xref: /linux/arch/alpha/mm/fault.c (revision 37744feebc086908fd89760650f458ab19071750)
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 
29 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
30 
31 
32 /*
33  * Force a new ASN for a task.
34  */
35 
36 #ifndef CONFIG_SMP
37 unsigned long last_asn = ASN_FIRST_VERSION;
38 #endif
39 
40 void
41 __load_new_mm_context(struct mm_struct *next_mm)
42 {
43 	unsigned long mmc;
44 	struct pcb_struct *pcb;
45 
46 	mmc = __get_new_mm_context(next_mm, smp_processor_id());
47 	next_mm->context[smp_processor_id()] = mmc;
48 
49 	pcb = &current_thread_info()->pcb;
50 	pcb->asn = mmc & HARDWARE_ASN_MASK;
51 	pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
52 
53 	__reload_thread(pcb);
54 }
55 
56 
57 /*
58  * This routine handles page faults.  It determines the address,
59  * and the problem, and then passes it off to handle_mm_fault().
60  *
61  * mmcsr:
62  *	0 = translation not valid
63  *	1 = access violation
64  *	2 = fault-on-read
65  *	3 = fault-on-execute
66  *	4 = fault-on-write
67  *
68  * cause:
69  *	-1 = instruction fetch
70  *	0 = load
71  *	1 = store
72  *
73  * Registers $9 through $15 are saved in a block just prior to `regs' and
74  * are saved and restored around the call to allow exception code to
75  * modify them.
76  */
77 
78 /* Macro for exception fixup code to access integer registers.  */
79 #define dpf_reg(r)							\
80 	(((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 :	\
81 				 (r) <= 18 ? (r)+10 : (r)-10])
82 
83 asmlinkage void
84 do_page_fault(unsigned long address, unsigned long mmcsr,
85 	      long cause, struct pt_regs *regs)
86 {
87 	struct vm_area_struct * vma;
88 	struct mm_struct *mm = current->mm;
89 	const struct exception_table_entry *fixup;
90 	int si_code = SEGV_MAPERR;
91 	vm_fault_t fault;
92 	unsigned int flags = FAULT_FLAG_DEFAULT;
93 
94 	/* As of EV6, a load into $31/$f31 is a prefetch, and never faults
95 	   (or is suppressed by the PALcode).  Support that for older CPUs
96 	   by ignoring such an instruction.  */
97 	if (cause == 0) {
98 		unsigned int insn;
99 		__get_user(insn, (unsigned int __user *)regs->pc);
100 		if ((insn >> 21 & 0x1f) == 0x1f &&
101 		    /* ldq ldl ldt lds ldg ldf ldwu ldbu */
102 		    (1ul << (insn >> 26) & 0x30f00001400ul)) {
103 			regs->pc += 4;
104 			return;
105 		}
106 	}
107 
108 	/* If we're in an interrupt context, or have no user context,
109 	   we must not take the fault.  */
110 	if (!mm || faulthandler_disabled())
111 		goto no_context;
112 
113 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
114 	if (address >= TASK_SIZE)
115 		goto vmalloc_fault;
116 #endif
117 	if (user_mode(regs))
118 		flags |= FAULT_FLAG_USER;
119 retry:
120 	down_read(&mm->mmap_sem);
121 	vma = find_vma(mm, address);
122 	if (!vma)
123 		goto bad_area;
124 	if (vma->vm_start <= address)
125 		goto good_area;
126 	if (!(vma->vm_flags & VM_GROWSDOWN))
127 		goto bad_area;
128 	if (expand_stack(vma, address))
129 		goto bad_area;
130 
131 	/* Ok, we have a good vm_area for this memory access, so
132 	   we can handle it.  */
133  good_area:
134 	si_code = SEGV_ACCERR;
135 	if (cause < 0) {
136 		if (!(vma->vm_flags & VM_EXEC))
137 			goto bad_area;
138 	} else if (!cause) {
139 		/* Allow reads even for write-only mappings */
140 		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
141 			goto bad_area;
142 	} else {
143 		if (!(vma->vm_flags & VM_WRITE))
144 			goto bad_area;
145 		flags |= FAULT_FLAG_WRITE;
146 	}
147 
148 	/* If for any reason at all we couldn't handle the fault,
149 	   make sure we exit gracefully rather than endlessly redo
150 	   the fault.  */
151 	fault = handle_mm_fault(vma, address, flags);
152 
153 	if (fault_signal_pending(fault, regs))
154 		return;
155 
156 	if (unlikely(fault & VM_FAULT_ERROR)) {
157 		if (fault & VM_FAULT_OOM)
158 			goto out_of_memory;
159 		else if (fault & VM_FAULT_SIGSEGV)
160 			goto bad_area;
161 		else if (fault & VM_FAULT_SIGBUS)
162 			goto do_sigbus;
163 		BUG();
164 	}
165 
166 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
167 		if (fault & VM_FAULT_MAJOR)
168 			current->maj_flt++;
169 		else
170 			current->min_flt++;
171 		if (fault & VM_FAULT_RETRY) {
172 			flags |= FAULT_FLAG_TRIED;
173 
174 			 /* No need to up_read(&mm->mmap_sem) as we would
175 			 * have already released it in __lock_page_or_retry
176 			 * in mm/filemap.c.
177 			 */
178 
179 			goto retry;
180 		}
181 	}
182 
183 	up_read(&mm->mmap_sem);
184 
185 	return;
186 
187 	/* Something tried to access memory that isn't in our memory map.
188 	   Fix it, but check if it's kernel or user first.  */
189  bad_area:
190 	up_read(&mm->mmap_sem);
191 
192 	if (user_mode(regs))
193 		goto do_sigsegv;
194 
195  no_context:
196 	/* Are we prepared to handle this fault as an exception?  */
197 	if ((fixup = search_exception_tables(regs->pc)) != 0) {
198 		unsigned long newpc;
199 		newpc = fixup_exception(dpf_reg, fixup, regs->pc);
200 		regs->pc = newpc;
201 		return;
202 	}
203 
204 	/* Oops. The kernel tried to access some bad page. We'll have to
205 	   terminate things with extreme prejudice.  */
206 	printk(KERN_ALERT "Unable to handle kernel paging request at "
207 	       "virtual address %016lx\n", address);
208 	die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
209 	do_exit(SIGKILL);
210 
211 	/* We ran out of memory, or some other thing happened to us that
212 	   made us unable to handle the page fault gracefully.  */
213  out_of_memory:
214 	up_read(&mm->mmap_sem);
215 	if (!user_mode(regs))
216 		goto no_context;
217 	pagefault_out_of_memory();
218 	return;
219 
220  do_sigbus:
221 	up_read(&mm->mmap_sem);
222 	/* Send a sigbus, regardless of whether we were in kernel
223 	   or user mode.  */
224 	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address, 0);
225 	if (!user_mode(regs))
226 		goto no_context;
227 	return;
228 
229  do_sigsegv:
230 	force_sig_fault(SIGSEGV, si_code, (void __user *) address, 0);
231 	return;
232 
233 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
234  vmalloc_fault:
235 	if (user_mode(regs))
236 		goto do_sigsegv;
237 	else {
238 		/* Synchronize this task's top level page-table
239 		   with the "reference" page table from init.  */
240 		long index = pgd_index(address);
241 		pgd_t *pgd, *pgd_k;
242 
243 		pgd = current->active_mm->pgd + index;
244 		pgd_k = swapper_pg_dir + index;
245 		if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
246 			pgd_val(*pgd) = pgd_val(*pgd_k);
247 			return;
248 		}
249 		goto no_context;
250 	}
251 #endif
252 }
253