1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * unaligned.c: Unaligned load/store trap handling with special
4 * cases for the kernel to do them more quickly.
5 *
6 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
7 * Copyright (C) 1996 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
8 */
9
10
11 #include <linux/kernel.h>
12 #include <linux/sched/signal.h>
13 #include <linux/mm.h>
14 #include <asm/ptrace.h>
15 #include <asm/processor.h>
16 #include <linux/uaccess.h>
17 #include <linux/smp.h>
18 #include <linux/perf_event.h>
19 #include <linux/extable.h>
20
21 #include <asm/setup.h>
22
23 #include "kernel.h"
24
25 enum direction {
26 load, /* ld, ldd, ldh, ldsh */
27 store, /* st, std, sth, stsh */
28 both, /* Swap, ldstub, etc. */
29 fpload,
30 fpstore,
31 invalid,
32 };
33
34 static inline enum direction decode_direction(unsigned int insn)
35 {
36 unsigned long tmp = (insn >> 21) & 1;
37
38 if(!tmp)
39 return load;
40 else {
41 if(((insn>>19)&0x3f) == 15)
42 return both;
43 else
44 return store;
45 }
46 }
47
48 /* 8 = double-word, 4 = word, 2 = half-word */
49 static inline int decode_access_size(unsigned int insn)
50 {
51 insn = (insn >> 19) & 3;
52
53 if(!insn)
54 return 4;
55 else if(insn == 3)
56 return 8;
57 else if(insn == 2)
58 return 2;
59 else {
60 printk("Impossible unaligned trap. insn=%08x\n", insn);
61 die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
62 return 4; /* just to keep gcc happy. */
63 }
64 }
65
66 /* 0x400000 = signed, 0 = unsigned */
67 static inline int decode_signedness(unsigned int insn)
68 {
69 return (insn & 0x400000);
70 }
71
72 static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
73 unsigned int rd)
74 {
75 if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
76 /* Wheee... */
77 __asm__ __volatile__("save %sp, -0x40, %sp\n\t"
78 "save %sp, -0x40, %sp\n\t"
79 "save %sp, -0x40, %sp\n\t"
80 "save %sp, -0x40, %sp\n\t"
81 "save %sp, -0x40, %sp\n\t"
82 "save %sp, -0x40, %sp\n\t"
83 "save %sp, -0x40, %sp\n\t"
84 "restore; restore; restore; restore;\n\t"
85 "restore; restore; restore;\n\t");
86 }
87 }
88
89 static inline int sign_extend_imm13(int imm)
90 {
91 return imm << 19 >> 19;
92 }
93
94 static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
95 {
96 struct reg_window32 *win;
97
98 if(reg < 16)
99 return (!reg ? 0 : regs->u_regs[reg]);
100
101 /* Ho hum, the slightly complicated case. */
102 win = (struct reg_window32 *) regs->u_regs[UREG_FP];
103 return win->locals[reg - 16]; /* yes, I know what this does... */
104 }
105
106 static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
107 {
108 struct reg_window32 __user *win;
109 unsigned long ret;
110
111 if (reg < 16)
112 return (!reg ? 0 : regs->u_regs[reg]);
113
114 /* Ho hum, the slightly complicated case. */
115 win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
116
117 if ((unsigned long)win & 3)
118 return -1;
119
120 if (get_user(ret, &win->locals[reg - 16]))
121 return -1;
122
123 return ret;
124 }
125
126 static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
127 {
128 struct reg_window32 *win;
129
130 if(reg < 16)
131 return ®s->u_regs[reg];
132 win = (struct reg_window32 *) regs->u_regs[UREG_FP];
133 return &win->locals[reg - 16];
134 }
135
136 static unsigned long compute_effective_address(struct pt_regs *regs,
137 unsigned int insn)
138 {
139 unsigned int rs1 = (insn >> 14) & 0x1f;
140 unsigned int rs2 = insn & 0x1f;
141 unsigned int rd = (insn >> 25) & 0x1f;
142
143 if(insn & 0x2000) {
144 maybe_flush_windows(rs1, 0, rd);
145 return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
146 } else {
147 maybe_flush_windows(rs1, rs2, rd);
148 return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
149 }
150 }
151
