xref: /openbmc/linux/arch/ia64/mm/fault.c (revision e0302638)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * MMU fault handling support.
4  *
5  * Copyright (C) 1998-2002 Hewlett-Packard Co
6  *	David Mosberger-Tang <davidm@hpl.hp.com>
7  */
8 #include <linux/sched/signal.h>
9 #include <linux/kernel.h>
10 #include <linux/mm.h>
11 #include <linux/extable.h>
12 #include <linux/interrupt.h>
13 #include <linux/kprobes.h>
14 #include <linux/kdebug.h>
15 #include <linux/prefetch.h>
16 #include <linux/uaccess.h>
17 #include <linux/perf_event.h>
18 
19 #include <asm/processor.h>
20 #include <asm/exception.h>
21 
22 extern int die(char *, struct pt_regs *, long);
23 
24 /*
25  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
26  * (inside region 5, on ia64) and that page is present.
27  */
28 static int
29 mapped_kernel_page_is_present (unsigned long address)
30 {
31 	pgd_t *pgd;
32 	p4d_t *p4d;
33 	pud_t *pud;
34 	pmd_t *pmd;
35 	pte_t *ptep, pte;
36 
37 	pgd = pgd_offset_k(address);
38 	if (pgd_none(*pgd) || pgd_bad(*pgd))
39 		return 0;
40 
41 	p4d = p4d_offset(pgd, address);
42 	if (p4d_none(*p4d) || p4d_bad(*p4d))
43 		return 0;
44 
45 	pud = pud_offset(p4d, address);
46 	if (pud_none(*pud) || pud_bad(*pud))
47 		return 0;
48 
49 	pmd = pmd_offset(pud, address);
50 	if (pmd_none(*pmd) || pmd_bad(*pmd))
51 		return 0;
52 
53 	ptep = pte_offset_kernel(pmd, address);
54 	if (!ptep)
55 		return 0;
56 
57 	pte = *ptep;
58 	return pte_present(pte);
59 }
60 
61 #	define VM_READ_BIT	0
62 #	define VM_WRITE_BIT	1
63 #	define VM_EXEC_BIT	2
64 
65 void __kprobes
66 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
67 {
68 	int signal = SIGSEGV, code = SEGV_MAPERR;
69 	struct vm_area_struct *vma, *prev_vma;
70 	struct mm_struct *mm = current->mm;
71 	unsigned long mask;
72 	vm_fault_t fault;
73 	unsigned int flags = FAULT_FLAG_DEFAULT;
74 
75 	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
76 		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
77 
78 	/* mmap_lock is performance critical.... */
79 	prefetchw(&mm->mmap_lock);
80 
81 	/*
82 	 * If we're in an interrupt or have no user context, we must not take the fault..
83 	 */
84 	if (faulthandler_disabled() || !mm)
85 		goto no_context;
86 
87 	/*
88 	 * This is to handle the kprobes on user space access instructions
89 	 */
90 	if (kprobe_page_fault(regs, TRAP_BRKPT))
91 		return;
92 
93 	if (user_mode(regs))
94 		flags |= FAULT_FLAG_USER;
95 	if (mask & VM_WRITE)
96 		flags |= FAULT_FLAG_WRITE;
97 
98 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
99 retry:
100 	mmap_read_lock(mm);
101 
102 	vma = find_vma_prev(mm, address, &prev_vma);
103 	if (!vma && !prev_vma )
104 		goto bad_area;
105 
106         /*
107          * find_vma_prev() returns vma such that address < vma->vm_end or NULL
108          *
109          * May find no vma, but could be that the last vm area is the
110          * register backing store that needs to expand upwards, in
111          * this case vma will be null, but prev_vma will ne non-null
112          */
113         if (( !vma && prev_vma ) || (address < vma->vm_start) )
114 		goto check_expansion;
115 
116   good_area:
117 	code = SEGV_ACCERR;
118 
119 	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
120 
121 #	if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
122 	    || (1 << VM_EXEC_BIT) != VM_EXEC)
123 #		error File is out of sync with <linux/mm.h>.  Please update.
124 #	endif
125 
126 	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
127 		goto bad_area;
128 
129 	if ((vma->vm_flags & mask) != mask)
130 		goto bad_area;
131 
132 	/*
133 	 * If for any reason at all we couldn't handle the fault, make
134 	 * sure we exit gracefully rather than endlessly redo the
135 	 * fault.
