arch/arc/kernel/unaligned.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011-2012 Synopsys (www.synopsys.com)
   4  *
   5  * vineetg : May 2011
   6  *  -Adapted (from .26 to .35)
   7  *  -original contribution by [email protected]
   8  */
   9
  10 #include <linux/types.h>
  11 #include <linux/perf_event.h>
  12 #include <linux/ptrace.h>
  13 #include <linux/uaccess.h>
  14 #include <asm/disasm.h>
  15
  16 #ifdef CONFIG_CPU_BIG_ENDIAN
  17 #define BE              1
  18 #define FIRST_BYTE_16   "swap %1, %1\n swape %1, %1\n"
  19 #define FIRST_BYTE_32   "swape %1, %1\n"
  20 #else
  21 #define BE              0
  22 #define FIRST_BYTE_16
  23 #define FIRST_BYTE_32
  24 #endif
  25
  26 #define __get8_unaligned_check(val, addr, err)          \
  27         __asm__(                                        \
  28         "1:     ldb.ab  %1, [%2, 1]\n"                  \
  29         "2:\n"                                          \
  30         "       .section .fixup,\"ax\"\n"               \
  31         "       .align  4\n"                            \
  32         "3:     mov     %0, 1\n"                        \
  33         "       j       2b\n"                           \
  34         "       .previous\n"                            \
  35         "       .section __ex_table,\"a\"\n"            \
  36         "       .align  4\n"                            \
  37         "       .long   1b, 3b\n"                       \
  38         "       .previous\n"                            \
  39         : "=r" (err), "=&r" (val), "=r" (addr)          \
  40         : "0" (err), "2" (addr))
  41
  42 #define get16_unaligned_check(val, addr)                \
  43         do {                                            \
  44                 unsigned int err = 0, v, a = addr;      \
  45                 __get8_unaligned_check(v, a, err);      \
  46                 val =  v << ((BE) ? 8 : 0);             \
  47                 __get8_unaligned_check(v, a, err);      \
  48                 val |= v << ((BE) ? 0 : 8);             \
  49                 if (err)                                \
  50                         goto fault;                     \
  51         } while (0)
  52
  53 #define get32_unaligned_check(val, addr)                \
  54         do {                                            \
  55                 unsigned int err = 0, v, a = addr;      \
  56                 __get8_unaligned_check(v, a, err);      \
  57                 val =  v << ((BE) ? 24 : 0);            \
  58                 __get8_unaligned_check(v, a, err);      \
  59                 val |= v << ((BE) ? 16 : 8);            \
  60                 __get8_unaligned_check(v, a, err);      \
  61                 val |= v << ((BE) ? 8 : 16);            \
  62                 __get8_unaligned_check(v, a, err);      \
  63                 val |= v << ((BE) ? 0 : 24);            \
  64                 if (err)                                \
  65                         goto fault;                     \
  66         } while (0)
  67
  68 #define put16_unaligned_check(val, addr)                \
  69         do {                                            \
  70                 unsigned int err = 0, v = val, a = addr;\
  71                                                         \
  72                 __asm__(                                \
  73                 FIRST_BYTE_16                           \
  74                 "1:     stb.ab  %1, [%2, 1]\n"          \
  75                 "       lsr %1, %1, 8\n"                \
  76                 "2:     stb     %1, [%2]\n"             \
  77                 "3:\n"                                  \
  78                 "       .section .fixup,\"ax\"\n"       \
  79                 "       .align  4\n"                    \
  80                 "4:     mov     %0, 1\n"                \
  81                 "       j       3b\n"                   \
  82                 "       .previous\n"                    \
  83                 "       .section __ex_table,\"a\"\n"    \
  84                 "       .align  4\n"                    \
  85                 "       .long   1b, 4b\n"               \
  86                 "       .long   2b, 4b\n"               \
  87                 "       .previous\n"                    \
  88                 : "=r" (err), "=&r" (v), "=&r" (a)      \
  89                 : "0" (err), "1" (v), "2" (a));         \
  90                                                         \
  91                 if (err)                                \
  92                         goto fault;                     \
  93         } while (0)
  94
  95 #define put32_unaligned_check(val, addr)                \
  96         do {                                            \
  97                 unsigned int err = 0, v = val, a = addr;\
  98                                                         \
  99                 __asm__(                                \
 100                 FIRST_BYTE_32                           \
 101                 "1:     stb.ab  %1, [%2, 1]\n"          \
 102                 "       lsr %1, %1, 8\n"                \
 103                 "2:     stb.ab  %1, [%2, 1]\n"          \
 104                 "       lsr %1, %1, 8\n"                \
 105                 "3:     stb.ab  %1, [%2, 1]\n"          \
 106                 "       lsr %1, %1, 8\n"                \
 107                 "4:     stb     %1, [%2]\n"             \
 108                 "5:\n"                                  \
 109                 "       .section .fixup,\"ax\"\n"       \
 110                 "       .align  4\n"                    \
 111                 "6:     mov     %0, 1\n"                \
 112                 "       j       5b\n"                   \
 113                 "       .previous\n"                    \
