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