xref: /openbmc/linux/arch/nios2/kernel/misaligned.c (revision 3fb39c48)
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 
get_reg_val(struct pt_regs * fp,int reg)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 
put_reg_val(struct pt_regs * fp,int reg,u32 val)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  */
handle_unaligned_c(struct pt_regs * fp,int cause)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 
misaligned_calc_reg_offsets(void)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 
misaligned_init(void)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