 114                 "       .section __ex_table,\"a\"\n"    \
 115                 "       .align  4\n"                    \
 116                 "       .long   1b, 6b\n"               \
 117                 "       .long   2b, 6b\n"               \
 118                 "       .long   3b, 6b\n"               \
 119                 "       .long   4b, 6b\n"               \
 120                 "       .previous\n"                    \
 121                 : "=r" (err), "=&r" (v), "=&r" (a)      \
 122                 : "0" (err), "1" (v), "2" (a));         \
 123                                                         \
 124                 if (err)                                \
 125                         goto fault;                     \
 126         } while (0)
 127
 128 /* sysctl hooks */
 129 int unaligned_enabled __read_mostly = 1;        /* Enabled by default */
 130 int no_unaligned_warning __read_mostly = 1;     /* Only 1 warning by default */
 131
 132 static void fixup_load(struct disasm_state *state, struct pt_regs *regs,
 133                         struct callee_regs *cregs)
 134 {
 135         int val;
 136
 137         /* register write back */
 138         if ((state->aa == 1) || (state->aa == 2)) {
 139                 set_reg(state->wb_reg, state->src1 + state->src2, regs, cregs);
 140
 141                 if (state->aa == 2)
 142                         state->src2 = 0;
 143         }
 144
 145         if (state->zz == 0) {
 146                 get32_unaligned_check(val, state->src1 + state->src2);
 147         } else {
 148                 get16_unaligned_check(val, state->src1 + state->src2);
 149
 150                 if (state->x)
 151                         val = (val << 16) >> 16;
 152         }
 153
 154         if (state->pref == 0)
 155                 set_reg(state->dest, val, regs, cregs);
 156
 157         return;
 158
 159 fault:  state->fault = 1;
 160 }
 161
 162 static void fixup_store(struct disasm_state *state, struct pt_regs *regs,
 163                         struct callee_regs *cregs)
 164 {
 165         /* register write back */
 166         if ((state->aa == 1) || (state->aa == 2)) {
 167                 set_reg(state->wb_reg, state->src2 + state->src3, regs, cregs);
 168
 169                 if (state->aa == 3)
 170                         state->src3 = 0;
 171         } else if (state->aa == 3) {
 172                 if (state->zz == 2) {
 173                         set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
 174                                 regs, cregs);
 175                 } else if (!state->zz) {
 176                         set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
 177                                 regs, cregs);
 178                 } else {
 179                         goto fault;
 180                 }
 181         }
 182
 183         /* write fix-up */
 184         if (!state->zz)
 185                 put32_unaligned_check(state->src1, state->src2 + state->src3);
 186         else
 187                 put16_unaligned_check(state->src1, state->src2 + state->src3);
 188
 189         return;
 190
 191 fault:  state->fault = 1;
 192 }
 193
 194 /*
 195  * Handle an unaligned access
 196  * Returns 0 if successfully handled, 1 if some error happened
 197  */
 198 int misaligned_fixup(unsigned long address, struct pt_regs *regs,
 199                      struct callee_regs *cregs)
 200 {
 201         struct disasm_state state;
 202         char buf[TASK_COMM_LEN];
 203
 204         /* handle user mode only and only if enabled by sysadmin */
 205         if (!user_mode(regs) || !unaligned_enabled)
 206                 return 1;
 207
 208         if (no_unaligned_warning) {
 209                 pr_warn_once("%s(%d) made unaligned access which was emulated"
 210                              " by kernel assist\n. This can degrade application"
 211                              " performance significantly\n. To enable further"
 212                              " logging of such instances, please \n"
 213                              " echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
 214                              get_task_comm(buf, current), task_pid_nr(current));
 215         } else {
 216                 /* Add rate limiting if it gets down to it */
 217                 pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
 218                         get_task_comm(buf, current), task_pid_nr(current),
 219                         address, regs->ret);
 220
 221         }
 222
 223         disasm_instr(regs->ret, &state, 1, regs, cregs);
 224
 225         if (state.fault)
 226                 goto fault;
 227
 228         /* ldb/stb should not have unaligned exception */
 229         if ((state.zz == 1) || (state.di))
 230                 goto fault;
 231
 232         if (!state.write)
 233                 fixup_load(&state, regs, cregs);
 234         else
 235                 fixup_store(&state, regs, cregs);
 236
 237         if (state.fault)
 238                 goto fault;
 239
 240         /* clear any remanants of delay slot */
 241         if (delay_mode(regs)) {
 242                 regs->ret = regs->bta & ~1U;
 243                 regs->status32 &= ~STATUS_DE_MASK;
 244         } else {
 245                 regs->ret += state.instr_len;
 246
 247                 /* handle zero-overhead-loop */
 248                 if ((regs->ret == regs->lp_end) && (regs->lp_count)) {
 249                         regs->ret = regs->lp_start;
 250                         regs->lp_count--;
 251                 }
 252         }
 253
 254         perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, address);
 255         return 0;
 256
 257 fault:
 258         pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
 259                 state.words[0], address);
 260
 261         return 1;
 262 }