linux/arch/sparc/kernel/unaligned.c
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   1/*
   2 * unaligned.c: Unaligned load/store trap handling with special
   3 *              cases for the kernel to do them more quickly.
   4 *
   5 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
   6 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
   7 */
   8
   9
  10#include <linux/kernel.h>
  11#include <linux/sched.h>
  12#include <linux/mm.h>
  13#include <linux/module.h>
  14#include <asm/ptrace.h>
  15#include <asm/processor.h>
  16#include <asm/system.h>
  17#include <asm/uaccess.h>
  18#include <linux/smp.h>
  19#include <linux/smp_lock.h>
  20
  21/* #define DEBUG_MNA */
  22
  23enum direction {
  24        load,    /* ld, ldd, ldh, ldsh */
  25        store,   /* st, std, sth, stsh */
  26        both,    /* Swap, ldstub, etc. */
  27        fpload,
  28        fpstore,
  29        invalid,
  30};
  31
  32#ifdef DEBUG_MNA
  33static char *dirstrings[] = {
  34  "load", "store", "both", "fpload", "fpstore", "invalid"
  35};
  36#endif
  37
  38static inline enum direction decode_direction(unsigned int insn)
  39{
  40        unsigned long tmp = (insn >> 21) & 1;
  41
  42        if(!tmp)
  43                return load;
  44        else {
  45                if(((insn>>19)&0x3f) == 15)
  46                        return both;
  47                else
  48                        return store;
  49        }
  50}
  51
  52/* 8 = double-word, 4 = word, 2 = half-word */
  53static inline int decode_access_size(unsigned int insn)
  54{
  55        insn = (insn >> 19) & 3;
  56
  57        if(!insn)
  58                return 4;
  59        else if(insn == 3)
  60                return 8;
  61        else if(insn == 2)
  62                return 2;
  63        else {
  64                printk("Impossible unaligned trap. insn=%08x\n", insn);
  65                die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
  66                return 4; /* just to keep gcc happy. */
  67        }
  68}
  69
  70/* 0x400000 = signed, 0 = unsigned */
  71static inline int decode_signedness(unsigned int insn)
  72{
  73        return (insn & 0x400000);
  74}
  75
  76static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
  77                                       unsigned int rd)
  78{
  79        if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
  80                /* Wheee... */
  81                __asm__ __volatile__("save %sp, -0x40, %sp\n\t"
  82                                     "save %sp, -0x40, %sp\n\t"
  83                                     "save %sp, -0x40, %sp\n\t"
  84                                     "save %sp, -0x40, %sp\n\t"
  85                                     "save %sp, -0x40, %sp\n\t"
  86                                     "save %sp, -0x40, %sp\n\t"
  87                                     "save %sp, -0x40, %sp\n\t"
  88                                     "restore; restore; restore; restore;\n\t"
  89                                     "restore; restore; restore;\n\t");
  90        }
  91}
  92
  93static inline int sign_extend_imm13(int imm)
  94{
  95        return imm << 19 >> 19;
  96}
  97
  98static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
  99{
 100        struct reg_window *win;
 101
 102        if(reg < 16)
 103                return (!reg ? 0 : regs->u_regs[reg]);
 104
 105        /* Ho hum, the slightly complicated case. */
 106        win = (struct reg_window *) regs->u_regs[UREG_FP];
 107        return win->locals[reg - 16]; /* yes, I know what this does... */
 108}
 109
 110static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
 111{
 112        struct reg_window __user *win;
 113        unsigned long ret;
 114
 115        if (reg < 16)
 116                return (!reg ? 0 : regs->u_regs[reg]);
 117
 118        /* Ho hum, the slightly complicated case. */
 119        win = (struct reg_window __user *) regs->u_regs[UREG_FP];
 120
 121        if ((unsigned long)win & 3)
 122                return -1;
 123
 124        if (get_user(ret, &win->locals[reg - 16]))
 125                return -1;
 126
 127        return ret;
 128}
 129
 130static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
 131{
 132        struct reg_window *win;
 133
 134        if(reg < 16)
 135                return &regs->u_regs[reg];
 136        win = (struct reg_window *) regs->u_regs[UREG_FP];
 137        return &win->locals[reg - 16];
 138}
 139
 140static unsigned long compute_effective_address(struct pt_regs *regs,
 141                                               unsigned int insn)
 142{
 143        unsigned int rs1 = (insn >> 14) & 0x1f;
 144        unsigned int rs2 = insn & 0x1f;
