1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Signal Handling for ARC 4 * 5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 6 * 7 * vineetg: Jan 2010 (Restarting of timer related syscalls) 8 * 9 * vineetg: Nov 2009 (Everything needed for TIF_RESTORE_SIGMASK) 10 * -do_signal() supports TIF_RESTORE_SIGMASK 11 * -do_signal() no loner needs oldset, required by OLD sys_sigsuspend 12 * -sys_rt_sigsuspend() now comes from generic code, so discard arch implemen 13 * -sys_sigsuspend() no longer needs to fudge ptregs, hence that arg removed 14 * -sys_sigsuspend() no longer loops for do_signal(), sets TIF_xxx and leaves 15 * the job to do_signal() 16 * 17 * vineetg: July 2009 18 * -Modified Code to support the uClibc provided userland sigreturn stub 19 * to avoid kernel synthesing it on user stack at runtime, costing TLB 20 * probes and Cache line flushes. 21 * 22 * vineetg: July 2009 23 * -In stash_usr_regs( ) and restore_usr_regs( ), save/restore of user regs 24 * in done in block copy rather than one word at a time. 25 * This saves around 2K of code and improves LMBench lat_sig <catch> 26 * 27 * rajeshwarr: Feb 2009 28 * - Support for Realtime Signals 29 * 30 * vineetg: Aug 11th 2008: Bug #94183 31 * -ViXS were still seeing crashes when using insmod to load drivers. 32 * It turned out that the code to change Execute permssions for TLB entries 33 * of user was not guarded for interrupts (mod_tlb_permission) 34 * This was causing TLB entries to be overwritten on unrelated indexes 35 * 36 * Vineetg: July 15th 2008: Bug #94183 37 * -Exception happens in Delay slot of a JMP, and before user space resumes, 38 * Signal is delivered (Ctrl + C) = >SIGINT. 39 * setup_frame( ) sets up PC,SP,BLINK to enable user space signal handler 40 * to run, but doesn't clear the Delay slot bit from status32. As a result, 41 * on resuming user mode, signal handler branches off to BTA of orig JMP 42 * -FIX: clear the DE bit from status32 in setup_frame( ) 43 * 44 * Rahul Trivedi, Kanika Nema: Codito Technologies 2004 45 */ 46 47 #include <linux/signal.h> 48 #include <linux/ptrace.h> 49 #include <linux/personality.h> 50 #include <linux/uaccess.h> 51 #include <linux/syscalls.h> 52 #include <linux/resume_user_mode.h> 53 #include <linux/sched/task_stack.h> 54 55 #include <asm/ucontext.h> 56 57 struct rt_sigframe { 58 struct siginfo info; 59 struct ucontext uc; 60 #define MAGIC_SIGALTSTK 0x07302004 61 unsigned int sigret_magic; 62 }; 63 64 static int save_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs) 65 { 66 int err = 0; 67 #ifndef CONFIG_ISA_ARCOMPACT 68 struct user_regs_arcv2 v2abi; 69 70 v2abi.r30 = regs->r30; 71 #ifdef CONFIG_ARC_HAS_ACCL_REGS 72 v2abi.r58 = regs->r58; 73 v2abi.r59 = regs->r59; 74 #else 75 v2abi.r58 = v2abi.r59 = 0; 76 #endif 77 err = __copy_to_user(&mctx->v2abi, &v2abi, sizeof(v2abi)); 78 #endif 79 return err; 80 } 81 82 static int restore_arcv2_regs(struct sigcontext *mctx, struct pt_regs *regs) 83 { 84 int err = 0; 85 #ifndef CONFIG_ISA_ARCOMPACT 86 struct user_regs_arcv2 v2abi; 87 88 err = __copy_from_user(&v2abi, &mctx->v2abi, sizeof(v2abi)); 89 90 regs->r30 = v2abi.r30; 91 #ifdef CONFIG_ARC_HAS_ACCL_REGS 92 regs->r58 = v2abi.r58; 93 regs->r59 = v2abi.r59; 94 #endif 95 #endif 96 return err; 97 } 98 99 static int 100 stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, 101 sigset_t *set) 102 { 103 int err; 104 struct user_regs_struct uregs; 105 106 uregs.scratch.bta = regs->bta; 107 uregs.scratch.lp_start = regs->lp_start; 108 uregs.scratch.lp_end = regs->lp_end; 109 uregs.scratch.lp_count = regs->lp_count; 110 uregs.scratch.status32 = regs->status32; 111 uregs.scratch.ret = regs->ret; 112 uregs.scratch.blink = regs->blink; 113 uregs.scratch.fp = regs->fp; 114 uregs.scratch.gp = regs->r26; 115 uregs.scratch.r12 = regs->r12; 116 uregs.scratch.r11 = regs->r11; 117 uregs.scratch.r10 = regs->r10; 118 uregs.scratch.r9 = regs->r9; 119 uregs.scratch.r8 = regs->r8; 120 uregs.scratch.r7 = regs->r7; 121 uregs.scratch.r6 = regs->r6; 122 uregs.scratch.r5 = regs->r5; 123 uregs.scratch.r4 = regs->r4; 124 uregs.scratch.r3 = regs->r3; 125 uregs.scratch.r2 = regs->r2; 126 uregs.scratch.r1 = regs->r1; 127 uregs.scratch.r0 = regs->r0; 128 uregs.scratch.sp = regs->sp; 129 130 err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), &uregs.scratch, 131 sizeof(sf->uc.uc_mcontext.regs.scratch)); 132 133 if (is_isa_arcv2()) 134 err |= save_arcv2_regs(&(sf->uc.uc_mcontext), regs); 135 136 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); 137 138 return err ? -EFAULT : 0; 139 } 140 141 static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) 142 { 143 sigset_t set; 144 int err; 145 struct user_regs_struct uregs; 146 147 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); 148 err |= __copy_from_user(&uregs.scratch, 149 &(sf->uc.uc_mcontext.regs.scratch), 150 sizeof(sf->uc.uc_mcontext.regs.scratch)); 151 152 if (is_isa_arcv2()) 153 err |= restore_arcv2_regs(&(sf->uc.uc_mcontext), regs); 154 155 if (err) 156 return -EFAULT; 157 158 set_current_blocked(&set); 159 regs->bta = uregs.scratch.bta; 160 regs->lp_start = uregs.scratch.lp_start; 161 regs->lp_end = uregs.scratch.lp_end; 162 regs->lp_count = uregs.scratch.lp_count; 163 regs->status32 = uregs.scratch.status32; 164 regs->ret = uregs.scratch.ret; 165 regs->blink = uregs.scratch.blink; 166 regs->fp = uregs.scratch.fp; 167 regs->r26 = uregs.scratch.gp; 168 regs->r12 = uregs.scratch.r12; 169 regs->r11 = uregs.scratch.r11; 170 regs->r10 = uregs.scratch.r10; 171 regs->r9 = uregs.scratch.r9; 172 regs->r8 = uregs.scratch.r8; 173 regs->r7 = uregs.scratch.r7; 174 regs->r6 = uregs.scratch.r6; 175 regs->r5 = uregs.scratch.r5; 176 regs->r4 = uregs.scratch.r4; 177 regs->r3 = uregs.scratch.r3; 178 regs->r2 = uregs.scratch.r2; 179 regs->r1 = uregs.scratch.r1; 180 regs->r0 = uregs.scratch.r0; 181 regs->sp = uregs.scratch.sp; 182 183 return 0; 184 } 185 186 static inline int is_do_ss_needed(unsigned int magic) 187 { 188 if (MAGIC_SIGALTSTK == magic) 189 return 1; 190 else 191 return 0; 192 } 193 194 SYSCALL_DEFINE0(rt_sigreturn) 195 { 196 struct rt_sigframe __user *sf; 197 unsigned int magic; 198 struct pt_regs *regs = current_pt_regs(); 199 200 /* Always make any pending restarted system calls return -EINTR */ 201 current->restart_block.fn = do_no_restart_syscall; 202 203 /* Since we stacked the signal on a word boundary, 204 * then 'sp' should be word aligned here. If it's 205 * not, then the user is trying to mess with us. 206 */ 207 if (regs->sp & 3) 208 goto badframe; 209 210 sf = (struct rt_sigframe __force __user *)(regs->sp); 