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/module.h>
  19 #include <linux/reboot.h>
  20 #include <linux/uaccess.h>
  21 #include <linux/ptrace.h>
  22 #include <asm/opcode-tile.h>
  23 #include <asm/opcode_constants.h>
  24 #include <asm/stack.h>
  25 #include <asm/traps.h>
  26
  27 #include <arch/interrupts.h>
  28 #include <arch/spr_def.h>
  29
  30 void __init trap_init(void)
  31 {
  32         /* Nothing needed here since we link code at .intrpt1 */
  33 }
  34
  35 int unaligned_fixup = 1;
  36
  37 static int __init setup_unaligned_fixup(char *str)
  38 {
  39         /*
  40          * Say "=-1" to completely disable it.  If you just do "=0", we
  41          * will still parse the instruction, then fire a SIGBUS with
  42          * the correct address from inside the single_step code.
  43          */
  44         long val;
  45         if (strict_strtol(str, 0, &val) != 0)
  46                 return 0;
  47         unaligned_fixup = val;
  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 #ifdef __tilegx__
 104 #define bundle_bits tilegx_bundle_bits
 105 #else
 106 #define bundle_bits tile_bundle_bits
 107 #endif
 108
 109 extern bundle_bits bpt_code;
 110
 111 asm(".pushsection .rodata.bpt_code,\"a\";"
 112     ".align 8;"
 113     "bpt_code: bpt;"
 114     ".size bpt_code,.-bpt_code;"
 115     ".popsection");
 116
 117 static int special_ill(bundle_bits bundle, int *sigp, int *codep)
 118 {
 119         int sig, code, maxcode;
 120
 121         if (bundle == bpt_code) {
 122                 *sigp = SIGTRAP;
 123                 *codep = TRAP_BRKPT;
 124                 return 1;
 125         }
 126
 127         /* If it's a "raise" bundle, then "ill" must be in pipe X1. */
 128 #ifdef __tilegx__
 129         if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
 130                 return 0;
 131         if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
 132                 return 0;
 133         if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
 134                 return 0;
 135         if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
 136                 return 0;
 137 #else
 138         if (bundle & TILE_BUNDLE_Y_ENCODING_MASK)
 139                 return 0;
 140         if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
 141                 return 0;
 142         if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
 143                 return 0;
 144         if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
 145                 return 0;
 146 #endif
 147
 148         /* Check that the magic distinguishers are set to mean "raise". */
 149         if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
 150                 return 0;
 151
 152         /* There must be an "addli zero, zero, VAL" in X0. */
 153         if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
 154                 return 0;
 155         if (get_Dest_X0(bundle) != TREG_ZERO)
 156                 return 0;
 157         if (get_SrcA_X0(bundle) != TREG_ZERO)
 158                 return 0;
 159
 160         /*
 161          * Validate the proposed signal number and si_code value.
 162          * Note that we embed these in the static instruction itself
 163          * so that we perturb the register state as little as possible
 164          * at the time of the actual fault; it's unlikely you'd ever
 165          * need to dynamically choose which kind of fault to raise
 166          * from user space.
 167          */
 168         sig = get_Imm16_X0(bundle) & 0x3f;
 169         switch (sig) {
 170         case SIGILL:
 171                 maxcode = NSIGILL;
 172                 break;
 173         case SIGFPE:
 174                 maxcode = NSIGFPE;
 175                 break;
 176         case SIGSEGV:
 177                 maxcode = NSIGSEGV;
 178                 break;
 179         case SIGBUS:
 180                 maxcode = NSIGBUS;
 181                 break;
 182         case SIGTRAP:
 183                 maxcode = NSIGTRAP;
 184                 break;
 185         default:
 186                 return 0;
 187         }
 188         code = (get_Imm16_X0(bundle) >> 6) & 0xf;
 189         if (code <= 0 || code > maxcode)
 190                 return 0;
 191
 192         /* Make it the requested signal. */
 193         *sigp = sig;
 194         *codep = code | __SI_FAULT;
 195         return 1;
 196 }
 197
 198 void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 199                        unsigned long reason)
 200 {
 201         siginfo_t info = { 0 };
 202         int signo, code;
 203         unsigned long address;
 204         bundle_bits instr;
 205
 206         /* Re-enable interrupts. */
 207         local_irq_enable();
 208
 209         /*
 210          * If it hits in kernel mode and we can't fix it up, just exit the
 211          * current process and hope for the best.
