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_start <= address)
97 goto good_area;
98 if (!(vma->vm_flags & VM_GROWSDOWN))
99 goto map_err;
100 if (user_mode(regs)) {
101 /* Accessing the stack below usp is always a bug. The
102 "+ 256" is there due to some instructions doing
103 pre-decrement on the stack and that doesn't show up
104 until later. */
105 if (address + 256 < rdusp())
106 goto map_err;
107 }
108 if (expand_stack(vma, address))
109 goto map_err;
110
111 /*
112 * Ok, we have a good vm_area for this memory access, so
113 * we can handle it..
114 */
115 good_area:
116 pr_debug("do_page_fault: good_area\n");
117 switch (error_code & 3) {
118 default: /* 3: write, present */
119 fallthrough;
120 case 2: /* write, not present */
121 if (!(vma->vm_flags & VM_WRITE))
122 goto acc_err;
123 flags |= FAULT_FLAG_WRITE;
124 break;
125 case 1: /* read, present */
126 goto acc_err;
127 case 0: /* read, not present */
128 if (unlikely(!vma_is_accessible(vma)))
129 goto acc_err;
130 }
131
132 /*
133 * If for any reason at all we couldn't handle the fault,
134 * make sure we exit gracefully rather than endlessly redo
135 * the fault.
136 */
137
138 fault = handle_mm_fault(vma, address, flags, regs);
139 pr_debug("handle_mm_fault returns %x\n", fault);
140
141 if (fault_signal_pending(fault, regs))
142 return 0;
143
144 /* The fault is fully completed (including releasing mmap lock) */
145 if (fault & VM_FAULT_COMPLETED)
146 return 0;
147
148 if (unlikely(fault & VM_FAULT_ERROR)) {
149 if (fault & VM_FAULT_OOM)
150 goto out_of_memory;
151 else if (fault & VM_FAULT_SIGSEGV)
152 goto map_err;
153 else if (fault & VM_FAULT_SIGBUS)
154 goto bus_err;
155 BUG();
156 }
157
158 if (fault & VM_FAULT_RETRY) {
159 flags |= FAULT_FLAG_TRIED;
160
161 /*
162 * No need to mmap_read_unlock(mm) as we would
163 * have already released it in __lock_page_or_retry
164 * in mm/filemap.c.
165 */
166
167 goto retry;
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