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unaligned_32.c
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1 /*
2  * unaligned.c: Unaligned load/store trap handling with special
3  * cases for the kernel to do them more quickly.
4  *
5  * Copyright (C) 1996 David S. Miller ([email protected])
6  * Copyright (C) 1996 Jakub Jelinek ([email protected])
7  */
8 
9 
10 #include <linux/kernel.h>
11 #include <linux/sched.h>
12 #include <linux/mm.h>
13 #include <asm/ptrace.h>
14 #include <asm/processor.h>
15 #include <asm/uaccess.h>
16 #include <linux/smp.h>
17 #include <linux/perf_event.h>
18 
19 enum direction {
20  load, /* ld, ldd, ldh, ldsh */
21  store, /* st, std, sth, stsh */
22  both, /* Swap, ldstub, etc. */
23  fpload,
24  fpstore,
25  invalid,
26 };
27 
28 static inline enum direction decode_direction(unsigned int insn)
29 {
30  unsigned long tmp = (insn >> 21) & 1;
31 
32  if(!tmp)
33  return load;
34  else {
35  if(((insn>>19)&0x3f) == 15)
36  return both;
37  else
38  return store;
39  }
40 }
41 
42 /* 8 = double-word, 4 = word, 2 = half-word */
43 static inline int decode_access_size(unsigned int insn)
44 {
45  insn = (insn >> 19) & 3;
46 
47  if(!insn)
48  return 4;
49  else if(insn == 3)
50  return 8;
51  else if(insn == 2)
52  return 2;
53  else {
54  printk("Impossible unaligned trap. insn=%08x\n", insn);
55  die_if_kernel("Byte sized unaligned access?!?!", current->thread.kregs);
56  return 4; /* just to keep gcc happy. */
57  }
58 }
59 
60 /* 0x400000 = signed, 0 = unsigned */
61 static inline int decode_signedness(unsigned int insn)
62 {
63  return (insn & 0x400000);
64 }
65 
66 static inline void maybe_flush_windows(unsigned int rs1, unsigned int rs2,
67  unsigned int rd)
68 {
69  if(rs2 >= 16 || rs1 >= 16 || rd >= 16) {
70  /* Wheee... */
71  __asm__ __volatile__("save %sp, -0x40, %sp\n\t"
72  "save %sp, -0x40, %sp\n\t"
73  "save %sp, -0x40, %sp\n\t"
74  "save %sp, -0x40, %sp\n\t"
75  "save %sp, -0x40, %sp\n\t"
76  "save %sp, -0x40, %sp\n\t"
77  "save %sp, -0x40, %sp\n\t"
78  "restore; restore; restore; restore;\n\t"
79  "restore; restore; restore;\n\t");
80  }
81 }
82 
83 static inline int sign_extend_imm13(int imm)
84 {
85  return imm << 19 >> 19;
86 }
87 
88 static inline unsigned long fetch_reg(unsigned int reg, struct pt_regs *regs)
89 {
90  struct reg_window32 *win;
91 
92  if(reg < 16)
93  return (!reg ? 0 : regs->u_regs[reg]);
94 
95  /* Ho hum, the slightly complicated case. */
96  win = (struct reg_window32 *) regs->u_regs[UREG_FP];
97  return win->locals[reg - 16]; /* yes, I know what this does... */
98 }
99 
100 static inline unsigned long safe_fetch_reg(unsigned int reg, struct pt_regs *regs)
101 {
102  struct reg_window32 __user *win;
103  unsigned long ret;
104 
105  if (reg < 16)
106  return (!reg ? 0 : regs->u_regs[reg]);
107 
108  /* Ho hum, the slightly complicated case. */
109  win = (struct reg_window32 __user *) regs->u_regs[UREG_FP];
110 
111  if ((unsigned long)win & 3)
112  return -1;
113 
114  if (get_user(ret, &win->locals[reg - 16]))
115  return -1;
116 
117  return ret;
118 }
119 
120 static inline unsigned long *fetch_reg_addr(unsigned int reg, struct pt_regs *regs)
121 {
122  struct reg_window32 *win;
123 
124  if(reg < 16)
125  return &regs->u_regs[reg];
126  win = (struct reg_window32 *) regs->u_regs[UREG_FP];
127  return &win->locals[reg - 16];
128 }
129 
130 static unsigned long compute_effective_address(struct pt_regs *regs,
131  unsigned int insn)
132 {
133  unsigned int rs1 = (insn >> 14) & 0x1f;
