arch/arm64/kernel/signal.c

   1 /*
   2  * Based on arch/arm/kernel/signal.c
   3  *
   4  * Copyright (C) 1995-2009 Russell King
   5  * Copyright (C) 2012 ARM Ltd.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/errno.h>
  21 #include <linux/signal.h>
  22 #include <linux/personality.h>
  23 #include <linux/freezer.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/tracehook.h>
  26 #include <linux/ratelimit.h>
  27
  28 #include <asm/compat.h>
  29 #include <asm/debug-monitors.h>
  30 #include <asm/elf.h>
  31 #include <asm/cacheflush.h>
  32 #include <asm/ucontext.h>
  33 #include <asm/unistd.h>
  34 #include <asm/fpsimd.h>
  35 #include <asm/signal32.h>
  36 #include <asm/vdso.h>
  37
  38 /*
  39  * Do a signal return; undo the signal stack. These are aligned to 128-bit.
  40  */
  41 struct rt_sigframe {
  42         struct siginfo info;
  43         struct ucontext uc;
  44         u64 fp;
  45         u64 lr;
  46 };
  47
  48 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
  49 {
  50         struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
  51         int err;
  52
  53         /* dump the hardware registers to the fpsimd_state structure */
  54         fpsimd_save_state(fpsimd);
  55
  56         /* copy the FP and status/control registers */
  57         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
  58         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
  59         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
  60
  61         /* copy the magic/size information */
  62         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
  63         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
  64
  65         return err ? -EFAULT : 0;
  66 }
  67
  68 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
  69 {
  70         struct fpsimd_state fpsimd;
  71         __u32 magic, size;
  72         int err = 0;
  73
  74         /* check the magic/size information */
  75         __get_user_error(magic, &ctx->head.magic, err);
  76         __get_user_error(size, &ctx->head.size, err);
  77         if (err)
  78                 return -EFAULT;
  79         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
  80                 return -EINVAL;
  81
  82         /* copy the FP and status/control registers */
  83         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
  84                                sizeof(fpsimd.vregs));
  85         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
  86         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
  87
  88         /* load the hardware registers from the fpsimd_state structure */
  89         if (!err) {
  90                 preempt_disable();
  91                 fpsimd_load_state(&fpsimd);
  92                 preempt_enable();
  93         }
  94
  95         return err ? -EFAULT : 0;
  96 }
  97
  98 static int restore_sigframe(struct pt_regs *regs,
  99                             struct rt_sigframe __user *sf)
 100 {
 101         sigset_t set;
 102         int i, err;
 103         struct aux_context __user *aux =
 104                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 105
 106         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 107         if (err == 0)
 108                 set_current_blocked(&set);
 109
 110         for (i = 0; i < 31; i++)
 111                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 112                                  err);
 113         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 114         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 115         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 116
 117         /*
 118          * Avoid sys_rt_sigreturn() restarting.
 119          */
 120         regs->syscallno = ~0UL;
 121
 122         err |= !valid_user_regs(&regs->user_regs);
 123
 124         if (err == 0)
 125                 err |= restore_fpsimd_context(&aux->fpsimd);
 126
 127         return err;
 128 }
 129
 130 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 131 {
 132         struct rt_sigframe __user *frame;
 133
 134         /* Always make any pending restarted system calls return -EINTR */
 135         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 136
 137         /*
 138          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 139          * be word aligned here.
