xref: /openbmc/linux/arch/parisc/mm/fault.c (revision 7587eb18)
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  *
7  * Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
8  * Copyright 1999 SuSE GmbH (Philipp Rumpf, prumpf@tux.org)
9  * Copyright 1999 Hewlett Packard Co.
10  *
11  */
12 
13 #include <linux/mm.h>
14 #include <linux/ptrace.h>
15 #include <linux/sched.h>
16 #include <linux/interrupt.h>
17 #include <linux/module.h>
18 #include <linux/uaccess.h>
19 
20 #include <asm/traps.h>
21 
22 /* Various important other fields */
23 #define bit22set(x)		(x & 0x00000200)
24 #define bits23_25set(x)		(x & 0x000001c0)
25 #define isGraphicsFlushRead(x)	((x & 0xfc003fdf) == 0x04001a80)
26 				/* extended opcode is 0x6a */
27 
28 #define BITSSET		0x1c0	/* for identifying LDCW */
29 
30 
31 DEFINE_PER_CPU(struct exception_data, exception_data);
32 
33 int show_unhandled_signals = 1;
34 
35 /*
36  * parisc_acctyp(unsigned int inst) --
37  *    Given a PA-RISC memory access instruction, determine if the
38  *    the instruction would perform a memory read or memory write
39  *    operation.
40  *
41  *    This function assumes that the given instruction is a memory access
42  *    instruction (i.e. you should really only call it if you know that
43  *    the instruction has generated some sort of a memory access fault).
44  *
45  * Returns:
46  *   VM_READ  if read operation
47  *   VM_WRITE if write operation
48  *   VM_EXEC  if execute operation
49  */
50 static unsigned long
51 parisc_acctyp(unsigned long code, unsigned int inst)
52 {
53 	if (code == 6 || code == 16)
54 	    return VM_EXEC;
55 
56 	switch (inst & 0xf0000000) {
57 	case 0x40000000: /* load */
58 	case 0x50000000: /* new load */
59 		return VM_READ;
60 
61 	case 0x60000000: /* store */
62 	case 0x70000000: /* new store */
63 		return VM_WRITE;
64 
65 	case 0x20000000: /* coproc */
66 	case 0x30000000: /* coproc2 */
67 		if (bit22set(inst))
68 			return VM_WRITE;
69 
70 	case 0x0: /* indexed/memory management */
71 		if (bit22set(inst)) {
72 			/*
73 			 * Check for the 'Graphics Flush Read' instruction.
74 			 * It resembles an FDC instruction, except for bits
75 			 * 20 and 21. Any combination other than zero will
76 			 * utilize the block mover functionality on some
77 			 * older PA-RISC platforms.  The case where a block
78 			 * move is performed from VM to graphics IO space
79 			 * should be treated as a READ.
80 			 *
81 			 * The significance of bits 20,21 in the FDC
82 			 * instruction is:
83 			 *
84 			 *   00  Flush data cache (normal instruction behavior)
85 			 *   01  Graphics flush write  (IO space -> VM)
86 			 *   10  Graphics flush read   (VM -> IO space)
87 			 *   11  Graphics flush read/write (VM <-> IO space)
88 			 */
89 			if (isGraphicsFlushRead(inst))
90 				return VM_READ;
91 			return VM_WRITE;
92 		} else {
93 			/*
94 			 * Check for LDCWX and LDCWS (semaphore instructions).
95 			 * If bits 23 through 25 are all 1's it is one of
96 			 * the above two instructions and is a write.
