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 };
  45
  46 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
  47 {
  48         struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
  49         int err;
  50
  51         /* dump the hardware registers to the fpsimd_state structure */
  52         fpsimd_save_state(fpsimd);
  53
  54         /* copy the FP and status/control registers */
  55         err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
  56         __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
  57         __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
  58
  59         /* copy the magic/size information */
  60         __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
  61         __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
  62
  63         return err ? -EFAULT : 0;
  64 }
  65
  66 static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
  67 {
  68         struct fpsimd_state fpsimd;
  69         __u32 magic, size;
  70         int err = 0;
  71
  72         /* check the magic/size information */
  73         __get_user_error(magic, &ctx->head.magic, err);
  74         __get_user_error(size, &ctx->head.size, err);
  75         if (err)
  76                 return -EFAULT;
  77         if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
  78                 return -EINVAL;
  79
  80         /* copy the FP and status/control registers */
  81         err = __copy_from_user(fpsimd.vregs, ctx->vregs,
  82                                sizeof(fpsimd.vregs));
  83         __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
  84         __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
  85
  86         /* load the hardware registers from the fpsimd_state structure */
  87         if (!err) {
  88                 preempt_disable();
  89                 fpsimd_load_state(&fpsimd);
  90                 preempt_enable();
  91         }
  92
  93         return err ? -EFAULT : 0;
  94 }
  95
  96 static int restore_sigframe(struct pt_regs *regs,
  97                             struct rt_sigframe __user *sf)
  98 {
  99         sigset_t set;
 100         int i, err;
 101         struct aux_context __user *aux =
 102                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 103
 104         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 105         if (err == 0)
 106                 set_current_blocked(&set);
 107
 108         for (i = 0; i < 31; i++)
 109                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 110                                  err);
 111         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 112         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 113         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 114
 115         /*
 116          * Avoid sys_rt_sigreturn() restarting.
 117          */
 118         regs->syscallno = ~0UL;
 119
 120         err |= !valid_user_regs(&regs->user_regs);
 121
 122         if (err == 0)
 123                 err |= restore_fpsimd_context(&aux->fpsimd);
 124
 125         return err;
 126 }
 127
 128 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 129 {
 130         struct rt_sigframe __user *frame;
 131
 132         /* Always make any pending restarted system calls return -EINTR */
 133         current_thread_info()->restart_block.fn = do_no_restart_syscall;
 134
 135         /*
 136          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 137          * be word aligned here.
 138          */
 139         if (regs->sp & 15)
 140                 goto badframe;
 141
 142         frame = (struct rt_sigframe __user *)regs->sp;
 143
 144         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 145                 goto badframe;
 146
 147         if (restore_sigframe(regs, frame))
 148                 goto badframe;
 149
 150         if (do_sigaltstack(&frame->uc.uc_stack,
 151                            NULL, regs->sp) == -EFAULT)
 152                 goto badframe;
 153
 154         return regs->regs[0];
 155
 156 badframe:
 157         if (show_unhandled_signals)
 158                 pr_info_ratelimited("%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
 159                                     current->comm, task_pid_nr(current), __func__,
 160                                     regs->pc, regs->sp);
 161         force_sig(SIGSEGV, current);
 162         return 0;
 163 }
 164
 165 asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
 166                                 unsigned long sp)
 167 {
 168         return do_sigaltstack(uss, uoss, sp);
 169 }
 170
 171 static int setup_sigframe(struct rt_sigframe __user *sf,
 172                           struct pt_regs *regs, sigset_t *set)
 173 {
 174         int i, err = 0;
 175         struct aux_context __user *aux =
 176                 (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
 177
 178         for (i = 0; i < 31; i++)
 179                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 180                                  err);
 181         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 182         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 183         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 184
 185         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 186
 187         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 188
 189         if (err == 0)
 190                 err |= preserve_fpsimd_context(&aux->fpsimd);
 191
 192         /* set the "end" magic */
 193         __put_user_error(0, &aux->end.magic, err);
 194         __put_user_error(0, &aux->end.size, err);
 195
 196         return err;
 197 }
 198
 199 static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
 200                                  int framesize)
 201 {
 202         unsigned long sp, sp_top;
 203         void __user *frame;
 204
 205         sp = sp_top = regs->sp;
 206
 207         /*
 208          * This is the X/Open sanctioned signal stack switching.
