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