arch/s390/kernel/signal.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Copyright IBM Corp. 1999, 2006
   4  *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
   5  *
   6  *    Based on Intel version
   7  *
   8  *  Copyright (C) 1991, 1992  Linus Torvalds
   9  *
  10  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
  11  */
  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/signal.h>
  19 #include <linux/errno.h>
  20 #include <linux/wait.h>
  21 #include <linux/ptrace.h>
  22 #include <linux/unistd.h>
  23 #include <linux/stddef.h>
  24 #include <linux/tty.h>
  25 #include <linux/personality.h>
  26 #include <linux/binfmts.h>
  27 #include <linux/tracehook.h>
  28 #include <linux/syscalls.h>
  29 #include <linux/compat.h>
  30 #include <asm/ucontext.h>
  31 #include <linux/uaccess.h>
  32 #include <asm/lowcore.h>
  33 #include <asm/switch_to.h>
  34 #include "entry.h"
  35
  36 /*
  37  * Layout of an old-style signal-frame:
  38  *      -----------------------------------------
  39  *      | save area (_SIGNAL_FRAMESIZE)         |
  40  *      -----------------------------------------
  41  *      | struct sigcontext                     |
  42  *      |       oldmask                         |
  43  *      |       _sigregs *                      |
  44  *      -----------------------------------------
  45  *      | _sigregs with                         |
  46  *      |       _s390_regs_common               |
  47  *      |       _s390_fp_regs                   |
  48  *      -----------------------------------------
  49  *      | int signo                             |
  50  *      -----------------------------------------
  51  *      | _sigregs_ext with                     |
  52  *      |       gprs_high 64 byte (opt)         |
  53  *      |       vxrs_low 128 byte (opt)         |
  54  *      |       vxrs_high 256 byte (opt)        |
  55  *      |       reserved 128 byte (opt)         |
  56  *      -----------------------------------------
  57  *      | __u16 svc_insn                        |
  58  *      -----------------------------------------
  59  * The svc_insn entry with the sigreturn system call opcode does not
  60  * have a fixed position and moves if gprs_high or vxrs exist.
  61  * Future extensions will be added to _sigregs_ext.
  62  */
  63 struct sigframe
  64 {
  65         __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
  66         struct sigcontext sc;
  67         _sigregs sregs;
  68         int signo;
  69         _sigregs_ext sregs_ext;
  70         __u16 svc_insn;         /* Offset of svc_insn is NOT fixed! */
  71 };
  72
  73 /*
  74  * Layout of an rt signal-frame:
  75  *      -----------------------------------------
  76  *      | save area (_SIGNAL_FRAMESIZE)         |
  77  *      -----------------------------------------
  78  *      | svc __NR_rt_sigreturn 2 byte          |
  79  *      -----------------------------------------
  80  *      | struct siginfo                        |
  81  *      -----------------------------------------
  82  *      | struct ucontext_extended with         |
  83  *      |       unsigned long uc_flags          |
  84  *      |       struct ucontext *uc_link        |
  85  *      |       stack_t uc_stack                |
  86  *      |       _sigregs uc_mcontext with       |
  87  *      |               _s390_regs_common       |
  88  *      |               _s390_fp_regs           |
  89  *      |       sigset_t uc_sigmask             |
  90  *      |       _sigregs_ext uc_mcontext_ext    |
  91  *      |               gprs_high 64 byte (opt) |
  92  *      |               vxrs_low 128 byte (opt) |
  93  *      |               vxrs_high 256 byte (opt)|
  94  *      |               reserved 128 byte (opt) |
  95  *      -----------------------------------------
  96  * Future extensions will be added to _sigregs_ext.
