xref: /openbmc/linux/arch/mips/mm/fault.c (revision 52fb57e7)
1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 1995 - 2000 by Ralf Baechle
7  */
8 #include <linux/context_tracking.h>
9 #include <linux/signal.h>
10 #include <linux/sched.h>
11 #include <linux/interrupt.h>
12 #include <linux/kernel.h>
13 #include <linux/errno.h>
14 #include <linux/string.h>
15 #include <linux/types.h>
16 #include <linux/ptrace.h>
17 #include <linux/ratelimit.h>
18 #include <linux/mman.h>
19 #include <linux/mm.h>
20 #include <linux/smp.h>
21 #include <linux/module.h>
22 #include <linux/kprobes.h>
23 #include <linux/perf_event.h>
24 
25 #include <asm/branch.h>
26 #include <asm/mmu_context.h>
27 #include <asm/uaccess.h>
28 #include <asm/ptrace.h>
29 #include <asm/highmem.h>		/* For VMALLOC_END */
30 #include <linux/kdebug.h>
31 
32 int show_unhandled_signals = 1;
33 
34 /*
35  * This routine handles page faults.  It determines the address,
36  * and the problem, and then passes it off to one of the appropriate
37  * routines.
38  */
39 static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
40 	unsigned long address)
41 {
42 	struct vm_area_struct * vma = NULL;
43 	struct task_struct *tsk = current;
44 	struct mm_struct *mm = tsk->mm;
45 	const int field = sizeof(unsigned long) * 2;
46 	siginfo_t info;
47 	int fault;
48 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
49 
50 	static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
51 
52 #if 0
53 	printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
54 	       current->comm, current->pid, field, address, write,
55 	       field, regs->cp0_epc);
56 #endif
57 
58 #ifdef CONFIG_KPROBES
59 	/*
60 	 * This is to notify the fault handler of the kprobes.	The
61 	 * exception code is redundant as it is also carried in REGS,
62 	 * but we pass it anyhow.
63 	 */
64 	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
65 		       (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
66 		return;
67 #endif
68 
69 	info.si_code = SEGV_MAPERR;
70 
71 	/*
72 	 * We fault-in kernel-space virtual memory on-demand. The
73 	 * 'reference' page table is init_mm.pgd.
74 	 *
75 	 * NOTE! We MUST NOT take any locks for this case. We may
76 	 * be in an interrupt or a critical region, and should
77 	 * only copy the information from the master page table,
78 	 * nothing more.
79 	 */
80 #ifdef CONFIG_64BIT
81 # define VMALLOC_FAULT_TARGET no_context
82 #else
83 # define VMALLOC_FAULT_TARGET vmalloc_fault
84 #endif
85 
86 	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
87 		goto VMALLOC_FAULT_TARGET;
88 #ifdef MODULE_START
89 	if (unlikely(address >= MODULE_START && address < MODULE_END))
90 		goto VMALLOC_FAULT_TARGET;
91 #endif
92 
93 	/*
94 	 * If we're in an interrupt or have no user
95 	 * context, we must not take the fault..
96 	 */
97 	if (in_atomic() || !mm)
98 		goto bad_area_nosemaphore;
99 
100 	if (user_mode(regs))
101 		flags |= FAULT_FLAG_USER;
102 retry:
103 	down_read(&mm->mmap_sem);
104 	vma = find_vma(mm, address);
105 	if (!vma)
106 		goto bad_area;
107 	if (vma->vm_start <= address)
108 		goto good_area;
109 	if (!(vma->vm_flags & VM_GROWSDOWN))
110 		goto bad_area;
111 	if (expand_stack(vma, address))
112 		goto bad_area;
113 /*
114  * Ok, we have a good vm_area for this memory access, so
115  * we can handle it..
116  */
117 good_area:
118 	info.si_code = SEGV_ACCERR;
119 
120 	if (write) {
121 		if (!(vma->vm_flags & VM_WRITE))
122 			goto bad_area;
123 		flags |= FAULT_FLAG_WRITE;
124 	} else {
125 		if (cpu_has_rixi) {
126 			if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
127 #if 0
128 				pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n",
129 					  raw_smp_processor_id(),
130 					  current->comm, current->pid,
131 					  field, address, write,
132 					  field, regs->cp0_epc);
133 #endif
134 				goto bad_area;
135 			}
136 			if (!(vma->vm_flags & VM_READ)) {
137 #if 0
138 				pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n",
139 					  raw_smp_processor_id(),
140 					  current->comm, current->pid,
141 					  field, address, write,
142 					  field, regs->cp0_epc);
143 #endif
144 				goto bad_area;
145 			}
146 		} else {
147 			if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
148 				goto bad_area;
149 		}
150 	}
151 
152 	/*
153 	 * If for any reason at all we couldn't handle the fault,
154 	 * make sure we exit gracefully rather than endlessly redo
155 	 * the fault.
156 	 */
157 	fault = handle_mm_fault(mm, vma, address, flags);
158 
159 	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
160 		return;
161 
162 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
163 	if (unlikely(fault & VM_FAULT_ERROR)) {
164 		if (fault & VM_FAULT_OOM)
165 			goto out_of_memory;
166 		else if (fault & VM_FAULT_SIGSEGV)
167 			goto bad_area;
168 		else if (fault & VM_FAULT_SIGBUS)
169 			goto do_sigbus;
170 		BUG();
171 	}
172 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
173 		if (fault & VM_FAULT_MAJOR) {
174 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
175 						  regs, address);
176 			tsk->maj_flt++;
177 		} else {
178 			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
179 						  regs, address);
180 			tsk->min_flt++;
181 		}
182 		if (fault & VM_FAULT_RETRY) {
183 			flags &= ~FAULT_FLAG_ALLOW_RETRY;
184 			flags |= FAULT_FLAG_TRIED;
185 
186 			/*
187 			 * No need to up_read(&mm->mmap_sem) as we would
188 			 * have already released it in __lock_page_or_retry
189 			 * in mm/filemap.c.
