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/entry-common.h> 20 #include <linux/errno.h> 21 #include <linux/wait.h> 22 #include <linux/ptrace.h> 23 #include <linux/unistd.h> 24 #include <linux/stddef.h> 25 #include <linux/tty.h> 26 #include <linux/personality.h> 27 #include <linux/binfmts.h> 28 #include <linux/tracehook.h> 29 #include <linux/syscalls.h> 30 #include <linux/compat.h> 31 #include <asm/ucontext.h> 32 #include <linux/uaccess.h> 33 #include <asm/lowcore.h> 34 #include <asm/switch_to.h> 35 #include <asm/vdso.h> 36 #include "entry.h" 37 38 /* 39 * Layout of an old-style signal-frame: 40 * ----------------------------------------- 41 * | save area (_SIGNAL_FRAMESIZE) | 42 * ----------------------------------------- 43 * | struct sigcontext | 44 * | oldmask | 45 * | _sigregs * | 46 * ----------------------------------------- 47 * | _sigregs with | 48 * | _s390_regs_common | 49 * | _s390_fp_regs | 50 * ----------------------------------------- 51 * | int signo | 52 * ----------------------------------------- 53 * | _sigregs_ext with | 54 * | gprs_high 64 byte (opt) | 55 * | vxrs_low 128 byte (opt) | 56 * | vxrs_high 256 byte (opt) | 57 * | reserved 128 byte (opt) | 58 * ----------------------------------------- 59 * | __u16 svc_insn | 60 * ----------------------------------------- 61 * The svc_insn entry with the sigreturn system call opcode does not 62 * have a fixed position and moves if gprs_high or vxrs exist. 63 * Future extensions will be added to _sigregs_ext. 64 */ 65 struct sigframe 66 { 67 __u8 callee_used_stack[__SIGNAL_FRAMESIZE]; 68 struct sigcontext sc; 69 _sigregs sregs; 70 int signo; 71 _sigregs_ext sregs_ext; 72 __u16 svc_insn; /* Offset of svc_insn is NOT fixed! */ 73 }; 74 75 /* 76 * Layout of an rt signal-frame: 77 * ----------------------------------------- 78 * | save area (_SIGNAL_FRAMESIZE) | 79 * ----------------------------------------- 80 * | svc __NR_rt_sigreturn 2 byte | 81 * ----------------------------------------- 82 * | struct siginfo | 83 * ----------------------------------------- 84 * | struct ucontext_extended with | 85 * | unsigned long uc_flags | 86 * | struct ucontext *uc_link | 87 * | stack_t uc_stack | 88 * | _sigregs uc_mcontext with | 89 * | _s390_regs_common | 90 * | _s390_fp_regs | 91 * | sigset_t uc_sigmask | 92 * | _sigregs_ext uc_mcontext_ext | 93 * | gprs_high 64 byte (opt) | 94 * | vxrs_low 128 byte (opt) | 95 * | vxrs_high 256 byte (opt)| 96 * | reserved 128 byte (opt) | 97 * ----------------------------------------- 98 * Future extensions will be added to _sigregs_ext. 99 */ 100 struct rt_sigframe 101 { 102 __u8 callee_used_stack[__SIGNAL_FRAMESIZE]; 103 __u16 svc_insn; 104 struct siginfo info; 105 struct ucontext_extended uc; 106 }; 107 108 /* Store registers needed to create the signal frame */ 109 static void store_sigregs(void) 110 { 111 save_access_regs(current->thread.acrs); 112 save_fpu_regs(); 113 } 114 115 /* Load registers after signal return */ 116 static void load_sigregs(void) 117 { 118 restore_access_regs(current->thread.acrs); 119 } 120 121 /* Returns non-zero on fault. */ 122 static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs) 123 { 124 _sigregs user_sregs; 125 126 /* Copy a 'clean' PSW mask to the user to avoid leaking 127 information about whether PER is currently on. */ 128 user_sregs.regs.psw.mask = PSW_USER_BITS | 129 (regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI)); 130 user_sregs.regs.psw.addr = regs->psw.addr; 131 memcpy(&user_sregs.regs.gprs, ®s->gprs, sizeof(sregs->regs.gprs)); 132 memcpy(&user_sregs.regs.acrs, current->thread.acrs, 133 sizeof(user_sregs.regs.acrs)); 134 fpregs_store(&user_sregs.fpregs, ¤t->thread.fpu); 135 if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs))) 136 return -EFAULT; 137 return 0; 138 } 139 140 static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs) 141 { 142 _sigregs user_sregs; 143 144 /* Alwys make any pending restarted system call return -EINTR */ 145 current->restart_block.fn = do_no_restart_syscall; 146 147 if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs))) 148 return -EFAULT; 149 150 