arch/tile/kernel/traps.c

   1 /*
   2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
   3  *
   4  *   This program is free software; you can redistribute it and/or
   5  *   modify it under the terms of the GNU General Public License
   6  *   as published by the Free Software Foundation, version 2.
   7  *
   8  *   This program is distributed in the hope that it will be useful, but
   9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  11  *   NON INFRINGEMENT.  See the GNU General Public License for
  12  *   more details.
  13  */
  14
  15 #include <linux/sched.h>
  16 #include <linux/sched/debug.h>
  17 #include <linux/kernel.h>
  18 #include <linux/kprobes.h>
  19 #include <linux/kdebug.h>
  20 #include <linux/module.h>
  21 #include <linux/reboot.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/ptrace.h>
  24 #include <linux/hardirq.h>
  25 #include <linux/nmi.h>
  26 #include <asm/stack.h>
  27 #include <asm/traps.h>
  28 #include <asm/setup.h>
  29
  30 #include <arch/interrupts.h>
  31 #include <arch/spr_def.h>
  32 #include <arch/opcode.h>
  33
  34 void __init trap_init(void)
  35 {
  36         /* Nothing needed here since we link code at .intrpt */
  37 }
  38
  39 int unaligned_fixup = 1;
  40
  41 static int __init setup_unaligned_fixup(char *str)
  42 {
  43         /*
  44          * Say "=-1" to completely disable it.  If you just do "=0", we
  45          * will still parse the instruction, then fire a SIGBUS with
  46          * the correct address from inside the single_step code.
  47          */
  48         if (kstrtoint(str, 0, &unaligned_fixup) != 0)
  49                 return 0;
  50
  51         pr_info("Fixups for unaligned data accesses are %s\n",
  52                 unaligned_fixup >= 0 ?
  53                 (unaligned_fixup ? "enabled" : "disabled") :
  54                 "completely disabled");
  55         return 1;
  56 }
  57 __setup("unaligned_fixup=", setup_unaligned_fixup);
  58
  59 #if CHIP_HAS_TILE_DMA()
  60
  61 static int dma_disabled;
  62
  63 static int __init nodma(char *str)
  64 {
  65         pr_info("User-space DMA is disabled\n");
  66         dma_disabled = 1;
  67         return 1;
  68 }
  69 __setup("nodma", nodma);
  70
  71 /* How to decode SPR_GPV_REASON */
  72 #define IRET_ERROR (1U << 31)
  73 #define MT_ERROR   (1U << 30)
  74 #define MF_ERROR   (1U << 29)
  75 #define SPR_INDEX  ((1U << 15) - 1)
  76 #define SPR_MPL_SHIFT  9  /* starting bit position for MPL encoded in SPR */
  77
  78 /*
  79  * See if this GPV is just to notify the kernel of SPR use and we can
  80  * retry the user instruction after adjusting some MPLs suitably.
  81  */
  82 static int retry_gpv(unsigned int gpv_reason)
  83 {
  84         int mpl;
  85
  86         if (gpv_reason & IRET_ERROR)
  87                 return 0;
  88
  89         BUG_ON((gpv_reason & (MT_ERROR|MF_ERROR)) == 0);
  90         mpl = (gpv_reason & SPR_INDEX) >> SPR_MPL_SHIFT;
  91         if (mpl == INT_DMA_NOTIFY && !dma_disabled) {
  92                 /* User is turning on DMA. Allow it and retry. */
  93                 printk(KERN_DEBUG "Process %d/%s is now enabled for DMA\n",
  94                        current->pid, current->comm);
  95                 BUG_ON(current->thread.tile_dma_state.enabled);
  96                 current->thread.tile_dma_state.enabled = 1;
  97                 grant_dma_mpls();
  98                 return 1;
  99         }
 100
 101         return 0;
 102 }
 103
 104 #endif /* CHIP_HAS_TILE_DMA() */
 105
 106 extern tile_bundle_bits bpt_code;
 107
 108 asm(".pushsection .rodata.bpt_code,\"a\";"
 109     ".align 8;"
 110     "bpt_code: bpt;"
 111     ".size bpt_code,.-bpt_code;"
 112     ".popsection");
 113
 114 static int special_ill(tile_bundle_bits bundle, int *sigp, int *codep)
 115 {
 116         int sig, code, maxcode;
 117
 118         if (bundle == bpt_code) {
 119                 *sigp = SIGTRAP;
 120                 *codep = TRAP_BRKPT;
 121                 return 1;
 122         }
 123
 124         /* If it's a "raise" bundle, then "ill" must be in pipe X1. */
 125 #ifdef __tilegx__
 126         if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
 127                 return 0;
 128         if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
 129                 return 0;
 130         if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
 131                 return 0;
 132         if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
 133                 return 0;
 134 #else
 135         if (bundle & TILEPRO_BUNDLE_Y_ENCODING_MASK)
 136                 return 0;
 137         if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
 138                 return 0;
 139         if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
 140                 return 0;
 141         if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
 142                 return 0;
 143 #endif
 144
 145         /* Check that the magic distinguishers are set to mean "raise". */
 146         if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
 147                 return 0;
 148
 149         /* There must be an "addli zero, zero, VAL" in X0. */
 150         if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
 151                 return 0;
 152         if (get_Dest_X0(bundle) != TREG_ZERO)
 153                 return 0;
 154         if (get_SrcA_X0(bundle) != TREG_ZERO)
 155                 return 0;
 156
 157         /*
 158          * Validate the proposed signal number and si_code value.
