| 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 cauing 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 <asm/ucontext.h> |
| 57 | |
| 58 | struct rt_sigframe { |
| 59 | struct siginfo info; |
| 60 | struct ucontext uc; |
| 61 | #define MAGIC_SIGALTSTK 0x07302004 |
| 62 | unsigned int sigret_magic; |
| 63 | }; |
| 64 | |
| 65 | static int |
| 66 | stash_usr_regs(struct rt_sigframe __user *sf, struct pt_regs *regs, |
| 67 | sigset_t *set) |
| 68 | { |
| 69 | int err; |
| 70 | err = __copy_to_user(&(sf->uc.uc_mcontext.regs.scratch), regs, |
| 71 | sizeof(sf->uc.uc_mcontext.regs.scratch)); |
| 72 | err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(sigset_t)); |
| 73 | |
| 74 | return err; |
| 75 | } |
| 76 | |
| 77 | static int restore_usr_regs(struct pt_regs *regs, struct rt_sigframe __user *sf) |
| 78 | { |
| 79 | sigset_t set; |
| 80 | int err; |
| 81 | |
| 82 | err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); |
| 83 | if (!err) |
| 84 | set_current_blocked(&set); |
| 85 | |
| 86 | err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs.scratch), |
| 87 | sizeof(sf->uc.uc_mcontext.regs.scratch)); |
| 88 | |
| 89 | return err; |
| 90 | } |
| 91 | |
| 92 | static inline int is_do_ss_needed(unsigned int magic) |
| 93 | { |
| 94 | if (MAGIC_SIGALTSTK == magic) |
| 95 | return 1; |
| 96 | else |
| 97 | return 0; |
| 98 | } |
| 99 | |
| 100 | SYSCALL_DEFINE0(rt_sigreturn) |
| 101 | { |
| 102 | struct rt_sigframe __user *sf; |
| 103 | unsigned int magic; |
| 104 | struct pt_regs *regs = current_pt_regs(); |
| 105 | |
| 106 | /* Always make any pending restarted system calls return -EINTR */ |
| 107 | current->restart_block.fn = do_no_restart_syscall; |
| 108 | |
| 109 | /* Since we stacked the signal on a word boundary, |
| 110 | * then 'sp' should be word aligned here. If it's |
| 111 | * not, then the user is trying to mess with us. |
| 112 | */ |
| 113 | if (regs->sp & 3) |
| 114 | goto badframe; |
| 115 | |
| 116 | sf = (struct rt_sigframe __force __user *)(regs->sp); |
| 117 | |
| 118 | if (!access_ok(VERIFY_READ, sf, sizeof(*sf))) |
| 119 | goto badframe; |
| 120 | |
| 121 | if (__get_user(magic, &sf->sigret_magic)) |
| 122 | goto badframe; |
| 123 | |
| 124 | if (unlikely(is_do_ss_needed(magic))) |
| 125 | if (restore_altstack(&sf->uc.uc_stack)) |
| 126 | goto badframe; |
| 127 | |
| 128 | if (restore_usr_regs(regs, sf)) |
| 129 | goto badframe; |
| 130 | |
| 131 | /* Don't restart from sigreturn */ |
| 132 | syscall_wont_restart(regs); |
| 133 | |
| 134 | /* |
| 135 | * Ensure that sigreturn always returns to user mode (in case the |
| 136 | * regs saved on user stack got fudged between save and sigreturn) |
| 137 | * Otherwise it is easy to panic the kernel with a custom |
| 138 | * signal handler and/or restorer which clobberes the status32/ret |
| 139 | * to return to a bogus location in kernel mode. |
| 140 | */ |
| 141 | regs->status32 |= STATUS_U_MASK; |
| 142 | |
| 143 | return regs->r0; |
| 144 | |
| 145 | badframe: |
| 146 | force_sig(SIGSEGV, current); |
| 147 | return 0; |
| 148 | } |
| 149 | |
| 150 | /* |
| 151 | * Determine which stack to use.. |
| 152 | */ |
| 153 | static inline void __user *get_sigframe(struct ksignal *ksig, |
| 154 | struct pt_regs *regs, |
| 155 | unsigned long framesize) |
| 156 | { |
| 157 | unsigned long sp = sigsp(regs->sp, ksig); |
| 158 | void __user *frame; |
| 159 | |
| 160 | /* No matter what happens, 'sp' must be word |
