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Linux/arch/m68k/mm/fault.c

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  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 
 16 #include <asm/setup.h>
 17 #include <asm/traps.h>
 18 #include <asm/pgalloc.h>
 19 
 20 extern void die_if_kernel(char *, struct pt_regs *, long);
 21 
 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                 do_exit(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  */
 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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 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 retry:
 89         down_read(&mm->mmap_sem);
 90 
 91         vma = find_vma(mm, address);
 92         if (!vma)
 93                 goto map_err;
 94         if (vma->vm_flags & VM_IO)
 95                 goto acc_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                         /* fall through */
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 (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
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);
139         pr_debug("handle_mm_fault returns %x\n", fault);
140 
141         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
142                 return 0;
143 
144         if (unlikely(fault & VM_FAULT_ERROR)) {
145                 if (fault & VM_FAULT_OOM)
146                         goto out_of_memory;
147                 else if (fault & VM_FAULT_SIGSEGV)
148                         goto map_err;
149                 else if (fault & VM_FAULT_SIGBUS)
150                         goto bus_err;
151                 BUG();
152         }
153 
154         /*
155          * Major/minor page fault accounting is only done on the
156          * initial attempt. If we go through a retry, it is extremely
157          * likely that the page will be found in page cache at that point.
158          */
159         if (flags & FAULT_FLAG_ALLOW_RETRY) {
160                 if (fault & VM_FAULT_MAJOR)
161                         current->maj_flt++;
162                 else
163                         current->min_flt++;
164                 if (fault & VM_FAULT_RETRY) {
165                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
166                          * of starvation. */
167                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
168                         flags |= FAULT_FLAG_TRIED;
169 
170                         /*
171                          * No need to up_read(&mm->mmap_sem) as we would
172                          * have already released it in __lock_page_or_retry
173                          * in mm/filemap.c.
174                          */
175 
176                         goto retry;
177                 }
178         }
179 
180         up_read(&mm->mmap_sem);
181         return 0;
182 
183 /*
184  * We ran out of memory, or some other thing happened to us that made
185  * us unable to handle the page fault gracefully.
186  */
187 out_of_memory:
188         up_read(&mm->mmap_sem);
189         if (!user_mode(regs))
190                 goto no_context;
191         pagefault_out_of_memory();
192         return 0;
193 
194 no_context:
195         current->thread.signo = SIGBUS;
196         current->thread.faddr = address;
197         return send_fault_sig(regs);
198 
199 bus_err:
200         current->thread.signo = SIGBUS;
201         current->thread.code = BUS_ADRERR;
202         current->thread.faddr = address;
203         goto send_sig;
204 
205 map_err:
206         current->thread.signo = SIGSEGV;
207         current->thread.code = SEGV_MAPERR;
208         current->thread.faddr = address;
209         goto send_sig;
210 
211 acc_err:
212         current->thread.signo = SIGSEGV;
213         current->thread.code = SEGV_ACCERR;
214         current->thread.faddr = address;
215 
216 send_sig:
217         up_read(&mm->mmap_sem);
218         return send_fault_sig(regs);
219 }
220 

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