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 Tim.yao@amlogic.com
  11  *
  12  */
  13
  14 #include <linux/types.h>
  15 #include <linux/perf_event.h>
  16 #include <linux/ptrace.h>
  17 #include <linux/uaccess.h>
  18 #include <asm/disasm.h>
  19
  20 #ifdef CONFIG_CPU_BIG_ENDIAN
  21 #define BE              1
  22 #define FIRST_BYTE_16   "swap %1, %1\n swape %1, %1\n"
  23 #define FIRST_BYTE_32   "swape %1, %1\n"
  24 #else
  25 #define BE              0
  26 #define FIRST_BYTE_16
  27 #define FIRST_BYTE_32
  28 #endif
  29
  30 #define __get8_unaligned_check(val, addr, err)          \
  31         __asm__(                                        \
  32         "1:     ldb.ab  %1, [%2, 1]\n"                  \
  33         "2:\n"                                          \
  34         "       .section .fixup,\"ax\"\n"               \
  35         "       .align  4\n"                            \
  36         "3:     mov     %0, 1\n"                        \
  37         "       j       2b\n"                           \
  38         "       .previous\n"                            \
  39         "       .section __ex_table,\"a\"\n"            \
  40         "       .align  4\n"                            \
  41         "       .long   1b, 3b\n"                       \
  42         "       .previous\n"                            \
  43         : "=r" (err), "=&r" (val), "=r" (addr)          \
  44         : "0" (err), "2" (addr))
  45
  46 #define get16_unaligned_check(val, addr)                \
  47         do {                                            \
  48                 unsigned int err = 0, v, a = addr;      \
  49                 __get8_unaligned_check(v, a, err);      \
  50                 val =  v << ((BE) ? 8 : 0);             \
  51                 __get8_unaligned_check(v, a, err);      \
  52                 val |= v << ((BE) ? 0 : 8);             \
  53                 if (err)                                \
  54                         goto fault;                     \
  55         } while (0)
  56
  57 #define get32_unaligned_check(val, addr)                \
  58         do {                                            \
  59                 unsigned int err = 0, v, a = addr;      \
  60                 __get8_unaligned_check(v, a, err);      \
  61                 val =  v << ((BE) ? 24 : 0);            \
  62                 __get8_unaligned_check(v, a, err);      \
  63                 val |= v << ((BE) ? 16 : 8);            \
  64                 __get8_unaligned_check(v, a, err);      \
  65                 val |= v << ((BE) ? 8 : 16);            \
  66                 __get8_unaligned_check(v, a, err);      \
  67                 val |= v << ((BE) ? 0 : 24);            \
  68                 if (err)                                \
  69                         goto fault;                     \
  70         } while (0)
  71
  72 #define put16_unaligned_check(val, addr)                \
  73         do {                                            \
  74                 unsigned int err = 0, v = val, a = addr;\
  75                                                         \
  76                 __asm__(                                \
  77                 FIRST_BYTE_16                           \
  78                 "1:     stb.ab  %1, [%2, 1]\n"          \
  79                 "       lsr %1, %1, 8\n"                \
  80                 "2:     stb     %1, [%2]\n"             \
  81                 "3:\n"                                  \
  82                 "       .section .fixup,\"ax\"\n"       \
  83                 "       .align  4\n"                    \
  84                 "4:     mov     %0, 1\n"                \
  85                 "       j       3b\n"                   \
  86                 "       .previous\n"                    \
  87                 "       .section __ex_table,\"a\"\n"    \
  88                 "       .align  4\n"                    \
  89                 "       .long   1b, 4b\n"               \
  90                 "       .long   2b, 4b\n"               \
  91                 "       .previous\n"                    \
  92                 : "=r" (err), "=&r" (v), "=&r" (a)      \
  93                 : "0" (err), "1" (v), "2" (a));         \
  94                                                         \
  95                 if (err)                                \
  96                         goto fault;                     \
  97         } while (0)
  98
  99 #define put32_unaligned_check(val, addr)                \
 100         do {                                            \
 101                 unsigned int err = 0, v = val, a = addr;\
 102                                                         \
 103                 __asm__(                                \
 104                 FIRST_BYTE_32                           \
 105                 "1:     stb.ab  %1, [%2, 1]\n"          \
 106                 "       lsr %1, %1, 8\n"                \
 107                 "2:     stb.ab  %1, [%2, 1]\n"          \
 108                 "       lsr %1, %1, 8\n"                \
 109                 "3:     stb.ab  %1, [%2, 1]\n"          \
 110                 "       lsr %1, %1, 8\n"                \
 111                 "4:     stb     %1, [%2]\n"             \
 112                 "5:\n"                                  \
 113                 "       .section .fixup,\"ax\"\n"       \
 114                 "       .align  4\n"                    \
 115                 "6:     mov     %0, 1\n"                \
 116                 "       j       5b\n"                   \
 117                 "       .previous\n"                    \
 118                 "       .section __ex_table,\"a\"\n"    \