97 			 *
98 			 * Note: With the limited bits we are looking at,
99 			 * this will also catch PROBEW and PROBEWI. However,
100 			 * these should never get in here because they don't
101 			 * generate exceptions of the type:
102 			 *   Data TLB miss fault/data page fault
103 			 *   Data memory protection trap
104 			 */
105 			if (bits23_25set(inst) == BITSSET)
106 				return VM_WRITE;
107 		}
108 		return VM_READ; /* Default */
109 	}
110 	return VM_READ; /* Default */
111 }
112 
113 #undef bit22set
114 #undef bits23_25set
115 #undef isGraphicsFlushRead
116 #undef BITSSET
117 
118 
119 #if 0
120 /* This is the treewalk to find a vma which is the highest that has
121  * a start < addr.  We're using find_vma_prev instead right now, but
122  * we might want to use this at some point in the future.  Probably
123  * not, but I want it committed to CVS so I don't lose it :-)
124  */
125 			while (tree != vm_avl_empty) {
126 				if (tree->vm_start > addr) {
127 					tree = tree->vm_avl_left;
128 				} else {
129 					prev = tree;
130 					if (prev->vm_next == NULL)
131 						break;
132 					if (prev->vm_next->vm_start > addr)
133 						break;
134 					tree = tree->vm_avl_right;
135 				}
136 			}
137 #endif
138 
139 int fixup_exception(struct pt_regs *regs)
140 {
141 	const struct exception_table_entry *fix;
142 
143 	fix = search_exception_tables(regs->iaoq[0]);
144 	if (fix) {
145 		struct exception_data *d;
146 		d = this_cpu_ptr(&exception_data);
147 		d->fault_ip = regs->iaoq[0];
148 		d->fault_gp = regs->gr[27];
149 		d->fault_space = regs->isr;
150 		d->fault_addr = regs->ior;
151 
152 		regs->iaoq[0] = (unsigned long)&fix->fixup + fix->fixup;
153 		regs->iaoq[0] &= ~3;
154 		/*
155 		 * NOTE: In some cases the faulting instruction
156 		 * may be in the delay slot of a branch. We
157 		 * don't want to take the branch, so we don't
158 		 * increment iaoq[1], instead we set it to be
159 		 * iaoq[0]+4, and clear the B bit in the PSW
160 		 */
161 		regs->iaoq[1] = regs->iaoq[0] + 4;
162 		regs->gr[0] &= ~PSW_B; /* IPSW in gr[0] */
163 
164 		return 1;
165 	}
166 
167 	return 0;
168 }
169 
170 /*
171  * Print out info about fatal segfaults, if the show_unhandled_signals
172  * sysctl is set:
173  */
174 static inline void
175 show_signal_msg(struct pt_regs *regs, unsigned long code,
176 		unsigned long address, struct task_struct *tsk,
177 		struct vm_area_struct *vma)
178 {
179 	if (!unhandled_signal(tsk, SIGSEGV))
180 		return;
181 
182 	if (!printk_ratelimit())
183 		return;
184 
185 	pr_warn("\n");
186 	pr_warn("do_page_fault() command='%s' type=%lu address=0x%08lx",
187 	    tsk->comm, code, address);
188 	print_vma_addr(KERN_CONT " in ", regs->iaoq[0]);
189 	if (vma)
190 		pr_warn(" vm_start = 0x%08lx, vm_end = 0x%08lx\n",
191 				vma->vm_start, vma->vm_end);
192 
193 	show_regs(regs);
194 }
195 
196 void do_page_fault(struct pt_regs *regs, unsigned long code,
197 			      unsigned long address)
198 {
199 	struct vm_area_struct *vma, *prev_vma;
200 	struct task_struct *tsk;
201 	struct mm_struct *mm;
202 	unsigned long acc_type;
203 	int fault;
204 	unsigned int flags;
205 
206 	if (faulthandler_disabled())
207 		goto no_context;
208 
209 	tsk = current;
210 	mm = tsk->mm;
211 	if (!mm)
212 		goto no_context;
213 
214 	flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
215 	if (user_mode(regs))
216 		flags |= FAULT_FLAG_USER;
217 
218 	acc_type = parisc_acctyp(code, regs->iir);
219 	if (acc_type & VM_WRITE)
220 		flags |= FAULT_FLAG_WRITE;
221 retry:
222 	down_read(&mm->mmap_sem);
223 	vma = find_vma_prev(mm, address, &prev_vma);
224 	if (!vma || address < vma->vm_start)
225 		goto check_expansion;
226 /*
227  * Ok, we have a good vm_area for this memory access. We still need to
228  * check the access permissions.
