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 
unhandled_fault(unsigned long address,struct task_struct * tsk,struct pt_regs * regs)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
show_signal_msg(struct pt_regs * regs,int sig,int code,unsigned long address,struct task_struct * tsk)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 
__do_fault_siginfo(int code,int sig,struct pt_regs * regs,unsigned long addr)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 
compute_si_addr(struct pt_regs * regs,int text_fault)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 
do_fault_siginfo(int code,int sig,struct pt_regs * regs,int text_fault)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 
do_sparc_fault(struct pt_regs * regs,int text_fault,int write,unsigned long address)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 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
147 
148 retry:
149 	mmap_read_lock(mm);
150 
151 	if (!from_user && address >= PAGE_OFFSET)
152 		goto bad_area;
153 
154 	vma = find_vma(mm, address);
155 	if (!vma)
156 		goto bad_area;
157 	if (vma->vm_start <= address)
158 		goto good_area;
159 	if (!(vma->vm_flags & VM_GROWSDOWN))
160 		goto bad_area;
161 	if (expand_stack(vma, address))
162 		goto bad_area;
163 	/*
164 	 * Ok, we have a good vm_area for this memory access, so
165 	 * we can handle it..
166 	 */
167 good_area:
168 	code = SEGV_ACCERR;
169 	if (write) {
170 		if (!(vma->vm_flags & VM_WRITE))
171 			goto bad_area;
172 	} else {
173 		/* Allow reads even for write-only mappings */
174 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
175 			goto bad_area;
176 	}
177 
178 	if (from_user)
179 		flags |= FAULT_FLAG_USER;
180 	if (write)
181 		flags |= FAULT_FLAG_WRITE;
182 
183 	/*
184 	 * If for any reason at all we couldn't handle the fault,
185 	 * make sure we exit gracefully rather than endlessly redo
186 	 * the fault.
187 	 */
188 	fault = handle_mm_fault(vma, address, flags, regs);
189 
190 	if (fault_signal_pending(fault, regs))
191 		return;
192 
193 	if (unlikely(fault & VM_FAULT_ERROR)) {
194 		if (fault & VM_FAULT_OOM)
195 			goto out_of_memory;
196 		else if (fault & VM_FAULT_SIGSEGV)
197 			goto bad_area;
198 		else if (fault & VM_FAULT_SIGBUS)
199 			goto do_sigbus;
200 		BUG();
201 	}
202 
203 	if (fault & VM_FAULT_RETRY) {
204 		flags |= FAULT_FLAG_TRIED;
205 
206 		/* No need to mmap_read_unlock(mm) as we would
207 		 * have already released it in __lock_page_or_retry
208 		 * in mm/filemap.c.
209 		 */
210 
211 		goto retry;
212 	}
213 
214 	mmap_read_unlock(mm);
215 	return;
216 
217 	/*
218 	 * Something tried to access memory that isn't in our memory map..
219 	 * Fix it, but check if it's kernel or user first..
220 	 */
221 bad_area:
222 	mmap_read_unlock(mm);
223 
224 bad_area_nosemaphore:
225 	/* User mode accesses just cause a SIGSEGV */
226 	if (from_user) {
227 		do_fault_siginfo(code, SIGSEGV, regs, text_fault);
228 		return;
229 	}
230 
231 	/* Is this in ex_table? */
232 no_context:
233 	if (!from_user) {
234 		const struct exception_table_entry *entry;
235 
236 		entry = search_exception_tables(regs->pc);
237 #ifdef DEBUG_EXCEPTIONS
238 		printk("Exception: PC<%08lx> faddr<%08lx>\n",
239 		       regs->pc, address);
240 		printk("EX_TABLE: insn<%08lx> fixup<%08x>\n",
241 			regs->pc, entry->fixup);
242 #endif
243 		regs->pc = entry->fixup;
244 		regs->npc = regs->pc + 4;
245 		return;
246 	}
247 
248 	unhandled_fault(address, tsk, regs);
249 
250 /*
251  * We ran out of memory, or some other thing happened to us that made
252  * us unable to handle the page fault gracefully.