 212          */
 213         if (!user_mode(regs)) {
 214                 if (fixup_exception(regs))  /* only UNALIGN_DATA in practice */
 215                         return;
 216                 pr_alert("Kernel took bad trap %d at PC %#lx\n",
 217                        fault_num, regs->pc);
 218                 if (fault_num == INT_GPV)
 219                         pr_alert("GPV_REASON is %#lx\n", reason);
 220                 show_regs(regs);
 221                 do_exit(SIGKILL);  /* FIXME: implement i386 die() */
 222                 return;
 223         }
 224
 225         switch (fault_num) {
 226         case INT_ILL:
 227                 if (copy_from_user(&instr, (void __user *)regs->pc,
 228                                    sizeof(instr))) {
 229                         pr_err("Unreadable instruction for INT_ILL:"
 230                                " %#lx\n", regs->pc);
 231                         do_exit(SIGKILL);
 232                         return;
 233                 }
 234                 if (!special_ill(instr, &signo, &code)) {
 235                         signo = SIGILL;
 236                         code = ILL_ILLOPC;
 237                 }
 238                 address = regs->pc;
 239                 break;
 240         case INT_GPV:
 241 #if CHIP_HAS_TILE_DMA()
 242                 if (retry_gpv(reason))
 243                         return;
 244 #endif
 245                 /*FALLTHROUGH*/
 246         case INT_UDN_ACCESS:
 247         case INT_IDN_ACCESS:
 248 #if CHIP_HAS_SN()
 249         case INT_SN_ACCESS:
 250 #endif
 251                 signo = SIGILL;
 252                 code = ILL_PRVREG;
 253                 address = regs->pc;
 254                 break;
 255         case INT_SWINT_3:
 256         case INT_SWINT_2:
 257         case INT_SWINT_0:
 258                 signo = SIGILL;
 259                 code = ILL_ILLTRP;
 260                 address = regs->pc;
 261                 break;
 262         case INT_UNALIGN_DATA:
 263 #ifndef __tilegx__  /* Emulated support for single step debugging */
 264                 if (unaligned_fixup >= 0) {
 265                         struct single_step_state *state =
 266                                 current_thread_info()->step_state;
 267                         if (!state ||
 268                             (void __user *)(regs->pc) != state->buffer) {
 269                                 single_step_once(regs);
 270                                 return;
 271                         }
 272                 }
 273 #endif
 274                 signo = SIGBUS;
 275                 code = BUS_ADRALN;
 276                 address = 0;
 277                 break;
 278         case INT_DOUBLE_FAULT:
 279                 /*
 280                  * For double fault, "reason" is actually passed as
 281                  * SYSTEM_SAVE_K_2, the hypervisor's double-fault info, so
 282                  * we can provide the original fault number rather than
 283                  * the uninteresting "INT_DOUBLE_FAULT" so the user can
 284                  * learn what actually struck while PL0 ICS was set.
 285                  */
 286                 fault_num = reason;
 287                 signo = SIGILL;
 288                 code = ILL_DBLFLT;
 289                 address = regs->pc;
 290                 break;
 291 #ifdef __tilegx__
 292         case INT_ILL_TRANS:
 293                 signo = SIGSEGV;
 294                 code = SEGV_MAPERR;
 295                 if (reason & SPR_ILL_TRANS_REASON__I_STREAM_VA_RMASK)
 296                         address = regs->pc;
 297                 else
 298                         address = 0;  /* FIXME: GX: single-step for address */
 299                 break;
 300 #endif
 301         default:
 302                 panic("Unexpected do_trap interrupt number %d", fault_num);
 303                 return;
 304         }
 305
 306         info.si_signo = signo;
 307         info.si_code = code;
 308         info.si_addr = (void __user *)address;
 309         if (signo == SIGILL)
 310                 info.si_trapno = fault_num;
 311         force_sig_info(signo, &info, current);
 312 }
 313
 314 void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 315 {
 316         _dump_stack(dummy, pc, lr, sp, r52);
 317         pr_emerg("Double fault: exiting\n");
 318         machine_halt();
 319 }