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 <asm/stack.h>
  24 #include <asm/traps.h>
  25 #include <asm/setup.h>
  26
  27 #include <arch/interrupts.h>
  28 #include <arch/spr_def.h>
  29 #include <arch/opcode.h>
  30
  31 void __init trap_init(void)
  32 {
  33         /* Nothing needed here since we link code at .intrpt1 */
  34 }
  35
  36 int unaligned_fixup = 1;
  37
  38 static int __init setup_unaligned_fixup(char *str)
  39 {
  40         /*
  41          * Say "=-1" to completely disable it.  If you just do "=0", we
  42          * will still parse the instruction, then fire a SIGBUS with
  43          * the correct address from inside the single_step code.
  44          */
  45         long val;
  46         if (strict_strtol(str, 0, &val) != 0)
  47                 return 0;
  48         unaligned_fixup = val;
  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 #ifdef __tilegx__
 105 #define bundle_bits tilegx_bundle_bits
 106 #else
 107 #define bundle_bits tile_bundle_bits
 108 #endif
 109
 110 extern bundle_bits bpt_code;
 111
 112 asm(".pushsection .rodata.bpt_code,\"a\";"
 113     ".align 8;"
 114     "bpt_code: bpt;"
 115     ".size bpt_code,.-bpt_code;"
 116     ".popsection");
 117
 118 static int special_ill(bundle_bits bundle, int *sigp, int *codep)
 119 {
 120         int sig, code, maxcode;
 121
 122         if (bundle == bpt_code) {
 123                 *sigp = SIGTRAP;
 124                 *codep = TRAP_BRKPT;
 125                 return 1;
 126         }
 127
 128         /* If it's a "raise" bundle, then "ill" must be in pipe X1. */
 129 #ifdef __tilegx__
 130         if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
 131                 return 0;
 132         if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
 133                 return 0;
 134         if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
 135                 return 0;
 136         if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
 137                 return 0;
 138 #else
 139         if (bundle & TILEPRO_BUNDLE_Y_ENCODING_MASK)
 140                 return 0;
 141         if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
 142                 return 0;
 143         if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
 144                 return 0;
 145         if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
 146                 return 0;
 147 #endif
 148
 149         /* Check that the magic distinguishers are set to mean "raise". */
 150         if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
 151                 return 0;
 152
 153         /* There must be an "addli zero, zero, VAL" in X0. */
 154         if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
 155                 return 0;
 156         if (get_Dest_X0(bundle) != TREG_ZERO)
 157                 return 0;
 158         if (get_SrcA_X0(bundle) != TREG_ZERO)
 159                 return 0;
 160
 161         /*
 162          * Validate the proposed signal number and si_code value.
 163          * Note that we embed these in the static instruction itself
 164          * so that we perturb the register state as little as possible
 165          * at the time of the actual fault; it's unlikely you'd ever
 166          * need to dynamically choose which kind of fault to raise
 167          * from user space.
 168          */
 169         sig = get_Imm16_X0(bundle) & 0x3f;
 170         switch (sig) {
 171         case SIGILL:
 172                 maxcode = NSIGILL;
 173                 break;
 174         case SIGFPE:
 175                 maxcode = NSIGFPE;
 176                 break;
 177         case SIGSEGV:
 178                 maxcode = NSIGSEGV;
 179                 break;
 180         case SIGBUS:
 181                 maxcode = NSIGBUS;
 182                 break;
 183         case SIGTRAP:
 184                 maxcode = NSIGTRAP;
 185                 break;
 186         default:
 187                 return 0;
 188         }
 189         code = (get_Imm16_X0(bundle) >> 6) & 0xf;
 190         if (code <= 0 || code > maxcode)
 191                 return 0;
 192
 193         /* Make it the requested signal. */
 194         *sigp = sig;
 195         *codep = code | __SI_FAULT;
 196         return 1;
 197 }
 198
 199 static const char *const int_name[] = {
 200         [INT_MEM_ERROR] = "Memory error",
 201         [INT_ILL] = "Illegal instruction",
 202         [INT_GPV] = "General protection violation",
 203         [INT_UDN_ACCESS] = "UDN access",
 204         [INT_IDN_ACCESS] = "IDN access",
 205 #if CHIP_HAS_SN()
 206         [INT_SN_ACCESS] = "SN access",
 207 #endif
 208         [INT_SWINT_3] = "Software interrupt 3",
 209         [INT_SWINT_2] = "Software interrupt 2",
 210         [INT_SWINT_0] = "Software interrupt 0",
 211         [INT_UNALIGN_DATA] = "Unaligned data",
 212         [INT_DOUBLE_FAULT] = "Double fault",
 213 #ifdef __tilegx__
 214         [INT_ILL_TRANS] = "Illegal virtual address",
 215 #endif
 216 };
 217
 218 static int do_bpt(struct pt_regs *regs)
 219 {
 220         unsigned long bundle, bcode, bpt;
 221
 222         bundle = *(unsigned long *)instruction_pointer(regs);
 223
 224         /*
 225          * bpt shoule be { bpt; nop }, which is 0x286a44ae51485000ULL.
