1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/arch/alpha/mm/fault.c
4  *
5  *  Copyright (C) 1995  Linus Torvalds
6  */
7 
8 #include <linux/sched/signal.h>
9 #include <linux/kernel.h>
10 #include <linux/mm.h>
11 #include <asm/io.h>
12 
13 #define __EXTERN_INLINE inline
14 #include <asm/mmu_context.h>
15 #include <asm/tlbflush.h>
16 #undef  __EXTERN_INLINE
17 
18 #include <linux/signal.h>
19 #include <linux/errno.h>
20 #include <linux/string.h>
21 #include <linux/types.h>
22 #include <linux/ptrace.h>
23 #include <linux/mman.h>
24 #include <linux/smp.h>
25 #include <linux/interrupt.h>
26 #include <linux/extable.h>
27 #include <linux/uaccess.h>
28 #include <linux/perf_event.h>
29 
30 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
31 
32 
33 /*
34  * Force a new ASN for a task.
35  */
36 
37 #ifndef CONFIG_SMP
38 unsigned long last_asn = ASN_FIRST_VERSION;
39 #endif
40 
41 void
__load_new_mm_context(struct mm_struct * next_mm)42 __load_new_mm_context(struct mm_struct *next_mm)
43 {
44 	unsigned long mmc;
45 	struct pcb_struct *pcb;
46 
47 	mmc = __get_new_mm_context(next_mm, smp_processor_id());
48 	next_mm->context[smp_processor_id()] = mmc;
49 
50 	pcb = &current_thread_info()->pcb;
51 	pcb->asn = mmc & HARDWARE_ASN_MASK;
52 	pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
53 
54 	__reload_thread(pcb);
55 }
56 
57 
58 /*
59  * This routine handles page faults.  It determines the address,
60  * and the problem, and then passes it off to handle_mm_fault().
61  *
62  * mmcsr:
63  *	0 = translation not valid
64  *	1 = access violation
65  *	2 = fault-on-read
66  *	3 = fault-on-execute
67  *	4 = fault-on-write
68  *
69  * cause:
70  *	-1 = instruction fetch
71  *	0 = load
72  *	1 = store
73  *
74  * Registers $9 through $15 are saved in a block just prior to `regs' and
75  * are saved and restored around the call to allow exception code to
76  * modify them.
77  */
78 
79 /* Macro for exception fixup code to access integer registers.  */
80 #define dpf_reg(r)							\
81 	(((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :	\
82 				 (r) <= 18 ? (r)+10 : (r)-10])
83 
84 asmlinkage void
do_page_fault(unsigned long address,unsigned long mmcsr,long cause,struct pt_regs * regs)85 do_page_fault(unsigned long address, unsigned long mmcsr,
86 	      long cause, struct pt_regs *regs)
87 {
88 	struct vm_area_struct * vma;
89 	struct mm_struct *mm = current->mm;
90 	const struct exception_table_entry *fixup;
91 	int si_code = SEGV_MAPERR;
92 	vm_fault_t fault;
93 	unsigned int flags = FAULT_FLAG_DEFAULT;
94 
95 	/* As of EV6, a load into $31/$f31 is a prefetch, and never faults
96 	   (or is suppressed by the PALcode).  Support that for older CPUs
97 	   by ignoring such an instruction.  */
98 	if (cause == 0) {
99 		unsigned int insn;
100 		__get_user(insn, (unsigned int __user *)regs->pc);
101 		if ((insn >> 21 & 0x1f) == 0x1f &&
102 		    /* ldq ldl ldt lds ldg ldf ldwu ldbu */
103 		    (1ul << (insn >> 26) & 0x30f00001400ul)) {
104 			regs->pc += 4;
105 			return;
106 		}
107 	}
108 
109 	/* If we're in an interrupt context, or have no user context,
110 	   we must not take the fault.  */
111 	if (!mm || faulthandler_disabled())
112 		goto no_context;
113 
114 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
115 	if (address >= TASK_SIZE)
116 		goto vmalloc_fault;
117 #endif
118 	if (user_mode(regs))
119 		flags |= FAULT_FLAG_USER;
120 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
121 retry:
122 	mmap_read_lock(mm);
123 	vma = find_vma(mm, address);
124 	if (!vma)
125 		goto bad_area;
126 	if (vma->vm_start <= address)
127 		goto good_area;
128 	if (!(vma->vm_flags & VM_GROWSDOWN))
