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 #include "fault.h"
21
22 extern void die_if_kernel(char *, struct pt_regs *, long);
23
24 int send_fault_sig(struct pt_regs *regs)
25 {
26 int signo, si_code;
27 void __user *addr;
28
29 signo = current->thread.signo;
30 si_code = current->thread.code;
31 addr = (void __user *)current->thread.faddr;
32 pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code);
33
34 if (user_mode(regs)) {
35 force_sig_fault(signo, si_code, addr);
36 } else {
37 if (fixup_exception(regs))
38 return -1;
39
40 //if (signo == SIGBUS)
41 // force_sig_fault(si_signo, si_code, addr);
42
43 /*
44 * Oops. The kernel tried to access some bad page. We'll have to
45 * terminate things with extreme prejudice.
46 */
47 if ((unsigned long)addr < PAGE_SIZE)
48 pr_alert("Unable to handle kernel NULL pointer dereference");
49 else
50 pr_alert("Unable to handle kernel access");
51 pr_cont(" at virtual address %p\n", addr);
52 die_if_kernel("Oops", regs, 0 /*error_code*/);
53 make_task_dead(SIGKILL);
54 }
55
56 return 1;
57 }
58
59 /*
60 * This routine handles page faults. It determines the problem, and
61 * then passes it off to one of the appropriate routines.
62 *
63 * error_code:
64 * bit 0 == 0 means no page found, 1 means protection fault
65 * bit 1 == 0 means read, 1 means write
66 *
67 * If this routine detects a bad access, it returns 1, otherwise it
68 * returns 0.
69 */
70 int do_page_fault(struct pt_regs *regs, unsigned long address,
71 unsigned long error_code)
72 {
73 struct mm_struct *mm = current->mm;
74 struct vm_area_struct * vma;
75 vm_fault_t fault;
76 unsigned int flags = FAULT_FLAG_DEFAULT;
77
78 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
79 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
80
81 /*
82 * If we're in an interrupt or have no user
83 * context, we must not take the fault..
84 */
85 if (faulthandler_disabled() || !mm)
86 goto no_context;
87
88 if (user_mode(regs))
89 flags |= FAULT_FLAG_USER;
90
91 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
92 retry:
93 mmap_read_lock(mm);
94
95 vma = find_vma(mm, address);
96 if (!vma)
97 goto map_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 vma = expand_stack(mm, address);
111 if (!vma)
112 goto map_err_nosemaphore;
113
114 /*
115 * Ok, we have a good vm_area for this memory access, so
116 * we can handle it..
117 */
118 good_area:
119 pr_debug("do_page_fault: good_area\n");
120 switch (error_code & 3) {
121 default: /* 3: write, present */
122 fallthrough;
123 case 2: /* write, not present */
124 if (!(vma->vm_flags & VM_WRITE))
125 goto acc_err;
126 flags |= FAULT_FLAG_WRITE;
127 break;
128 case 1: /* read, present */
129 goto acc_err;
130 case 0: /* read, not present */
131 if (unlikely(!vma_is_accessible(vma)))
132 goto acc_err;
133 }
134
135 /*
136 * If for any reason at all we couldn't handle the fault,
137 * make sure we exit gracefully rather than endlessly redo
138 * the fault.
139 */
140
141 fault = handle_mm_fault(vma, address, flags, regs);
142 pr_debug("handle_mm_fault returns %x\n", fault);
143
144 if (fault_signal_pending(fault, regs)) {
145 if (!user_mode(regs))
146 goto no_context;
147 return 0;
148 }
149
150 /* The fault is fully completed (including releasing mmap lock) */
151 if (fault & VM_FAULT_COMPLETED)
152 return 0;
153
154 if (unlikely(fault & VM_FAULT_ERROR)) {
155 if (fault & VM_FAULT_OOM)
156 goto out_of_memory;
157 else if (fault & VM_FAULT_SIGSEGV)
158 goto map_err;
159 else if (fault & VM_FAULT_SIGBUS)
160 goto bus_err;
161 BUG();
162 }
163
164 if (fault & VM_FAULT_RETRY) {
165 flags |= FAULT_FLAG_TRIED;
166
167 /*
168 * No need to mmap_read_unlock(mm) as we would
169 * have already released it in __lock_page_or_retry
170 * in mm/filemap.c.
171 */
172
173 goto retry;
174 }
175
176 mmap_read_unlock(mm);
177 return 0;
178
179 /*
180 * We ran out of memory, or some other thing happened to us that made
181 * us unable to handle the page fault gracefully.
182 */
183 out_of_memory:
184 mmap_read_unlock(mm);
185 if (!user_mode(regs))
186 goto no_context;
187 pagefault_out_of_memory();
188 return 0;
189
190 no_context:
191 current->thread.signo = SIGBUS;
192 current->thread.faddr = address;
193 return send_fault_sig(regs);
194
195 bus_err:
196 current->thread.signo = SIGBUS;
197 current->thread.code = BUS_ADRERR;
198 current->thread.faddr = address;
199 goto send_sig;
200
201 map_err:
202 mmap_read_unlock(mm);
203 map_err_nosemaphore:
204 current->thread.signo = SIGSEGV;
205 current->thread.code = SEGV_MAPERR;
206 current->thread.faddr = address;
207 return send_fault_sig(regs);
208
209 acc_err:
210 current->thread.signo = SIGSEGV;
211 current->thread.code = SEGV_ACCERR;
212 current->thread.faddr = address;
213
214 send_sig:
215 mmap_read_unlock(mm);
216 return send_fault_sig(regs);
217 }
218
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