 209          */
 210         if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
 211                 sp = sp_top = current->sas_ss_sp + current->sas_ss_size;
 212
 213         /* room for stack frame (FP, LR) */
 214         sp -= 16;
 215
 216         sp = (sp - framesize) & ~15;
 217         frame = (void __user *)sp;
 218
 219         /*
 220          * Check that we can actually write to the signal frame.
 221          */
 222         if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
 223                 frame = NULL;
 224
 225         return frame;
 226 }
 227
 228 static int setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 229                         void __user *frame, int usig)
 230 {
 231         int err = 0;
 232         __sigrestore_t sigtramp;
 233         unsigned long __user *sp = (unsigned long __user *)regs->sp;
 234
 235         /* set up the stack frame */
 236         __put_user_error(regs->regs[29], sp - 2, err);
 237         __put_user_error(regs->regs[30], sp - 1, err);
 238
 239         regs->regs[0] = usig;
 240         regs->regs[29] = regs->sp - 16;
 241         regs->sp = (unsigned long)frame;
 242         regs->pc = (unsigned long)ka->sa.sa_handler;
 243
 244         if (ka->sa.sa_flags & SA_RESTORER)
 245                 sigtramp = ka->sa.sa_restorer;
 246         else
 247                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 248
 249         regs->regs[30] = (unsigned long)sigtramp;
 250
 251         return err;
 252 }
 253
 254 static int setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 255                           sigset_t *set, struct pt_regs *regs)
 256 {
 257         struct rt_sigframe __user *frame;
 258         stack_t stack;
 259         int err = 0;
 260
 261         frame = get_sigframe(ka, regs, sizeof(*frame));
 262         if (!frame)
 263                 return 1;
 264
 265         __put_user_error(0, &frame->uc.uc_flags, err);
 266         __put_user_error(NULL, &frame->uc.uc_link, err);
 267
 268         memset(&stack, 0, sizeof(stack));
 269         stack.ss_sp = (void __user *)current->sas_ss_sp;
 270         stack.ss_flags = sas_ss_flags(regs->sp);
 271         stack.ss_size = current->sas_ss_size;
 272         err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));
 273
 274         err |= setup_sigframe(frame, regs, set);
 275         if (err == 0)
 276                 err = setup_return(regs, ka, frame, usig);
 277
 278         if (err == 0 && ka->sa.sa_flags & SA_SIGINFO) {
 279                 err |= copy_siginfo_to_user(&frame->info, info);
 280                 regs->regs[1] = (unsigned long)&frame->info;
 281                 regs->regs[2] = (unsigned long)&frame->uc;
 282         }
 283
 284         return err;
 285 }
 286
 287 static void setup_restart_syscall(struct pt_regs *regs)
 288 {
 289         if (is_compat_task())
 290                 compat_setup_restart_syscall(regs);
 291         else
 292                 regs->regs[8] = __NR_restart_syscall;
 293 }
 294
 295 /*
 296  * OK, we're invoking a handler
 297  */
 298 static void handle_signal(unsigned long sig, struct k_sigaction *ka,
 299                           siginfo_t *info, struct pt_regs *regs)
 300 {
 301         struct thread_info *thread = current_thread_info();
 302         struct task_struct *tsk = current;
 303         sigset_t *oldset = sigmask_to_save();
 304         int usig = sig;
 305         int ret;
 306
 307         /*
 308          * translate the signal
 309          */
 310         if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
 311                 usig = thread->exec_domain->signal_invmap[usig];
 312
 313         /*
 314          * Set up the stack frame
 315          */
 316         if (is_compat_task()) {
 317                 if (ka->sa.sa_flags & SA_SIGINFO)
 318                         ret = compat_setup_rt_frame(usig, ka, info, oldset,
 319                                                     regs);
 320                 else
 321                         ret = compat_setup_frame(usig, ka, oldset, regs);
 322         } else {
 323                 ret = setup_rt_frame(usig, ka, info, oldset, regs);
 324         }
 325
 326         /*
 327          * Check that the resulting registers are actually sane.