if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI)) 151 return -EINVAL; 152 153 /* Test the floating-point-control word. */ 154 if (test_fp_ctl(user_sregs.fpregs.fpc)) 155 return -EINVAL; 156 157 /* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */ 158 regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) | 159 (user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI)); 160 /* Check for invalid user address space control. */ 161 if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME) 162 regs->psw.mask = PSW_ASC_PRIMARY | 163 (regs->psw.mask & ~PSW_MASK_ASC); 164 /* Check for invalid amode */ 165 if (regs->psw.mask & PSW_MASK_EA) 166 regs->psw.mask |= PSW_MASK_BA; 167 regs->psw.addr = user_sregs.regs.psw.addr; 168 memcpy(®s->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs)); 169 memcpy(¤t->thread.acrs, &user_sregs.regs.acrs, 170 sizeof(current->thread.acrs)); 171 172 fpregs_load(&user_sregs.fpregs, ¤t->thread.fpu); 173 174 clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */ 175 return 0; 176 } 177 178 /* Returns non-zero on fault. */ 179 static int save_sigregs_ext(struct pt_regs *regs, 180 _sigregs_ext __user *sregs_ext) 181 { 182 __u64 vxrs[__NUM_VXRS_LOW]; 183 int i; 184 185 /* Save vector registers to signal stack */ 186 if (MACHINE_HAS_VX) { 187 for (i = 0; i < __NUM_VXRS_LOW; i++) 188 vxrs[i] = *((__u64 *)(current->thread.fpu.vxrs + i) + 1); 189 if (__copy_to_user(&sregs_ext->vxrs_low, vxrs, 190 sizeof(sregs_ext->vxrs_low)) || 191 __copy_to_user(&sregs_ext->vxrs_high, 192 current->thread.fpu.vxrs + __NUM_VXRS_LOW, 193 sizeof(sregs_ext->vxrs_high))) 194 return -EFAULT; 195 } 196 return 0; 197 } 198 199 static int restore_sigregs_ext(struct pt_regs *regs, 200 _sigregs_ext __user *sregs_ext) 201 { 202 __u64 vxrs[__NUM_VXRS_LOW]; 203 int i; 204 205 /* Restore vector registers from signal stack */ 206 if (MACHINE_HAS_VX) { 207 if (__copy_from_user(vxrs, &sregs_ext->vxrs_low, 208 sizeof(sregs_ext->vxrs_low)) || 209 __copy_from_user(current->thread.fpu.vxrs + __NUM_VXRS_LOW, 210 &sregs_ext->vxrs_high, 211 sizeof(sregs_ext->vxrs_high))) 212 return -EFAULT; 213 for (i = 0; i < __NUM_VXRS_LOW; i++) 214 *((__u64 *)(current->thread.fpu.vxrs + i) + 1) = vxrs[i]; 215 } 216 return 0; 217 } 218 219 SYSCALL_DEFINE0(sigreturn) 220 { 221 struct pt_regs *regs = task_pt_regs(current); 222 struct sigframe __user *frame = 223 (struct sigframe __user *) regs->gprs[15]; 224 sigset_t set; 225 226 if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE)) 227 goto badframe; 228 set_current_blocked(&set); 229 save_fpu_regs(); 230 if (restore_sigregs(regs, &frame->sregs)) 231 goto badframe; 232 if (restore_sigregs_ext(regs, &frame->sregs_ext)) 233 goto badframe; 234 load_sigregs(); 235 return regs->gprs[2]; 236 badframe: 237 force_sig(SIGSEGV); 238 return 0; 239 } 240 241 SYSCALL_DEFINE0(rt_sigreturn) 242 { 243 struct pt_regs *regs = task_pt_regs(current); 244 struct rt_sigframe __user *frame = 245 (struct rt_sigframe __user *)regs->gprs[15]; 246 sigset_t set; 247 248 if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set))) 249 goto badframe; 250 set_current_blocked(&set); 251 if (restore_altstack(&frame->uc.uc_stack)) 252 goto badframe; 253 save_fpu_regs(); 254 if (restore_sigregs(regs, &frame->uc.uc_mcontext)) 255 goto badframe; 256 if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext)) 257 goto badframe; 258 load_sigregs(); 259 return regs->gprs[2]; 260 badframe: 261 force_sig(SIGSEGV); 262 return 0; 263 } 264 265 /* 266 * Determine which stack to use.. 267 */ 268 static inline void __user * 269 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size) 270 { 271 unsigned long sp; 272 273 /* Default to using normal stack */ 274 sp = regs->gprs[15]; 275 276 /* Overflow on alternate signal stack gives SIGSEGV. */ 277 if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL)) 278 return (void __user *) -1UL; 279 280 /* This is the X/Open sanctioned signal stack switching. */ 281 if (ka->sa.sa_flags & SA_ONSTACK) { 282 if (! sas_ss_flags(sp)) 283 sp = current->sas_ss_sp + current->sas_ss_size; 284 } 285 286 return (void __user *)((sp - frame_size) & -8ul); 287 } 288 289 static int setup_frame(int sig, struct k_sigaction *ka, 290 sigset_t *set, struct pt_regs * regs) 291 { 292 struct sigframe __user *frame; 293 struct sigcontext sc; 294 unsigned long restorer; 295 size_t frame_size; 296 297 /* 298 * gprs_high are only present for a 31-bit task running on 299 * a 64-bit kernel (see compat_signal.c) but the space for 300 * gprs_high need to be allocated if vector registers are 301 * included in the signal frame on a 31-bit system. 