1/*
2 *  linux/arch/m68k/mm/fault.c
3 *
4 *  Copyright (C) 1995  Hamish Macdonald
5 */
6
7#include <linux/mman.h>
8#include <linux/mm.h>
9#include <linux/kernel.h>
10#include <linux/ptrace.h>
11#include <linux/interrupt.h>
12#include <linux/module.h>
13
14#include <asm/setup.h>
15#include <asm/traps.h>
16#include <asm/uaccess.h>
17#include <asm/pgalloc.h>
18
19extern void die_if_kernel(char *, struct pt_regs *, long);
20
21int send_fault_sig(struct pt_regs *regs)
22{
23	siginfo_t siginfo = { 0, 0, 0, };
24
25	siginfo.si_signo = current->thread.signo;
26	siginfo.si_code = current->thread.code;
27	siginfo.si_addr = (void *)current->thread.faddr;
28	pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr,
29		 siginfo.si_signo, siginfo.si_code);
30
31	if (user_mode(regs)) {
32		force_sig_info(siginfo.si_signo,
33			       &siginfo, current);
34	} else {
35		if (handle_kernel_fault(regs))
36			return -1;
37
38		//if (siginfo.si_signo == SIGBUS)
39		//	force_sig_info(siginfo.si_signo,
40		//		       &siginfo, current);
41
42		/*
43		 * Oops. The kernel tried to access some bad page. We'll have to
44		 * terminate things with extreme prejudice.
45		 */
46		if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
47			pr_alert("Unable to handle kernel NULL pointer dereference");
48		else
49			pr_alert("Unable to handle kernel access");
50		pr_cont(" at virtual address %p\n", siginfo.si_addr);
51		die_if_kernel("Oops", regs, 0 /*error_code*/);
52		do_exit(SIGKILL);
53	}
54
55	return 1;
56}
57
58/*
59 * This routine handles page faults.  It determines the problem, and
60 * then passes it off to one of the appropriate routines.
61 *
62 * error_code:
63 *	bit 0 == 0 means no page found, 1 means protection fault
64 *	bit 1 == 0 means read, 1 means write
65 *
66 * If this routine detects a bad access, it returns 1, otherwise it
67 * returns 0.
68 */
69int do_page_fault(struct pt_regs *regs, unsigned long address,
70			      unsigned long error_code)
71{
72	struct mm_struct *mm = current->mm;
73	struct vm_area_struct * vma;
74	int fault;
75	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
76
77	pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
78		regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
79
80	/*
81	 * If we're in an interrupt or have no user
82	 * context, we must not take the fault..
83	 */
84	if (in_atomic() || !mm)
85		goto no_context;
86
87	if (user_mode(regs))
88		flags |= FAULT_FLAG_USER;
89retry:
90	down_read(&mm->mmap_sem);
91
92	vma = find_vma(mm, address);
93	if (!vma)
94		goto map_err;
95	if (vma->vm_flags & VM_IO)
96		goto acc_err;
97	if (vma->vm_start <= address)
98		goto good_area;
99	if (!(vma->vm_flags & VM_GROWSDOWN))
100		goto map_err;
101	if (user_mode(regs)) {
102		/* Accessing the stack below usp is always a bug.  The
103		   "+ 256" is there due to some instructions doing
104		   pre-decrement on the stack and that doesn't show up
105		   until later.  */
106		if (address + 256 < rdusp())
107			goto map_err;
108	}
109	if (expand_stack(vma, address))
110		goto map_err;
111
112/*
113 * Ok, we have a good vm_area for this memory access, so
114 * we can handle it..
115 */
116good_area:
117	pr_debug("do_page_fault: good_area\n");
118	switch (error_code & 3) {
119		default:	/* 3: write, present */
120			/* fall through */
121		case 2:		/* write, not present */
122			if (!(vma->vm_flags & VM_WRITE))
123				goto acc_err;
124			flags |= FAULT_FLAG_WRITE;
125			break;
126		case 1:		/* read, present */
127			goto acc_err;
128		case 0:		/* read, not present */
129			if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
130				goto acc_err;
131	}
132
133	/*
134	 * If for any reason at all we couldn't handle the fault,
135	 * make sure we exit gracefully rather than endlessly redo
136	 * the fault.
137	 */
138
139	fault = handle_mm_fault(mm, vma, address, flags);
140	pr_debug("handle_mm_fault returns %d\n", fault);
141
142	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
143		return 0;
144
145	if (unlikely(fault & VM_FAULT_ERROR)) {
146		if (fault & VM_FAULT_OOM)
147			goto out_of_memory;
148		else if (fault & VM_FAULT_SIGSEGV)
149			goto map_err;
150		else if (fault & VM_FAULT_SIGBUS)
151			goto bus_err;
152		BUG();
153	}
154
155	/*
156	 * Major/minor page fault accounting is only done on the
157	 * initial attempt. If we go through a retry, it is extremely
158	 * likely that the page will be found in page cache at that point.
159	 */
160	if (flags & FAULT_FLAG_ALLOW_RETRY) {
161		if (fault & VM_FAULT_MAJOR)
162			current->maj_flt++;
163		else
164			current->min_flt++;
165		if (fault & VM_FAULT_RETRY) {
166			/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
167			 * of starvation. */
168			flags &= ~FAULT_FLAG_ALLOW_RETRY;
169			flags |= FAULT_FLAG_TRIED;
170
171			/*
172			 * No need to up_read(&mm->mmap_sem) as we would
173			 * have already released it in __lock_page_or_retry
174			 * in mm/filemap.c.
175			 */
176
177			goto retry;
178		}
179	}
180
181	up_read(&mm->mmap_sem);
182	return 0;
183
184/*
185 * We ran out of memory, or some other thing happened to us that made
186 * us unable to handle the page fault gracefully.
187 */
188out_of_memory:
189	up_read(&mm->mmap_sem);
190	if (!user_mode(regs))
191		goto no_context;
192	pagefault_out_of_memory();
193	return 0;
194
195no_context:
196	current->thread.signo = SIGBUS;
197	current->thread.faddr = address;
198	return send_fault_sig(regs);
199
200bus_err:
201	current->thread.signo = SIGBUS;
202	current->thread.code = BUS_ADRERR;
203	current->thread.faddr = address;
204	goto send_sig;
205
206map_err:
207	current->thread.signo = SIGSEGV;
208	current->thread.code = SEGV_MAPERR;
209	current->thread.faddr = address;
210	goto send_sig;
211
212acc_err:
213	current->thread.signo = SIGSEGV;
214	current->thread.code = SEGV_ACCERR;
215	current->thread.faddr = address;
216
217send_sig:
218	up_read(&mm->mmap_sem);
219	return send_fault_sig(regs);
220}
221