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