSCALL_DEFINE0(rt_sigreturn)
 637 {
 638         struct pt_regs *regs = current_pt_regs();
 639         struct rt_sigframe __user *frame;
 640         sigset_t set;
 641         unsigned long uc_flags;
 642
 643         frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
 644         if (!access_ok(frame, sizeof(*frame)))
 645                 goto badframe;
 646         if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
 647                 goto badframe;
 648         if (__get_user(uc_flags, &frame->uc.uc_flags))
 649                 goto badframe;
 650
 651         set_current_blocked(&set);
 652
 653         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 654                 goto badframe;
 655
 656         if (restore_altstack(&frame->uc.uc_stack))
 657                 goto badframe;
 658
 659         return regs->ax;
 660
 661 badframe:
 662         signal_fault(regs, frame, "rt_sigreturn");
 663         return 0;
 664 }
 665
 666 static inline int is_ia32_compat_frame(struct ksignal *ksig)
 667 {
 668         return IS_ENABLED(CONFIG_IA32_EMULATION) &&
 669                 ksig->ka.sa.sa_flags & SA_IA32_ABI;
 670 }
 671
 672 static inline int is_ia32_frame(struct ksignal *ksig)
 673 {
 674         return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
 675 }
 676
 677 static inline int is_x32_frame(struct ksignal *ksig)
 678 {
 679         return IS_ENABLED(CONFIG_X86_X32_ABI) &&
 680                 ksig->ka.sa.sa_flags & SA_X32_ABI;
 681 }
 682
 683 static int
 684 setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
 685 {
 686         int usig = ksig->sig;
 687         sigset_t *set = sigmask_to_save();
 688         compat_sigset_t *cset = (compat_sigset_t *) set;
 689
 690         /* Perform fixup for the pre-signal frame. */
 691         rseq_signal_deliver(ksig, regs);
 692
 693         /* Set up the stack frame */
 694         if (is_ia32_frame(ksig)) {
 695                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 696                         return ia32_setup_rt_frame(usig, ksig, cset, regs);
 697                 else
 698                         return ia32_setup_frame(usig, ksig, cset, regs);
 699         } else if (is_x32_frame(ksig)) {
 700                 return x32_setup_rt_frame(ksig, cset, regs);
 701         } else {
 702                 return __setup_rt_frame(ksig->sig, ksig, set, regs);
 703         }
 704 }
 705
 706 static void
 707 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 708 {
 709         bool stepping, failed;
 710         struct fpu *fpu = &current->thread.fpu;
 711
 712         if (v8086_mode(regs))
 713                 save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
 714
 715         /* Are we from a system call? */
 716         if (syscall_get_nr(current, regs) >= 0) {
 717                 /* If so, check system call restarting.. */
 718                 switch (syscall_get_error(current, regs)) {
 719                 case -ERESTART_RESTARTBLOCK:
 720                 case -ERESTARTNOHAND:
 721                         regs->ax = -EINTR;
 722                         break;
 723
 724                 case -ERESTARTSYS:
 725                         if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
 726                                 regs->ax = -EINTR;
 727                                 break;
 728                         }
 729                         fallthrough;
 730                 case -ERESTARTNOINTR:
 731                         regs->ax = regs->orig_ax;
 732                         regs->ip -= 2;
 733                         break;
 734                 }
 735         }
 736
 737         /*
 738          * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
 739          * so that register information in the sigcontext is correct and
 740          * then notify the tracer before entering the signal handler.
 741          */
 742         stepping = test_thread_flag(TIF_SINGLESTEP);
 743         if (stepping)
 744                 user_disable_single_step(current);
 745
 746         failed = (setup_rt_frame(ksig, regs) < 0);
 747         if (!failed) {
 748                 /*
 749                  * Clear the direction flag as per the ABI for function entry.
 750                  *
 751                  * Clear RF when entering the signal handler, because
 752                  * it might disable possible debug exception from the
 753                  * signal handler.
 754                  *
 755                  * Clear TF for the case when it wasn't set by debugger to
 756                  * avoid the recursive send_sigtrap() in SIGTRAP handler.
 757                  */
 758                 regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
 759                 /*
 760                  * Ensure the signal handler starts with the new fpu state.