 226          * we encode the unused least significant bits for other purpose.
 227          */
 228         bpt = bundle & ~((1ULL << 12) - 1);
 229         if (bpt != TILE_BPT_BUNDLE)
 230                 return 0;
 231
 232         bcode = bundle & ((1ULL << 12) - 1);
 233         /*
 234          * notify the kprobe handlers, if instruction is likely to
 235          * pertain to them.
 236          */
 237         switch (bcode) {
 238         /* breakpoint_insn */
 239         case 0:
 240                 notify_die(DIE_BREAK, "debug", regs, bundle,
 241                         INT_ILL, SIGTRAP);
 242                 break;
 243         /* breakpoint2_insn */
 244         case DIE_SSTEPBP:
 245                 notify_die(DIE_SSTEPBP, "single_step", regs, bundle,
 246                         INT_ILL, SIGTRAP);
 247                 break;
 248         default:
 249                 return 0;
 250         }
 251
 252         return 1;
 253 }
 254
 255 void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 256                        unsigned long reason)
 257 {
 258         siginfo_t info = { 0 };
 259         int signo, code;
 260         unsigned long address = 0;
 261         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                 return;
 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                         return;
 281                 if (fault_num >= 0 &&
 282                     fault_num < sizeof(int_name)/sizeof(int_name[0]) &&
 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                 return;
 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:"
 311                                " %#lx\n", regs->pc);
 312                         do_exit(SIGKILL);
 313                         return;
 314                 }
 315                 if (!special_ill(instr, &signo, &code)) {
 316                         signo = SIGILL;
 317                         code = ILL_ILLOPC;
 318                 }
 319                 address = regs->pc;
 320                 break;
 321         case INT_GPV:
 322 #if CHIP_HAS_TILE_DMA()
 323                 if (retry_gpv(reason))
 324                         return;
 325 #endif
 326                 /*FALLTHROUGH*/
 327         case INT_UDN_ACCESS:
 328         case INT_IDN_ACCESS:
 329 #if CHIP_HAS_SN()
 330         case INT_SN_ACCESS:
 331 #endif
 332                 signo = SIGILL;
 333                 code = ILL_PRVREG;
 334                 address = regs->pc;
 335                 break;
 336         case INT_SWINT_3:
 337         case INT_SWINT_2:
 338         case INT_SWINT_0:
 339                 signo = SIGILL;
 340                 code = ILL_ILLTRP;
 341                 address = regs->pc;
 342                 break;
 343         case INT_UNALIGN_DATA:
 344 #ifndef __tilegx__  /* Emulated support for single step debugging */
 345                 if (unaligned_fixup >= 0) {
 346                         struct single_step_state *state =
 347                                 current_thread_info()->step_state;
 348                         if (!state ||
 349                             (void __user *)(regs->pc) != state->buffer) {
 350                                 single_step_once(regs);
 351                                 return;
 352                         }
 353                 }
 354 #endif
 355                 signo = SIGBUS;
 356                 code = BUS_ADRALN;
 357                 address = 0;
 358                 break;
 359         case INT_DOUBLE_FAULT:
 360                 /*
 361                  * For double fault, "reason" is actually passed as
 362                  * SYSTEM_SAVE_K_2, the hypervisor's double-fault info, so
 363                  * we can provide the original fault number rather than
 364                  * the uninteresting "INT_DOUBLE_FAULT" so the user can
 365                  * learn what actually struck while PL0 ICS was set.
 366                  */
 367                 fault_num = reason;
 368                 signo = SIGILL;
 369                 code = ILL_DBLFLT;
 370                 address = regs->pc;
 371                 break;
 372 #ifdef __tilegx__
 373         case INT_ILL_TRANS: {
 374                 /* Avoid a hardware erratum with the return address stack. */
 375                 fill_ra_stack();
 376
 377                 signo = SIGSEGV;
 378                 address = reason;
 379                 code = SEGV_MAPERR;
 380                 break;
 381         }
 382 #endif
 383         default:
 384                 panic("Unexpected do_trap interrupt number %d", fault_num);
 385                 return;
 386         }
 387
 388         info.si_signo = signo;
 389         info.si_code = code;
 390         info.si_addr = (void __user *)address;
 391         if (signo == SIGILL)
 392                 info.si_trapno = fault_num;
 393         if (signo != SIGTRAP)
 394                 trace_unhandled_signal("trap", regs, address, signo);
 395         force_sig_info(signo, &info, current);
 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 }