 328          */
 329         ret |= !valid_user_regs(&regs->user_regs);
 330
 331         if (ret != 0) {
 332                 force_sigsegv(sig, tsk);
 333                 return;
 334         }
 335
 336         /*
 337          * Fast forward the stepping logic so we step into the signal
 338          * handler.
 339          */
 340         user_fastforward_single_step(tsk);
 341
 342         signal_delivered(sig, info, ka, regs, 0);
 343 }
 344
 345 /*
 346  * Note that 'init' is a special process: it doesn't get signals it doesn't
 347  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 348  * mistake.
 349  *
 350  * Note that we go through the signals twice: once to check the signals that
 351  * the kernel can handle, and then we build all the user-level signal handling
 352  * stack-frames in one go after that.
 353  */
 354 static void do_signal(struct pt_regs *regs)
 355 {
 356         unsigned long continue_addr = 0, restart_addr = 0;
 357         struct k_sigaction ka;
 358         siginfo_t info;
 359         int signr, retval = 0;
 360         int syscall = (int)regs->syscallno;
 361
 362         /*
 363          * If we were from a system call, check for system call restarting...
 364          */
 365         if (syscall >= 0) {
 366                 continue_addr = regs->pc;
 367                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 368                 retval = regs->regs[0];
 369
 370                 /*
 371                  * Avoid additional syscall restarting via ret_to_user.
 372                  */
 373                 regs->syscallno = ~0UL;
 374
 375                 /*
 376                  * Prepare for system call restart. We do this here so that a
 377                  * debugger will see the already changed PC.
 378                  */
 379                 switch (retval) {
 380                 case -ERESTARTNOHAND:
 381                 case -ERESTARTSYS:
 382                 case -ERESTARTNOINTR:
 383                 case -ERESTART_RESTARTBLOCK:
 384                         regs->regs[0] = regs->orig_x0;
 385                         regs->pc = restart_addr;
 386                         break;
 387                 }
 388         }
 389
 390         /*
 391          * Get the signal to deliver. When running under ptrace, at this point
 392          * the debugger may change all of our registers.
 393          */
 394         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 395         if (signr > 0) {
 396                 /*
 397                  * Depending on the signal settings, we may need to revert the
 398                  * decision to restart the system call, but skip this if a
 399                  * debugger has chosen to restart at a different PC.
 400                  */
 401                 if (regs->pc == restart_addr &&
 402                     (retval == -ERESTARTNOHAND ||
 403                      retval == -ERESTART_RESTARTBLOCK ||
 404                      (retval == -ERESTARTSYS &&
 405                       !(ka.sa.sa_flags & SA_RESTART)))) {
 406                         regs->regs[0] = -EINTR;
 407                         regs->pc = continue_addr;
 408                 }
 409
 410                 handle_signal(signr, &ka, &info, regs);
 411                 return;
 412         }
 413
 414         /*
 415          * Handle restarting a different system call. As above, if a debugger
 416          * has chosen to restart at a different PC, ignore the restart.
 417          */
 418         if (syscall >= 0 && regs->pc == restart_addr) {
 419                 if (retval == -ERESTART_RESTARTBLOCK)
 420                         setup_restart_syscall(regs);
 421                 user_rewind_single_step(current);
 422         }
 423
 424         restore_saved_sigmask();
 425 }
 426
 427 asmlinkage void do_notify_resume(struct pt_regs *regs,
 428                                  unsigned int thread_flags)
 429 {
 430         if (thread_flags & _TIF_SIGPENDING)
 431                 do_signal(regs);
 432
 433         if (thread_flags & _TIF_NOTIFY_RESUME) {
 434                 clear_thread_flag(TIF_NOTIFY_RESUME);
 435                 tracehook_notify_resume(regs);
 436         }
 437 }