136 	 */
137 	fault = handle_mm_fault(vma, address, flags, regs);
138 
139 	if (fault_signal_pending(fault, regs))
140 		return;
141 
142 	if (unlikely(fault & VM_FAULT_ERROR)) {
143 		/*
144 		 * We ran out of memory, or some other thing happened
145 		 * to us that made us unable to handle the page fault
146 		 * gracefully.
147 		 */
148 		if (fault & VM_FAULT_OOM) {
149 			goto out_of_memory;
150 		} else if (fault & VM_FAULT_SIGSEGV) {
151 			goto bad_area;
152 		} else if (fault & VM_FAULT_SIGBUS) {
153 			signal = SIGBUS;
154 			goto bad_area;
155 		}
156 		BUG();
157 	}
158 
159 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
160 		if (fault & VM_FAULT_RETRY) {
161 			flags |= FAULT_FLAG_TRIED;
162 
163 			 /* No need to mmap_read_unlock(mm) as we would
164 			 * have already released it in __lock_page_or_retry
165 			 * in mm/filemap.c.
166 			 */
167 
168 			goto retry;
169 		}
170 	}
171 
172 	mmap_read_unlock(mm);
173 	return;
174 
175   check_expansion:
176 	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
177 		if (!vma)
178 			goto bad_area;
179 		if (!(vma->vm_flags & VM_GROWSDOWN))
180 			goto bad_area;
181 		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
182 		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
183 			goto bad_area;
184 		if (expand_stack(vma, address))
185 			goto bad_area;
186 	} else {
187 		vma = prev_vma;
188 		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
189 		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
190 			goto bad_area;
191 		/*
192 		 * Since the register backing store is accessed sequentially,
193 		 * we disallow growing it by more than a page at a time.
194 		 */
195 		if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
196 			goto bad_area;
197 		if (expand_upwards(vma, address))
198 			goto bad_area;
199 	}
200 	goto good_area;
201 
202   bad_area:
203 	mmap_read_unlock(mm);
204 	if ((isr & IA64_ISR_SP)
205 	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
206 	{
207 		/*
208 		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
209 		 * bit in the psr to ensure forward progress.  (Target register will get a
210 		 * NaT for ld.s, lfetch will be canceled.)
211 		 */
212 		ia64_psr(regs)->ed = 1;
213 		return;
214 	}
215 	if (user_mode(regs)) {
216 		force_sig_fault(signal, code, (void __user *) address,
217 				0, __ISR_VALID, isr);
218 		return;
219 	}
220 
221   no_context:
222 	if ((isr & IA64_ISR_SP)
223 	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
224 	{
225 		/*
226 		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
227 		 * bit in the psr to ensure forward progress.  (Target register will get a
228 		 * NaT for ld.s, lfetch will be canceled.)
229 		 */
230 		ia64_psr(regs)->ed = 1;
231 		return;
232 	}
233 
234 	/*
235 	 * Since we have no vma's for region 5, we might get here even if the address is
236 	 * valid, due to the VHPT walker inserting a non present translation that becomes
237 	 * stale. If that happens, the non present fault handler already purged the stale
238 	 * translation, which fixed the problem. So, we check to see if the translation is
239 	 * valid, and return if it is.
240 	 */
241 	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
242 		return;
243 
244 	if (ia64_done_with_exception(regs))
245 		return;
246 
247 	/*
248 	 * Oops. The kernel tried to access some bad page. We'll have to terminate things
249 	 * with extreme prejudice.
250 	 */
251 	bust_spinlocks(1);
252 
253 	if (address < PAGE_SIZE)
254 		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
255 	else
256 		printk(KERN_ALERT "Unable to handle kernel paging request at "
257 		       "virtual address %016lx\n", address);
258 	if (die("Oops", regs, isr))
259 		regs = NULL;
260 	bust_spinlocks(0);
261 	if (regs)
262 		do_exit(SIGKILL);
263 	return;
264 
265   out_of_memory:
266 	mmap_read_unlock(mm);
267 	if (!user_mode(regs))
268 		goto no_context;
269 	pagefault_out_of_memory();
270 }
271