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
27#include <asm/system.h>
28#include <asm/uaccess.h>
29
30extern 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
38unsigned long last_asn = ASN_FIRST_VERSION;
39#endif
40
41void
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)+8 : (r)-10])
83
84asmlinkage void
85do_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 fault, si_code = SEGV_MAPERR;
92	siginfo_t info;
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 || in_atomic())
111		goto no_context;
112
113#ifdef CONFIG_ALPHA_LARGE_VMALLOC
114	if (address >= TASK_SIZE)
115		goto vmalloc_fault;
116#endif
117
118	down_read(&mm->mmap_sem);
119	vma = find_vma(mm, address);
120	if (!vma)
121		goto bad_area;
122	if (vma->vm_start <= address)
123		goto good_area;
124	if (!(vma->vm_flags & VM_GROWSDOWN))
125		goto bad_area;
126	if (expand_stack(vma, address))
127		goto bad_area;
128
129	/* Ok, we have a good vm_area for this memory access, so
130	   we can handle it.  */
131 good_area:
132	si_code = SEGV_ACCERR;
133	if (cause < 0) {
134		if (!(vma->vm_flags & VM_EXEC))
135			goto bad_area;
136	} else if (!cause) {
137		/* Allow reads even for write-only mappings */
138		if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
139			goto bad_area;
140	} else {
141		if (!(vma->vm_flags & VM_WRITE))
142			goto bad_area;
143	}
144
145 survive:
146	/* If for any reason at all we couldn't handle the fault,
147	   make sure we exit gracefully rather than endlessly redo
148	   the fault.  */
149	fault = handle_mm_fault(mm, vma, address, cause > 0);
150	up_read(&mm->mmap_sem);
151
152	switch (fault) {
153	      case VM_FAULT_MINOR:
154		current->min_flt++;
155		break;
156	      case VM_FAULT_MAJOR:
157		current->maj_flt++;
158		break;
159	      case VM_FAULT_SIGBUS:
160		goto do_sigbus;
161	      case VM_FAULT_OOM:
162		goto out_of_memory;
163	      default:
164		BUG();
165	}
166	return;
167
168	/* Something tried to access memory that isn't in our memory map.
169	   Fix it, but check if it's kernel or user first.  */
170 bad_area:
171	up_read(&mm->mmap_sem);
172
173	if (user_mode(regs))
174		goto do_sigsegv;
175
176 no_context:
177	/* Are we prepared to handle this fault as an exception?  */
178	if ((fixup = search_exception_tables(regs->pc)) != 0) {
179		unsigned long newpc;
180		newpc = fixup_exception(dpf_reg, fixup, regs->pc);
181		regs->pc = newpc;
182		return;
183	}
184
185	/* Oops. The kernel tried to access some bad page. We'll have to
186	   terminate things with extreme prejudice.  */
187	printk(KERN_ALERT "Unable to handle kernel paging request at "
188	       "virtual address %016lx\n", address);
189	die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16);
190	do_exit(SIGKILL);
191
192	/* We ran out of memory, or some other thing happened to us that
193	   made us unable to handle the page fault gracefully.  */
194 out_of_memory:
195	if (is_init(current)) {
196		yield();
197		down_read(&mm->mmap_sem);
198		goto survive;
199	}
200	printk(KERN_ALERT "VM: killing process %s(%d)\n",
201	       current->comm, current->pid);
202	if (!user_mode(regs))
203		goto no_context;
204	do_exit(SIGKILL);
205
206 do_sigbus:
207	/* Send a sigbus, regardless of whether we were in kernel
208	   or user mode.  */
209	info.si_signo = SIGBUS;
210	info.si_errno = 0;
211	info.si_code = BUS_ADRERR;
212	info.si_addr = (void __user *) address;
213	force_sig_info(SIGBUS, &info, current);
214	if (!user_mode(regs))
215		goto no_context;
216	return;
217
218 do_sigsegv:
219	info.si_signo = SIGSEGV;
220	info.si_errno = 0;
221	info.si_code = si_code;
222	info.si_addr = (void __user *) address;
223	force_sig_info(SIGSEGV, &info, current);
224	return;
225
226#ifdef CONFIG_ALPHA_LARGE_VMALLOC
227 vmalloc_fault:
228	if (user_mode(regs))
229		goto do_sigsegv;
230	else {
231		/* Synchronize this task's top level page-table
232		   with the "reference" page table from init.  */
233		long index = pgd_index(address);
234		pgd_t *pgd, *pgd_k;
235
236		pgd = current->active_mm->pgd + index;
237		pgd_k = swapper_pg_dir + index;
238		if (!pgd_present(*pgd) && pgd_present(*pgd_k)) {
239			pgd_val(*pgd) = pgd_val(*pgd_k);
240			return;
241		}
242		goto no_context;
243	}
244#endif
245}
246