  97  */
  98 struct rt_sigframe
  99 {
 100         __u8 callee_used_stack[__SIGNAL_FRAMESIZE];
 101         __u16 svc_insn;
 102         struct siginfo info;
 103         struct ucontext_extended uc;
 104 };
 105
 106 /* Store registers needed to create the signal frame */
 107 static void store_sigregs(void)
 108 {
 109         save_access_regs(current->thread.acrs);
 110         save_fpu_regs();
 111 }
 112
 113 /* Load registers after signal return */
 114 static void load_sigregs(void)
 115 {
 116         restore_access_regs(current->thread.acrs);
 117 }
 118
 119 /* Returns non-zero on fault. */
 120 static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
 121 {
 122         _sigregs user_sregs;
 123
 124         /* Copy a 'clean' PSW mask to the user to avoid leaking
 125            information about whether PER is currently on.  */
 126         user_sregs.regs.psw.mask = PSW_USER_BITS |
 127                 (regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
 128         user_sregs.regs.psw.addr = regs->psw.addr;
 129         memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
 130         memcpy(&user_sregs.regs.acrs, current->thread.acrs,
 131                sizeof(user_sregs.regs.acrs));
 132         fpregs_store(&user_sregs.fpregs, &current->thread.fpu);
 133         if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
 134                 return -EFAULT;
 135         return 0;
 136 }
 137
 138 static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
 139 {
 140         _sigregs user_sregs;
 141
 142         /* Alwys make any pending restarted system call return -EINTR */
 143         current->restart_block.fn = do_no_restart_syscall;
 144
 145         if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
 146                 return -EFAULT;
 147
 148         if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI))
 149                 return -EINVAL;
 150
 151         /* Test the floating-point-control word. */
 152         if (test_fp_ctl(user_sregs.fpregs.fpc))
 153                 return -EINVAL;
 154
 155         /* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
 156         regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) |
 157                 (user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
 158         /* Check for invalid user address space control. */
 159         if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME)
 160                 regs->psw.mask = PSW_ASC_PRIMARY |
 161                         (regs->psw.mask & ~PSW_MASK_ASC);
 162         /* Check for invalid amode */
 163         if (regs->psw.mask & PSW_MASK_EA)
 164                 regs->psw.mask |= PSW_MASK_BA;
 165         regs->psw.addr = user_sregs.regs.psw.addr;
 166         memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
 167         memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
 168                sizeof(current->thread.acrs));
 169
 170         fpregs_load(&user_sregs.fpregs, &current->thread.fpu);
 171
 172         clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */
 173         return 0;
 174 }
 175
 176 /* Returns non-zero on fault. */
 177 static int save_sigregs_ext(struct pt_regs *regs,
 178                             _sigregs_ext __user *sregs_ext)
 179 {
 180         __u64 vxrs[__NUM_VXRS_LOW];
 181         int i;
 182
 183         /* Save vector registers to signal stack */
 184         if (MACHINE_HAS_VX) {
 185                 for (i = 0; i < __NUM_VXRS_LOW; i++)
 186                         vxrs[i] = *((__u64 *)(current->thread.fpu.vxrs + i) + 1);
 187                 if (__copy_to_user(&sregs_ext->vxrs_low, vxrs,
 188                                    sizeof(sregs_ext->vxrs_low)) ||
 189                     __copy_to_user(&sregs_ext->vxrs_high,
 190                                    current->thread.fpu.vxrs + __NUM_VXRS_LOW,
 191                                    sizeof(sregs_ext->vxrs_high)))
 192                         return -EFAULT;
 193         }
 194         return 0;
 195 }
 196
 197 static int restore_sigregs_ext(struct pt_regs *regs,
 198                                _sigregs_ext __user *sregs_ext)
 199 {
 200         __u64 vxrs[__NUM_VXRS_LOW];
 201         int i;
 202
 203         /* Restore vector registers from signal stack */
 204         if (MACHINE_HAS_VX) {
 205                 if (__copy_from_user(vxrs, &sregs_ext->vxrs_low,
 206                                      sizeof(sregs_ext->vxrs_low)) ||
 207                     __copy_from_user(current->thread.fpu.vxrs + __NUM_VXRS_LOW,
 208                                      &sregs_ext->vxrs_high,
 209                                      sizeof(sregs_ext->vxrs_high)))
 210                         return -EFAULT;
 211                 for (i = 0; i < __NUM_VXRS_LOW; i++)
 212                         *((__u64 *)(current->thread.fpu.vxrs + i) + 1) = vxrs[i];
 213         }
 214         return 0;
 215 }
 216
 217 SYSCALL_DEFINE0(sigreturn)
 218 {
 219         struct pt_regs *regs = task_pt_regs(current);
 220         struct sigframe __user *frame =
 221                 (struct sigframe __user *) regs->gprs[15];
 222         sigset_t set;
 223
 224         if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
 225                 goto badframe;
