1 | // SPDX-License-Identifier: GPL-2.0-or-later |
2 | /* |
3 | * OpenRISC fault.c |
4 | * |
5 | * Linux architectural port borrowing liberally from similar works of |
6 | * others. All original copyrights apply as per the original source |
7 | * declaration. |
8 | * |
9 | * Modifications for the OpenRISC architecture: |
10 | * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com> |
11 | * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se> |
12 | */ |
13 | |
14 | #include <linux/mm.h> |
15 | #include <linux/interrupt.h> |
16 | #include <linux/extable.h> |
17 | #include <linux/sched/signal.h> |
18 | #include <linux/perf_event.h> |
19 | |
20 | #include <linux/uaccess.h> |
21 | #include <asm/bug.h> |
22 | #include <asm/mmu_context.h> |
23 | #include <asm/siginfo.h> |
24 | #include <asm/signal.h> |
25 | |
26 | #define NUM_TLB_ENTRIES 64 |
27 | #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1)) |
28 | |
29 | /* __PHX__ :: - check the vmalloc_fault in do_page_fault() |
30 | * - also look into include/asm/mmu_context.h |
31 | */ |
32 | volatile pgd_t *current_pgd[NR_CPUS]; |
33 | |
34 | asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address, |
35 | unsigned long vector, int write_acc); |
36 | |
37 | /* |
38 | * This routine handles page faults. It determines the address, |
39 | * and the problem, and then passes it off to one of the appropriate |
40 | * routines. |
41 | * |
42 | * If this routine detects a bad access, it returns 1, otherwise it |
43 | * returns 0. |
44 | */ |
45 | |
46 | asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address, |
47 | unsigned long vector, int write_acc) |
48 | { |
49 | struct task_struct *tsk; |
50 | struct mm_struct *mm; |
51 | struct vm_area_struct *vma; |
52 | int si_code; |
53 | vm_fault_t fault; |
54 | unsigned int flags = FAULT_FLAG_DEFAULT; |
55 | |
56 | tsk = current; |
57 | |
58 | /* |
59 | * We fault-in kernel-space virtual memory on-demand. The |
60 | * 'reference' page table is init_mm.pgd. |
61 | * |
62 | * NOTE! We MUST NOT take any locks for this case. We may |
63 | * be in an interrupt or a critical region, and should |
64 | * only copy the information from the master page table, |
65 | * nothing more. |
66 | * |
67 | * NOTE2: This is done so that, when updating the vmalloc |
68 | * mappings we don't have to walk all processes pgdirs and |
69 | * add the high mappings all at once. Instead we do it as they |
70 | * are used. However vmalloc'ed page entries have the PAGE_GLOBAL |
71 | * bit set so sometimes the TLB can use a lingering entry. |
72 | * |
73 | * This verifies that the fault happens in kernel space |
74 | * and that the fault was not a protection error. |
75 | */ |
76 | |
77 | if (address >= VMALLOC_START && |
78 | (vector != 0x300 && vector != 0x400) && |
79 | !user_mode(regs)) |
80 | goto vmalloc_fault; |
81 | |
82 | /* If exceptions were enabled, we can reenable them here */ |
83 | if (user_mode(regs)) { |
84 | /* Exception was in userspace: reenable interrupts */ |
85 | local_irq_enable(); |
86 | flags |= FAULT_FLAG_USER; |
87 | } else { |
88 | /* If exception was in a syscall, then IRQ's may have |
89 | * been enabled or disabled. If they were enabled, |
90 | * reenable them. |
91 | */ |
92 | if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE)) |
93 | local_irq_enable(); |
94 | } |
95 | |
96 | mm = tsk->mm; |
97 | si_code = SEGV_MAPERR; |
98 | |
99 | /* |
100 | * If we're in an interrupt or have no user |
101 | * context, we must not take the fault.. |
102 | */ |
103 | |
104 | if (in_interrupt() || !mm) |
105 | goto no_context; |
106 | |
107 | perf_sw_event(event_id: PERF_COUNT_SW_PAGE_FAULTS, nr: 1, regs, addr: address); |