152 unsigned long safe_compute_effective_address(struct pt_regs *regs,
153 unsigned int insn)
154 {
155 unsigned int rs1 = (insn >> 14) & 0x1f;
156 unsigned int rs2 = insn & 0x1f;
157 unsigned int rd = (insn >> 25) & 0x1f;
158
159 if(insn & 0x2000) {
160 maybe_flush_windows(rs1, 0, rd);
161 return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
162 } else {
163 maybe_flush_windows(rs1, rs2, rd);
164 return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
165 }
166 }
167
168 /* This is just to make gcc think panic does return... */
169 static void unaligned_panic(char *str)
170 {
171 panic("%s", str);
172 }
173
174 /* una_asm.S */
175 extern int do_int_load(unsigned long *dest_reg, int size,
176 unsigned long *saddr, int is_signed);
177 extern int __do_int_store(unsigned long *dst_addr, int size,
178 unsigned long *src_val);
179
180 static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
181 struct pt_regs *regs)
182 {
183 unsigned long zero[2] = { 0, 0 };
184 unsigned long *src_val;
185
186 if (reg_num)
187 src_val = fetch_reg_addr(reg_num, regs);
188 else {
189 src_val = &zero[0];
190 if (size == 8)
191 zero[1] = fetch_reg(1, regs);
192 }
193 return __do_int_store(dst_addr, size, src_val);
194 }
195
196 extern void smp_capture(void);
197 extern void smp_release(void);
198
199 static inline void advance(struct pt_regs *regs)
200 {
201 regs->pc = regs->npc;
202 regs->npc += 4;
203 }
204
205 static inline int floating_point_load_or_store_p(unsigned int insn)
206 {
207 return (insn >> 24) & 1;
208 }
209
210 static inline int ok_for_kernel(unsigned int insn)
211 {
212 return !floating_point_load_or_store_p(insn);
213 }
214
215 static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
216 {
217 const struct exception_table_entry *entry;
218
219 entry = search_exception_tables(regs->pc);
220 if (!entry) {
221 unsigned long address = compute_effective_address(regs, insn);
222 if(address < PAGE_SIZE) {
223 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
224 } else
225 printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
226 printk(KERN_ALERT " at virtual address %08lx\n",address);
227 printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
228 (current->mm ? current->mm->context :
229 current->active_mm->context));
230 printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
231 (current->mm ? (unsigned long) current->mm->pgd :
232 (unsigned long) current->active_mm->pgd));
233 die_if_kernel("Oops", regs);
234 /* Not reached */
235 }
236 regs->pc = entry->fixup;
237 regs->npc = regs->pc + 4;
238 }
239
240 asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
241 {
242 enum direction dir = decode_direction(insn);
243 int size = decode_access_size(insn);
244
245 if(!ok_for_kernel(insn) || dir == both) {
246 printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
247 regs->pc);
248 unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
249 } else {
250 unsigned long addr = compute_effective_address(regs, insn);
251 int err;
252
253 perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
254 switch (dir) {
255 case load:
256 err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
257 regs),
258 size, (unsigned long *) addr,
259 decode_signedness(insn));
260 break;
261
262 case store:
263 err = do_int_store(((insn>>25)&0x1f), size,
264 (unsigned long *) addr, regs);
265 break;
266 default:
267 panic("Impossible kernel unaligned trap.");
268 /* Not reached... */
269 }
270 if (err)
271 kernel_mna_trap_fault(regs, insn);
272 else
273 advance(regs);
274 }
275 }
276
277 asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
278 {
279 send_sig_fault(SIGBUS, BUS_ADRALN,
280 (void __user *)safe_compute_effective_address(regs, insn),
281 current);
282 }
283
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