134  unsigned int rs2 = insn & 0x1f;
135  unsigned int rd = (insn >> 25) & 0x1f;
136 
137  if(insn & 0x2000) {
138  maybe_flush_windows(rs1, 0, rd);
139  return (fetch_reg(rs1, regs) + sign_extend_imm13(insn));
140  } else {
141  maybe_flush_windows(rs1, rs2, rd);
142  return (fetch_reg(rs1, regs) + fetch_reg(rs2, regs));
143  }
144 }
145 
146 unsigned long safe_compute_effective_address(struct pt_regs *regs,
147  unsigned int insn)
148 {
149  unsigned int rs1 = (insn >> 14) & 0x1f;
150  unsigned int rs2 = insn & 0x1f;
151  unsigned int rd = (insn >> 25) & 0x1f;
152 
153  if(insn & 0x2000) {
154  maybe_flush_windows(rs1, 0, rd);
155  return (safe_fetch_reg(rs1, regs) + sign_extend_imm13(insn));
156  } else {
157  maybe_flush_windows(rs1, rs2, rd);
158  return (safe_fetch_reg(rs1, regs) + safe_fetch_reg(rs2, regs));
159  }
160 }
161 
162 /* This is just to make gcc think panic does return... */
163 static void unaligned_panic(char *str)
164 {
165  panic(str);
166 }
167 
168 /* una_asm.S */
169 extern int do_int_load(unsigned long *dest_reg, int size,
170  unsigned long *saddr, int is_signed);
171 extern int __do_int_store(unsigned long *dst_addr, int size,
172  unsigned long *src_val);
173 
174 static int do_int_store(int reg_num, int size, unsigned long *dst_addr,
175  struct pt_regs *regs)
176 {
177  unsigned long zero[2] = { 0, 0 };
178  unsigned long *src_val;
179 
180  if (reg_num)
181  src_val = fetch_reg_addr(reg_num, regs);
182  else {
183  src_val = &zero[0];
184  if (size == 8)
185  zero[1] = fetch_reg(1, regs);
186  }
187  return __do_int_store(dst_addr, size, src_val);
188 }
189 
190 extern void smp_capture(void);
191 extern void smp_release(void);
192 
193 static inline void advance(struct pt_regs *regs)
194 {
195  regs->pc = regs->npc;
196  regs->npc += 4;
197 }
198 
199 static inline int floating_point_load_or_store_p(unsigned int insn)
200 {
201  return (insn >> 24) & 1;
202 }
203 
204 static inline int ok_for_kernel(unsigned int insn)
205 {
206  return !floating_point_load_or_store_p(insn);
207 }
208 
209 static void kernel_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
210 {
211  unsigned long g2 = regs->u_regs [UREG_G2];
212  unsigned long fixup = search_extables_range(regs->pc, &g2);
213 
214  if (!fixup) {
215  unsigned long address = compute_effective_address(regs, insn);
216  if(address < PAGE_SIZE) {
217  printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference in mna handler");
218  } else
219  printk(KERN_ALERT "Unable to handle kernel paging request in mna handler");
220  printk(KERN_ALERT " at virtual address %08lx\n",address);
221  printk(KERN_ALERT "current->{mm,active_mm}->context = %08lx\n",
222  (current->mm ? current->mm->context :
223  current->active_mm->context));
224  printk(KERN_ALERT "current->{mm,active_mm}->pgd = %08lx\n",
225  (current->mm ? (unsigned long) current->mm->pgd :
226  (unsigned long) current->active_mm->pgd));
227  die_if_kernel("Oops", regs);
228  /* Not reached */
229  }
230  regs->pc = fixup;
231  regs->npc = regs->pc + 4;
232  regs->u_regs [UREG_G2] = g2;
233 }
234 
235 asmlinkage void kernel_unaligned_trap(struct pt_regs *regs, unsigned int insn)
236 {
237  enum direction dir = decode_direction(insn);
238  int size = decode_access_size(insn);
239 
240  if(!ok_for_kernel(insn) || dir == both) {
241  printk("Unsupported unaligned load/store trap for kernel at <%08lx>.\n",
242  regs->pc);
243  unaligned_panic("Wheee. Kernel does fpu/atomic unaligned load/store.");
