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 int ma_usermode;
  36 #define UM_WARN         0x01
  37 #define UM_FIXUP        0x02
  38 #define UM_SIGNAL       0x04
  39 #define KM_WARN         0x08
  40
  41 /* see arch/nios2/include/asm/ptrace.h */
  42 static u8 sys_stack_frame_reg_offset[] = {
  43         /* struct pt_regs */
  44         8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4, 5, 6, 7, 0,
  45         /* struct switch_stack */
  46         16, 17, 18, 19, 20, 21, 22, 23, 0, 0, 0, 0, 0, 0, 0, 0
  47 };
  48
  49 static int reg_offsets[32];
  50
  51 static inline u32 get_reg_val(struct pt_regs *fp, int reg)
  52 {
  53         u8 *p = ((u8 *)fp) + reg_offsets[reg];
  54         return *(u32 *)p;
  55 }
  56
  57 static inline void put_reg_val(struct pt_regs *fp, int reg, u32 val)
  58 {
  59         u8 *p = ((u8 *)fp) + reg_offsets[reg];
  60         *(u32 *)p = val;
  61 }
  62
  63 /*
  64  * (mis)alignment handler
  65  */
  66 asmlinkage void handle_unaligned_c(struct pt_regs *fp, int cause)
  67 {
  68         u32 isn, addr, val;
  69         int in_kernel;
  70         u8 a, b, d0, d1, d2, d3;
  71         s16 imm16;
  72         unsigned int fault;
  73
  74         /* back up one instruction */
  75         fp->ea -= 4;
  76
  77         if (fixup_exception(fp)) {
  78                 return;
  79         }
  80
  81         in_kernel = !user_mode(fp);
  82
  83         isn = *(unsigned long *)(fp->ea);
  84
  85         fault = 0;
  86
  87         /* do fixup if in kernel or mode turned on */
  88         if (in_kernel || (ma_usermode & UM_FIXUP)) {
  89                 /* decompose instruction */
  90                 a = (isn >> 27) & 0x1f;
  91                 b = (isn >> 22) & 0x1f;
  92                 imm16 = (isn >> 6) & 0xffff;
  93                 addr = get_reg_val(fp, a) + imm16;
  94
  95                 /* do fixup to saved registers */
  96                 switch (isn & 0x3f) {
  97                 case INST_LDHU:
  98                         fault |= __get_user(d0, (u8 *)(addr+0));
  99                         fault |= __get_user(d1, (u8 *)(addr+1));
 100                         val = (d1 << 8) | d0;
 101                         put_reg_val(fp, b, val);
 102                         break;
 103                 case INST_STH:
 104                         val = get_reg_val(fp, b);
 105                         d1 = val >> 8;
 106                         d0 = val >> 0;
 107                         if (in_kernel) {
 108                                 *(u8 *)(addr+0) = d0;
 109                                 *(u8 *)(addr+1) = d1;
 110                         } else {
 111                                 fault |= __put_user(d0, (u8 *)(addr+0));
 112                                 fault |= __put_user(d1, (u8 *)(addr+1));
 113                         }
 114                         break;
 115                 case INST_LDH:
 116                         fault |= __get_user(d0, (u8 *)(addr+0));
 117                         fault |= __get_user(d1, (u8 *)(addr+1));
 118                         val = (short)((d1 << 8) | d0);
 119                         put_reg_val(fp, b, val);
 120                         break;
 121                 case INST_STW:
 122                         val = get_reg_val(fp, b);
 123                         d3 = val >> 24;
 124                         d2 = val >> 16;
 125                         d1 = val >> 8;
 126                         d0 = val >> 0;
 127                         if (in_kernel) {
 128                                 *(u8 *)(addr+0) = d0;
 129                                 *(u8 *)(addr+1) = d1;
 130                                 *(u8 *)(addr+2) = d2;
 131                                 *(u8 *)(addr+3) = d3;
 132                         } else {
 133                                 fault |= __put_user(d0, (u8 *)(addr+0));
 134                                 fault |= __put_user(d1, (u8 *)(addr+1));
