1 /*
2 * linux/arch/alpha/mm/fault.c
3 *
4 * Copyright (C) 1995 Linus Torvalds
5 */
6
7 #include <linux/sched.h>
8 #include <linux/kernel.h>
9 #include <linux/mm.h>
10 #include <asm/io.h>
11
12 #define __EXTERN_INLINE inline
13 #include <asm/mmu_context.h>
14 #include <asm/tlbflush.h>
15 #undef __EXTERN_INLINE
16
17 #include <linux/signal.h>
18 #include <linux/errno.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21 #include <linux/ptrace.h>
22 #include <linux/mman.h>
23 #include <linux/smp.h>
24 #include <linux/interrupt.h>
25 #include <linux/module.h>
26 #include <linux/uaccess.h>
27
28 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *);
29
30
31 /*
32 * Force a new ASN for a task.
33 */
34
35 #ifndef CONFIG_SMP
36 unsigned long last_asn = ASN_FIRST_VERSION;
37 #endif
38
39 void
__load_new_mm_context(struct mm_struct * next_mm)40 __load_new_mm_context(struct mm_struct *next_mm)
41 {
42 unsigned long mmc;
43 struct pcb_struct *pcb;
44
45 mmc = __get_new_mm_context(next_mm, smp_processor_id());
46 next_mm->context[smp_processor_id()] = mmc;
47
48 pcb = ¤t_thread_info()->pcb;
49 pcb->asn = mmc & HARDWARE_ASN_MASK;
50 pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT;
51
52 __reload_thread(pcb);
53 }
54
55
56 /*
57 * This routine handles page faults. It determines the address,
58 * and the problem, and then passes it off to handle_mm_fault().
59 *
60 * mmcsr:
61 * 0 = translation not valid
62 * 1 = access violation
63 * 2 = fault-on-read
64 * 3 = fault-on-execute
65 * 4 = fault-on-write
66 *
67 * cause:
68 * -1 = instruction fetch
69 * 0 = load
70 * 1 = store
71 *
72 * Registers $9 through $15 are saved in a block just prior to `regs' and
73 * are saved and restored around the call to allow exception code to
74 * modify them.
75 */
76
77 /* Macro for exception fixup code to access integer registers. */
78 #define dpf_reg(r) \
79 (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 : \
80 (r) <= 18 ? (r)+10 : (r)-10])
81
82 asmlinkage void
do_page_fault(unsigned long address,unsigned long mmcsr,long cause,struct pt_regs * regs)83 do_page_fault(unsigned long address, unsigned long mmcsr,
84 long cause, struct pt_regs *regs)
85 {
86 struct vm_area_struct * vma;
87 struct mm_struct *mm = current->mm;
88 const struct exception_table_entry *fixup;
89 int fault, si_code = SEGV_MAPERR;
90 siginfo_t info;
91 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
92
93 /* As of EV6, a load into $31/$f31 is a prefetch, and never faults
94 (or is suppressed by the PALcode). Support that for older CPUs
95 by ignoring such an instruction. */
96 if (cause == 0) {
97 unsigned int insn;
98 __get_user(insn, (unsigned int __user *)regs->pc);
99 if ((insn >> 21 & 0x1f) == 0x1f &&
100 /* ldq ldl ldt lds ldg ldf ldwu ldbu */
101 (1ul << (insn >> 26) & 0x30f00001400ul)) {
102 regs->pc += 4;
103 return;
104 }
105 }
106
107 /* If we're in an interrupt context, or have no user context,
108 we must not take the fault. */
109 if (!mm || faulthandler_disabled())
110 goto no_context;
111
112 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
113 if (address >= TASK_SIZE)
114 goto vmalloc_fault;
115 #endif
116 if (user_mode(regs))
117 flags |= FAULT_FLAG_USER;
118 retry:
119 down_read(&mm->mmap_sem);
120 vma = find_vma(mm, address);
121 if (!vma)
122 goto bad_area;
123 if (vma->vm_start <= address)
124 goto good_area;
125 if (!(vma->vm_flags & VM_GROWSDOWN))
126 goto bad_area;
127 if (expand_stack(vma, address))
128 goto bad_area;
129
