LXR linux/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
  31void __init trap_init(void)
  32{
  33        /* Nothing needed here since we link code at .intrpt */
  34}
  35
  36int unaligned_fixup = 1;
  37
  38static 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
  59static int dma_disabled;
  60
  61static 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 */
  80static 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
 104extern tile_bundle_bits bpt_code;
 105
 106asm(".pushsection .rodata.bpt_code,\"a\";"
 107    ".align 8;"
 108    "bpt_code: bpt;"
 109    ".size bpt_code,.-bpt_code;"
 110    ".popsection");
 111
 112static 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
 193static 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
 212static 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
 254void __kprobes do_trap(struct pt_regs *regs, int fault_num,
 255                       unsigned long reason)
 256{
 257        siginfo_t info = { 0 };
 258        int signo, code;
 259        unsigned long address = 0;
 260        tile_bundle_bits instr;
 261        int is_kernel = !user_mode(regs);
 262
 263        /* Handle breakpoints, etc. */
 264        if (is_kernel && fault_num == INT_ILL && do_bpt(regs))
 265                return;
 266
 267        /* Re-enable interrupts, if they were previously enabled. */
 268        if (!(regs->flags & PT_FLAGS_DISABLE_IRQ))
 269                local_irq_enable();
 270
 271        /*
 272         * If it hits in kernel mode and we can't fix it up, just exit the
 273         * current process and hope for the best.
 274         */
 275        if (is_kernel) {
 276                const char *name;
 277                char buf[100];
 278                if (fixup_exception(regs))  /* ILL_TRANS or UNALIGN_DATA */
 279                        return;
 280                if (fault_num >= 0 &&
 281                    fault_num < sizeof(int_name)/sizeof(int_name[0]) &&
 282                    int_name[fault_num] != NULL)
 283                        name = int_name[fault_num];
 284                else
 285                        name = "Unknown interrupt";
 286                if (fault_num == INT_GPV)
 287                        snprintf(buf, sizeof(buf), "; GPV_REASON %#lx", reason);
 288#ifdef __tilegx__
 289                else if (fault_num == INT_ILL_TRANS)
 290                        snprintf(buf, sizeof(buf), "; address %#lx", reason);
 291#endif
 292                else
 293                        buf[0] = '\0';
 294                pr_alert("Kernel took bad trap %d (%s) at PC %#lx%s\n",
 295                         fault_num, name, regs->pc, buf);
 296                show_regs(regs);
 297                do_exit(SIGKILL);  /* FIXME: implement i386 die() */
 298                return;
 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:"
 310                               " %#lx\n", regs->pc);
 311                        do_exit(SIGKILL);
 312                        return;
 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                return;
 385        }
 386
 387        info.si_signo = signo;
 388        info.si_code = code;
 389        info.si_addr = (void __user *)address;
 390        if (signo == SIGILL)
 391                info.si_trapno = fault_num;
 392        if (signo != SIGTRAP)
 393                trace_unhandled_signal("trap", regs, address, signo);
 394        force_sig_info(signo, &info, current);
 395}
 396
 397void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 398{
 399        _dump_stack(dummy, pc, lr, sp, r52);
 400        pr_emerg("Double fault: exiting\n");
 401        machine_halt();
 402}
 403