190 			 */
191 
192 			goto retry;
193 		}
194 	}
195 
196 	up_read(&mm->mmap_sem);
197 	return;
198 
199 /*
200  * Something tried to access memory that isn't in our memory map..
201  * Fix it, but check if it's kernel or user first..
202  */
203 bad_area:
204 	up_read(&mm->mmap_sem);
205 
206 bad_area_nosemaphore:
207 	/* User mode accesses just cause a SIGSEGV */
208 	if (user_mode(regs)) {
209 		tsk->thread.cp0_badvaddr = address;
210 		tsk->thread.error_code = write;
211 		if (show_unhandled_signals &&
212 		    unhandled_signal(tsk, SIGSEGV) &&
213 		    __ratelimit(&ratelimit_state)) {
214 			pr_info("\ndo_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx",
215 				tsk->comm,
216 				write ? "write access to" : "read access from",
217 				field, address);
218 			pr_info("epc = %0*lx in", field,
219 				(unsigned long) regs->cp0_epc);
220 			print_vma_addr(" ", regs->cp0_epc);
221 			pr_info("ra  = %0*lx in", field,
222 				(unsigned long) regs->regs[31]);
223 			print_vma_addr(" ", regs->regs[31]);
224 			pr_info("\n");
225 		}
226 		info.si_signo = SIGSEGV;
227 		info.si_errno = 0;
228 		/* info.si_code has been set above */
229 		info.si_addr = (void __user *) address;
230 		force_sig_info(SIGSEGV, &info, tsk);
231 		return;
232 	}
233 
234 no_context:
235 	/* Are we prepared to handle this kernel fault?	 */
236 	if (fixup_exception(regs)) {
237 		current->thread.cp0_baduaddr = address;
238 		return;
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 	bust_spinlocks(1);
246 
247 	printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
248 	       "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
249 	       raw_smp_processor_id(), field, address, field, regs->cp0_epc,
250 	       field,  regs->regs[31]);
251 	die("Oops", regs);
252 
253 out_of_memory:
254 	/*
255 	 * We ran out of memory, call the OOM killer, and return the userspace
256 	 * (which will retry the fault, or kill us if we got oom-killed).
257 	 */
258 	up_read(&mm->mmap_sem);
259 	if (!user_mode(regs))
260 		goto no_context;
261 	pagefault_out_of_memory();
262 	return;
263 
264 do_sigbus:
265 	up_read(&mm->mmap_sem);
266 
267 	/* Kernel mode? Handle exceptions or die */
268 	if (!user_mode(regs))
269 		goto no_context;
270 	else
271 	/*
272 	 * Send a sigbus, regardless of whether we were in kernel
273 	 * or user mode.
274 	 */
275 #if 0
276 		printk("do_page_fault() #3: sending SIGBUS to %s for "
277 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
278 		       tsk->comm,
279 		       write ? "write access to" : "read access from",
280 		       field, address,
281 		       field, (unsigned long) regs->cp0_epc,
282 		       field, (unsigned long) regs->regs[31]);
283 #endif
284 	tsk->thread.cp0_badvaddr = address;
285 	info.si_signo = SIGBUS;
286 	info.si_errno = 0;
287 	info.si_code = BUS_ADRERR;
288 	info.si_addr = (void __user *) address;
289 	force_sig_info(SIGBUS, &info, tsk);
290 
291 	return;
292 #ifndef CONFIG_64BIT
293 vmalloc_fault:
294 	{
295 		/*
296 		 * Synchronize this task's top level page-table
297 		 * with the 'reference' page table.
298 		 *
299 		 * Do _not_ use "tsk" here. We might be inside
300 		 * an interrupt in the middle of a task switch..
301 		 */
302 		int offset = __pgd_offset(address);
303 		pgd_t *pgd, *pgd_k;
304 		pud_t *pud, *pud_k;
305 		pmd_t *pmd, *pmd_k;
306 		pte_t *pte_k;
307 
308 		pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
309 		pgd_k = init_mm.pgd + offset;
310 
311 		if (!pgd_present(*pgd_k))
312 			goto no_context;
313 		set_pgd(pgd, *pgd_k);
314 
315 		pud = pud_offset(pgd, address);
316 		pud_k = pud_offset(pgd_k, address);
317 		if (!pud_present(*pud_k))
318 			goto no_context;
319 
320 		pmd = pmd_offset(pud, address);
321 		pmd_k = pmd_offset(pud_k, address);
322 		if (!pmd_present(*pmd_k))
323 			goto no_context;
324 		set_pmd(pmd, *pmd_k);
325 
326 		pte_k = pte_offset_kernel(pmd_k, address);
327 		if (!pte_present(*pte_k))
328 			goto no_context;
329 		return;
330 	}
331 #endif
332 }
333 
334 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
335 	unsigned long write, unsigned long address)
336 {
337 	enum ctx_state prev_state;
338 
339 	prev_state = exception_enter();
340 	__do_page_fault(regs, write, address);
341 	exception_exit(prev_state);
342 }
343