211 212 if (!access_ok(sf, sizeof(*sf))) 213 goto badframe; 214 215 if (__get_user(magic, &sf->sigret_magic)) 216 goto badframe; 217 218 if (unlikely(is_do_ss_needed(magic))) 219 if (restore_altstack(&sf->uc.uc_stack)) 220 goto badframe; 221 222 if (restore_usr_regs(regs, sf)) 223 goto badframe; 224 225 /* Don't restart from sigreturn */ 226 syscall_wont_restart(regs); 227 228 /* 229 * Ensure that sigreturn always returns to user mode (in case the 230 * regs saved on user stack got fudged between save and sigreturn) 231 * Otherwise it is easy to panic the kernel with a custom 232 * signal handler and/or restorer which clobberes the status32/ret 233 * to return to a bogus location in kernel mode. 234 */ 235 regs->status32 |= STATUS_U_MASK; 236 237 return regs->r0; 238 239 badframe: 240 force_sig(SIGSEGV); 241 return 0; 242 } 243 244 /* 245 * Determine which stack to use.. 246 */ 247 static inline void __user *get_sigframe(struct ksignal *ksig, 248 struct pt_regs *regs, 249 unsigned long framesize) 250 { 251 unsigned long sp = sigsp(regs->sp, ksig); 252 void __user *frame; 253 254 /* No matter what happens, 'sp' must be word 255 * aligned otherwise nasty things could happen 256 */ 257 258 /* ATPCS B01 mandates 8-byte alignment */ 259 frame = (void __user *)((sp - framesize) & ~7); 260 261 /* Check that we can actually write to the signal frame */ 262 if (!access_ok(frame, framesize)) 263 frame = NULL; 264 265 return frame; 266 } 267 268 static int 269 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) 270 { 271 struct rt_sigframe __user *sf; 272 unsigned int magic = 0; 273 int err = 0; 274 275 sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); 276 if (!sf) 277 return 1; 278 279 /* 280 * w/o SA_SIGINFO, struct ucontext is partially populated (only 281 * uc_mcontext/uc_sigmask) for kernel's normal user state preservation 282 * during signal handler execution. This works for SA_SIGINFO as well 283 * although the semantics are now overloaded (the same reg state can be 284 * inspected by userland: but are they allowed to fiddle with it ? 285 */ 286 err |= stash_usr_regs(sf, regs, set); 287 288 /* 289 * SA_SIGINFO requires 3 args to signal handler: 290 * #1: sig-no (common to any handler) 291 * #2: struct siginfo 292 * #3: struct ucontext (completely populated) 293 */ 294 if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { 295 err |= copy_siginfo_to_user(&sf->info, &ksig->info); 296 err |= __put_user(0, &sf->uc.uc_flags); 297 err |= __put_user(NULL, &sf->uc.uc_link); 298 err |= __save_altstack(&sf->uc.uc_stack, regs->sp); 299 300 /* setup args 2 and 3 for user mode handler */ 301 regs->r1 = (unsigned long)&sf->info; 302 regs->r2 = (unsigned long)&sf->uc; 303 304 /* 305 * small optim to avoid unconditionally calling do_sigaltstack 306 * in sigreturn path, now that we only have rt_sigreturn 307 */ 308 magic = MAGIC_SIGALTSTK; 309 } 310 311 err |= __put_user(magic, &sf->sigret_magic); 312 if (err) 313 return err; 314 315 /* #1 arg to the user Signal handler */ 316 regs->r0 = ksig->sig; 317 318 /* setup PC of user space signal handler */ 319 regs->ret = (unsigned long)ksig->ka.sa.sa_handler; 320 321 /* 322 * handler returns using sigreturn stub provided already by userspace 323 * If not, nuke the process right away 324 */ 325 