 226         set_current_blocked(&set);
 227         save_fpu_regs();
 228         if (restore_sigregs(regs, &frame->sregs))
 229                 goto badframe;
 230         if (restore_sigregs_ext(regs, &frame->sregs_ext))
 231                 goto badframe;
 232         load_sigregs();
 233         return regs->gprs[2];
 234 badframe:
 235         force_sig(SIGSEGV);
 236         return 0;
 237 }
 238
 239 SYSCALL_DEFINE0(rt_sigreturn)
 240 {
 241         struct pt_regs *regs = task_pt_regs(current);
 242         struct rt_sigframe __user *frame =
 243                 (struct rt_sigframe __user *)regs->gprs[15];
 244         sigset_t set;
 245
 246         if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
 247                 goto badframe;
 248         set_current_blocked(&set);
 249         if (restore_altstack(&frame->uc.uc_stack))
 250                 goto badframe;
 251         save_fpu_regs();
 252         if (restore_sigregs(regs, &frame->uc.uc_mcontext))
 253                 goto badframe;
 254         if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
 255                 goto badframe;
 256         load_sigregs();
 257         return regs->gprs[2];
 258 badframe:
 259         force_sig(SIGSEGV);
 260         return 0;
 261 }
 262
 263 /*
 264  * Determine which stack to use..
 265  */
 266 static inline void __user *
 267 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 268 {
 269         unsigned long sp;
 270
 271         /* Default to using normal stack */
 272         sp = regs->gprs[15];
 273
 274         /* Overflow on alternate signal stack gives SIGSEGV. */
 275         if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
 276                 return (void __user *) -1UL;
 277
 278         /* This is the X/Open sanctioned signal stack switching.  */
 279         if (ka->sa.sa_flags & SA_ONSTACK) {
 280                 if (! sas_ss_flags(sp))
 281                         sp = current->sas_ss_sp + current->sas_ss_size;
 282         }
 283
 284         return (void __user *)((sp - frame_size) & -8ul);
 285 }
 286
 287 static int setup_frame(int sig, struct k_sigaction *ka,
 288                        sigset_t *set, struct pt_regs * regs)
 289 {
 290         struct sigframe __user *frame;
 291         struct sigcontext sc;
 292         unsigned long restorer;
 293         size_t frame_size;
 294
 295         /*
 296          * gprs_high are only present for a 31-bit task running on
 297          * a 64-bit kernel (see compat_signal.c) but the space for
 298          * gprs_high need to be allocated if vector registers are
 299          * included in the signal frame on a 31-bit system.
 300          */
 301         frame_size = sizeof(*frame) - sizeof(frame->sregs_ext);
 302         if (MACHINE_HAS_VX)
 303                 frame_size += sizeof(frame->sregs_ext);
 304         frame = get_sigframe(ka, regs, frame_size);
 305         if (frame == (void __user *) -1UL)
 306                 return -EFAULT;
 307
 308         /* Set up backchain. */
 309         if (__put_user(regs->gprs[15], (addr_t __user *) frame))
 310                 return -EFAULT;
 311
 312         /* Create struct sigcontext on the signal stack */
 313         memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE);
 314         sc.sregs = (_sigregs __user __force *) &frame->sregs;
 315         if (__copy_to_user(&frame->sc, &sc, sizeof(frame->sc)))
 316                 return -EFAULT;
 317
 318         /* Store registers needed to create the signal frame */
 319         store_sigregs();
 320
 321         /* Create _sigregs on the signal stack */
 322         if (save_sigregs(regs, &frame->sregs))
 323                 return -EFAULT;
 324
 325         /* Place signal number on stack to allow backtrace from handler.  */
 326         if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
 327                 return -EFAULT;
 328
 329         /* Create _sigregs_ext on the signal stack */
 330         if (save_sigregs_ext(regs, &frame->sregs_ext))
 331                 return -EFAULT;
 332
 333         /* Set up to return from userspace.  If provided, use a stub
 334            already in userspace.  */
 335         if (ka->sa.sa_flags & SA_RESTORER) {
 336                 restorer = (unsigned long) ka->sa.sa_restorer;
 337         } else {
 338                 /* Signal frame without vector registers are short ! */
 339                 __u16 __user *svc = (void __user *) frame + frame_size - 2;
 340                 if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn, svc))
 341                         return -EFAULT;
 342                 restorer = (unsigned long) svc;
 343         }
 344
 345         /* Set up registers for signal handler */
 346         regs->gprs[14] = restorer;
 347         regs->gprs[15] = (unsigned long) frame;
 348         /* Force default amode and default user address space control. */
 349         regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
 350                 (PSW_USER_BITS & PSW_MASK_ASC) |
 351                 (regs->psw.mask & ~PSW_MASK_ASC);
 352         regs->psw.addr = (unsigned long) ka->sa.sa_handler;
 353
 354         regs->gprs[2] = sig;
 355         regs->gprs[3] = (unsigned long) &frame->sc;
 356
 357         /* We forgot to include these in the sigcontext.