 140          */
 141         if (regs->sp & 15)
 142                 goto badframe;
 143
 144         frame = (struct rt_sigframe __user *)regs->sp;
 145
 146         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 147                 goto badframe;
 148
 149         if (restore_sigframe(regs, frame))
 150                 goto badframe;
 151
 152         if (restore_altstack(&frame->uc.uc_stack))
 153                 goto badframe;
 154
 155         return regs->regs[0];
 156
 157 badframe:
 158         if (show_unhandled_signals)
 159                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 160                                     current->comm, task_pid_nr(current), __func__,
 161                                     regs->pc, regs->sp);
 162         force_sig(SIGSEGV, current);
 163         return 0;
 164 }
 165
 166 static int setup_sigframe(struct rt_sigframe __user *sf,
 167                           struct pt_regs *regs, sigset_t *set)
 168 {
 169         int i, err = 0;
 170         struct aux_context __user *aux =
 171                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 172
 173         /* set up the stack frame for unwinding */
 174         __put_user_error(regs->regs[29], &sf->fp, err);
 175         __put_user_error(regs->regs[30], &sf->lr, err);
 176
 177         for (i = 0; i < 31; i++)
 178                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 179                                  err);
 180         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 181         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 182         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 183
 184         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 185
 186         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 187
 188         if (err == 0)
 189                 err |= preserve_fpsimd_context(&aux->fpsimd);
 190
 191         /* set the "end" magic */
 192         __put_user_error(0, &aux->end.magic, err);
 193         __put_user_error(0, &aux->end.size, err);
 194
 195         return err;
 196 }
 197
 198 static struct rt_sigframe __user *get_sigframe(struct k_sigaction *ka,
 199                                                struct pt_regs *regs)
 200 {
 201         unsigned long sp, sp_top;
 202         struct rt_sigframe __user *frame;
 203
 204         sp = sp_top = regs->sp;
 205
 206         /*
 207          * This is the X/Open sanctioned signal stack switching.
 208          */
 209         if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
 210                 sp = sp_top = current->sas_ss_sp + current->sas_ss_size;
 211
 212         sp = (sp - sizeof(struct rt_sigframe)) & ~15;
 213         frame = (struct rt_sigframe __user *)sp;
 214
 215         /*
 216          * Check that we can actually write to the signal frame.
 217          */
 218         if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
 219                 frame = NULL;
 220
 221         return frame;
 222 }
 223
 224 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 225                          void __user *frame, int usig)
 226 {
 227         __sigrestore_t sigtramp;
 228
 229         regs->regs[0] = usig;
 230         regs->sp = (unsigned long)frame;
 231         regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
 232         regs->pc = (unsigned long)ka->sa.sa_handler;
 233
 234         if (ka->sa.sa_flags & SA_RESTORER)
 235                 sigtramp = ka->sa.sa_restorer;
 236         else
 237                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 238
 239         regs->regs[30] = (unsigned long)sigtramp;
 240 }
 241
 242 static int setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 243                           sigset_t *set, struct pt_regs *regs)
 244 {
 245         struct rt_sigframe __user *frame;
 246         int err = 0;
 247
 248         frame = get_sigframe(ka, regs);
 249         if (!frame)
 250                 return 1;
 251
 252         __put_user_error(0, &frame->uc.uc_flags, err);
 253         __put_user_error(NULL, &frame->uc.uc_link, err);
 254
 255         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 256         err |= setup_sigframe(frame, regs, set);
 257         if (err == 0) {
 258                 setup_return(regs, ka, frame, usig);
 259                 if (ka->sa.sa_flags & SA_SIGINFO) {
 260                         err |= copy_siginfo_to_user(&frame->info, info);
 261                         regs->regs[1] = (unsigned long)&frame->info;
 262                         regs->regs[2] = (unsigned long)&frame->uc;
 263                 }
 264         }
 265
 266         return err;
 267 }
 268
 269 static void setup_restart_syscall(struct pt_regs *regs)
 270 {
 271         if (is_compat_task())
 272                 compat_setup_restart_syscall(regs);
 273         else
 274                 regs->regs[8] = __NR_restart_syscall;
 275 }
 276
 277 /*
 278  * OK, we're invoking a handler
 279  */
 280 static void handle_signal(unsigned long sig, struct k_sigaction *ka,
 281                           siginfo_t *info, struct pt_regs *regs)
 282 {
 283         struct thread_info *thread = current_thread_info();
 284         struct task_struct *tsk = current;
 285         sigset_t *oldset = sigmask_to_save();
 286         int usig = sig;
 287         int ret;
 288
 289         /*
 290          * translate the signal
 291          */
 292         if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
 293                 usig = thread->exec_domain->signal_invmap[usig];
 294
 295         /*
 296          * Set up the stack frame
 297          */
 298         if (is_compat_task()) {
 299                 if (ka->sa.sa_flags & SA_SIGINFO)
 300                         ret = compat_setup_rt_frame(usig, ka, info, oldset,
 301                                                     regs);
 302                 else
 303                         ret = compat_setup_frame(usig, ka, oldset, regs);
 304         } else {
 305                 ret = setup_rt_frame(usig, ka, info, oldset, regs);
 306         }
 307
 308         /*
 309          * Check that the resulting registers are actually sane.
