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 .intrpt */
  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         if (kstrtoint(str, 0, &unaligned_fixup) != 0)
  46                 return 0;
  47
  48         pr_info("Fixups for unaligned data accesses are %s\n",
  49                 unaligned_fixup >= 0 ?
  50                 (unaligned_fixup ? "enabled" : "disabled") :
  51                 "completely disabled");
  52         return 1;
  53 }
  54 __setup("unaligned_fixup=", setup_unaligned_fixup);
  55
  56 #if CHIP_HAS_TILE_DMA()
  57
  58 static int dma_disabled;
  59
  60 static int __init nodma(char *str)
  61 {
  62         pr_info("User-space DMA is disabled\n");
  63         dma_disabled = 1;
  64         return 1;
  65 }
  66 __setup("nodma", nodma);
  67
  68 /* How to decode SPR_GPV_REASON */
  69 #define IRET_ERROR (1U << 31)
  70 #define MT_ERROR   (1U << 30)
  71 #define MF_ERROR   (1U << 29)
  72 #define SPR_INDEX  ((1U << 15) - 1)
  73 #define SPR_MPL_SHIFT  9  /* starting bit position for MPL encoded in SPR */
  74
  75 /*
  76  * See if this GPV is just to notify the kernel of SPR use and we can
  77  * retry the user instruction after adjusting some MPLs suitably.
  78  */
  79 static int retry_gpv(unsigned int gpv_reason)
  80 {
  81         int mpl;
  82
  83         if (gpv_reason & IRET_ERROR)
  84                 return 0;
  85
  86         BUG_ON((gpv_reason & (MT_ERROR|MF_ERROR)) == 0);
  87         mpl = (gpv_reason & SPR_INDEX) >> SPR_MPL_SHIFT;
  88         if (mpl == INT_DMA_NOTIFY && !dma_disabled) {
  89                 /* User is turning on DMA. Allow it and retry. */
  90                 printk(KERN_DEBUG "Process %d/%s is now enabled for DMA\n",
  91                        current->pid, current->comm);
  92                 BUG_ON(current->thread.tile_dma_state.enabled);
  93                 current->thread.tile_dma_state.enabled = 1;
  94                 grant_dma_mpls();
  95                 return 1;
  96         }
  97
  98         return 0;
  99 }
 100
 101 #endif /* CHIP_HAS_TILE_DMA() */
 102
 103 extern tile_bundle_bits bpt_code;
 104
 105 asm(".pushsection .rodata.bpt_code,\"a\";"
 106     ".align 8;"
 107     "bpt_code: bpt;"
 108     ".size bpt_code,.-bpt_code;"
 109     ".popsection");
 110
 111 static int special_ill(tile_bundle_bits bundle, int *sigp, int *codep)
 112 {
 113         int sig, code, maxcode;
 114
 115         if (bundle == bpt_code) {
 116                 *sigp = SIGTRAP;
 117                 *codep = TRAP_BRKPT;
 118                 return 1;
 119         }
 120
 121         /* If it's a "raise" bundle, then "ill" must be in pipe X1. */
 122 #ifdef __tilegx__
 123         if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
 124                 return 0;
 125         if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
 126                 return 0;
 127         if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
 128                 return 0;
 129         if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
 130                 return 0;
 131 #else
 132         if (bundle & TILEPRO_BUNDLE_Y_ENCODING_MASK)
 133                 return 0;
 134         if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
 135                 return 0;
 136         if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
 137                 return 0;
 138         if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
 139                 return 0;
 140 #endif
 141
 142         /* Check that the magic distinguishers are set to mean "raise". */
 143         if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
 144                 return 0;
 145
 146         /* There must be an "addli zero, zero, VAL" in X0. */
 147         if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
 148                 return 0;
 149         if (get_Dest_X0(bundle) != TREG_ZERO)
 150                 return 0;
 151         if (get_SrcA_X0(bundle) != TREG_ZERO)
 152                 return 0;
 153
 154         /*
 155          * Validate the proposed signal number and si_code value.
 156          * Note that we embed these in the static instruction itself
 157          * so that we perturb the register state as little as possible
 158          * at the time of the actual fault; it's unlikely you'd ever
 159          * need to dynamically choose which kind of fault to raise
 160          * from user space.