302 */ 303 frame_size = sizeof(*frame) - sizeof(frame->sregs_ext); 304 if (MACHINE_HAS_VX) 305 frame_size += sizeof(frame->sregs_ext); 306 frame = get_sigframe(ka, regs, frame_size); 307 if (frame == (void __user *) -1UL) 308 return -EFAULT; 309 310 /* Set up backchain. */ 311 if (__put_user(regs->gprs[15], (addr_t __user *) frame)) 312 return -EFAULT; 313 314 /* Create struct sigcontext on the signal stack */ 315 memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE); 316 sc.sregs = (_sigregs __user __force *) &frame->sregs; 317 if (__copy_to_user(&frame->sc, &sc, sizeof(frame->sc))) 318 return -EFAULT; 319 320 /* Store registers needed to create the signal frame */ 321 store_sigregs(); 322 323 /* Create _sigregs on the signal stack */ 324 if (save_sigregs(regs, &frame->sregs)) 325 return -EFAULT; 326 327 /* Place signal number on stack to allow backtrace from handler. */ 328 if (__put_user(regs->gprs[2], (int __user *) &frame->signo)) 329 return -EFAULT; 330 331 /* Create _sigregs_ext on the signal stack */ 332 if (save_sigregs_ext(regs, &frame->sregs_ext)) 333 return -EFAULT; 334 335 /* Set up to return from userspace. If provided, use a stub 336 already in userspace. */ 337 if (ka->sa.sa_flags & SA_RESTORER) 338 restorer = (unsigned long) ka->sa.sa_restorer; 339 else 340 restorer = VDSO64_SYMBOL(current, sigreturn); 341 342 /* Set up registers for signal handler */ 343 regs->gprs[14] = restorer; 344 regs->gprs[15] = (unsigned long) frame; 345 /* Force default amode and default user address space control. */ 346 regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA | 347 (PSW_USER_BITS & PSW_MASK_ASC) | 348 (regs->psw.mask & ~PSW_MASK_ASC); 349 regs->psw.addr = (unsigned long) ka->sa.sa_handler; 350 351 regs->gprs[2] = sig; 352 regs->gprs[3] = (unsigned long) &frame->sc; 353 354 /* We forgot to include these in the sigcontext. 355 To avoid breaking binary compatibility, they are passed as args. */ 356 if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL || 357 sig == SIGTRAP || sig == SIGFPE) { 358 /* set extra registers only for synchronous signals */ 359 regs->gprs[4] = regs->int_code & 127; 360 regs->gprs[5] = regs->int_parm_long; 361 regs->gprs[6] = current->thread.last_break; 362 } 363 return 0; 364 } 365 366 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, 367 struct pt_regs *regs) 368 { 369 struct rt_sigframe __user *frame; 370 unsigned long uc_flags, restorer; 371 size_t frame_size; 372 373 frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext); 374 /* 375 * gprs_high are only present for a 31-bit task running on 376 * a 64-bit kernel (see compat_signal.c) but the space for 377 * gprs_high need to be allocated if vector registers are 378 * included in the signal frame on a 31-bit system. 379 */ 380 uc_flags = 0; 381 if (MACHINE_HAS_VX) { 382 frame_size += sizeof(_sigregs_ext); 383 uc_flags |= UC_VXRS; 384 } 385 frame = get_sigframe(&ksig->ka, regs, frame_size); 386 if (frame == (void __user *) -1UL) 387 return -EFAULT; 388 389 /* Set up backchain. */ 390 if (__put_user(regs->gprs[15], (addr_t __user *) frame)) 391 return -EFAULT; 392 393 /* Set up to return from userspace. If provided, use a stub 394 already in userspace. */ 395 if (ksig->ka.sa.sa_flags & SA_RESTORER) 396 restorer = (unsigned long) ksig->ka.sa.sa_restorer; 397 else 398 restorer = VDSO64_SYMBOL(current, rt_sigreturn); 399 400 /* Create siginfo on the signal stack */ 401 if (copy_siginfo_to_user(&frame->info, &ksig->info)) 402 return -EFAULT; 403 404 /* Store registers needed to create the signal frame */ 405 store_sigregs(); 406 407 /* Create ucontext on the signal stack. */ 