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Linux/arch/sparc/kernel/unaligned_32.c

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  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 &regs->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                        0, current);
282 }
283 

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