 145        unsigned int rd = (insn >> 25) & 0x1f;
 146
 147        if(insn & 0x2000) {
 148                maybe_flush_windows(rs1, 0, rd);
 149                return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
 150        } else {
 151                maybe_flush_windows(rs1, rs2, rd);
 152                return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
 153        }
 154}
 155
 156unsigned long safe_compute_effective_address(struct pt_regs *regs,
 157                                             unsigned int insn)
 158{
 159        unsigned int rs1 = (insn >> 14) & 0x1f;
 160        unsigned int rs2 = insn & 0x1f;
 161        unsigned int rd = (insn >> 25) & 0x1f;
 162
 163        if(insn & 0x2000) {
 164                maybe_flush_windows(rs1, 0, rd);
 165                return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
 166        } else {
 167                maybe_flush_windows(rs1, rs2, rd);
 168                return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
 169        }
 170}
 171
 172/* This is just to make gcc think panic does return... */
 173static void unaligned_panic(char *str)
 174{
 175        panic(str);
 176}
 177
 178/* una_asm.S */
 179extern int do_int_load(unsigned long *dest_reg, int size,
 180                       unsigned long *saddr, int is_signed);
 181extern int __do_int_store(unsigned long *dst_addr, int size,
 182                          unsigned long *src_val);
 183
 184static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
 185                        struct pt_regs *regs)
 186{
 187        unsigned long zero[2] = { 0, 0 };
 188        unsigned long *src_val;
 189
 190        if (reg_num)
 191                src_val = fetch_reg_addr(reg_num, regs);
 192        else {
 193                src_val = &zero[0];
 194                if (size == 8)
 195                        zero[1] = fetch_reg(1, regs);
 196        }
 197        return __do_int_store(dst_addr, size, src_val);
 198}
 199
 200extern void smp_capture(void);
 201extern void smp_release(void);
 202
 203static inline void advance(struct pt_regs *regs)
 204{
 205        regs->pc   = regs->npc;
 206        regs->npc += 4;
 207}
 208
 209static inline int floating_point_load_or_store_p(unsigned int insn)
 210{
 211        return (insn >> 24) & 1;
 212}
 213
 214static inline int ok_for_kernel(unsigned int insn)
 215{
 216        return !floating_point_load_or_store_p(insn);
 217}
 218
 219static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
 220{
 221        unsigned long g2 = regs->u_regs [UREG_G2];
 222        unsigned long fixup = search_extables_range(regs->pc, &g2);
 223
 224        if (!fixup) {
 225                unsigned long address = compute_effective_address(regs, insn);
 226                if(address < PAGE_SIZE) {
 227                        printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
 228                } else
 229                        printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
 230                printk(KERN_ALERT " at virtual address %08lx\n",address);
 231                printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
 232                        (current->mm ? current->mm->context :
 233                        current->active_mm->context));
 234                printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
 235                        (current->mm ? (unsigned long) current->mm->pgd :
 236                        (unsigned long) current->active_mm->pgd));
 237                die_if_kernel("Oops", regs);
 238                /* Not reached */
 239        }
 240        regs->pc = fixup;
 241        regs->npc = regs->pc + 4;
 242        regs->u_regs [UREG_G2] = g2;
 243}
 244
 245asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
 246{
 247        enum direction dir = decode_direction(insn);
 248        int size = decode_access_size(insn);
 249
 250        if(!ok_for_kernel(insn) || dir == both) {
 251                printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
 252                       regs->pc);
 253                unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
 254        } else {
 255                unsigned long addr = compute_effective_address(regs, insn);
 256                int err;
 257
 258#ifdef DEBUG_MNA
 259                printk("KMNA: pc=%08lx [dir=%s addr=%08lx size=%d] retpc[%08lx]\n",
 260                       regs->pc, dirstrings[dir], addr, size, regs->u_regs[UREG_RETPC]);
 261#endif
 262                switch (dir) {
 263                case load:
 264                        err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
 265                                                         regs),