 310          */
 311         ret |= !valid_user_regs(&regs->user_regs);
 312
 313         if (ret != 0) {
 314                 force_sigsegv(sig, tsk);
 315                 return;
 316         }
 317
 318         /*
 319          * Fast forward the stepping logic so we step into the signal
 320          * handler.
 321          */
 322         user_fastforward_single_step(tsk);
 323
 324         signal_delivered(sig, info, ka, regs, 0);
 325 }
 326
 327 /*
 328  * Note that 'init' is a special process: it doesn't get signals it doesn't
 329  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 330  * mistake.
 331  *
 332  * Note that we go through the signals twice: once to check the signals that
 333  * the kernel can handle, and then we build all the user-level signal handling
 334  * stack-frames in one go after that.
 335  */
 336 static void do_signal(struct pt_regs *regs)
 337 {
 338         unsigned long continue_addr = 0, restart_addr = 0;
 339         struct k_sigaction ka;
 340         siginfo_t info;
 341         int signr, retval = 0;
 342         int syscall = (int)regs->syscallno;
 343
 344         /*
 345          * If we were from a system call, check for system call restarting...
 346          */
 347         if (syscall >= 0) {
 348                 continue_addr = regs->pc;
 349                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 350                 retval = regs->regs[0];
 351
 352                 /*
 353                  * Avoid additional syscall restarting via ret_to_user.
 354                  */
 355                 regs->syscallno = ~0UL;
 356
 357                 /*
 358                  * Prepare for system call restart. We do this here so that a
 359                  * debugger will see the already changed PC.
 360                  */
 361                 switch (retval) {
 362                 case -ERESTARTNOHAND:
 363                 case -ERESTARTSYS:
 364                 case -ERESTARTNOINTR:
 365                 case -ERESTART_RESTARTBLOCK:
 366                         regs->regs[0] = regs->orig_x0;
 367                         regs->pc = restart_addr;
 368                         break;
 369                 }
 370         }
 371
 372         /*
 373          * Get the signal to deliver. When running under ptrace, at this point
 374          * the debugger may change all of our registers.
 375          */
 376         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 377         if (signr > 0) {
 378                 /*
 379                  * Depending on the signal settings, we may need to revert the
 380                  * decision to restart the system call, but skip this if a
 381                  * debugger has chosen to restart at a different PC.
 382                  */
 383                 if (regs->pc == restart_addr &&
 384                     (retval == -ERESTARTNOHAND ||
 385                      retval == -ERESTART_RESTARTBLOCK ||
 386                      (retval == -ERESTARTSYS &&
 387                       !(ka.sa.sa_flags & SA_RESTART)))) {
 388                         regs->regs[0] = -EINTR;
 389                         regs->pc = continue_addr;
 390                 }
 391
 392                 handle_signal(signr, &ka, &info, regs);
 393                 return;
 394         }
 395
 396         /*
 397          * Handle restarting a different system call. As above, if a debugger
 398          * has chosen to restart at a different PC, ignore the restart.
 399          */
 400         if (syscall >= 0 && regs->pc == restart_addr) {
 401                 if (retval == -ERESTART_RESTARTBLOCK)
 402                         setup_restart_syscall(regs);
 403                 user_rewind_single_step(current);
 404         }
 405
 406         restore_saved_sigmask();
 407 }
 408
 409 asmlinkage void do_notify_resume(struct pt_regs *regs,
 410                                  unsigned int thread_flags)
 411 {
 412         if (thread_flags & _TIF_SIGPENDING)
 413                 do_signal(regs);
 414
 415         if (thread_flags & _TIF_NOTIFY_RESUME) {
 416                 clear_thread_flag(TIF_NOTIFY_RESUME);
 417                 tracehook_notify_resume(regs);
 418         }
 419 }