 159          * Note that we embed these in the static instruction itself
 160          * so that we perturb the register state as little as possible
 161          * at the time of the actual fault; it's unlikely you'd ever
 162          * need to dynamically choose which kind of fault to raise
 163          * from user space.
 164          */
 165         sig = get_Imm16_X0(bundle) & 0x3f;
 166         switch (sig) {
 167         case SIGILL:
 168                 maxcode = NSIGILL;
 169                 break;
 170         case SIGFPE:
 171                 maxcode = NSIGFPE;
 172                 break;
 173         case SIGSEGV:
 174                 maxcode = NSIGSEGV;
 175                 break;
 176         case SIGBUS:
 177                 maxcode = NSIGBUS;
 178                 break;
 179         case SIGTRAP:
 180                 maxcode = NSIGTRAP;
 181                 break;
 182         default:
 183                 return 0;
 184         }
 185         code = (get_Imm16_X0(bundle) >> 6) & 0xf;
 186         if (code <= 0 || code > maxcode)
 187                 return 0;
 188
 189         /* Make it the requested signal. */
 190         *sigp = sig;
 191         *codep = code;
 192         return 1;
 193 }
 194
 195 static const char *const int_name[] = {
 196         [INT_MEM_ERROR] = "Memory error",
 197         [INT_ILL] = "Illegal instruction",
 198         [INT_GPV] = "General protection violation",
 199         [INT_UDN_ACCESS] = "UDN access",
 200         [INT_IDN_ACCESS] = "IDN access",
 201 #if CHIP_HAS_SN()
 202         [INT_SN_ACCESS] = "SN access",
 203 #endif
 204         [INT_SWINT_3] = "Software interrupt 3",
 205         [INT_SWINT_2] = "Software interrupt 2",
 206         [INT_SWINT_0] = "Software interrupt 0",
 207         [INT_UNALIGN_DATA] = "Unaligned data",
 208         [INT_DOUBLE_FAULT] = "Double fault",
 209 #ifdef __tilegx__
 210         [INT_ILL_TRANS] = "Illegal virtual address",
 211 #endif
 212 };
 213
 214 static int do_bpt(struct pt_regs *regs)
 215 {
 216         unsigned long bundle, bcode, bpt;
 217
 218         bundle = *(unsigned long *)instruction_pointer(regs);
 219
 220         /*
 221          * bpt shoule be { bpt; nop }, which is 0x286a44ae51485000ULL.
 222          * we encode the unused least significant bits for other purpose.
 223          */
 224         bpt = bundle & ~((1ULL << 12) - 1);
 225         if (bpt != TILE_BPT_BUNDLE)
 226                 return 0;
 227
 228         bcode = bundle & ((1ULL << 12) - 1);
 229         /*
 230          * notify the kprobe handlers, if instruction is likely to
 231          * pertain to them.
 232          */
 233         switch (bcode) {
 234         /* breakpoint_insn */
 235         case 0:
 236                 notify_die(DIE_BREAK, "debug", regs, bundle,
 237                         INT_ILL, SIGTRAP);
 238                 break;
 239         /* compiled_bpt */
 240         case DIE_COMPILED_BPT:
 241                 notify_die(DIE_COMPILED_BPT, "debug", regs, bundle,
 242                         INT_ILL, SIGTRAP);
 243                 break;
 244         /* breakpoint2_insn */
 245         case DIE_SSTEPBP:
 246                 notify_die(DIE_SSTEPBP, "single_step", regs, bundle,
 247                         INT_ILL, SIGTRAP);
 248                 break;
 249         default:
 250                 return 0;
 251         }
 252
 253         return 1;
 254 }
 255
 256 void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 257                        unsigned long reason)
 258 {
 259         siginfo_t info = { 0 };
 260         int signo, code;
 261         unsigned long address = 0;
 262         tile_bundle_bits instr;
 263         int is_kernel = !user_mode(regs);
 264
 265         /* Handle breakpoints, etc. */
 266         if (is_kernel && fault_num == INT_ILL && do_bpt(regs))
 267                 return;
 268
 269         /* Re-enable interrupts, if they were previously enabled. */
 270         if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
 271                 local_irq_enable();
 272
 273         /*
 274          * If it hits in kernel mode and we can't fix it up, just exit the
 275          * current process and hope for the best.
