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);
239
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