129 		goto bad_area;
130 	if (expand_stack(vma, address))
131 		goto bad_area;
132 
133 	/* Ok, we have a good vm_area for this memory access, so
134 	   we can handle it.  */
135  good_area:
136 	si_code = SEGV_ACCERR;
137 	if (cause < 0) {
138 		if (!(vma->vm_flags & VM_EXEC))
139 			goto bad_area;
140 	} else if (!cause) {
141 		/* Allow reads even for write-only mappings */
142 		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
143 			goto bad_area;
144 	} else {
145 		if (!(vma->vm_flags & VM_WRITE))
146 			goto bad_area;
147 		flags |= FAULT_FLAG_WRITE;
148 	}
149 
150 	/* If for any reason at all we couldn't handle the fault,
151 	   make sure we exit gracefully rather than endlessly redo
152 	   the fault.  */
153 	fault = handle_mm_fault(vma, address, flags, regs);
154 
155 	if (fault_signal_pending(fault, regs)) {
156 		if (!user_mode(regs))
157 			goto no_context;
158 		return;
159 	}
160 
161 	/* The fault is fully completed (including releasing mmap lock) */
162 	if (fault & VM_FAULT_COMPLETED)
163 		return;
164 
165 	if (unlikely(fault & VM_FAULT_ERROR)) {
166 		if (fault & VM_FAULT_OOM)
167 			goto out_of_memory;
168 		else if (fault & VM_FAULT_SIGSEGV)
169 			goto bad_area;
170 		else if (fault & VM_FAULT_SIGBUS)
171 			goto do_sigbus;
172 		BUG();
173 	}
174 
175 	if (fault & VM_FAULT_RETRY) {
176 		flags |= FAULT_FLAG_TRIED;
177 
178 		/* No need to mmap_read_unlock(mm) as we would
179 		 * have already released it in __lock_page_or_retry
180 		 * in mm/filemap.c.
181 		 */
182 
183 		goto retry;
184 	}
185 
186 	mmap_read_unlock(mm);
187 
188 	return;
189 
190 	/* Something tried to access memory that isn't in our memory map.
191 	   Fix it, but check if it's kernel or user first.  */
192  bad_area:
193 	mmap_read_unlock(mm);
194 
195 	if (user_mode(regs))
196 		goto do_sigsegv;
197 
198  no_context:
199 	/* Are we prepared to handle this fault as an exception?  */
200 	if ((fixup = search_exception_tables(regs->pc)) != 0) {
201 		unsigned long newpc;
202 		newpc = fixup_exception(dpf_reg, fixup, regs->pc);
203 		regs->pc = newpc;
204 		return;
205 	}
206 
207 	/* Oops. The kernel tried to access some bad page. We'll have to
208 	   terminate things with extreme prejudice.  */
209 	printk(KERN_ALERT "Unable to handle kernel paging request at "
210 	       "virtual address %016lx\n", address);
211 	die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
212 	make_task_dead(SIGKILL);
213 
214 	/* We ran out of memory, or some other thing happened to us that
215 	   made us unable to handle the page fault gracefully.  */
216  out_of_memory:
217 	mmap_read_unlock(mm);
218 	if (!user_mode(regs))
219 		goto no_context;
220 	pagefault_out_of_memory();
221 	return;
222 
223  do_sigbus:
224 	mmap_read_unlock(mm);
225 	/* Send a sigbus, regardless of whether we were in kernel
226 	   or user mode.  */
227 	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address);
228 	if (!user_mode(regs))
229 		goto no_context;
230 	return;
231 
232  do_sigsegv:
233 	force_sig_fault(SIGSEGV, si_code, (void __user *) address);
234 	return;
235 
236 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
237  vmalloc_fault:
238 	if (user_mode(regs))
239 		goto do_sigsegv;
240 	else {
241 		/* Synchronize this task's top level page-table
242 		   with the "reference" page table from init.  */
243 		long index = pgd_index(address);
244 		pgd_t *pgd, *pgd_k;
245 
246 		pgd = current->active_mm->pgd + index;
247 		pgd_k = swapper_pg_dir + index;
248 		if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
249 			pgd_val(*pgd) = pgd_val(*pgd_k);
250 			return;
251 		}
252 		goto no_context;
253 	}
254 #endif
255 }
256