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/compat.h>
  21 #include <linux/errno.h>
  22 #include <linux/signal.h>
  23 #include <linux/personality.h>
  24 #include <linux/freezer.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/tracehook.h>
  27 #include <linux/ratelimit.h>
  28
  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_preserve_current_state();
  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                 fpsimd_update_current_state(&fpsimd);
  91
  92         return err ? -EFAULT : 0;
  93 }
  94
  95 static int restore_sigframe(struct pt_regs *regs,
  96                             struct rt_sigframe __user *sf)
  97 {
  98         sigset_t set;
  99         int i, err;
 100         void *aux = sf->uc.uc_mcontext.__reserved;
 101
 102         err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
 103         if (err == 0)
 104                 set_current_blocked(&set);
 105
 106         for (i = 0; i < 31; i++)
 107                 __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 108                                  err);
 109         __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 110         __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 111         __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 112
 113         /*
 114          * Avoid sys_rt_sigreturn() restarting.
 115          */
 116         regs->syscallno = ~0UL;
 117
 118         err |= !valid_user_regs(&regs->user_regs, current);
 119
 120         if (err == 0) {
 121                 struct fpsimd_context *fpsimd_ctx =
 122                         container_of(aux, struct fpsimd_context, head);
 123                 err |= restore_fpsimd_context(fpsimd_ctx);
 124         }
 125
 126         return err;
 127 }
 128
 129 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
 130 {
 131         struct rt_sigframe __user *frame;
 132
 133         /* Always make any pending restarted system calls return -EINTR */
 134         current->restart_block.fn = do_no_restart_syscall;
 135
 136         /*
 137          * Since we stacked the signal on a 128-bit boundary, then 'sp' should
 138          * be word aligned here.
 139          */
 140         if (regs->sp & 15)
 141                 goto badframe;
 142
 143         frame = (struct rt_sigframe __user *)regs->sp;
 144
 145         if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
 146                 goto badframe;
 147
 148         if (restore_sigframe(regs, frame))
 149                 goto badframe;
 150
 151         if (restore_altstack(&frame->uc.uc_stack))
 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 static int setup_sigframe(struct rt_sigframe __user *sf,
 166                           struct pt_regs *regs, sigset_t *set)
 167 {
 168         int i, err = 0;
 169         void *aux = sf->uc.uc_mcontext.__reserved;
 170         struct _aarch64_ctx *end;
 171
 172         /* set up the stack frame for unwinding */
 173         __put_user_error(regs->regs[29], &sf->fp, err);
 174         __put_user_error(regs->regs[30], &sf->lr, err);
 175
 176         for (i = 0; i < 31; i++)
 177                 __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
 178                                  err);
 179         __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
 180         __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
 181         __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
 182
 183         __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
 184
 185         err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
 186
 187         if (err == 0) {
 188                 struct fpsimd_context *fpsimd_ctx =
 189                         container_of(aux, struct fpsimd_context, head);
 190                 err |= preserve_fpsimd_context(fpsimd_ctx);
 191                 aux += sizeof(*fpsimd_ctx);
 192         }
 193
 194         /* fault information, if valid */
 195         if (current->thread.fault_code) {
 196                 struct esr_context *esr_ctx =
 197                         container_of(aux, struct esr_context, head);
 198                 __put_user_error(ESR_MAGIC, &esr_ctx->head.magic, err);
 199                 __put_user_error(sizeof(*esr_ctx), &esr_ctx->head.size, err);
 200                 __put_user_error(current->thread.fault_code, &esr_ctx->esr, err);
 201                 aux += sizeof(*esr_ctx);
 202         }
 203
 204         /* set the "end" magic */
 205         end = aux;
 206         __put_user_error(0, &end->magic, err);
 207         __put_user_error(0, &end->size, err);
 208
 209         return err;
 210 }
 211
 212 static struct rt_sigframe __user *get_sigframe(struct ksignal *ksig,
 213                                                struct pt_regs *regs)
 214 {
 215         unsigned long sp, sp_top;
 216         struct rt_sigframe __user *frame;
 217
 218         sp = sp_top = sigsp(regs->sp, ksig);
 219
 220         sp = (sp - sizeof(struct rt_sigframe)) & ~15;
 221         frame = (struct rt_sigframe __user *)sp;
 222
 223         /*
 224          * Check that we can actually write to the signal frame.
 225          */
 226         if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
 227                 frame = NULL;
 228
 229         return frame;
 230 }
 231
 232 static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
 233                          void __user *frame, int usig)
 234 {
 235         __sigrestore_t sigtramp;
 236
 237         regs->regs[0] = usig;
 238         regs->sp = (unsigned long)frame;
 239         regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
 240         regs->pc = (unsigned long)ka->sa.sa_handler;
 241
 242         if (ka->sa.sa_flags & SA_RESTORER)
 243                 sigtramp = ka->sa.sa_restorer;
 244         else
 245                 sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
 246
 247         regs->regs[30] = (unsigned long)sigtramp;
 248 }
 249
 250 static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
 251                           struct pt_regs *regs)
 252 {
 253         struct rt_sigframe __user *frame;
 254         int err = 0;
 255
 256         frame = get_sigframe(ksig, regs);
 257         if (!frame)
 258                 return 1;
 259
 260         __put_user_error(0, &frame->uc.uc_flags, err);
 261         __put_user_error(NULL, &frame->uc.uc_link, err);
 262
 263         err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
 264         err |= setup_sigframe(frame, regs, set);
 265         if (err == 0) {
 266                 setup_return(regs, &ksig->ka, frame, usig);
 267                 if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
 268                         err |= copy_siginfo_to_user(&frame->info, &ksig->info);
 269                         regs->regs[1] = (unsigned long)&frame->info;
 270                         regs->regs[2] = (unsigned long)&frame->uc;
 271                 }
 272         }
 273
 274         return err;
 275 }
 276
 277 static void setup_restart_syscall(struct pt_regs *regs)
 278 {
 279         if (is_compat_task())
 280                 compat_setup_restart_syscall(regs);
 281         else
 282                 regs->regs[8] = __NR_restart_syscall;
 283 }
 284
 285 /*
 286  * OK, we're invoking a handler
 287  */
 288 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 289 {
 290         struct task_struct *tsk = current;
 291         sigset_t *oldset = sigmask_to_save();
 292         int usig = ksig->sig;
 293         int ret;
 294
 295         /*
 296          * Set up the stack frame
 297          */
 298         if (is_compat_task()) {
 299                 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 300                         ret = compat_setup_rt_frame(usig, ksig, oldset, regs);
 301                 else
 302                         ret = compat_setup_frame(usig, ksig, oldset, regs);
 303         } else {
 304                 ret = setup_rt_frame(usig, ksig, oldset, regs);
 305         }
 306
 307         /*
 308          * Check that the resulting registers are actually sane.