108 | |
109 | retry: |
110 | mmap_read_lock(mm); |
111 | vma = find_vma(mm, addr: address); |
112 | |
113 | if (!vma) |
114 | goto bad_area; |
115 | |
116 | if (vma->vm_start <= address) |
117 | goto good_area; |
118 | |
119 | if (!(vma->vm_flags & VM_GROWSDOWN)) |
120 | goto bad_area; |
121 | |
122 | if (user_mode(regs)) { |
123 | /* |
124 | * accessing the stack below usp is always a bug. |
125 | * we get page-aligned addresses so we can only check |
126 | * if we're within a page from usp, but that might be |
127 | * enough to catch brutal errors at least. |
128 | */ |
129 | if (address + PAGE_SIZE < regs->sp) |
130 | goto bad_area; |
131 | } |
132 | vma = expand_stack(mm, addr: address); |
133 | if (!vma) |
134 | goto bad_area_nosemaphore; |
135 | |
136 | /* |
137 | * Ok, we have a good vm_area for this memory access, so |
138 | * we can handle it.. |
139 | */ |
140 | |
141 | good_area: |
142 | si_code = SEGV_ACCERR; |
143 | |
144 | /* first do some preliminary protection checks */ |
145 | |
146 | if (write_acc) { |
147 | if (!(vma->vm_flags & VM_WRITE)) |
148 | goto bad_area; |
149 | flags |= FAULT_FLAG_WRITE; |
150 | } else { |
151 | /* not present */ |
152 | if (!(vma->vm_flags & (VM_READ | VM_EXEC))) |
153 | goto bad_area; |
154 | } |
155 | |
156 | /* are we trying to execute nonexecutable area */ |
157 | if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC)) |
158 | goto bad_area; |
159 | |
160 | /* |
161 | * If for any reason at all we couldn't handle the fault, |
162 | * make sure we exit gracefully rather than endlessly redo |
163 | * the fault. |
164 | */ |
165 | |
166 | fault = handle_mm_fault(vma, address, flags, regs); |
167 | |
168 | if (fault_signal_pending(fault_flags: fault, regs)) { |
169 | if (!user_mode(regs)) |
170 | goto no_context; |
171 | return; |
172 | } |
173 | |
174 | /* The fault is fully completed (including releasing mmap lock) */ |
175 | if (fault & VM_FAULT_COMPLETED) |
176 | return; |
177 | |
178 | if (unlikely(fault & VM_FAULT_ERROR)) { |
179 | if (fault & VM_FAULT_OOM) |
180 | goto out_of_memory; |
181 | else if (fault & VM_FAULT_SIGSEGV) |
182 | goto bad_area; |
183 | else if (fault & VM_FAULT_SIGBUS) |
184 | goto do_sigbus; |
185 | BUG(); |
186 | } |
187 | |
188 | /*RGD modeled on Cris */ |
189 | if (fault & VM_FAULT_RETRY) { |
190 | flags |= FAULT_FLAG_TRIED; |
191 | |
192 | /* No need to mmap_read_unlock(mm) as we would |
193 | * have already released it in __lock_page_or_retry |
194 | * in mm/filemap.c. |
195 | */ |
196 | |
197 | goto retry; |
198 | } |
199 | |
200 | mmap_read_unlock(mm); |
201 | return; |
202 | |
203 | /* |
204 | * Something tried to access memory that isn't in our memory map.. |
205 | * Fix it, but check if it's kernel or user first.. |
206 | */ |
207 | |
208 | bad_area: |
209 | mmap_read_unlock(mm); |
210 | |
211 | bad_area_nosemaphore: |
212 | |
213 | /* User mode accesses just cause a SIGSEGV */ |
214 | |
215 | if (user_mode(regs)) { |
216 | force_sig_fault(SIGSEGV, code: si_code, addr: (void __user *)address); |
217 | return; |
218 | } |
219 | |
220 | no_context: |
221 | |
222 | /* Are we prepared to handle this kernel fault? |
223 | * |
224 | * (The kernel has valid exception-points in the source |
225 | * when it acesses user-memory. When it fails in one |
226 | * of those points, we find it in a table and do a jump |
227 | * to some fixup code that loads an appropriate error |
228 | * code) |
229 | */ |
230 | |
231 | { |
232 | const struct exception_table_entry *entry; |
233 | |
234 | if ((entry = search_exception_tables(add: regs->pc)) != NULL) { |
235 | /* Adjust the instruction pointer in the stackframe */ |
