1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/m68k/mm/fault.c
4 *
5 * Copyright (C) 1995 Hamish Macdonald
6 */
7
8 #include <linux/mman.h>
9 #include <linux/mm.h>
10 #include <linux/kernel.h>
11 #include <linux/ptrace.h>
12 #include <linux/interrupt.h>
13 #include <linux/module.h>
14 #include <linux/uaccess.h>
15 #include <linux/perf_event.h>
16
17 #include <asm/setup.h>
18 #include <asm/traps.h>
19
20 extern void die_if_kernel(char *, struct pt_regs *, long);
21
send_fault_sig(struct pt_regs * regs)22 int send_fault_sig(struct pt_regs *regs)
23 {
24 int signo, si_code;
25 void __user *addr;
26
27 signo = current->thread.signo;
28 si_code = current->thread.code;
29 addr = (void __user *)current->thread.faddr;
30 pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code);
31
32 if (user_mode(regs)) {
33 force_sig_fault(signo, si_code, addr);
34 } else {
35 if (fixup_exception(regs))
36 return -1;
37
38 //if (signo == SIGBUS)
39 // force_sig_fault(si_signo, si_code, addr);
40
41 /*
42 * Oops. The kernel tried to access some bad page. We'll have to
43 * terminate things with extreme prejudice.
44 */
45 if ((unsigned long)addr < PAGE_SIZE)
46 pr_alert("Unable to handle kernel NULL pointer dereference");
47 else
48 pr_alert("Unable to handle kernel access");
49 pr_cont(" at virtual address %p\n", addr);
50 die_if_kernel("Oops", regs, 0 /*error_code*/);
51 make_task_dead(SIGKILL);
52 }
53
54 return 1;
55 }
56
57 /*
58 * This routine handles page faults. It determines the problem, and
59 * then passes it off to one of the appropriate routines.
60 *
61 * error_code:
62 * bit 0 == 0 means no page found, 1 means protection fault
63 * bit 1 == 0 means read, 1 means write
64 *
65 * If this routine detects a bad access, it returns 1, otherwise it
66 * returns 0.
67 */
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned long error_code)68 int do_page_fault(struct pt_regs *regs, unsigned long address,
69 unsigned long error_code)
70 {
71 struct mm_struct *mm = current->mm;
72 struct vm_area_struct * vma;
73 vm_fault_t fault;
74 unsigned int flags = FAULT_FLAG_DEFAULT;
75
76 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
77 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
78
79 /*
80 * If we're in an interrupt or have no user
81 * context, we must not take the fault..
82 */
83 if (faulthandler_disabled() || !mm)
84 goto no_context;
85
86 if (user_mode(regs))
87 flags |= FAULT_FLAG_USER;
88
89 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
90 retry:
91 mmap_read_lock(mm);
92
93 vma = find_vma(mm, address);
94 if (!vma)
95 goto map_err;
96 if (vma->vm_flags & VM_IO)
97 goto acc_err;
98 if (vma->vm_start <= address)
99 goto good_area;
100 if (!(vma->vm_flags & VM_GROWSDOWN))
101 goto map_err;
102 if (user_mode(regs)) {
103 /* Accessing the stack below usp is always a bug. The
104 "+ 256" is there due to some instructions doing
105 pre-decrement on the stack and that doesn't show up
106 until later. */
107 if (address + 256 < rdusp())
108 goto map_err;
109 }
110 if (expand_stack(vma, address))
111 goto map_err;
112
113 /*
114 * Ok, we have a good vm_area for this memory access, so
115 * we can handle it..
116 */
117 good_area:
118 pr_debug("do_page_fault: good_area\n");
119 switch (error_code & 3) {
120 default: /* 3: write, present */
121 fallthrough;
122 case 2: /* write, not present */
123 if (!(vma->vm_flags & VM_WRITE))
124 goto acc_err;
125 flags |= FAULT_FLAG_WRITE;
126 break;
127 case 1: /* read, present */
128 goto acc_err;
129 case 0: /* read, not present */
130 if (unlikely(!vma_is_accessible(vma)))
131 goto acc_err;
132 }
133
134 /*
135 * If for any reason at all we couldn't handle the fault,
136 * make sure we exit gracefully rather than endlessly redo
137 * the fault.
138 */
139
140 fault = handle_mm_fault(vma, address, flags, regs);
141 pr_debug("handle_mm_fault returns %x\n", fault);
142
143 if (fault_signal_pending(fault, regs))
144 return 0;
145
146 if (unlikely(fault & VM_FAULT_ERROR)) {
147 if (fault & VM_FAULT_OOM)
148 goto out_of_memory;
149 else if (fault & VM_FAULT_SIGSEGV)
150 goto map_err;
151 else if (fault & VM_FAULT_SIGBUS)
152 goto bus_err;
153 BUG();
154 }
155
156 if (flags & FAULT_FLAG_ALLOW_RETRY) {
157 if (fault & VM_FAULT_RETRY) {
158 flags |= FAULT_FLAG_TRIED;
159
160 /*
161 * No need to mmap_read_unlock(mm) as we would
162 * have already released it in __lock_page_or_retry
163 * in mm/filemap.c.
164 */
165
166 goto retry;
167 }
168 }
169
170 mmap_read_unlock(mm);
171 return 0;
172
173 /*
174 * We ran out of memory, or some other thing happened to us that made
175 * us unable to handle the page fault gracefully.
176 */
177 out_of_memory:
178 mmap_read_unlock(mm);
179 if (!user_mode(regs))
180 goto no_context;
181 pagefault_out_of_memory();
182 return 0;
183
184 no_context:
185 current->thread.signo = SIGBUS;
186 current->thread.faddr = address;
187 return send_fault_sig(regs);
188
189 bus_err:
190 current->thread.signo = SIGBUS;
191 current->thread.code = BUS_ADRERR;
192 current->thread.faddr = address;
193 goto send_sig;
194
195 map_err:
196 current->thread.signo = SIGSEGV;
197 current->thread.code = SEGV_MAPERR;
198 current->thread.faddr = address;
199 goto send_sig;
200
201 acc_err:
202 current->thread.signo = SIGSEGV;
203 current->thread.code = SEGV_ACCERR;
204 current->thread.faddr = address;
205
206 send_sig:
207 mmap_read_unlock(mm);
208 return send_fault_sig(regs);
209 }
210