130 /* Ok, we have a good vm_area for this memory access, so
131 we can handle it. */
132 good_area:
133 si_code = SEGV_ACCERR;
134 if (cause < 0) {
135 if (!(vma->vm_flags & VM_EXEC))
136 goto bad_area;
137 } else if (!cause) {
138 /* Allow reads even for write-only mappings */
139 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
140 goto bad_area;
141 } else {
142 if (!(vma->vm_flags & VM_WRITE))
143 goto bad_area;
144 flags |= FAULT_FLAG_WRITE;
145 }
146
147 /* If for any reason at all we couldn't handle the fault,
148 make sure we exit gracefully rather than endlessly redo
149 the fault. */
150 fault = handle_mm_fault(mm, vma, address, flags);
151
152 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
153 return;
154
155 if (unlikely(fault & VM_FAULT_ERROR)) {
156 if (fault & VM_FAULT_OOM)
157 goto out_of_memory;
158 else if (fault & VM_FAULT_SIGSEGV)
159 goto bad_area;
160 else if (fault & VM_FAULT_SIGBUS)
161 goto do_sigbus;
162 BUG();
163 }
164
165 if (flags & FAULT_FLAG_ALLOW_RETRY) {
166 if (fault & VM_FAULT_MAJOR)
167 current->maj_flt++;
168 else
169 current->min_flt++;
170 if (fault & VM_FAULT_RETRY) {
171 flags &= ~FAULT_FLAG_ALLOW_RETRY;
172
173 /* No need to up_read(&mm->mmap_sem) as we would
174 * have already released it in __lock_page_or_retry
175 * in mm/filemap.c.
176 */
177
178 goto retry;
179 }
180 }
181
182 up_read(&mm->mmap_sem);
183
184 return;
185
186 /* Something tried to access memory that isn't in our memory map.
187 Fix it, but check if it's kernel or user first. */
188 bad_area:
189 up_read(&mm->mmap_sem);
190
191 if (user_mode(regs))
192 goto do_sigsegv;
193
194 no_context:
195 /* Are we prepared to handle this fault as an exception? */
196 if ((fixup = search_exception_tables(regs->pc)) != 0) {
197 unsigned long newpc;
198 newpc = fixup_exception(dpf_reg, fixup, regs->pc);
199 regs->pc = newpc;
200 return;
201 }
202
203 /* Oops. The kernel tried to access some bad page. We'll have to
204 terminate things with extreme prejudice. */
205 printk(KERN_ALERT "Unable to handle kernel paging request at "
206 "virtual address %016lx\n", address);
207 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
208 do_exit(SIGKILL);
209
210 /* We ran out of memory, or some other thing happened to us that
211 made us unable to handle the page fault gracefully. */
212 out_of_memory:
213 up_read(&mm->mmap_sem);
214 if (!user_mode(regs))
215 goto no_context;
216 pagefault_out_of_memory();
217 return;
218
219 do_sigbus:
220 up_read(&mm->mmap_sem);
221 /* Send a sigbus, regardless of whether we were in kernel
222 or user mode. */
223 info.si_signo = SIGBUS;
224 info.si_errno = 0;
225 info.si_code = BUS_ADRERR;
226 info.si_addr = (void __user *) address;
227 force_sig_info(SIGBUS, &info, current);
228 if (!user_mode(regs))
229 goto no_context;
230 return;
231
232 do_sigsegv:
233 info.si_signo = SIGSEGV;
234 info.si_errno = 0;
235 info.si_code = si_code;
236 info.si_addr = (void __user *) address;
237 force_sig_info(SIGSEGV, &info, current);
238 return;
239
240 #ifdef CONFIG_ALPHA_LARGE_VMALLOC
241 vmalloc_fault:
242 if (user_mode(regs))
243 goto do_sigsegv;
244 else {
245 /* Synchronize this task's top level page-table
246 with the "reference" page table from init. */
247 long index = pgd_index(address);
248 pgd_t *pgd, *pgd_k;
249
250 pgd = current->active_mm->pgd + index;
251 pgd_k = swapper_pg_dir + index;
252 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
253 pgd_val(*pgd) = pgd_val(*pgd_k);
254 return;
255 }
256 goto no_context;
257 }
258 #endif
259 }
260