arch/nios2/kernel/misaligned.c

   1 /*
   2  *  linux/arch/nios2/kernel/misaligned.c
   3  *
   4  *  basic emulation for mis-aligned accesses on the NIOS II cpu
   5  *  modelled after the version for arm in arm/alignment.c
   6  *
   7  *  Brad Parker <brad@heeltoe.com>
   8  *  Copyright (C) 2010 Ambient Corporation
   9  *  Copyright (c) 2010 Altera Corporation, San Jose, California, USA.
  10  *  Copyright (c) 2010 Arrow Electronics, Inc.
  11  *
  12  * This file is subject to the terms and conditions of the GNU General
  13  * Public License.  See the file COPYING in the main directory of
  14  * this archive for more details.
  15  */
  16
  17 #include <linux/errno.h>
  18 #include <linux/string.h>
  19 #include <linux/proc_fs.h>
  20 #include <linux/init.h>
  21 #include <linux/sched.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/seq_file.h>
  24
  25 #include <asm/traps.h>
  26 #include <asm/unaligned.h>
  27
  28 /* instructions we emulate */
  29 #define INST_LDHU       0x0b
  30 #define INST_STH        0x0d
  31 #define INST_LDH        0x0f
  32 #define INST_STW        0x15
  33 #define INST_LDW        0x17
  34
  35 static unsigned long ma_user, ma_kern, ma_skipped, ma_half, ma_word;
  36
  37 static unsigned int ma_usermode;
  38 #define UM_WARN         0x01
  39 #define UM_FIXUP        0x02
  40 #define UM_SIGNAL       0x04
  41 #define KM_WARN         0x08
  42
  43 /* see arch/nios2/include/asm/ptrace.h */
  44 static u8 sys_stack_frame_reg_offset[] = {
  45         /* struct pt_regs */
  46         8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4, 5, 6, 7, 0,
  47         /* struct switch_stack */
  48         16, 17, 18, 19, 20, 21, 22, 23, 0, 0, 0, 0, 0, 0, 0, 0
  49 };
  50
  51 static int reg_offsets[32];
  52
  53 static inline u32 get_reg_val(struct pt_regs *fp, int reg)
  54 {
  55         u8 *p = ((u8 *)fp) + reg_offsets[reg];
  56
  57         return *(u32 *)p;
  58 }
  59
  60 static inline void put_reg_val(struct pt_regs *fp, int reg, u32 val)
  61 {
  62         u8 *p = ((u8 *)fp) + reg_offsets[reg];
  63         *(u32 *)p = val;
  64 }
  65
  66 /*
  67  * (mis)alignment handler
  68  */
  69 asmlinkage void handle_unaligned_c(struct pt_regs *fp, int cause)
  70 {
  71         u32 isn, addr, val;
  72         int in_kernel;
  73         u8 a, b, d0, d1, d2, d3;
  74         u16 imm16;
  75         unsigned int fault;
  76
  77         /* back up one instruction */
  78         fp->ea -= 4;
  79
  80         if (fixup_exception(fp)) {
  81                 ma_skipped++;
  82                 return;
  83         }
  84
  85         in_kernel = !user_mode(fp);
  86
  87         isn = *(unsigned long *)(fp->ea);
  88
  89         fault = 0;
  90
  91         /* do fixup if in kernel or mode turned on */
  92         if (in_kernel || (ma_usermode & UM_FIXUP)) {
  93                 /* decompose instruction */
  94                 a = (isn >> 27) & 0x1f;
  95                 b = (isn >> 22) & 0x1f;
  96                 imm16 = (isn >> 6) & 0xffff;
  97                 addr = get_reg_val(fp, a) + imm16;
  98
  99                 /* do fixup to saved registers */
 100                 switch (isn & 0x3f) {
 101                 case INST_LDHU:
 102                         fault |= __get_user(d0, (u8 *)(addr+0));
 103                         fault |= __get_user(d1, (u8 *)(addr+1));
 104                         val = (d1 << 8) | d0;
 105                         put_reg_val(fp, b, val);
 106                         ma_half++;
 107                         break;
 108                 case INST_STH:
 109                         val = get_reg_val(fp, b);
 110                         d1 = val >> 8;
 111                         d0 = val >> 0;
 112
 113                         pr_debug("sth: ra=%d (%08x) rb=%d (%08x), imm16 %04x addr %08x val %08x\n",
 114                                 a, get_reg_val(fp, a),
 115                                 b, get_reg_val(fp, b),
 116                                 imm16, addr, val);
 117
 118                         if (in_kernel) {
 119                                 *(u8 *)(addr+0) = d0;
 120                                 *(u8 *)(addr+1) = d1;
 121                         } else {
 122                                 fault |= __put_user(d0, (u8 *)(addr+0));
 123                                 fault |= __put_user(d1, (u8 *)(addr+1));
 124                         }
 125                         ma_half++;
 126                         break;
 127                 case INST_LDH:
 128                         fault |= __get_user(d0, (u8 *)(addr+0));
 129                         fault |= __get_user(d1, (u8 *)(addr+1));
 130                         val = (short)((d1 << 8) | d0);
 131                         put_reg_val(fp, b, val);
 132                         ma_half++;
