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 vma = expand_stack(mm, address);
109 if (!vma)
110 goto map_err_nosemaphore;
111
112 /*
113 * Ok, we have a good vm_area for this memory access, so
114 * we can handle it..
115 */
116 good_area:
117 pr_debug("do_page_fault: good_area\n");
118 switch (error_code & 3) {
119 default: /* 3: write, present */
120 fallthrough;
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 (unlikely(!vma_is_accessible(vma)))
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(vma, address, flags, regs);
140 pr_debug("handle_mm_fault returns %x\n", fault);
141
142 if (fault_signal_pending(fault, regs)) {
143 if (!user_mode(regs))
144 goto no_context;
145 return 0;
146 }
147
148 /* The fault is fully completed (including releasing mmap lock) */
149 if (fault & VM_FAULT_COMPLETED)
150 return 0;
151
152 if (unlikely(fault & VM_FAULT_ERROR)) {
153 if (fault & VM_FAULT_OOM)
154 goto out_of_memory;
155 else if (fault & VM_FAULT_SIGSEGV)
156 goto map_err;
157 else if (fault & VM_FAULT_SIGBUS)
158 goto bus_err;
159 BUG();
160 }
161
162 if (fault & VM_FAULT_RETRY) {
163 flags |= FAULT_FLAG_TRIED;
164
165 /*
166 * No need to mmap_read_unlock(mm) as we would
167 * have already released it in __lock_page_or_retry
168 * in mm/filemap.c.
169 */
170
171 goto retry;
172 }
173
174 mmap_read_unlock(mm);
175 return 0;
176
177 /*
178 * We ran out of memory, or some other thing happened to us that made
179 * us unable to handle the page fault gracefully.
180 */
181 out_of_memory:
182 mmap_read_unlock(mm);
183 if (!user_mode(regs))
184 goto no_context;
185 pagefault_out_of_memory();
186 return 0;
187
188 no_context:
189 current->thread.signo = SIGBUS;
190 current->thread.faddr = address;
191 return send_fault_sig(regs);
192
193 bus_err:
194 current->thread.signo = SIGBUS;
195 current->thread.code = BUS_ADRERR;
196 current->thread.faddr = address;
197 goto send_sig;
198
199 map_err:
200 mmap_read_unlock(mm);
201 map_err_nosemaphore:
202 current->thread.signo = SIGSEGV;
203 current->thread.code = SEGV_MAPERR;
204 current->thread.faddr = address;
205 return send_fault_sig(regs);
206
207 acc_err:
208 current->thread.signo = SIGSEGV;
209 current->thread.code = SEGV_ACCERR;
210 current->thread.faddr = address;
211
212 send_sig:
213 mmap_read_unlock(mm);
214 return send_fault_sig(regs);
215 }
216