236 | regs->pc = entry->fixup; |
237 | return; |
238 | } |
239 | } |
240 | |
241 | /* |
242 | * Oops. The kernel tried to access some bad page. We'll have to |
243 | * terminate things with extreme prejudice. |
244 | */ |
245 | |
246 | if ((unsigned long)(address) < PAGE_SIZE) |
247 | printk(KERN_ALERT |
248 | "Unable to handle kernel NULL pointer dereference" ); |
249 | else |
250 | printk(KERN_ALERT "Unable to handle kernel access" ); |
251 | printk(" at virtual address 0x%08lx\n" , address); |
252 | |
253 | die("Oops" , regs, write_acc); |
254 | |
255 | /* |
256 | * We ran out of memory, or some other thing happened to us that made |
257 | * us unable to handle the page fault gracefully. |
258 | */ |
259 | |
260 | out_of_memory: |
261 | mmap_read_unlock(mm); |
262 | if (!user_mode(regs)) |
263 | goto no_context; |
264 | pagefault_out_of_memory(); |
265 | return; |
266 | |
267 | do_sigbus: |
268 | mmap_read_unlock(mm); |
269 | |
270 | /* |
271 | * Send a sigbus, regardless of whether we were in kernel |
272 | * or user mode. |
273 | */ |
274 | force_sig_fault(SIGBUS, BUS_ADRERR, addr: (void __user *)address); |
275 | |
276 | /* Kernel mode? Handle exceptions or die */ |
277 | if (!user_mode(regs)) |
278 | goto no_context; |
279 | return; |
280 | |
281 | vmalloc_fault: |
282 | { |
283 | /* |
284 | * Synchronize this task's top level page-table |
285 | * with the 'reference' page table. |
286 | * |
287 | * Use current_pgd instead of tsk->active_mm->pgd |
288 | * since the latter might be unavailable if this |
289 | * code is executed in a misfortunately run irq |
290 | * (like inside schedule() between switch_mm and |
291 | * switch_to...). |
292 | */ |
293 | |
294 | int offset = pgd_index(address); |
295 | pgd_t *pgd, *pgd_k; |
296 | p4d_t *p4d, *p4d_k; |
297 | pud_t *pud, *pud_k; |
298 | pmd_t *pmd, *pmd_k; |
299 | pte_t *pte_k; |
300 | |
301 | /* |
302 | phx_warn("do_page_fault(): vmalloc_fault will not work, " |
303 | "since current_pgd assign a proper value somewhere\n" |
304 | "anyhow we don't need this at the moment\n"); |
305 | |
306 | phx_mmu("vmalloc_fault"); |
307 | */ |
308 | pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset; |
309 | pgd_k = init_mm.pgd + offset; |
310 | |
311 | /* Since we're two-level, we don't need to do both |
312 | * set_pgd and set_pmd (they do the same thing). If |
313 | * we go three-level at some point, do the right thing |
314 | * with pgd_present and set_pgd here. |
315 | * |
316 | * Also, since the vmalloc area is global, we don't |
317 | * need to copy individual PTE's, it is enough to |
318 | * copy the pgd pointer into the pte page of the |
319 | * root task. If that is there, we'll find our pte if |
320 | * it exists. |
321 | */ |
322 | |
323 | p4d = p4d_offset(pgd, address); |
324 | p4d_k = p4d_offset(pgd: pgd_k, address); |
325 | if (!p4d_present(p4d: *p4d_k)) |
326 | goto no_context; |
327 | |
328 | pud = pud_offset(p4d, address); |
329 | pud_k = pud_offset(p4d: p4d_k, address); |
330 | if (!pud_present(pud: *pud_k)) |
331 | goto no_context; |
332 | |
333 | pmd = pmd_offset(pud, address); |
334 | pmd_k = pmd_offset(pud: pud_k, address); |
335 | |
336 | if (!pmd_present(pmd: *pmd_k)) |
337 | goto bad_area_nosemaphore; |
338 | |
339 | set_pmd(pmdp: pmd, pmd: *pmd_k); |
340 | |
341 | /* Make sure the actual PTE exists as well to |
342 | * catch kernel vmalloc-area accesses to non-mapped |
343 | * addresses. If we don't do this, this will just |
344 | * silently loop forever. |
345 | */ |
346 | |
347 | pte_k = pte_offset_kernel(pmd: pmd_k, address); |
348 | if (!pte_present(a: *pte_k)) |
349 | goto no_context; |
350 | |
351 | return; |
352 | } |
353 | } |
354 | |