 358            To avoid breaking binary compatibility, they are passed as args. */
 359         if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
 360             sig == SIGTRAP || sig == SIGFPE) {
 361                 /* set extra registers only for synchronous signals */
 362                 regs->gprs[4] = regs->int_code & 127;
 363                 regs->gprs[5] = regs->int_parm_long;
 364                 regs->gprs[6] = current->thread.last_break;
 365         }
 366         return 0;
 367 }
 368
 369 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
 370                           struct pt_regs *regs)
 371 {
 372         struct rt_sigframe __user *frame;
 373         unsigned long uc_flags, restorer;
 374         size_t frame_size;
 375
 376         frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext);
 377         /*
 378          * gprs_high are only present for a 31-bit task running on
 379          * a 64-bit kernel (see compat_signal.c) but the space for
 380          * gprs_high need to be allocated if vector registers are
 381          * included in the signal frame on a 31-bit system.
 382          */
 383         uc_flags = 0;
 384         if (MACHINE_HAS_VX) {
 385                 frame_size += sizeof(_sigregs_ext);
 386                 uc_flags |= UC_VXRS;
 387         }
 388         frame = get_sigframe(&ksig->ka, regs, frame_size);
 389         if (frame == (void __user *) -1UL)
 390                 return -EFAULT;
 391
 392         /* Set up backchain. */
 393         if (__put_user(regs->gprs[15], (addr_t __user *) frame))
 394                 return -EFAULT;
 395
 396         /* Set up to return from userspace.  If provided, use a stub
 397            already in userspace.  */
 398         if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 399                 restorer = (unsigned long) ksig->ka.sa.sa_restorer;
 400         } else {
 401                 __u16 __user *svc = &frame->svc_insn;
 402                 if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn, svc))
 403                         return -EFAULT;
 404                 restorer = (unsigned long) svc;
 405         }
 406
 407         /* Create siginfo on the signal stack */
 408         if (copy_siginfo_to_user(&frame->info, &ksig->info))
 409                 return -EFAULT;
 410
 411         /* Store registers needed to create the signal frame */
 412         store_sigregs();
 413
 414         /* Create ucontext on the signal stack. */
 415         if (__put_user(uc_flags, &frame->uc.uc_flags) ||
 416             __put_user(NULL, &frame->uc.uc_link) ||
 417             __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) ||
 418             save_sigregs(regs, &frame->uc.uc_mcontext) ||
 419             __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)) ||
 420             save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
 421                 return -EFAULT;
 422
 423         /* Set up registers for signal handler */
 424         regs->gprs[14] = restorer;
 425         regs->gprs[15] = (unsigned long) frame;
 426         /* Force default amode and default user address space control. */
 427         regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
 428                 (PSW_USER_BITS & PSW_MASK_ASC) |
 429                 (regs->psw.mask & ~PSW_MASK_ASC);
 430         regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler;
 431
 432         regs->gprs[2] = ksig->sig;
 433         regs->gprs[3] = (unsigned long) &frame->info;
 434         regs->gprs[4] = (unsigned long) &frame->uc;
 435         regs->gprs[5] = current->thread.last_break;
 436         return 0;
 437 }
 438
 439 static void handle_signal(struct ksignal *ksig, sigset_t *oldset,
 440                           struct pt_regs *regs)
 441 {
 442         int ret;
 443
 444         /* Set up the stack frame */
 445         if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 446                 ret = setup_rt_frame(ksig, oldset, regs);
 447         else
 448                 ret = setup_frame(ksig->sig, &ksig->ka, oldset, regs);
 449
 450         signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLE_STEP));
 451 }
 452
 453 /*
 454  * Note that 'init' is a special process: it doesn't get signals it doesn't
 455  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 456  * mistake.