408 if (__put_user(uc_flags, &frame->uc.uc_flags) || 409 __put_user(NULL, &frame->uc.uc_link) || 410 __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) || 411 save_sigregs(regs, &frame->uc.uc_mcontext) || 412 __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)) || 413 save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext)) 414 return -EFAULT; 415 416 /* Set up registers for signal handler */ 417 regs->gprs[14] = restorer; 418 regs->gprs[15] = (unsigned long) frame; 419 /* Force default amode and default user address space control. */ 420 regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA | 421 (PSW_USER_BITS & PSW_MASK_ASC) | 422 (regs->psw.mask & ~PSW_MASK_ASC); 423 regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler; 424 425 regs->gprs[2] = ksig->sig; 426 regs->gprs[3] = (unsigned long) &frame->info; 427 regs->gprs[4] = (unsigned long) &frame->uc; 428 regs->gprs[5] = current->thread.last_break; 429 return 0; 430 } 431 432 static void handle_signal(struct ksignal *ksig, sigset_t *oldset, 433 struct pt_regs *regs) 434 { 435 int ret; 436 437 /* Set up the stack frame */ 438 if (ksig->ka.sa.sa_flags & SA_SIGINFO) 439 ret = setup_rt_frame(ksig, oldset, regs); 440 else 441 ret = setup_frame(ksig->sig, &ksig->ka, oldset, regs); 442 443 signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLE_STEP)); 444 } 445 446 /* 447 * Note that 'init' is a special process: it doesn't get signals it doesn't 448 * want to handle. Thus you cannot kill init even with a SIGKILL even by 449 * mistake. 450 * 451 * Note that we go through the signals twice: once to check the signals that 452 * the kernel can handle, and then we build all the user-level signal handling 453 * stack-frames in one go after that. 454 */ 455 456 void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) 457 { 458 struct ksignal ksig; 459 sigset_t *oldset = sigmask_to_save(); 460 461 /* 462 * Get signal to deliver. When running under ptrace, at this point 463 * the debugger may change all our registers, including the system 464 * call information. 465 */ 466 current->thread.system_call = 467 test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0; 468 469 if (has_signal && get_signal(&ksig)) { 470 /* Whee! Actually deliver the signal. */ 471 if (current->thread.system_call) { 472 regs->int_code = current->thread.system_call; 473 /* Check for system call restarting. */ 474 switch (regs->gprs[2]) { 475 case -ERESTART_RESTARTBLOCK: 476 case -ERESTARTNOHAND: 477 regs->gprs[2] = -EINTR; 478 break; 479 case -ERESTARTSYS: 480 if (!(ksig.ka.sa.sa_flags & SA_RESTART)) { 481 regs->gprs[2] = -EINTR; 482 break; 483 } 484 fallthrough; 485 case -ERESTARTNOINTR: 486 regs->gprs[2] = regs->orig_gpr2; 487 regs->psw.addr = 488 __rewind_psw(regs->psw, 489 regs->int_code >> 16); 490 break; 491 } 492 } 493 /* No longer in a system call */ 494 clear_pt_regs_flag(regs, PIF_SYSCALL); 495 496 rseq_signal_deliver(&ksig, regs); 497 if (is_compat_task()) 498 handle_signal32(&ksig, oldset, regs); 499 else 500 handle_signal(&ksig, oldset, regs); 501 return; 502 } 503 504 /* No handlers present - check for system call restart */ 505 clear_pt_regs_flag(regs, PIF_SYSCALL); 506 if (current->thread.system_call) { 507 regs->int_code = current->thread.system_call; 508 switch (regs->gprs[2]) { 509 case -ERESTART_RESTARTBLOCK: 510 /* Restart with sys_restart_syscall */ 511 regs->gprs[2] = regs->orig_gpr2; 512 current->restart_block.arch_data = regs->psw.addr; 513 if (is_compat_task()) 514 regs->psw.addr = VDSO32_SYMBOL(current, restart_syscall); 515 else 516 regs->psw.addr = VDSO64_SYMBOL(current, restart_syscall); 517 if (test_thread_flag(TIF_SINGLE_STEP)) 518 clear_thread_flag(TIF_PER_TRAP); 519 break; 520 case -ERESTARTNOHAND: 521 case -ERESTARTSYS: 522 case -ERESTARTNOINTR: 523 regs->gprs[2] = regs->orig_gpr2; 524 regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); 525 if (test_thread_flag(TIF_SINGLE_STEP)) 526 clear_thread_flag(TIF_PER_TRAP); 527 break; 528 } 529 } 530 531 /* 532 * If there's no signal to deliver, we just put the saved sigmask back. 533 */ 534 restore_saved_sigmask(); 535 } 536