1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * fault.c: Page fault handlers for the Sparc.
4 *
5 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
6 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
7 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
8 */
9
10 #include <asm/head.h>
11
12 #include <linux/string.h>
13 #include <linux/types.h>
14 #include <linux/sched.h>
15 #include <linux/ptrace.h>
16 #include <linux/mman.h>
17 #include <linux/threads.h>
18 #include <linux/kernel.h>
19 #include <linux/signal.h>
20 #include <linux/mm.h>
21 #include <linux/smp.h>
22 #include <linux/perf_event.h>
23 #include <linux/interrupt.h>
24 #include <linux/kdebug.h>
25 #include <linux/uaccess.h>
26 #include <linux/extable.h>
27
28 #include <asm/page.h>
29 #include <asm/openprom.h>
30 #include <asm/oplib.h>
31 #include <asm/setup.h>
32 #include <asm/smp.h>
33 #include <asm/traps.h>
34
35 #include "mm_32.h"
36
37 int show_unhandled_signals = 1;
38
39 static void __noreturn unhandled_fault(unsigned long address,
40 struct task_struct *tsk,
41 struct pt_regs *regs)
42 {
43 if ((unsigned long) address < PAGE_SIZE) {
44 printk(KERN_ALERT
45 "Unable to handle kernel NULL pointer dereference\n");
46 } else {
47 printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n",
48 address);
49 }
50 printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
51 (tsk->mm ? tsk->mm->context : tsk->active_mm->context));
52 printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
53 (tsk->mm ? (unsigned long) tsk->mm->pgd :
54 (unsigned long) tsk->active_mm->pgd));
55 die_if_kernel("Oops", regs);
56 }
57
58 static inline void
59 show_signal_msg(struct pt_regs *regs, int sig, int code,
60 unsigned long address, struct task_struct *tsk)
61 {
62 if (!unhandled_signal(tsk, sig))
63 return;
64
65 if (!printk_ratelimit())
66 return;
67
68 printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x",
69 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
70 tsk->comm, task_pid_nr(tsk), address,
71 (void *)regs->pc, (void *)regs->u_regs[UREG_I7],
72 (void *)regs->u_regs[UREG_FP], code);
73
74 print_vma_addr(KERN_CONT " in ", regs->pc);
75
76 printk(KERN_CONT "\n");
77 }
78
79 static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
80 unsigned long addr)
81 {
82 if (unlikely(show_unhandled_signals))
83 show_signal_msg(regs, sig, code,
84 addr, current);
85
86 force_sig_fault(sig, code, (void __user *) addr);
87 }
88
89 static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
90 {
91 unsigned int insn;
92
93 if (text_fault)
94 return regs->pc;
95
96 if (regs->psr & PSR_PS)
97 insn = *(unsigned int *) regs->pc;
98 else
99 __get_user(insn, (unsigned int *) regs->pc);
100
101 return safe_compute_effective_address(regs, insn);
102 }
103
104 static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
105 int text_fault)
106 {
107 unsigned long addr = compute_si_addr(regs, text_fault);
108
109 __do_fault_siginfo(code, sig, regs, addr);
110 }
111
112 asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
113 unsigned long address)
114 {
115 struct vm_area_struct *vma;
116 struct task_struct *tsk = current;
117 struct mm_struct *mm = tsk->mm;
118 int from_user = !(regs->psr & PSR_PS);
119 int code;
120 vm_fault_t fault;
121 unsigned int flags = FAULT_FLAG_DEFAULT;
122
123 if (text_fault)
124 address = regs->pc;
125
126 /*
127 * We fault-in kernel-space virtual memory on-demand. The
128 * 'reference' page table is init_mm.pgd.
129 *
130 * NOTE! We MUST NOT take any locks for this case. We may
131 * be in an interrupt or a critical region, and should
132 * only copy the information from the master page table,
133 * nothing more.
134 */
135 code = SEGV_MAPERR;
136 if (address >= TASK_SIZE)
137 goto vmalloc_fault;
138
139 /*
140 * If we're in an interrupt or have no user
141 * context, we must not take the fault..
142 */
143 if (pagefault_disabled() || !mm)
144 goto no_context;
145
146 if (!from_user && address >= PAGE_OFFSET)
147 goto no_context;
148
149 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
150
151 retry:
152 vma = lock_mm_and_find_vma(mm, address, regs);
153 if (!vma)
154 goto bad_area_nosemaphore;
155 /*
156 * Ok, we have a good vm_area for this memory access, so
157 * we can handle it..
158 */
159 code = SEGV_ACCERR;
160 if (write) {
161 if (!(vma->vm_flags & VM_WRITE))
162 goto bad_area;
163 } else {
164 /* Allow reads even for write-only mappings */
165 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
166 goto bad_area;
167 }
168
169 if (from_user)
170 flags |= FAULT_FLAG_USER;
171 if (write)
172 flags |= FAULT_FLAG_WRITE;
173
174 /*
175 * If for any reason at all we couldn't handle the fault,
176 * make sure we exit gracefully rather than endlessly redo
177 * the fault.
178 */
179 fault = handle_mm_fault(vma, address, flags, regs);
180
181 if (fault_signal_pending(fault, regs)) {
182 if (!from_user)
183 goto no_context;
184 return;
185 }
186
187 /* The fault is fully completed (including releasing mmap lock) */
188 if (fault & VM_FAULT_COMPLETED)
189 return;
190
191 if (unlikely(fault & VM_FAULT_ERROR)) {
192 if (fault & VM_FAULT_OOM)
193 goto out_of_memory;
194 else if (fault & VM_FAULT_SIGSEGV)
195 goto bad_area;
196 else if (fault & VM_FAULT_SIGBUS)
197 goto do_sigbus;
198 BUG();
199 }
200
201 if (fault & VM_FAULT_RETRY) {
202 flags |= FAULT_FLAG_TRIED;
203
204 /* No need to mmap_read_unlock(mm) as we would
205 * have already released it in __lock_page_or_retry
206 * in mm/filemap.c.
