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