| 161 | * aligned otherwise nasty things could happen |
| 162 | */ |
| 163 | |
| 164 | /* ATPCS B01 mandates 8-byte alignment */ |
| 165 | frame = (void __user *)((sp - framesize) & ~7); |
| 166 | |
| 167 | /* Check that we can actually write to the signal frame */ |
| 168 | if (!access_ok(VERIFY_WRITE, frame, framesize)) |
| 169 | frame = NULL; |
| 170 | |
| 171 | return frame; |
| 172 | } |
| 173 | |
| 174 | /* |
| 175 | * translate the signal |
| 176 | */ |
| 177 | static inline int map_sig(int sig) |
| 178 | { |
| 179 | struct thread_info *thread = current_thread_info(); |
| 180 | if (thread->exec_domain && thread->exec_domain->signal_invmap |
| 181 | && sig < 32) |
| 182 | sig = thread->exec_domain->signal_invmap[sig]; |
| 183 | return sig; |
| 184 | } |
| 185 | |
| 186 | static int |
| 187 | setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) |
| 188 | { |
| 189 | struct rt_sigframe __user *sf; |
| 190 | unsigned int magic = 0; |
| 191 | int err = 0; |
| 192 | |
| 193 | sf = get_sigframe(ksig, regs, sizeof(struct rt_sigframe)); |
| 194 | if (!sf) |
| 195 | return 1; |
| 196 | |
| 197 | /* |
| 198 | * w/o SA_SIGINFO, struct ucontext is partially populated (only |
| 199 | * uc_mcontext/uc_sigmask) for kernel's normal user state preservation |
| 200 | * during signal handler execution. This works for SA_SIGINFO as well |
| 201 | * although the semantics are now overloaded (the same reg state can be |
| 202 | * inspected by userland: but are they allowed to fiddle with it ? |
| 203 | */ |
| 204 | err |= stash_usr_regs(sf, regs, set); |
| 205 | |
| 206 | /* |
| 207 | * SA_SIGINFO requires 3 args to signal handler: |
| 208 | * #1: sig-no (common to any handler) |
| 209 | * #2: struct siginfo |
| 210 | * #3: struct ucontext (completely populated) |
| 211 | */ |
| 212 | if (unlikely(ksig->ka.sa.sa_flags & SA_SIGINFO)) { |
| 213 | err |= copy_siginfo_to_user(&sf->info, &ksig->info); |
| 214 | err |= __put_user(0, &sf->uc.uc_flags); |
| 215 | err |= __put_user(NULL, &sf->uc.uc_link); |
| 216 | err |= __save_altstack(&sf->uc.uc_stack, regs->sp); |
| 217 | |
| 218 | /* setup args 2 and 3 for user mode handler */ |
| 219 | regs->r1 = (unsigned long)&sf->info; |
| 220 | regs->r2 = (unsigned long)&sf->uc; |
| 221 | |
| 222 | /* |
| 223 | * small optim to avoid unconditonally calling do_sigaltstack |
| 224 | * in sigreturn path, now that we only have rt_sigreturn |
| 225 | */ |
| 226 | magic = MAGIC_SIGALTSTK; |
| 227 | } |
| 228 | |
| 229 | err |= __put_user(magic, &sf->sigret_magic); |
| 230 | if (err) |
| 231 | return err; |
| 232 | |
| 233 | /* #1 arg to the user Signal handler */ |
| 234 | regs->r0 = map_sig(ksig->sig); |
| 235 | |
| 236 | /* setup PC of user space signal handler */ |
| 237 | regs->ret = (unsigned long)ksig->ka.sa.sa_handler; |
| 238 | |
| 239 | /* |
| 240 | * handler returns using sigreturn stub provided already by userpsace |
| 241 | * If not, nuke the process right away |
| 242 | */ |
| 243 | if(!(ksig->ka.sa.sa_flags & SA_RESTORER)) |
| 244 | return 1; |
| 245 | |
| 246 | regs->blink = (unsigned long)ksig->ka.sa.sa_restorer; |
| 247 | |
| 248 | /* User Stack for signal handler will be above the frame just carved */ |
| 249 | regs->sp = (unsigned long)sf; |
| 250 | |
| 251 | /* |
| 252 | * Bug 94183, Clear the DE bit, so that when signal handler |
| 253 | * starts to run, it doesn't use BTA |
| 254 | */ |
| 255 | regs->status32 &= ~STATUS_DE_MASK; |