 119                 "       .align  4\n"                    \
 120                 "       .long   1b, 6b\n"               \
 121                 "       .long   2b, 6b\n"               \
 122                 "       .long   3b, 6b\n"               \
 123                 "       .long   4b, 6b\n"               \
 124                 "       .previous\n"                    \
 125                 : "=r" (err), "=&r" (v), "=&r" (a)      \
 126                 : "0" (err), "1" (v), "2" (a));         \
 127                                                         \
 128                 if (err)                                \
 129                         goto fault;                     \
 130         } while (0)
 131
 132 /* sysctl hooks */
 133 int unaligned_enabled __read_mostly = 1;        /* Enabled by default */
 134 int no_unaligned_warning __read_mostly = 1;     /* Only 1 warning by default */
 135
 136 static void fixup_load(struct disasm_state *state, struct pt_regs *regs,
 137                         struct callee_regs *cregs)
 138 {
 139         int val;
 140
 141         /* register write back */
 142         if ((state->aa == 1) || (state->aa == 2)) {
 143                 set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs);
 144
 145                 if (state->aa == 2)
 146                         state->src2 = 0;
 147         }
 148
 149         if (state->zz == 0) {
 150                 get32_unaligned_check(val, state->src1 + state->src2);
 151         } else {
 152                 get16_unaligned_check(val, state->src1 + state->src2);
 153
 154                 if (state->x)
 155                         val = (val << 16) >> 16;
 156         }
 157
 158         if (state->pref == 0)
 159                 set_reg(state->dest, val, regs, cregs);
 160
 161         return;
 162
 163 fault:  state->fault = 1;
 164 }
 165
 166 static void fixup_store(struct disasm_state *state, struct pt_regs *regs,
 167                         struct callee_regs *cregs)
 168 {
 169         /* register write back */
 170         if ((state->aa == 1) || (state->aa == 2)) {
 171                 set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs);
 172
 173                 if (state->aa == 3)
 174                         state->src3 = 0;
 175         } else if (state->aa == 3) {
 176                 if (state->zz == 2) {
 177                         set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
 178                                 regs, cregs);
 179                 } else if (!state->zz) {
 180                         set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
 181                                 regs, cregs);
 182                 } else {
 183                         goto fault;
 184                 }
 185         }
 186
 187         /* write fix-up */
 188         if (!state->zz)
 189                 put32_unaligned_check(state->src1, state->src2 + state->src3);
 190         else
 191                 put16_unaligned_check(state->src1, state->src2 + state->src3);
 192
 193         return;
 194
 195 fault:  state->fault = 1;
 196 }
 197
 198 /*
 199  * Handle an unaligned access
 200  * Returns 0 if successfully handled, 1 if some error happened
 201  */
 202 int misaligned_fixup(unsigned long address, struct pt_regs *regs,
 203                      struct callee_regs *cregs)
 204 {
 205         struct disasm_state state;
 206         char buf[TASK_COMM_LEN];
 207
 208         /* handle user mode only and only if enabled by sysadmin */
 209         if (!user_mode(regs) || !unaligned_enabled)
 210                 return 1;
 211
 212         if (no_unaligned_warning) {
 213                 pr_warn_once("%s(%d) made unaligned access which was emulated"
 214                              " by kernel assist\n. This can degrade application"
 215                              " performance significantly\n. To enable further"
 216                              " logging of such instances, please \n"
 217                              " echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
 218                              get_task_comm(buf, current), task_pid_nr(current));
 219         } else {
 220                 /* Add rate limiting if it gets down to it */
 221                 pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
 222                         get_task_comm(buf, current), task_pid_nr(current),
 223                         address, regs->ret);
 224
 225         }
 226
 227         disasm_instr(regs->ret, &state, 1, regs, cregs);
 228
 229         if (state.fault)
 230                 goto fault;
 231
 232         /* ldb/stb should not have unaligned exception */
 233         if ((state.zz == 1) || (state.di))
 234                 goto fault;
 235
 236         if (!state.write)
 237                 fixup_load(&state, regs, cregs);
 238         else
 239                 fixup_store(&state, regs, cregs);
 240
 241         if (state.fault)
 242                 goto fault;
 243
 244         if (delay_mode(regs)) {
 245                 regs->ret = regs->bta;
 246                 regs->status32 &= ~STATUS_DE_MASK;
 247         } else {
 248                 regs->ret += state.instr_len;
 249
 250                 /* handle zero-overhead-loop */
 251                 if ((regs->ret == regs->lp_end) && (regs->lp_count)) {
 252                         regs->ret = regs->lp_start;
 253                         regs->lp_count--;
 254                 }
 255         }
 256
 257         perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, address);
 258         return 0;
 259
 260 fault:
 261         pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
 262                 state.words[0], address);
 263
 264         return 1;
 265 }