244  } else {
245  unsigned long addr = compute_effective_address(regs, insn);
246  int err;
247 
248  perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
249  switch (dir) {
250  case load:
251  err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
252  regs),
253  size, (unsigned long *) addr,
254  decode_signedness(insn));
255  break;
256 
257  case store:
258  err = do_int_store(((insn>>25)&0x1f), size,
259  (unsigned long *) addr, regs);
260  break;
261  default:
262  panic("Impossible kernel unaligned trap.");
263  /* Not reached... */
264  }
265  if (err)
266  kernel_mna_trap_fault(regs, insn);
267  else
268  advance(regs);
269  }
270 }
271 
272 static inline int ok_for_user(struct pt_regs *regs, unsigned int insn,
273  enum direction dir)
274 {
275  unsigned int reg;
276  int check = (dir == load) ? VERIFY_READ : VERIFY_WRITE;
277  int size = ((insn >> 19) & 3) == 3 ? 8 : 4;
278 
279  if ((regs->pc | regs->npc) & 3)
280  return 0;
281 
282  /* Must access_ok() in all the necessary places. */
283 #define WINREG_ADDR(regnum) \
284  ((void __user *)(((unsigned long *)regs->u_regs[UREG_FP])+(regnum)))
285 
286  reg = (insn >> 25) & 0x1f;
287  if (reg >= 16) {
288  if (!access_ok(check, WINREG_ADDR(reg - 16), size))
289  return -EFAULT;
290  }
291  reg = (insn >> 14) & 0x1f;
292  if (reg >= 16) {
293  if (!access_ok(check, WINREG_ADDR(reg - 16), size))
294  return -EFAULT;
295  }
296  if (!(insn & 0x2000)) {
297  reg = (insn & 0x1f);
298  if (reg >= 16) {
299  if (!access_ok(check, WINREG_ADDR(reg - 16), size))
300  return -EFAULT;
301  }
302  }
303 #undef WINREG_ADDR
304  return 0;
305 }
306 
307 static void user_mna_trap_fault(struct pt_regs *regs, unsigned int insn)
308 {
309  siginfo_t info;
310 
311  info.si_signo = SIGBUS;
312  info.si_errno = 0;
313  info.si_code = BUS_ADRALN;
314  info.si_addr = (void __user *)safe_compute_effective_address(regs, insn);
315  info.si_trapno = 0;
316  send_sig_info(SIGBUS, &info, current);
317 }
318 
319 asmlinkage void user_unaligned_trap(struct pt_regs *regs, unsigned int insn)
320 {
321  enum direction dir;
322 
323  if(!(current->thread.flags & SPARC_FLAG_UNALIGNED) ||
324  (((insn >> 30) & 3) != 3))
325  goto kill_user;
326  dir = decode_direction(insn);
327  if(!ok_for_user(regs, insn, dir)) {
328  goto kill_user;
329  } else {
330  int err, size = decode_access_size(insn);
331  unsigned long addr;
332 
333  if(floating_point_load_or_store_p(insn)) {
334  printk("User FPU load/store unaligned unsupported.\n");
335  goto kill_user;
336  }
337 
338  addr = compute_effective_address(regs, insn);
339  perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
340  switch(dir) {
341  case load:
342  err = do_int_load(fetch_reg_addr(((insn>>25)&0x1f),
343  regs),
344  size, (unsigned long *) addr,
345  decode_signedness(insn));
346  break;
347 
348  case store:
349  err = do_int_store(((insn>>25)&0x1f), size,
350  (unsigned long *) addr, regs);
351  break;
352 
353  case both:
354  /*
355  * This was supported in 2.4. However, we question
356  * the value of SWAP instruction across word boundaries.
357  */
358  printk("Unaligned SWAP unsupported.\n");
359  err = -EFAULT;
360  break;
361 
362  default:
363  unaligned_panic("Impossible user unaligned trap.");
364  goto out;
365  }
366  if (err)
367  goto kill_user;
368  else
369  advance(regs);
370  goto out;
371  }
372 
373 kill_user:
374  user_mna_trap_fault(regs, insn);
375 out:
376  ;
377 }
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