arch/arc/kernel/unaligned.c

   1 /*
   2  * Copyright (C) 2011-2012 Synopsys (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * vineetg : May 2011
   9  *  -Adapted (from .26 to .35)
  10  *  -original contribution by [email protected]
  11  *
  12  */
  13
  14 #include <linux/types.h>
  15 #include <linux/ptrace.h>
  16 #include <linux/uaccess.h>
  17 #include <asm/disasm.h>
  18
  19 #ifdef CONFIG_CPU_BIG_ENDIAN
  20 #define BE              1
  21 #define FIRST_BYTE_16   "swap %1, %1\n swape %1, %1\n"
  22 #define FIRST_BYTE_32   "swape %1, %1\n"
  23 #else
  24 #define BE              0
  25 #define FIRST_BYTE_16
  26 #define FIRST_BYTE_32
  27 #endif
  28
  29 #define __get8_unaligned_check(val, addr, err)          \
  30         __asm__(                                        \
  31         "1:     ldb.ab  %1, [%2, 1]\n"                  \
  32         "2:\n"                                          \
  33         "       .section .fixup,\"ax\"\n"               \
  34         "       .align  4\n"                            \
  35         "3:     mov     %0, 1\n"                        \
  36         "       b       2b\n"                           \
  37         "       .previous\n"                            \
  38         "       .section __ex_table,\"a\"\n"            \
  39         "       .align  4\n"                            \
  40         "       .long   1b, 3b\n"                       \
  41         "       .previous\n"                            \
  42         : "=r" (err), "=&r" (val), "=r" (addr)          \
  43         : "0" (err), "2" (addr))
  44
  45 #define get16_unaligned_check(val, addr)                \
  46         do {                                            \
  47                 unsigned int err = 0, v, a = addr;      \
  48                 __get8_unaligned_check(v, a, err);      \
  49                 val =  v << ((BE) ? 8 : 0);             \
  50                 __get8_unaligned_check(v, a, err);      \
  51                 val |= v << ((BE) ? 0 : 8);             \
  52                 if (err)                                \
  53                         goto fault;                     \
  54         } while (0)
  55
  56 #define get32_unaligned_check(val, addr)                \
  57         do {                                            \
  58                 unsigned int err = 0, v, a = addr;      \
  59                 __get8_unaligned_check(v, a, err);      \
  60                 val =  v << ((BE) ? 24 : 0);            \
  61                 __get8_unaligned_check(v, a, err);      \
  62                 val |= v << ((BE) ? 16 : 8);            \
  63                 __get8_unaligned_check(v, a, err);      \
  64                 val |= v << ((BE) ? 8 : 16);            \
  65                 __get8_unaligned_check(v, a, err);      \
  66                 val |= v << ((BE) ? 0 : 24);            \
  67                 if (err)                                \
  68                         goto fault;                     \
  69         } while (0)
  70
  71 #define put16_unaligned_check(val, addr)                \
  72         do {                                            \
  73                 unsigned int err = 0, v = val, a = addr;\
  74                                                         \
  75                 __asm__(                                \
  76                 FIRST_BYTE_16                           \
  77                 "1:     stb.ab  %1, [%2, 1]\n"          \
  78                 "       lsr %1, %1, 8\n"                \
  79                 "2:     stb     %1, [%2]\n"             \
  80                 "3:\n"                                  \
  81                 "       .section .fixup,\"ax\"\n"       \
  82                 "       .align  4\n"                    \
  83                 "4:     mov     %0, 1\n"                \
  84                 "       b       3b\n"                   \
  85                 "       .previous\n"                    \
  86                 "       .section __ex_table,\"a\"\n"    \
  87                 "       .align  4\n"                    \
  88                 "       .long   1b, 4b\n"               \
  89                 "       .long   2b, 4b\n"               \
  90                 "       .previous\n"                    \
  91                 : "=r" (err), "=&r" (v), "=&r" (a)      \
  92                 : "0" (err), "1" (v), "2" (a));         \
  93                                                         \
  94                 if (err)                                \
  95                         goto fault;                     \
  96         } while (0)
  97
  98 #define put32_unaligned_check(val, addr)                \
  99         do {                                            \
 100                 unsigned int err = 0, v = val, a = addr;\
 101                                                         \
 102                 __asm__(                                \
 103                 FIRST_BYTE_32                           \
 104                 "1:     stb.ab  %1, [%2, 1]\n"          \
 105                 "       lsr %1, %1, 8\n"                \
 106                 "2:     stb.ab  %1, [%2, 1]\n"          \
 107                 "       lsr %1, %1, 8\n"                \
 108                 "3:     stb.ab  %1, [%2, 1]\n"          \
 109                 "       lsr %1, %1, 8\n"                \
 110                 "4:     stb     %1, [%2]\n"             \
 111                 "5:\n"                                  \
 112                 "       .section .fixup,\"ax\"\n"       \
 113                 "       .align  4\n"                    \
 114                 "6:     mov     %0, 1\n"                \
 115                 "       b       5b\n"                   \