 276          */
 277         if (is_kernel) {
 278                 const char *name;
 279                 char buf[100];
 280                 if (fixup_exception(regs))  /* ILL_TRANS or UNALIGN_DATA */
 281                         return;
 282                 if (fault_num >= 0 &&
 283                     fault_num < ARRAY_SIZE(int_name) &&
 284                     int_name[fault_num] != NULL)
 285                         name = int_name[fault_num];
 286                 else
 287                         name = "Unknown interrupt";
 288                 if (fault_num == INT_GPV)
 289                         snprintf(buf, sizeof(buf), "; GPV_REASON %#lx", reason);
 290 #ifdef __tilegx__
 291                 else if (fault_num == INT_ILL_TRANS)
 292                         snprintf(buf, sizeof(buf), "; address %#lx", reason);
 293 #endif
 294                 else
 295                         buf[0] = '\0';
 296                 pr_alert("Kernel took bad trap %d (%s) at PC %#lx%s\n",
 297                          fault_num, name, regs->pc, buf);
 298                 show_regs(regs);
 299                 do_exit(SIGKILL);  /* FIXME: implement i386 die() */
 300         }
 301
 302         switch (fault_num) {
 303         case INT_MEM_ERROR:
 304                 signo = SIGBUS;
 305                 code = BUS_OBJERR;
 306                 break;
 307         case INT_ILL:
 308                 if (copy_from_user(&instr, (void __user *)regs->pc,
 309                                    sizeof(instr))) {
 310                         pr_err("Unreadable instruction for INT_ILL: %#lx\n",
 311                                regs->pc);
 312                         do_exit(SIGKILL);
 313                 }
 314                 if (!special_ill(instr, &signo, &code)) {
 315                         signo = SIGILL;
 316                         code = ILL_ILLOPC;
 317                 }
 318                 address = regs->pc;
 319                 break;
 320         case INT_GPV:
 321 #if CHIP_HAS_TILE_DMA()
 322                 if (retry_gpv(reason))
 323                         return;
 324 #endif
 325                 /*FALLTHROUGH*/
 326         case INT_UDN_ACCESS:
 327         case INT_IDN_ACCESS:
 328 #if CHIP_HAS_SN()
 329         case INT_SN_ACCESS:
 330 #endif
 331                 signo = SIGILL;
 332                 code = ILL_PRVREG;
 333                 address = regs->pc;
 334                 break;
 335         case INT_SWINT_3:
 336         case INT_SWINT_2:
 337         case INT_SWINT_0:
 338                 signo = SIGILL;
 339                 code = ILL_ILLTRP;
 340                 address = regs->pc;
 341                 break;
 342         case INT_UNALIGN_DATA:
 343 #ifndef __tilegx__  /* Emulated support for single step debugging */
 344                 if (unaligned_fixup >= 0) {
 345                         struct single_step_state *state =
 346                                 current_thread_info()->step_state;
 347                         if (!state ||
 348                             (void __user *)(regs->pc) != state->buffer) {
 349                                 single_step_once(regs);
 350                                 return;
 351                         }
 352                 }
 353 #endif
 354                 signo = SIGBUS;
 355                 code = BUS_ADRALN;
 356                 address = 0;
 357                 break;
 358         case INT_DOUBLE_FAULT:
 359                 /*
 360                  * For double fault, "reason" is actually passed as
 361                  * SYSTEM_SAVE_K_2, the hypervisor's double-fault info, so
 362                  * we can provide the original fault number rather than
 363                  * the uninteresting "INT_DOUBLE_FAULT" so the user can
 364                  * learn what actually struck while PL0 ICS was set.
 365                  */
 366                 fault_num = reason;
 367                 signo = SIGILL;
 368                 code = ILL_DBLFLT;
 369                 address = regs->pc;
 370                 break;
 371 #ifdef __tilegx__
 372         case INT_ILL_TRANS: {
 373                 /* Avoid a hardware erratum with the return address stack. */
 374                 fill_ra_stack();
 375
 376                 signo = SIGSEGV;
 377                 address = reason;
 378                 code = SEGV_MAPERR;
 379                 break;
 380         }
 381 #endif
 382         default:
 383                 panic("Unexpected do_trap interrupt number %d", fault_num);
 384         }
 385
 386         info.si_signo = signo;
 387         info.si_code = code;
 388         info.si_addr = (void __user *)address;
 389         if (signo == SIGILL)
 390                 info.si_trapno = fault_num;
 391         if (signo != SIGTRAP)
 392                 trace_unhandled_signal("trap", regs, address, signo);
 393         force_sig_info(signo, &info, current);
 394 }
 395
 396 void do_nmi(struct pt_regs *regs, int fault_num, unsigned long reason)
 397 {
 398         nmi_enter();
 399         switch (reason) {
 400 #ifdef arch_trigger_cpumask_backtrace
 401         case TILE_NMI_DUMP_STACK:
 402                 nmi_cpu_backtrace(regs);
 403                 break;
 404 #endif
 405         default:
 406                 panic("Unexpected do_nmi type %ld", reason);
 407         }
 408         nmi_exit();
 409 }
 410
 411 /* Deprecated function currently only used here. */
 412 extern void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52);
 413
 414 void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 415 {
 416         _dump_stack(dummy, pc, lr, sp, r52);
 417         pr_emerg("Double fault: exiting\n");
 418         machine_halt();
 419 }