 761                  */
 762                 fpu__clear_user_states(fpu);
 763         }
 764         signal_setup_done(failed, ksig, stepping);
 765 }
 766
 767 static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
 768 {
 769         /*
 770          * This function is fundamentally broken as currently
 771          * implemented.
 772          *
 773          * The idea is that we want to trigger a call to the
 774          * restart_block() syscall and that we want in_ia32_syscall(),
 775          * in_x32_syscall(), etc. to match whatever they were in the
 776          * syscall being restarted.  We assume that the syscall
 777          * instruction at (regs->ip - 2) matches whatever syscall
 778          * instruction we used to enter in the first place.
 779          *
 780          * The problem is that we can get here when ptrace pokes
 781          * syscall-like values into regs even if we're not in a syscall
 782          * at all.
 783          *
 784          * For now, we maintain historical behavior and guess based on
 785          * stored state.  We could do better by saving the actual
 786          * syscall arch in restart_block or (with caveats on x32) by
 787          * checking if regs->ip points to 'int $0x80'.  The current
 788          * behavior is incorrect if a tracer has a different bitness
 789          * than the tracee.
 790          */
 791 #ifdef CONFIG_IA32_EMULATION
 792         if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
 793                 return __NR_ia32_restart_syscall;
 794 #endif
 795 #ifdef CONFIG_X86_X32_ABI
 796         return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
 797 #else
 798         return __NR_restart_syscall;
 799 #endif
 800 }
 801
 802 /*
 803  * Note that 'init' is a special process: it doesn't get signals it doesn't
 804  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 805  * mistake.
 806  */
 807 void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
 808 {
 809         struct ksignal ksig;
 810
 811         if (has_signal && get_signal(&ksig)) {
 812                 /* Whee! Actually deliver the signal.  */
 813                 handle_signal(&ksig, regs);
 814                 return;
 815         }
 816
 817         /* Did we come from a system call? */
 818         if (syscall_get_nr(current, regs) >= 0) {
 819                 /* Restart the system call - no handlers present */
 820                 switch (syscall_get_error(current, regs)) {
 821                 case -ERESTARTNOHAND:
 822                 case -ERESTARTSYS:
 823                 case -ERESTARTNOINTR:
 824                         regs->ax = regs->orig_ax;
 825                         regs->ip -= 2;
 826                         break;
 827
 828                 case -ERESTART_RESTARTBLOCK:
 829                         regs->ax = get_nr_restart_syscall(regs);
 830                         regs->ip -= 2;
 831                         break;
 832                 }
 833         }
 834
 835         /*
 836          * If there's no signal to deliver, we just put the saved sigmask
 837          * back.
 838          */
 839         restore_saved_sigmask();
 840 }
 841
 842 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 843 {
 844         struct task_struct *me = current;
 845
 846         if (show_unhandled_signals && printk_ratelimit()) {
 847                 printk("%s"
 848                        "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 849                        task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 850                        me->comm, me->pid, where, frame,
 851                        regs->ip, regs->sp, regs->orig_ax);
 852                 print_vma_addr(KERN_CONT " in ", regs->ip);
 853                 pr_cont("\n");
 854         }
 855
 856         force_sig(SIGSEGV);
 857 }
 858
 859 #ifdef CONFIG_X86_X32_ABI
 860 COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
 861 {
 862         struct pt_regs *regs = current_pt_regs();
 863         struct rt_sigframe_x32 __user *frame;
 864         sigset_t set;
 865         unsigned long uc_flags;
 866
 867         frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
 868
 869         if (!access_ok(frame, sizeof(*frame)))
 870                 goto badframe;
 871         if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
 872                 goto badframe;
 873         if (__get_user(uc_flags, &frame->uc.uc_flags))
 874                 goto badframe;
 875
 876         set_current_blocked(&set);
 877
 878         if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
 879                 goto badframe;
 880
 881         if (compat_restore_altstack(&frame->uc.uc_stack))
 882                 goto badframe;
 883
 884         return regs->ax;
 885
 886 badframe:
 887         signal_fault(regs, frame, "x32 rt_sigreturn");
 888         return 0;
 889 }
 890 #endif