arch/powerpc/kernel/signal.c

   1 /*
   2  * Common signal handling code for both 32 and 64 bits
   3  *
   4  *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Corporation
   5  *    Extracted from signal_32.c and signal_64.c
   6  *
   7  * This file is subject to the terms and conditions of the GNU General
   8  * Public License.  See the file README.legal in the main directory of
   9  * this archive for more details.
  10  */
  11
  12 #include <linux/tracehook.h>
  13 #include <linux/signal.h>
  14 #include <linux/uprobes.h>
  15 #include <linux/key.h>
  16 #include <linux/context_tracking.h>
  17 #include <linux/livepatch.h>
  18 #include <linux/syscalls.h>
  19 #include <asm/hw_breakpoint.h>
  20 #include <linux/uaccess.h>
  21 #include <asm/switch_to.h>
  22 #include <asm/unistd.h>
  23 #include <asm/debug.h>
  24 #include <asm/tm.h>
  25
  26 #include "signal.h"
  27
  28 #ifdef CONFIG_VSX
  29 unsigned long copy_fpr_to_user(void __user *to,
  30                                struct task_struct *task)
  31 {
  32         u64 buf[ELF_NFPREG];
  33         int i;
  34
  35         /* save FPR copy to local buffer then write to the thread_struct */
  36         for (i = 0; i < (ELF_NFPREG - 1) ; i++)
  37                 buf[i] = task->thread.TS_FPR(i);
  38         buf[i] = task->thread.fp_state.fpscr;
  39         return __copy_to_user(to, buf, ELF_NFPREG * sizeof(double));
  40 }
  41
  42 unsigned long copy_fpr_from_user(struct task_struct *task,
  43                                  void __user *from)
  44 {
  45         u64 buf[ELF_NFPREG];
  46         int i;
  47
  48         if (__copy_from_user(buf, from, ELF_NFPREG * sizeof(double)))
  49                 return 1;
  50         for (i = 0; i < (ELF_NFPREG - 1) ; i++)
  51                 task->thread.TS_FPR(i) = buf[i];
  52         task->thread.fp_state.fpscr = buf[i];
  53
  54         return 0;
  55 }
  56
  57 unsigned long copy_vsx_to_user(void __user *to,
  58                                struct task_struct *task)
  59 {
  60         u64 buf[ELF_NVSRHALFREG];
  61         int i;
  62
  63         /* save FPR copy to local buffer then write to the thread_struct */
  64         for (i = 0; i < ELF_NVSRHALFREG; i++)
  65                 buf[i] = task->thread.fp_state.fpr[i][TS_VSRLOWOFFSET];
  66         return __copy_to_user(to, buf, ELF_NVSRHALFREG * sizeof(double));
  67 }
  68
  69 unsigned long copy_vsx_from_user(struct task_struct *task,
  70                                  void __user *from)
  71 {
  72         u64 buf[ELF_NVSRHALFREG];
  73         int i;
  74
  75         if (__copy_from_user(buf, from, ELF_NVSRHALFREG * sizeof(double)))
  76                 return 1;
  77         for (i = 0; i < ELF_NVSRHALFREG ; i++)
  78                 task->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = buf[i];
  79         return 0;
  80 }
  81
  82 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
  83 unsigned long copy_ckfpr_to_user(void __user *to,
  84                                   struct task_struct *task)
  85 {
  86         u64 buf[ELF_NFPREG];
  87         int i;
  88
  89         /* save FPR copy to local buffer then write to the thread_struct */
  90         for (i = 0; i < (ELF_NFPREG - 1) ; i++)
  91                 buf[i] = task->thread.TS_CKFPR(i);
  92         buf[i] = task->thread.ckfp_state.fpscr;
  93         return __copy_to_user(to, buf, ELF_NFPREG * sizeof(double));
  94 }
  95
  96 unsigned long copy_ckfpr_from_user(struct task_struct *task,
  97                                           void __user *from)
  98 {
  99         u64 buf[ELF_NFPREG];
 100         int i;
 101
 102         if (__copy_from_user(buf, from, ELF_NFPREG * sizeof(double)))
 103                 return 1;
 104         for (i = 0; i < (ELF_NFPREG - 1) ; i++)
 105                 task->thread.TS_CKFPR(i) = buf[i];
 106         task->thread.ckfp_state.fpscr = buf[i];
 107
 108         return 0;
 109 }
 110
 111 unsigned long copy_ckvsx_to_user(void __user *to,
 112                                   struct task_struct *task)
 113 {
 114         u64 buf[ELF_NVSRHALFREG];
 115         int i;
 116
 117         /* save FPR copy to local buffer then write to the thread_struct */
 118         for (i = 0; i < ELF_NVSRHALFREG; i++)
 119                 buf[i] = task->thread.ckfp_state.fpr[i][TS_VSRLOWOFFSET];
 120         return __copy_to_user(to, buf, ELF_NVSRHALFREG * sizeof(double));
 121 }
 122
 123 unsigned long copy_ckvsx_from_user(struct task_struct *task,
 124                                           void __user *from)
 125 {
 126         u64 buf[ELF_NVSRHALFREG];
 127         int i;
 128
 129         if (__copy_from_user(buf, from, ELF_NVSRHALFREG * sizeof(double)))
 130                 return 1;
 131         for (i = 0; i < ELF_NVSRHALFREG ; i++)
 132                 task->thread.ckfp_state.fpr[i][TS_VSRLOWOFFSET] = buf[i];
 133         return 0;
 134 }
 135 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
 136 #endif
 137
 138 /* Log an error when sending an unhandled signal to a process. Controlled
 139  * through debug.exception-trace sysctl.