 133                         break;
 134                 case INST_STW:
 135                         val = get_reg_val(fp, b);
 136                         d3 = val >> 24;
 137                         d2 = val >> 16;
 138                         d1 = val >> 8;
 139                         d0 = val >> 0;
 140                         if (in_kernel) {
 141                                 *(u8 *)(addr+0) = d0;
 142                                 *(u8 *)(addr+1) = d1;
 143                                 *(u8 *)(addr+2) = d2;
 144                                 *(u8 *)(addr+3) = d3;
 145                         } else {
 146                                 fault |= __put_user(d0, (u8 *)(addr+0));
 147                                 fault |= __put_user(d1, (u8 *)(addr+1));
 148                                 fault |= __put_user(d2, (u8 *)(addr+2));
 149                                 fault |= __put_user(d3, (u8 *)(addr+3));
 150                         }
 151                         ma_word++;
 152                         break;
 153                 case INST_LDW:
 154                         fault |= __get_user(d0, (u8 *)(addr+0));
 155                         fault |= __get_user(d1, (u8 *)(addr+1));
 156                         fault |= __get_user(d2, (u8 *)(addr+2));
 157                         fault |= __get_user(d3, (u8 *)(addr+3));
 158                         val = (d3 << 24) | (d2 << 16) | (d1 << 8) | d0;
 159                         put_reg_val(fp, b, val);
 160                         ma_word++;
 161                         break;
 162                 }
 163         }
 164
 165         addr = RDCTL(CTL_BADADDR);
 166         cause >>= 2;
 167
 168         if (fault) {
 169                 if (in_kernel) {
 170                         pr_err("fault during kernel misaligned fixup @ %#lx; addr 0x%08x; isn=0x%08x\n",
 171                                 fp->ea, (unsigned int)addr,
 172                                 (unsigned int)isn);
 173                 } else {
 174                         pr_err("fault during user misaligned fixup @ %#lx; isn=%08x addr=0x%08x sp=0x%08lx pid=%d\n",
 175                                 fp->ea,
 176                                 (unsigned int)isn, addr, fp->sp,
 177                                 current->pid);
 178
 179                         _exception(SIGSEGV, fp, SEGV_MAPERR, fp->ea);
 180                         return;
 181                 }
 182         }
 183
 184         /*
 185          * kernel mode -
 186          *  note exception and skip bad instruction (return)
 187          */
 188         if (in_kernel) {
 189                 ma_kern++;
 190                 fp->ea += 4;
 191
 192                 if (ma_usermode & KM_WARN) {
 193                         pr_err("kernel unaligned access @ %#lx; BADADDR 0x%08x; cause=%d, isn=0x%08x\n",
 194                                 fp->ea,
 195                                 (unsigned int)addr, cause,
 196                                 (unsigned int)isn);
 197                         /* show_regs(fp); */
 198                 }
 199
 200                 return;
 201         }
 202
 203         ma_user++;
 204
 205         /*
 206          * user mode -
 207          *  possibly warn,
 208          *  possibly send SIGBUS signal to process
 209          */
 210         if (ma_usermode & UM_WARN) {
 211                 pr_err("user unaligned access @ %#lx; isn=0x%08lx ea=0x%08lx ra=0x%08lx sp=0x%08lx\n",
 212                         (unsigned long)addr, (unsigned long)isn,
 213                         fp->ea, fp->ra, fp->sp);
 214         }
 215
 216         if (ma_usermode & UM_SIGNAL)
 217                 _exception(SIGBUS, fp, BUS_ADRALN, fp->ea);
 218         else
 219                 fp->ea += 4;    /* else advance */
 220 }
 221
 222 static void __init misaligned_calc_reg_offsets(void)
 223 {
 224         int i, r, offset;
 225
 226         /* pre-calc offsets of registers on sys call stack frame */
 227         offset = 0;
 228
 229         /* struct pt_regs */
 230         for (i = 0; i < 16; i++) {
 231                 r = sys_stack_frame_reg_offset[i];
 232                 reg_offsets[r] = offset;
 233                 offset += 4;
 234         }
 235
 236         /* struct switch_stack */
 237         offset = -sizeof(struct switch_stack);
 238         for (i = 16; i < 32; i++) {
 239                 r = sys_stack_frame_reg_offset[i];
 240                 reg_offsets[r] = offset;
 241                 offset += 4;
 242         }
 243 }
 244
 245
 246 static int __init misaligned_init(void)
 247 {
 248         /* default mode - silent fix */
 249         ma_usermode = UM_FIXUP | KM_WARN;
 250
 251         misaligned_calc_reg_offsets();
 252
 253         return 0;
 254 }
 255
 256 fs_initcall(misaligned_init);