 457  *
 458  * Note that we go through the signals twice: once to check the signals that
 459  * the kernel can handle, and then we build all the user-level signal handling
 460  * stack-frames in one go after that.
 461  */
 462 void do_signal(struct pt_regs *regs)
 463 {
 464         struct ksignal ksig;
 465         sigset_t *oldset = sigmask_to_save();
 466
 467         /*
 468          * Get signal to deliver. When running under ptrace, at this point
 469          * the debugger may change all our registers, including the system
 470          * call information.
 471          */
 472         current->thread.system_call =
 473                 test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;
 474
 475         if (get_signal(&ksig)) {
 476                 /* Whee!  Actually deliver the signal.  */
 477                 if (current->thread.system_call) {
 478                         regs->int_code = current->thread.system_call;
 479                         /* Check for system call restarting. */
 480                         switch (regs->gprs[2]) {
 481                         case -ERESTART_RESTARTBLOCK:
 482                         case -ERESTARTNOHAND:
 483                                 regs->gprs[2] = -EINTR;
 484                                 break;
 485                         case -ERESTARTSYS:
 486                                 if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
 487                                         regs->gprs[2] = -EINTR;
 488                                         break;
 489                                 }
 490                                 fallthrough;
 491                         case -ERESTARTNOINTR:
 492                                 regs->gprs[2] = regs->orig_gpr2;
 493                                 regs->psw.addr =
 494                                         __rewind_psw(regs->psw,
 495                                                      regs->int_code >> 16);
 496                                 break;
 497                         }
 498                 }
 499                 /* No longer in a system call */
 500                 clear_pt_regs_flag(regs, PIF_SYSCALL);
 501                 rseq_signal_deliver(&ksig, regs);
 502                 if (is_compat_task())
 503                         handle_signal32(&ksig, oldset, regs);
 504                 else
 505                         handle_signal(&ksig, oldset, regs);
 506                 return;
 507         }
 508
 509         /* No handlers present - check for system call restart */
 510         clear_pt_regs_flag(regs, PIF_SYSCALL);
 511         if (current->thread.system_call) {
 512                 regs->int_code = current->thread.system_call;
 513                 switch (regs->gprs[2]) {
 514                 case -ERESTART_RESTARTBLOCK:
 515                         /* Restart with sys_restart_syscall */
 516                         regs->int_code = __NR_restart_syscall;
 517                         fallthrough;
 518                 case -ERESTARTNOHAND:
 519                 case -ERESTARTSYS:
 520                 case -ERESTARTNOINTR:
 521                         /* Restart system call with magic TIF bit. */
 522                         regs->gprs[2] = regs->orig_gpr2;
 523                         set_pt_regs_flag(regs, PIF_SYSCALL);
 524                         if (test_thread_flag(TIF_SINGLE_STEP))
 525                                 clear_pt_regs_flag(regs, PIF_PER_TRAP);
 526                         break;
 527                 }
 528         }
 529
 530         /*
 531          * If there's no signal to deliver, we just put the saved sigmask back.
 532          */
 533         restore_saved_sigmask();
 534 }
 535
 536 void do_notify_resume(struct pt_regs *regs)
 537 {
 538         clear_thread_flag(TIF_NOTIFY_RESUME);
 539         tracehook_notify_resume(regs);
 540         rseq_handle_notify_resume(NULL, regs);
 541 }