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 <linux/hardirq.h>
  24#include <linux/nmi.h>
  25#include <asm/stack.h>
  26#include <asm/traps.h>
  27#include <asm/setup.h>
  28
  29#include <arch/interrupts.h>
  30#include <arch/spr_def.h>
  31#include <arch/opcode.h>
  32
  33void __init trap_init(void)
  34{
  35        /* Nothing needed here since we link code at .intrpt */
  36}
  37
  38int unaligned_fixup = 1;
  39
  40static int __init setup_unaligned_fixup(char *str)
  41{
  42        /*
  43         * Say "=-1" to completely disable it.  If you just do "=0", we
  44         * will still parse the instruction, then fire a SIGBUS with
  45         * the correct address from inside the single_step code.
  46         */
  47        if (kstrtoint(str, 0, &unaligned_fixup) != 0)
  48                return 0;
  49
  50        pr_info("Fixups for unaligned data accesses are %s\n",
  51                unaligned_fixup >= 0 ?
  52                (unaligned_fixup ? "enabled" : "disabled") :
  53                "completely disabled");
  54        return 1;
  55}
  56__setup("unaligned_fixup=", setup_unaligned_fixup);
  57
  58#if CHIP_HAS_TILE_DMA()
  59
  60static int dma_disabled;
  61
  62static int __init nodma(char *str)
  63{
  64        pr_info("User-space DMA is disabled\n");
  65        dma_disabled = 1;
  66        return 1;
  67}
  68__setup("nodma", nodma);
  69
  70/* How to decode SPR_GPV_REASON */
  71#define IRET_ERROR (1U << 31)
  72#define MT_ERROR   (1U << 30)
  73#define MF_ERROR   (1U << 29)
  74#define SPR_INDEX  ((1U << 15) - 1)
  75#define SPR_MPL_SHIFT  9  /* starting bit position for MPL encoded in SPR */
  76
  77/*
  78 * See if this GPV is just to notify the kernel of SPR use and we can
  79 * retry the user instruction after adjusting some MPLs suitably.
  80 */
  81static int retry_gpv(unsigned int gpv_reason)
  82{
  83        int mpl;
  84
  85        if (gpv_reason & IRET_ERROR)
  86                return 0;
  87
  88        BUG_ON((gpv_reason & (MT_ERROR|MF_ERROR)) == 0);
  89        mpl = (gpv_reason & SPR_INDEX) >> SPR_MPL_SHIFT;
  90        if (mpl == INT_DMA_NOTIFY && !dma_disabled) {
  91                /* User is turning on DMA. Allow it and retry. */
  92                printk(KERN_DEBUG "Process %d/%s is now enabled for DMA\n",
  93                       current->pid, current->comm);
  94                BUG_ON(current->thread.tile_dma_state.enabled);
  95                current->thread.tile_dma_state.enabled = 1;
  96                grant_dma_mpls();
  97                return 1;
  98        }
  99
 100        return 0;
 101}
 102
 103#endif /* CHIP_HAS_TILE_DMA() */
 104
 105extern tile_bundle_bits bpt_code;
 106
 107asm(".pushsection .rodata.bpt_code,\"a\";"
 108    ".align 8;"
 109    "bpt_code: bpt;"
 110    ".size bpt_code,.-bpt_code;"
 111    ".popsection");
 112
 113static int special_ill(tile_bundle_bits bundle, int *sigp, int *codep)
 114{
 115        int sig, code, maxcode;
 116
 117        if (bundle == bpt_code) {
 118                *sigp = SIGTRAP;
 119                *codep = TRAP_BRKPT;
 120                return 1;
 121        }
 122
 123        /* If it's a "raise" bundle, then "ill" must be in pipe X1. */
 124#ifdef __tilegx__
 125        if ((bundle & TILEGX_BUNDLE_MODE_MASK) != 0)
 126                return 0;
 127        if (get_Opcode_X1(bundle) != RRR_0_OPCODE_X1)
 128                return 0;
 129        if (get_RRROpcodeExtension_X1(bundle) != UNARY_RRR_0_OPCODE_X1)
 130                return 0;
 131        if (get_UnaryOpcodeExtension_X1(bundle) != ILL_UNARY_OPCODE_X1)
 132                return 0;
 133#else
 134        if (bundle & TILEPRO_BUNDLE_Y_ENCODING_MASK)
 135                return 0;
 136        if (get_Opcode_X1(bundle) != SHUN_0_OPCODE_X1)
 137                return 0;
 138        if (get_UnShOpcodeExtension_X1(bundle) != UN_0_SHUN_0_OPCODE_X1)
 139                return 0;
 140        if (get_UnOpcodeExtension_X1(bundle) != ILL_UN_0_SHUN_0_OPCODE_X1)
 141                return 0;
 142#endif
 143
 144        /* Check that the magic distinguishers are set to mean "raise". */
 145        if (get_Dest_X1(bundle) != 29 || get_SrcA_X1(bundle) != 37)
 146                return 0;
 147
 148        /* There must be an "addli zero, zero, VAL" in X0. */
 149        if (get_Opcode_X0(bundle) != ADDLI_OPCODE_X0)
 150                return 0;
 151        if (get_Dest_X0(bundle) != TREG_ZERO)
 152                return 0;
 153        if (get_SrcA_X0(bundle) != TREG_ZERO)
 154                return 0;
 155
 156        /*
 157         * Validate the proposed signal number and si_code value.