 140  */
 141
 142 int show_unhandled_signals = 1;
 143
 144 /*
 145  * Allocate space for the signal frame
 146  */
 147 static unsigned long get_tm_stackpointer(struct task_struct *tsk);
 148
 149 void __user *get_sigframe(struct ksignal *ksig, struct task_struct *tsk,
 150                           size_t frame_size, int is_32)
 151 {
 152         unsigned long oldsp, newsp;
 153         unsigned long sp = get_tm_stackpointer(tsk);
 154
 155         /* Default to using normal stack */
 156         if (is_32)
 157                 oldsp = sp & 0x0ffffffffUL;
 158         else
 159                 oldsp = sp;
 160         oldsp = sigsp(oldsp, ksig);
 161         newsp = (oldsp - frame_size) & ~0xFUL;
 162
 163         return (void __user *)newsp;
 164 }
 165
 166 static void check_syscall_restart(struct pt_regs *regs, struct k_sigaction *ka,
 167                                   int has_handler)
 168 {
 169         unsigned long ret = regs->gpr[3];
 170         int restart = 1;
 171
 172         /* syscall ? */
 173         if (!trap_is_syscall(regs))
 174                 return;
 175
 176         if (trap_norestart(regs))
 177                 return;
 178
 179         /* error signalled ? */
 180         if (trap_is_scv(regs)) {
 181                 /* 32-bit compat mode sign extend? */
 182                 if (!IS_ERR_VALUE(ret))
 183                         return;
 184                 ret = -ret;
 185         } else if (!(regs->ccr & 0x10000000)) {
 186                 return;
 187         }
 188
 189         switch (ret) {
 190         case ERESTART_RESTARTBLOCK:
 191         case ERESTARTNOHAND:
 192                 /* ERESTARTNOHAND means that the syscall should only be
 193                  * restarted if there was no handler for the signal, and since
 194                  * we only get here if there is a handler, we dont restart.
 195                  */
 196                 restart = !has_handler;
 197                 break;
 198         case ERESTARTSYS:
 199                 /* ERESTARTSYS means to restart the syscall if there is no
 200                  * handler or the handler was registered with SA_RESTART
 201                  */
 202                 restart = !has_handler || (ka->sa.sa_flags & SA_RESTART) != 0;
 203                 break;
 204         case ERESTARTNOINTR:
 205                 /* ERESTARTNOINTR means that the syscall should be
 206                  * called again after the signal handler returns.
 207                  */
 208                 break;
 209         default:
 210                 return;
 211         }
 212         if (restart) {
 213                 if (ret == ERESTART_RESTARTBLOCK)
 214                         regs->gpr[0] = __NR_restart_syscall;
 215                 else
 216                         regs->gpr[3] = regs->orig_gpr3;
 217                 regs->nip -= 4;
 218                 regs->result = 0;
 219         } else {
 220                 if (trap_is_scv(regs)) {
 221                         regs->result = -EINTR;
 222                         regs->gpr[3] = -EINTR;
 223                 } else {
 224                         regs->result = -EINTR;
 225                         regs->gpr[3] = EINTR;
 226                         regs->ccr |= 0x10000000;
 227                 }
 228         }
 229 }
 230
 231 static void do_signal(struct task_struct *tsk)
 232 {
 233         sigset_t *oldset = sigmask_to_save();
 234         struct ksignal ksig = { .sig = 0 };
 235         int ret;
 236
 237         BUG_ON(tsk != current);
 238
 239         get_signal(&ksig);
 240
 241         /* Is there any syscall restart business here ? */
 242         check_syscall_restart(tsk->thread.regs, &ksig.ka, ksig.sig > 0);
 243
 244         if (ksig.sig <= 0) {
 245                 /* No signal to deliver -- put the saved sigmask back */
 246                 restore_saved_sigmask();
 247                 set_trap_norestart(tsk->thread.regs);
 248                 return;               /* no signals delivered */
 249         }
 250
 251         /*
 252          * Reenable the DABR before delivering the signal to
 253          * user space. The DABR will have been cleared if it
 254          * triggered inside the kernel.