207 */
208
209 goto retry;
210 }
211
212 mmap_read_unlock(mm);
213 return;
214
215 /*
216 * Something tried to access memory that isn't in our memory map..
217 * Fix it, but check if it's kernel or user first..
218 */
219 bad_area:
220 mmap_read_unlock(mm);
221
222 bad_area_nosemaphore:
223 /* User mode accesses just cause a SIGSEGV */
224 if (from_user) {
225 do_fault_siginfo(code, SIGSEGV, regs, text_fault);
226 return;
227 }
228
229 /* Is this in ex_table? */
230 no_context:
231 if (!from_user) {
232 const struct exception_table_entry *entry;
233
234 entry = search_exception_tables(regs->pc);
235 #ifdef DEBUG_EXCEPTIONS
236 printk("Exception: PC<%08lx> faddr<%08lx>\n",
237 regs->pc, address);
238 printk("EX_TABLE: insn<%08lx> fixup<%08x>\n",
239 regs->pc, entry->fixup);
240 #endif
241 regs->pc = entry->fixup;
242 regs->npc = regs->pc + 4;
243 return;
244 }
245
246 unhandled_fault(address, tsk, regs);
247
248 /*
249 * We ran out of memory, or some other thing happened to us that made
250 * us unable to handle the page fault gracefully.
251 */
252 out_of_memory:
253 mmap_read_unlock(mm);
254 if (from_user) {
255 pagefault_out_of_memory();
256 return;
257 }
258 goto no_context;
259
260 do_sigbus:
261 mmap_read_unlock(mm);
262 do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
263 if (!from_user)
264 goto no_context;
265
266 vmalloc_fault:
267 {
268 /*
269 * Synchronize this task's top level page-table
270 * with the 'reference' page table.
271 */
272 int offset = pgd_index(address);
273 pgd_t *pgd, *pgd_k;
274 p4d_t *p4d, *p4d_k;
275 pud_t *pud, *pud_k;
276 pmd_t *pmd, *pmd_k;
277
278 pgd = tsk->active_mm->pgd + offset;
279 pgd_k = init_mm.pgd + offset;
280
281 if (!pgd_present(*pgd)) {
282 if (!pgd_present(*pgd_k))
283 goto bad_area_nosemaphore;
284 pgd_val(*pgd) = pgd_val(*pgd_k);
285 return;
286 }
287
288 p4d = p4d_offset(pgd, address);
289 pud = pud_offset(p4d, address);
290 pmd = pmd_offset(pud, address);
291
292 p4d_k = p4d_offset(pgd_k, address);
293 pud_k = pud_offset(p4d_k, address);
294 pmd_k = pmd_offset(pud_k, address);
295
296 if (pmd_present(*pmd) || !pmd_present(*pmd_k))
297 goto bad_area_nosemaphore;
298
299 *pmd = *pmd_k;
300 return;
301 }
302 }
303
304 /* This always deals with user addresses. */
305 static void force_user_fault(unsigned long address, int write)
306 {
307 struct vm_area_struct *vma;
308 struct task_struct *tsk = current;
309 struct mm_struct *mm = tsk->mm;
310 unsigned int flags = FAULT_FLAG_USER;
311 int code;
312
313 code = SEGV_MAPERR;
314
315 vma = lock_mm_and_find_vma(mm, address, NULL);
316 if (!vma)
317 goto bad_area_nosemaphore;
318 code = SEGV_ACCERR;
319 if (write) {
320 if (!(vma->vm_flags & VM_WRITE))
321 goto bad_area;
322 flags |= FAULT_FLAG_WRITE;
323 } else {
324 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
325 goto bad_area;
326 }
327 switch (handle_mm_fault(vma, address, flags, NULL)) {
328 case VM_FAULT_SIGBUS:
329 case VM_FAULT_OOM:
330 goto do_sigbus;
331 }
332 mmap_read_unlock(mm);
333 return;
334 bad_area:
335 mmap_read_unlock(mm);
336 bad_area_nosemaphore:
337 __do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
338 return;
339
340 do_sigbus:
341 mmap_read_unlock(mm);
342 __do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
343 }
344
345 static void check_stack_aligned(unsigned long sp)
346 {
347 if (sp & 0x7UL)
348 force_sig(SIGILL);
349 }
350
351 void window_overflow_fault(void)
352 {
353 unsigned long sp;
354
355 sp = current_thread_info()->rwbuf_stkptrs[0];
356 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
357 force_user_fault(sp + 0x38, 1);
358 force_user_fault(sp, 1);
359
360 check_stack_aligned(sp);
361 }
362
363 void window_underflow_fault(unsigned long sp)
364 {
365 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
366 force_user_fault(sp + 0x38, 0);
367 force_user_fault(sp, 0);
368
369 check_stack_aligned(sp);
370 }
371
372 void window_ret_fault(struct pt_regs *regs)
373 {
374 unsigned long sp;
375
376 sp = regs->u_regs[UREG_FP];
377 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
378 force_user_fault(sp + 0x38, 0);
379 force_user_fault(sp, 0);
380
381 check_stack_aligned(sp);
382 }
383
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