 309          */
 310         ret |= !valid_user_regs(&regs->user_regs, current);
 311
 312         /*
 313          * Fast forward the stepping logic so we step into the signal
 314          * handler.
 315          */
 316         if (!ret)
 317                 user_fastforward_single_step(tsk);
 318
 319         signal_setup_done(ret, ksig, 0);
 320 }
 321
 322 /*
 323  * Note that 'init' is a special process: it doesn't get signals it doesn't
 324  * want to handle. Thus you cannot kill init even with a SIGKILL even by
 325  * mistake.
 326  *
 327  * Note that we go through the signals twice: once to check the signals that
 328  * the kernel can handle, and then we build all the user-level signal handling
 329  * stack-frames in one go after that.
 330  */
 331 static void do_signal(struct pt_regs *regs)
 332 {
 333         unsigned long continue_addr = 0, restart_addr = 0;
 334         int retval = 0;
 335         int syscall = (int)regs->syscallno;
 336         struct ksignal ksig;
 337
 338         /*
 339          * If we were from a system call, check for system call restarting...
 340          */
 341         if (syscall >= 0) {
 342                 continue_addr = regs->pc;
 343                 restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
 344                 retval = regs->regs[0];
 345
 346                 /*
 347                  * Avoid additional syscall restarting via ret_to_user.
 348                  */
 349                 regs->syscallno = ~0UL;
 350
 351                 /*
 352                  * Prepare for system call restart. We do this here so that a
 353                  * debugger will see the already changed PC.
 354                  */
 355                 switch (retval) {
 356                 case -ERESTARTNOHAND:
 357                 case -ERESTARTSYS:
 358                 case -ERESTARTNOINTR:
 359                 case -ERESTART_RESTARTBLOCK:
 360                         regs->regs[0] = regs->orig_x0;
 361                         regs->pc = restart_addr;
 362                         break;
 363                 }
 364         }
 365
 366         /*
 367          * Get the signal to deliver. When running under ptrace, at this point
 368          * the debugger may change all of our registers.
 369          */
 370         if (get_signal(&ksig)) {
 371                 /*
 372                  * Depending on the signal settings, we may need to revert the
 373                  * decision to restart the system call, but skip this if a
 374                  * debugger has chosen to restart at a different PC.
 375                  */
 376                 if (regs->pc == restart_addr &&
 377                     (retval == -ERESTARTNOHAND ||
 378                      retval == -ERESTART_RESTARTBLOCK ||
 379                      (retval == -ERESTARTSYS &&
 380                       !(ksig.ka.sa.sa_flags & SA_RESTART)))) {
 381                         regs->regs[0] = -EINTR;
 382                         regs->pc = continue_addr;
 383                 }
 384
 385                 handle_signal(&ksig, regs);
 386                 return;
 387         }
 388
 389         /*
 390          * Handle restarting a different system call. As above, if a debugger
 391          * has chosen to restart at a different PC, ignore the restart.
 392          */
 393         if (syscall >= 0 && regs->pc == restart_addr) {
 394                 if (retval == -ERESTART_RESTARTBLOCK)
 395                         setup_restart_syscall(regs);
 396                 user_rewind_single_step(current);
 397         }
 398
 399         restore_saved_sigmask();
 400 }
 401
 402 asmlinkage void do_notify_resume(struct pt_regs *regs,
 403                                  unsigned int thread_flags)
 404 {
 405         /*
 406          * The assembly code enters us with IRQs off, but it hasn't
 407          * informed the tracing code of that for efficiency reasons.
 408          * Update the trace code with the current status.
 409          */
 410         trace_hardirqs_off();
 411         do {
 412                 if (thread_flags & _TIF_NEED_RESCHED) {
 413                         schedule();
 414                 } else {
 415                         local_irq_enable();
 416
 417                         if (thread_flags & _TIF_SIGPENDING)
 418                                 do_signal(regs);
 419
 420                         if (thread_flags & _TIF_NOTIFY_RESUME) {
 421                                 clear_thread_flag(TIF_NOTIFY_RESUME);
 422                                 tracehook_notify_resume(regs);
 423                         }
 424
 425                         if (thread_flags & _TIF_FOREIGN_FPSTATE)
 426                                 fpsimd_restore_current_state();
 427                 }
 428
 429                 local_irq_disable();
 430                 thread_flags = READ_ONCE(current_thread_info()->flags);
 431         } while (thread_flags & _TIF_WORK_MASK);
 432 }