229  */
230 
231 good_area:
232 
233 	if ((vma->vm_flags & acc_type) != acc_type)
234 		goto bad_area;
235 
236 	/*
237 	 * If for any reason at all we couldn't handle the fault, make
238 	 * sure we exit gracefully rather than endlessly redo the
239 	 * fault.
240 	 */
241 
242 	fault = handle_mm_fault(mm, vma, address, flags);
243 
244 	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
245 		return;
246 
247 	if (unlikely(fault & VM_FAULT_ERROR)) {
248 		/*
249 		 * We hit a shared mapping outside of the file, or some
250 		 * other thing happened to us that made us unable to
251 		 * handle the page fault gracefully.
252 		 */
253 		if (fault & VM_FAULT_OOM)
254 			goto out_of_memory;
255 		else if (fault & VM_FAULT_SIGSEGV)
256 			goto bad_area;
257 		else if (fault & VM_FAULT_SIGBUS)
258 			goto bad_area;
259 		BUG();
260 	}
261 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
262 		if (fault & VM_FAULT_MAJOR)
263 			current->maj_flt++;
264 		else
265 			current->min_flt++;
266 		if (fault & VM_FAULT_RETRY) {
267 			flags &= ~FAULT_FLAG_ALLOW_RETRY;
268 
269 			/*
270 			 * No need to up_read(&mm->mmap_sem) as we would
271 			 * have already released it in __lock_page_or_retry
272 			 * in mm/filemap.c.
273 			 */
274 
275 			goto retry;
276 		}
277 	}
278 	up_read(&mm->mmap_sem);
279 	return;
280 
281 check_expansion:
282 	vma = prev_vma;
283 	if (vma && (expand_stack(vma, address) == 0))
284 		goto good_area;
285 
286 /*
287  * Something tried to access memory that isn't in our memory map..
288  */
289 bad_area:
290 	up_read(&mm->mmap_sem);
291 
292 	if (user_mode(regs)) {
293 		struct siginfo si;
294 
295 		show_signal_msg(regs, code, address, tsk, vma);
296 
297 		switch (code) {
298 		case 15:	/* Data TLB miss fault/Data page fault */
299 			/* send SIGSEGV when outside of vma */
300 			if (!vma ||
301 			    address < vma->vm_start || address > vma->vm_end) {
302 				si.si_signo = SIGSEGV;
303 				si.si_code = SEGV_MAPERR;
304 				break;
305 			}
306 
307 			/* send SIGSEGV for wrong permissions */
308 			if ((vma->vm_flags & acc_type) != acc_type) {
309 				si.si_signo = SIGSEGV;
310 				si.si_code = SEGV_ACCERR;
311 				break;
312 			}
313 
314 			/* probably address is outside of mapped file */
315 			/* fall through */
316 		case 17:	/* NA data TLB miss / page fault */
317 		case 18:	/* Unaligned access - PCXS only */
318 			si.si_signo = SIGBUS;
319 			si.si_code = (code == 18) ? BUS_ADRALN : BUS_ADRERR;
320 			break;
321 		case 16:	/* Non-access instruction TLB miss fault */
322 		case 26:	/* PCXL: Data memory access rights trap */
323 		default:
324 			si.si_signo = SIGSEGV;
325 			si.si_code = (code == 26) ? SEGV_ACCERR : SEGV_MAPERR;
326 			break;
327 		}
328 		si.si_errno = 0;
329 		si.si_addr = (void __user *) address;
330 		force_sig_info(si.si_signo, &si, current);
331 		return;
332 	}
333 
334 no_context:
335 
336 	if (!user_mode(regs) && fixup_exception(regs)) {
337 		return;
338 	}
339 
340 	parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);
341 
342   out_of_memory:
343 	up_read(&mm->mmap_sem);
344 	if (!user_mode(regs))
345 		goto no_context;
346 	pagefault_out_of_memory();
347 }
348