 116                 "       .previous\n"                    \
 117                 "       .section __ex_table,\"a\"\n"    \
 118                 "       .align  4\n"                    \
 119                 "       .long   1b, 6b\n"               \
 120                 "       .long   2b, 6b\n"               \
 121                 "       .long   3b, 6b\n"               \
 122                 "       .long   4b, 6b\n"               \
 123                 "       .previous\n"                    \
 124                 : "=r" (err), "=&r" (v), "=&r" (a)      \
 125                 : "0" (err), "1" (v), "2" (a));         \
 126                                                         \
 127                 if (err)                                \
 128                         goto fault;                     \
 129         } while (0)
 130
 131 /* sysctl hooks */
 132 int unaligned_enabled __read_mostly = 1;        /* Enabled by default */
 133 int no_unaligned_warning __read_mostly = 1;     /* Only 1 warning by default */
 134
 135 static void fixup_load(struct disasm_state *state, struct pt_regs *regs,
 136                         struct callee_regs *cregs)
 137 {
 138         int val;
 139
 140         /* register write back */
 141         if ((state->aa == 1) || (state->aa == 2)) {
 142                 set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs);
 143
 144                 if (state->aa == 2)
 145                         state->src2 = 0;
 146         }
 147
 148         if (state->zz == 0) {
 149                 get32_unaligned_check(val, state->src1 + state->src2);
 150         } else {
 151                 get16_unaligned_check(val, state->src1 + state->src2);
 152
 153                 if (state->x)
 154                         val = (val << 16) >> 16;
 155         }
 156
 157         if (state->pref == 0)
 158                 set_reg(state->dest, val, regs, cregs);
 159
 160         return;
 161
 162 fault:  state->fault = 1;
 163 }
 164
 165 static void fixup_store(struct disasm_state *state, struct pt_regs *regs,
 166                         struct callee_regs *cregs)
 167 {
 168         /* register write back */
 169         if ((state->aa == 1) || (state->aa == 2)) {
 170                 set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs);
 171
 172                 if (state->aa == 3)
 173                         state->src3 = 0;
 174         } else if (state->aa == 3) {
 175                 if (state->zz == 2) {
 176                         set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
 177                                 regs, cregs);
 178                 } else if (!state->zz) {
 179                         set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
 180                                 regs, cregs);
 181                 } else {
 182                         goto fault;
 183                 }
 184         }
 185
 186         /* write fix-up */
 187         if (!state->zz)
 188                 put32_unaligned_check(state->src1, state->src2 + state->src3);
 189         else
 190                 put16_unaligned_check(state->src1, state->src2 + state->src3);
 191
 192         return;
 193
 194 fault:  state->fault = 1;
 195 }
 196
 197 /*
 198  * Handle an unaligned access
 199  * Returns 0 if successfully handled, 1 if some error happened
 200  */
 201 int misaligned_fixup(unsigned long address, struct pt_regs *regs,
 202                      struct callee_regs *cregs)
 203 {
 204         struct disasm_state state;
 205         char buf[TASK_COMM_LEN];
 206
 207         /* handle user mode only and only if enabled by sysadmin */
 208         if (!user_mode(regs) || !unaligned_enabled)
 209                 return 1;
 210
 211         if (no_unaligned_warning) {
 212                 pr_warn_once("%s(%d) made unaligned access which was emulated"
 213                              " by kernel assist\n. This can degrade application"
 214                              " performance significantly\n. To enable further"
 215                              " logging of such instances, please \n"
 216                              " echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
 217                              get_task_comm(buf, current), task_pid_nr(current));
 218         } else {
 219                 /* Add rate limiting if it gets down to it */
 220                 pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
 221                         get_task_comm(buf, current), task_pid_nr(current),
 222                         address, regs->ret);
 223
 224         }
 225
 226         disasm_instr(regs->ret, &state, 1, regs, cregs);
 227
 228         if (state.fault)
 229                 goto fault;
 230
 231         /* ldb/stb should not have unaligned exception */
 232         if ((state.zz == 1) || (state.di))
 233                 goto fault;
 234
 235         if (!state.write)
 236                 fixup_load(&state, regs, cregs);
 237         else
 238                 fixup_store(&state, regs, cregs);
 239
 240         if (state.fault)
 241                 goto fault;
 242
 243         if (delay_mode(regs)) {
 244                 regs->ret = regs->bta;
 245                 regs->status32 &= ~STATUS_DE_MASK;
 246         } else {
 247                 regs->ret += state.instr_len;
 248
 249                 /* handle zero-overhead-loop */
 250                 if ((regs->ret == regs->lp_end) && (regs->lp_count)) {
 251                         regs->ret = regs->lp_start;
 252                         regs->lp_count--;
 253                 }
 254         }
 255
 256         return 0;
 257
 258 fault:
 259         pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
 260                 state.words[0], address);
 261
 262         return 1;
 263 }