| 256 | regs->status32 |= STATUS_L_MASK; |
| 257 | |
| 258 | return err; |
| 259 | } |
| 260 | |
| 261 | static void arc_restart_syscall(struct k_sigaction *ka, struct pt_regs *regs) |
| 262 | { |
| 263 | switch (regs->r0) { |
| 264 | case -ERESTART_RESTARTBLOCK: |
| 265 | case -ERESTARTNOHAND: |
| 266 | /* |
| 267 | * ERESTARTNOHAND means that the syscall should |
| 268 | * only be restarted if there was no handler for |
| 269 | * the signal, and since we only get here if there |
| 270 | * is a handler, we don't restart |
| 271 | */ |
| 272 | regs->r0 = -EINTR; /* ERESTART_xxx is internal */ |
| 273 | break; |
| 274 | |
| 275 | case -ERESTARTSYS: |
| 276 | /* |
| 277 | * ERESTARTSYS means to restart the syscall if |
| 278 | * there is no handler or the handler was |
| 279 | * registered with SA_RESTART |
| 280 | */ |
| 281 | if (!(ka->sa.sa_flags & SA_RESTART)) { |
| 282 | regs->r0 = -EINTR; |
| 283 | break; |
| 284 | } |
| 285 | /* fallthrough */ |
| 286 | |
| 287 | case -ERESTARTNOINTR: |
| 288 | /* |
| 289 | * ERESTARTNOINTR means that the syscall should |
| 290 | * be called again after the signal handler returns. |
| 291 | * Setup reg state just as it was before doing the trap |
| 292 | * r0 has been clobbered with sys call ret code thus it |
| 293 | * needs to be reloaded with orig first arg to syscall |
| 294 | * in orig_r0. Rest of relevant reg-file: |
| 295 | * r8 (syscall num) and (r1 - r7) will be reset to |
| 296 | * their orig user space value when we ret from kernel |
| 297 | */ |
| 298 | regs->r0 = regs->orig_r0; |
| 299 | regs->ret -= 4; |
| 300 | break; |
| 301 | } |
| 302 | } |
| 303 | |
| 304 | /* |
| 305 | * OK, we're invoking a handler |
| 306 | */ |
| 307 | static void |
| 308 | handle_signal(struct ksignal *ksig, struct pt_regs *regs) |
| 309 | { |
| 310 | sigset_t *oldset = sigmask_to_save(); |
| 311 | int failed; |
| 312 | |
| 313 | /* Set up the stack frame */ |
| 314 | failed = setup_rt_frame(ksig, oldset, regs); |
| 315 | |
| 316 | signal_setup_done(failed, ksig, 0); |
| 317 | } |
| 318 | |
| 319 | void do_signal(struct pt_regs *regs) |
| 320 | { |
| 321 | struct ksignal ksig; |
| 322 | int restart_scall; |
| 323 | |
| 324 | restart_scall = in_syscall(regs) && syscall_restartable(regs); |
| 325 | |
| 326 | if (get_signal(&ksig)) { |
| 327 | if (restart_scall) { |
| 328 | arc_restart_syscall(&ksig.ka, regs); |
| 329 | syscall_wont_restart(regs); /* No more restarts */ |
| 330 | } |
| 331 | handle_signal(&ksig, regs); |
| 332 | return; |
| 333 | } |
| 334 | |
| 335 | if (restart_scall) { |
| 336 | /* No handler for syscall: restart it */ |
| 337 | if (regs->r0 == -ERESTARTNOHAND || |
| 338 | regs->r0 == -ERESTARTSYS || regs->r0 == -ERESTARTNOINTR) { |
| 339 | regs->r0 = regs->orig_r0; |
| 340 | regs->ret -= 4; |
| 341 | } else if (regs->r0 == -ERESTART_RESTARTBLOCK) { |
| 342 | regs->r8 = __NR_restart_syscall; |
| 343 | regs->ret -= 4; |
| 344 | } |
| 345 | syscall_wont_restart(regs); /* No more restarts */ |
| 346 | } |
| 347 | |
| 348 | /* If there's no signal to deliver, restore the saved sigmask back */ |
| 349 | restore_saved_sigmask(); |
| 350 | } |
| 351 | |
| 352 | void do_notify_resume(struct pt_regs *regs) |
| 353 | { |
| 354 | /* |
| 355 | * ASM glue gaurantees that this is only called when returning to |
| 356 | * user mode |
| 357 | */ |
| 358 | if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME)) |
| 359 | tracehook_notify_resume(regs); |
| 360 | } |