 158         * Note that we embed these in the static instruction itself
 159         * so that we perturb the register state as little as possible
 160         * at the time of the actual fault; it's unlikely you'd ever
 161         * need to dynamically choose which kind of fault to raise
 162         * from user space.
 163         */
 164        sig = get_Imm16_X0(bundle) & 0x3f;
 165        switch (sig) {
 166        case SIGILL:
 167                maxcode = NSIGILL;
 168                break;
 169        case SIGFPE:
 170                maxcode = NSIGFPE;
 171                break;
 172        case SIGSEGV:
 173                maxcode = NSIGSEGV;
 174                break;
 175        case SIGBUS:
 176                maxcode = NSIGBUS;
 177                break;
 178        case SIGTRAP:
 179                maxcode = NSIGTRAP;
 180                break;
 181        default:
 182                return 0;
 183        }
 184        code = (get_Imm16_X0(bundle) >> 6) & 0xf;
 185        if (code <= 0 || code > maxcode)
 186                return 0;
 187
 188        /* Make it the requested signal. */
 189        *sigp = sig;
 190        *codep = code | __SI_FAULT;
 191        return 1;
 192}
 193
 194static const char *const int_name[] = {
 195        [INT_MEM_ERROR] = "Memory error",
 196        [INT_ILL] = "Illegal instruction",
 197        [INT_GPV] = "General protection violation",
 198        [INT_UDN_ACCESS] = "UDN access",
 199        [INT_IDN_ACCESS] = "IDN access",
 200#if CHIP_HAS_SN()
 201        [INT_SN_ACCESS] = "SN access",
 202#endif
 203        [INT_SWINT_3] = "Software interrupt 3",
 204        [INT_SWINT_2] = "Software interrupt 2",
 205        [INT_SWINT_0] = "Software interrupt 0",
 206        [INT_UNALIGN_DATA] = "Unaligned data",
 207        [INT_DOUBLE_FAULT] = "Double fault",
 208#ifdef __tilegx__
 209        [INT_ILL_TRANS] = "Illegal virtual address",
 210#endif
 211};
 212
 213static int do_bpt(struct pt_regs *regs)
 214{
 215        unsigned long bundle, bcode, bpt;
 216
 217        bundle = *(unsigned long *)instruction_pointer(regs);
 218
 219        /*
 220         * bpt shoule be { bpt; nop }, which is 0x286a44ae51485000ULL.
 221         * we encode the unused least significant bits for other purpose.
 222         */
 223        bpt = bundle & ~((1ULL << 12) - 1);
 224        if (bpt != TILE_BPT_BUNDLE)
 225                return 0;
 226
 227        bcode = bundle & ((1ULL << 12) - 1);
 228        /*
 229         * notify the kprobe handlers, if instruction is likely to
 230         * pertain to them.
 231         */
 232        switch (bcode) {
 233        /* breakpoint_insn */
 234        case 0:
 235                notify_die(DIE_BREAK, "debug", regs, bundle,
 236                        INT_ILL, SIGTRAP);
 237                break;
 238        /* compiled_bpt */
 239        case DIE_COMPILED_BPT:
 240                notify_die(DIE_COMPILED_BPT, "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
 255void __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        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                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 < 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                        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        }
 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
 395void do_nmi(struct pt_regs *regs, int fault_num, unsigned long reason)
 396{
 397        nmi_enter();
 398        switch (reason) {
 399#ifdef arch_trigger_cpumask_backtrace
 400        case TILE_NMI_DUMP_STACK:
 401                nmi_cpu_backtrace(regs);
 402                break;
 403#endif
 404        default:
 405                panic("Unexpected do_nmi type %ld", reason);
 406        }
 407        nmi_exit();
 408}
 409
 410/* Deprecated function currently only used here. */
 411extern void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52);
 412
 413void kernel_double_fault(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
 414{
 415        _dump_stack(dummy, pc, lr, sp, r52);
 416        pr_emerg("Double fault: exiting\n");
 417        machine_halt();
 418}
 419