 161          */
 162         sig = get_Imm16_X0(bundle) & 0x3f;
 163         switch (sig) {
 164         case SIGILL:
 165                 maxcode = NSIGILL;
 166                 break;
 167         case SIGFPE:
 168                 maxcode = NSIGFPE;
 169                 break;
 170         case SIGSEGV:
 171                 maxcode = NSIGSEGV;
 172                 break;
 173         case SIGBUS:
 174                 maxcode = NSIGBUS;
 175                 break;
 176         case SIGTRAP:
 177                 maxcode = NSIGTRAP;
 178                 break;
 179         default:
 180                 return 0;
 181         }
 182         code = (get_Imm16_X0(bundle) >> 6) & 0xf;
 183         if (code <= 0 || code > maxcode)
 184                 return 0;
 185
 186         /* Make it the requested signal. */
 187         *sigp = sig;
 188         *codep = code | __SI_FAULT;
 189         return 1;
 190 }
 191
 192 static const char *const int_name[] = {
 193         [INT_MEM_ERROR] = "Memory error",
 194         [INT_ILL] = "Illegal instruction",
 195         [INT_GPV] = "General protection violation",
 196         [INT_UDN_ACCESS] = "UDN access",
 197         [INT_IDN_ACCESS] = "IDN access",
 198 #if CHIP_HAS_SN()
 199         [INT_SN_ACCESS] = "SN access",
 200 #endif
 201         [INT_SWINT_3] = "Software interrupt 3",
 202         [INT_SWINT_2] = "Software interrupt 2",
 203         [INT_SWINT_0] = "Software interrupt 0",
 204         [INT_UNALIGN_DATA] = "Unaligned data",
 205         [INT_DOUBLE_FAULT] = "Double fault",
 206 #ifdef __tilegx__
 207         [INT_ILL_TRANS] = "Illegal virtual address",
 208 #endif
 209 };
 210
 211 static int do_bpt(struct pt_regs *regs)
 212 {
 213         unsigned long bundle, bcode, bpt;
 214
 215         bundle = *(unsigned long *)instruction_pointer(regs);
 216
 217         /*
 218          * bpt shoule be { bpt; nop }, which is 0x286a44ae51485000ULL.
 219          * we encode the unused least significant bits for other purpose.
 220          */
 221         bpt = bundle & ~((1ULL << 12) - 1);
 222         if (bpt != TILE_BPT_BUNDLE)
 223                 return 0;
 224
 225         bcode = bundle & ((1ULL << 12) - 1);
 226         /*
 227          * notify the kprobe handlers, if instruction is likely to
 228          * pertain to them.
 229          */
 230         switch (bcode) {
 231         /* breakpoint_insn */
 232         case 0:
 233                 notify_die(DIE_BREAK, "debug", regs, bundle,
 234                         INT_ILL, SIGTRAP);
 235                 break;
 236         /* compiled_bpt */
 237         case DIE_COMPILED_BPT:
 238                 notify_die(DIE_COMPILED_BPT, "debug", regs, bundle,
 239                         INT_ILL, SIGTRAP);
 240                 break;
 241         /* breakpoint2_insn */
 242         case DIE_SSTEPBP:
 243                 notify_die(DIE_SSTEPBP, "single_step", regs, bundle,
 244                         INT_ILL, SIGTRAP);
 245                 break;
 246         default:
 247                 return 0;
 248         }
 249
 250         return 1;
 251 }
 252
 253 void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 254                        unsigned long reason)
 255 {
 256         siginfo_t info = { 0 };
 257         int signo, code;
 258         unsigned long address = 0;
 259         tile_bundle_bits instr;
 260         int is_kernel = !user_mode(regs);
 261
 262         /* Handle breakpoints, etc. */
 263         if (is_kernel && fault_num == INT_ILL && do_bpt(regs))
 264                 return;
 265
 266         /* Re-enable interrupts, if they were previously enabled. */
 267         if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
 268                 local_irq_enable();
 269
 270         /*
 271          * If it hits in kernel mode and we can't fix it up, just exit the
 272          * current process and hope for the best.
 273          */
 274         if (is_kernel) {
 275                 const char *name;
 276                 char buf[100];
 277                 if (fixup_exception(regs))  /* ILL_TRANS or UNALIGN_DATA */
 278                         return;
 279                 if (fault_num >= 0 &&
 280                     fault_num < ARRAY_SIZE(int_name) &&
 281                     int_name[fault_num] != NULL)
 282                         name = int_name[fault_num];
 283                 else
 284                         name = "Unknown interrupt";
 285                 if (fault_num == INT_GPV)
 286                         snprintf(buf, sizeof(buf), "; GPV_REASON %#lx", reason);
 287 #ifdef __tilegx__
 288                 else if (fault_num == INT_ILL_TRANS)
 289                         snprintf(buf, sizeof(buf), "; address %#lx", reason);
 290 #endif
 291                 else
 292                         buf[0] = '\0';
 293                 pr_alert("Kernel took bad trap %d (%s) at PC %#lx%s\n",
 294                          fault_num, name, regs->pc, buf);
 295                 show_regs(regs);
 296                 do_exit(SIGKILL);  /* FIXME: implement i386 die() */
 297                 return;
 298         }
 299
 300         switch (fault_num) {
 301         case INT_MEM_ERROR:
 302                 signo = SIGBUS;
 303                 code = BUS_OBJERR;
 304                 break;
 305         case INT_ILL:
 306                 if (copy_from_user(&instr, (void __user *)regs->pc,
 307                                    sizeof(instr))) {
 308                         pr_err("Unreadable instruction for INT_ILL: %#lx\n",
 309                                regs->pc);
 310                         do_exit(SIGKILL);
 311                         return;
 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                         return;
 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                                 return;
 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                 return;
 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 kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 397 {
 398         _dump_stack(dummy, pc, lr, sp, r52);
 399         pr_emerg("Double fault: exiting\n");
 400         machine_halt();
 401 }