 266                                          size, (unsigned long *) addr,
 267                                          decode_signedness(insn));
 268                        break;
 269
 270                case store:
 271                        err = do_int_store(((insn>>25)&0x1f), size,
 272                                           (unsigned long *) addr, regs);
 273                        break;
 274                default:
 275                        panic("Impossible kernel unaligned trap.");
 276                        /* Not reached... */
 277                }
 278                if (err)
 279                        kernel_mna_trap_fault(regs, insn);
 280                else
 281                        advance(regs);
 282        }
 283}
 284
 285static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
 286                              enum direction dir)
 287{
 288        unsigned int reg;
 289        int check = (dir == load) ? VERIFY_READ : VERIFY_WRITE;
 290        int size = ((insn >> 19) & 3) == 3 ? 8 : 4;
 291
 292        if ((regs->pc | regs->npc) & 3)
 293                return 0;
 294
 295        /* Must access_ok() in all the necessary places. */
 296#define WINREG_ADDR(regnum) \
 297        ((void __user *)(((unsigned long *)regs->u_regs[UREG_FP])+(regnum)))
 298
 299        reg = (insn >> 25) & 0x1f;
 300        if (reg >= 16) {
 301                if (!access_ok(check, WINREG_ADDR(reg - 16), size))
 302                        return -EFAULT;
 303        }
 304        reg = (insn >> 14) & 0x1f;
 305        if (reg >= 16) {
 306                if (!access_ok(check, WINREG_ADDR(reg - 16), size))
 307                        return -EFAULT;
 308        }
 309        if (!(insn & 0x2000)) {
 310                reg = (insn & 0x1f);
 311                if (reg >= 16) {
 312                        if (!access_ok(check, WINREG_ADDR(reg - 16), size))
 313                                return -EFAULT;
 314                }
 315        }
 316#undef WINREG_ADDR
 317        return 0;
 318}
 319
 320static void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
 321{
 322        siginfo_t info;
 323
 324        info.si_signo = SIGBUS;
 325        info.si_errno = 0;
 326        info.si_code = BUS_ADRALN;
 327        info.si_addr = (void __user *)safe_compute_effective_address(regs, insn);
 328        info.si_trapno = 0;
 329        send_sig_info(SIGBUS, &info, current);
 330}
 331
 332asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
 333{
 334        enum direction dir;
 335
 336        lock_kernel();
 337        if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
 338           (((insn >> 30) & 3) != 3))
 339                goto kill_user;
 340        dir = decode_direction(insn);
 341        if(!ok_for_user(regs, insn, dir)) {
 342                goto kill_user;
 343        } else {
 344                int err, size = decode_access_size(insn);
 345                unsigned long addr;
 346
 347                if(floating_point_load_or_store_p(insn)) {
 348                        printk("User FPU load/store unaligned unsupported.\n");
 349                        goto kill_user;
 350                }
 351
 352                addr = compute_effective_address(regs, insn);
 353                switch(dir) {
 354                case load:
 355                        err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
 356                                                         regs),
 357                                          size, (unsigned long *) addr,
 358                                          decode_signedness(insn));
 359                        break;
 360
 361                case store:
 362                        err = do_int_store(((insn>>25)&0x1f), size,
 363                                           (unsigned long *) addr, regs);
 364                        break;
 365
 366                case both:
 367                        /*
 368                         * This was supported in 2.4. However, we question
 369                         * the value of SWAP instruction across word boundaries.
 370                         */
 371                        printk("Unaligned SWAP unsupported.\n");
 372                        err = -EFAULT;
 373                        break;
 374
 375                default:
 376                        unaligned_panic("Impossible user unaligned trap.");
 377                        goto out;
 378                }
 379                if (err)
 380                        goto kill_user;
 381                else
 382                        advance(regs);
 383                goto out;
 384        }
 385
 386kill_user:
 387        user_mna_trap_fault(regs, insn);
 388out:
 389        unlock_kernel();
 390}
 391