if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) 326 return 1; 327 328 regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; 329 330 /* User Stack for signal handler will be above the frame just carved */ 331 regs->sp = (unsigned long)sf; 332 333 /* 334 * Bug 94183, Clear the DE bit, so that when signal handler 335 * starts to run, it doesn't use BTA 336 */ 337 regs->status32 &= ~STATUS_DE_MASK; 338 regs->status32 |= STATUS_L_MASK; 339 340 return err; 341 } 342 343 static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) 344 { 345 switch (regs->r0) { 346 case -ERESTART_RESTARTBLOCK: 347 case -ERESTARTNOHAND: 348 /* 349 * ERESTARTNOHAND means that the syscall should 350 * only be restarted if there was no handler for 351 * the signal, and since we only get here if there 352 * is a handler, we don't restart 353 */ 354 regs->r0 = -EINTR; /* ERESTART_xxx is internal */ 355 break; 356 357 case -ERESTARTSYS: 358 /* 359 * ERESTARTSYS means to restart the syscall if 360 * there is no handler or the handler was 361 * registered with SA_RESTART 362 */ 363 if (!(ka->sa.sa_flags & SA_RESTART)) { 364 regs->r0 = -EINTR; 365 break; 366 } 367 fallthrough; 368 369 case -ERESTARTNOINTR: 370 /* 371 * ERESTARTNOINTR means that the syscall should 372 * be called again after the signal handler returns. 373 * Setup reg state just as it was before doing the trap 374 * r0 has been clobbered with sys call ret code thus it 375 * needs to be reloaded with orig first arg to syscall 376 * in orig_r0. Rest of relevant reg-file: 377 * r8 (syscall num) and (r1 - r7) will be reset to 378 * their orig user space value when we ret from kernel 379 */ 380 regs->r0 = regs->orig_r0; 381 regs->ret -= is_isa_arcv2() ? 2 : 4; 382 break; 383 } 384 } 385 386 /* 387 * OK, we're invoking a handler 388 */ 389 static void 390 handle_signal(struct ksignal *ksig, struct pt_regs *regs) 391 { 392 sigset_t *oldset = sigmask_to_save(); 393 int failed; 394 395 /* Set up the stack frame */ 396 failed = setup_rt_frame(ksig, oldset, regs); 397 398 signal_setup_done(failed, ksig, 0); 399 } 400 401 void do_signal(struct pt_regs *regs) 402 { 403 struct ksignal ksig; 404 int restart_scall; 405 406 restart_scall = in_syscall(regs) && syscall_restartable(regs); 407 408 if (test_thread_flag(TIF_SIGPENDING) && get_signal(&ksig)) { 409 if (restart_scall) { 410 arc_restart_syscall(&ksig.ka, regs); 411 syscall_wont_restart(regs); /* No more restarts */ 412 } 413 handle_signal(&ksig, regs); 414 return; 415 } 416 417 if (restart_scall) { 418 /* No handler for syscall: restart it */ 419 if (regs->r0 == -ERESTARTNOHAND || 420 regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { 421 regs->r0 = regs->orig_r0; 422 regs->ret -= is_isa_arcv2() ? 2 : 4; 423 } else if (regs->r0 == -ERESTART_RESTARTBLOCK) { 424 regs->r8 = __NR_restart_syscall; 425 regs->ret -= is_isa_arcv2() ? 2 : 4; 426 } 427 syscall_wont_restart(regs); /* No more restarts */ 428 } 429 430 /* If there's no signal to deliver, restore the saved sigmask back */ 431 restore_saved_sigmask(); 432 } 433 434 void do_notify_resume(struct pt_regs *regs) 435 { 436 /* 437 * ASM glue guarantees that this is only called when returning to 438 * user mode 439 */ 440 if (test_thread_flag(TIF_NOTIFY_RESUME)) 441 resume_user_mode_work(regs); 442 } 443