 135                                 fault |= __put_user(d2, (u8 *)(addr+2));
 136                                 fault |= __put_user(d3, (u8 *)(addr+3));
 137                         }
 138                         break;
 139                 case INST_LDW:
 140                         fault |= __get_user(d0, (u8 *)(addr+0));
 141                         fault |= __get_user(d1, (u8 *)(addr+1));
 142                         fault |= __get_user(d2, (u8 *)(addr+2));
 143                         fault |= __get_user(d3, (u8 *)(addr+3));
 144                         val = (d3 << 24) | (d2 << 16) | (d1 << 8) | d0;
 145                         put_reg_val(fp, b, val);
 146                         break;
 147                 }
 148         }
 149
 150         addr = RDCTL(CTL_BADADDR);
 151         cause >>= 2;
 152
 153         if (fault) {
 154                 if (in_kernel) {
 155                         pr_err("fault during kernel misaligned fixup @ %#lx; addr 0x%08x; isn=0x%08x\n",
 156                                 fp->ea, (unsigned int)addr,
 157                                 (unsigned int)isn);
 158                 } else {
 159                         pr_err("fault during user misaligned fixup @ %#lx; isn=%08x addr=0x%08x sp=0x%08lx pid=%d\n",
 160                                 fp->ea,
 161                                 (unsigned int)isn, addr, fp->sp,
 162                                 current->pid);
 163
 164                         _exception(SIGSEGV, fp, SEGV_MAPERR, fp->ea);
 165                         return;
 166                 }
 167         }
 168
 169         /*
 170          * kernel mode -
 171          *  note exception and skip bad instruction (return)
 172          */
 173         if (in_kernel) {
 174                 fp->ea += 4;
 175
 176                 if (ma_usermode & KM_WARN) {
 177                         pr_err("kernel unaligned access @ %#lx; BADADDR 0x%08x; cause=%d, isn=0x%08x\n",
 178                                 fp->ea,
 179                                 (unsigned int)addr, cause,
 180                                 (unsigned int)isn);
 181                         /* show_regs(fp); */
 182                 }
 183
 184                 return;
 185         }
 186
 187         /*
 188          * user mode -
 189          *  possibly warn,
 190          *  possibly send SIGBUS signal to process
 191          */
 192         if (ma_usermode & UM_WARN) {
 193                 pr_err("user unaligned access @ %#lx; isn=0x%08lx ea=0x%08lx ra=0x%08lx sp=0x%08lx\n",
 194                         (unsigned long)addr, (unsigned long)isn,
 195                         fp->ea, fp->ra, fp->sp);
 196         }
 197
 198         if (ma_usermode & UM_SIGNAL)
 199                 _exception(SIGBUS, fp, BUS_ADRALN, fp->ea);
 200         else
 201                 fp->ea += 4;    /* else advance */
 202 }
 203
 204 static void __init misaligned_calc_reg_offsets(void)
 205 {
 206         int i, r, offset;
 207
 208         /* pre-calc offsets of registers on sys call stack frame */
 209         offset = 0;
 210
 211         /* struct pt_regs */
 212         for (i = 0; i < 16; i++) {
 213                 r = sys_stack_frame_reg_offset[i];
 214                 reg_offsets[r] = offset;
 215                 offset += 4;
 216         }
 217
 218         /* struct switch_stack */
 219         offset = -sizeof(struct switch_stack);
 220         for (i = 16; i < 32; i++) {
 221                 r = sys_stack_frame_reg_offset[i];
 222                 reg_offsets[r] = offset;
 223                 offset += 4;
 224         }
 225 }
 226
 227
 228 static int __init misaligned_init(void)
 229 {
 230         /* default mode - silent fix */
 231         ma_usermode = UM_FIXUP | KM_WARN;
 232
 233         misaligned_calc_reg_offsets();
 234
 235         return 0;
 236 }
 237
 238 fs_initcall(misaligned_init);