 255          */
 256         if (!IS_ENABLED(CONFIG_PPC_ADV_DEBUG_REGS)) {
 257                 int i;
 258
 259                 for (i = 0; i < nr_wp_slots(); i++) {
 260                         if (tsk->thread.hw_brk[i].address && tsk->thread.hw_brk[i].type)
 261                                 __set_breakpoint(i, &tsk->thread.hw_brk[i]);
 262                 }
 263         }
 264
 265         /* Re-enable the breakpoints for the signal stack */
 266         thread_change_pc(tsk, tsk->thread.regs);
 267
 268         rseq_signal_deliver(&ksig, tsk->thread.regs);
 269
 270         if (is_32bit_task()) {
 271                 if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 272                         ret = handle_rt_signal32(&ksig, oldset, tsk);
 273                 else
 274                         ret = handle_signal32(&ksig, oldset, tsk);
 275         } else {
 276                 ret = handle_rt_signal64(&ksig, oldset, tsk);
 277         }
 278
 279         set_trap_norestart(tsk->thread.regs);
 280         signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
 281 }
 282
 283 void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 284 {
 285         user_exit();
 286
 287         if (thread_info_flags & _TIF_UPROBE)
 288                 uprobe_notify_resume(regs);
 289
 290         if (thread_info_flags & _TIF_PATCH_PENDING)
 291                 klp_update_patch_state(current);
 292
 293         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
 294                 BUG_ON(regs != current->thread.regs);
 295                 do_signal(current);
 296         }
 297
 298         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 299                 tracehook_notify_resume(regs);
 300                 rseq_handle_notify_resume(NULL, regs);
 301         }
 302
 303         user_enter();
 304 }
 305
 306 static unsigned long get_tm_stackpointer(struct task_struct *tsk)
 307 {
 308         /* When in an active transaction that takes a signal, we need to be
 309          * careful with the stack.  It's possible that the stack has moved back
 310          * up after the tbegin.  The obvious case here is when the tbegin is
 311          * called inside a function that returns before a tend.  In this case,
 312          * the stack is part of the checkpointed transactional memory state.
 313          * If we write over this non transactionally or in suspend, we are in
 314          * trouble because if we get a tm abort, the program counter and stack
 315          * pointer will be back at the tbegin but our in memory stack won't be
 316          * valid anymore.
 317          *
 318          * To avoid this, when taking a signal in an active transaction, we
 319          * need to use the stack pointer from the checkpointed state, rather
 320          * than the speculated state.  This ensures that the signal context
 321          * (written tm suspended) will be written below the stack required for
 322          * the rollback.  The transaction is aborted because of the treclaim,
 323          * so any memory written between the tbegin and the signal will be
 324          * rolled back anyway.
 325          *
 326          * For signals taken in non-TM or suspended mode, we use the
 327          * normal/non-checkpointed stack pointer.
 328          */
 329
 330         unsigned long ret = tsk->thread.regs->gpr[1];
 331
 332 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 333         BUG_ON(tsk != current);
 334
 335         if (MSR_TM_ACTIVE(tsk->thread.regs->msr)) {
 336                 preempt_disable();
 337                 tm_reclaim_current(TM_CAUSE_SIGNAL);
 338                 if (MSR_TM_TRANSACTIONAL(tsk->thread.regs->msr))
 339                         ret = tsk->thread.ckpt_regs.gpr[1];
 340
 341                 /*
 342                  * If we treclaim, we must clear the current thread's TM bits
 343                  * before re-enabling preemption. Otherwise we might be
 344                  * preempted and have the live MSR[TS] changed behind our back
 345                  * (tm_recheckpoint_new_task() would recheckpoint). Besides, we
 346                  * enter the signal handler in non-transactional state.
 347                  */
 348                 tsk->thread.regs->msr &= ~MSR_TS_MASK;
 349                 preempt_enable();
 350         }
 351 #endif
 352         return ret;
 353 }
 354
 355 static const char fm32[] = KERN_INFO "%s[%d]: bad frame in %s: %p nip %08lx lr %08lx\n";
 356 static const char fm64[] = KERN_INFO "%s[%d]: bad frame in %s: %p nip %016lx lr %016lx\n";
 357
 358 void signal_fault(struct task_struct *tsk, struct pt_regs *regs,
 359                   const char *where, void __user *ptr)
 360 {
 361         if (show_unhandled_signals)
 362                 printk_ratelimited(regs->msr & MSR_64BIT ? fm64 : fm32, tsk->comm,
 363                                    task_pid_nr(tsk), where, ptr, regs->nip, regs->link);
 364 }