253  */
254 out_of_memory:
255 	mmap_read_unlock(mm);
256 	if (from_user) {
257 		pagefault_out_of_memory();
258 		return;
259 	}
260 	goto no_context;
261 
262 do_sigbus:
263 	mmap_read_unlock(mm);
264 	do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
265 	if (!from_user)
266 		goto no_context;
267 
268 vmalloc_fault:
269 	{
270 		/*
271 		 * Synchronize this task's top level page-table
272 		 * with the 'reference' page table.
273 		 */
274 		int offset = pgd_index(address);
275 		pgd_t *pgd, *pgd_k;
276 		p4d_t *p4d, *p4d_k;
277 		pud_t *pud, *pud_k;
278 		pmd_t *pmd, *pmd_k;
279 
280 		pgd = tsk->active_mm->pgd + offset;
281 		pgd_k = init_mm.pgd + offset;
282 
283 		if (!pgd_present(*pgd)) {
284 			if (!pgd_present(*pgd_k))
285 				goto bad_area_nosemaphore;
286 			pgd_val(*pgd) = pgd_val(*pgd_k);
287 			return;
288 		}
289 
290 		p4d = p4d_offset(pgd, address);
291 		pud = pud_offset(p4d, address);
292 		pmd = pmd_offset(pud, address);
293 
294 		p4d_k = p4d_offset(pgd_k, address);
295 		pud_k = pud_offset(p4d_k, address);
296 		pmd_k = pmd_offset(pud_k, address);
297 
298 		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
299 			goto bad_area_nosemaphore;
300 
301 		*pmd = *pmd_k;
302 		return;
303 	}
304 }
305 
306 /* This always deals with user addresses. */
force_user_fault(unsigned long address,int write)307 static void force_user_fault(unsigned long address, int write)
308 {
309 	struct vm_area_struct *vma;
310 	struct task_struct *tsk = current;
311 	struct mm_struct *mm = tsk->mm;
312 	unsigned int flags = FAULT_FLAG_USER;
313 	int code;
314 
315 	code = SEGV_MAPERR;
316 
317 	mmap_read_lock(mm);
318 	vma = find_vma(mm, address);
319 	if (!vma)
320 		goto bad_area;
321 	if (vma->vm_start <= address)
322 		goto good_area;
323 	if (!(vma->vm_flags & VM_GROWSDOWN))
324 		goto bad_area;
325 	if (expand_stack(vma, address))
326 		goto bad_area;
327 good_area:
328 	code = SEGV_ACCERR;
329 	if (write) {
330 		if (!(vma->vm_flags & VM_WRITE))
331 			goto bad_area;
332 		flags |= FAULT_FLAG_WRITE;
333 	} else {
334 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
335 			goto bad_area;
336 	}
337 	switch (handle_mm_fault(vma, address, flags, NULL)) {
338 	case VM_FAULT_SIGBUS:
339 	case VM_FAULT_OOM:
340 		goto do_sigbus;
341 	}
342 	mmap_read_unlock(mm);
343 	return;
344 bad_area:
345 	mmap_read_unlock(mm);
346 	__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
347 	return;
348 
349 do_sigbus:
350 	mmap_read_unlock(mm);
351 	__do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
352 }
353 
check_stack_aligned(unsigned long sp)354 static void check_stack_aligned(unsigned long sp)
355 {
356 	if (sp & 0x7UL)
357 		force_sig(SIGILL);
358 }
359 
window_overflow_fault(void)360 void window_overflow_fault(void)
361 {
362 	unsigned long sp;
363 
364 	sp = current_thread_info()->rwbuf_stkptrs[0];
365 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
366 		force_user_fault(sp + 0x38, 1);
367 	force_user_fault(sp, 1);
368 
369 	check_stack_aligned(sp);
370 }
371 
window_underflow_fault(unsigned long sp)372 void window_underflow_fault(unsigned long sp)
373 {
374 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
375 		force_user_fault(sp + 0x38, 0);
376 	force_user_fault(sp, 0);
377 
378 	check_stack_aligned(sp);
379 }
380 
window_ret_fault(struct pt_regs * regs)381 void window_ret_fault(struct pt_regs *regs)
382 {
383 	unsigned long sp;
384 
385 	sp = regs->u_regs[UREG_FP];
386 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
387 		force_user_fault(sp + 0x38, 0);
388 	force_user_fault(sp, 0);
389 
390 	check_stack_aligned(sp);
391 }
392