xref: /openbmc/linux/arch/mips/mm/fault.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 1995 - 2000 by Ralf Baechle
7  */
8 #include <linux/signal.h>
9 #include <linux/sched.h>
10 #include <linux/interrupt.h>
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/string.h>
14 #include <linux/types.h>
15 #include <linux/ptrace.h>
16 #include <linux/mman.h>
17 #include <linux/mm.h>
18 #include <linux/smp.h>
19 #include <linux/smp_lock.h>
20 #include <linux/vt_kern.h>		/* For unblank_screen() */
21 #include <linux/module.h>
22 
23 #include <asm/branch.h>
24 #include <asm/mmu_context.h>
25 #include <asm/system.h>
26 #include <asm/uaccess.h>
27 #include <asm/ptrace.h>
28 #include <asm/highmem.h>		/* For VMALLOC_END */
29 
30 /*
31  * This routine handles page faults.  It determines the address,
32  * and the problem, and then passes it off to one of the appropriate
33  * routines.
34  */
35 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
36 			      unsigned long address)
37 {
38 	struct vm_area_struct * vma = NULL;
39 	struct task_struct *tsk = current;
40 	struct mm_struct *mm = tsk->mm;
41 	const int field = sizeof(unsigned long) * 2;
42 	siginfo_t info;
43 
44 #if 0
45 	printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", smp_processor_id(),
46 	       current->comm, current->pid, field, address, write,
47 	       field, regs->cp0_epc);
48 #endif
49 
50 	info.si_code = SEGV_MAPERR;
51 
52 	/*
53 	 * We fault-in kernel-space virtual memory on-demand. The
54 	 * 'reference' page table is init_mm.pgd.
55 	 *
56 	 * NOTE! We MUST NOT take any locks for this case. We may
57 	 * be in an interrupt or a critical region, and should
58 	 * only copy the information from the master page table,
59 	 * nothing more.
60 	 */
61 	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
62 		goto vmalloc_fault;
63 
64 	/*
65 	 * If we're in an interrupt or have no user
66 	 * context, we must not take the fault..
67 	 */
68 	if (in_atomic() || !mm)
69 		goto bad_area_nosemaphore;
70 
71 	down_read(&mm->mmap_sem);
72 	vma = find_vma(mm, address);
73 	if (!vma)
74 		goto bad_area;
75 	if (vma->vm_start <= address)
76 		goto good_area;
77 	if (!(vma->vm_flags & VM_GROWSDOWN))
78 		goto bad_area;
79 	if (expand_stack(vma, address))
80 		goto bad_area;
81 /*
82  * Ok, we have a good vm_area for this memory access, so
83  * we can handle it..
84  */
85 good_area:
86 	info.si_code = SEGV_ACCERR;
87 
88 	if (write) {
89 		if (!(vma->vm_flags & VM_WRITE))
90 			goto bad_area;
91 	} else {
92 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
93 			goto bad_area;
94 	}
95 
96 survive:
97 	/*
98 	 * If for any reason at all we couldn't handle the fault,
99 	 * make sure we exit gracefully rather than endlessly redo
100 	 * the fault.
101 	 */
102 	switch (handle_mm_fault(mm, vma, address, write)) {
103 	case VM_FAULT_MINOR:
104 		tsk->min_flt++;
105 		break;
106 	case VM_FAULT_MAJOR:
107 		tsk->maj_flt++;
108 		break;
109 	case VM_FAULT_SIGBUS:
110 		goto do_sigbus;
111 	case VM_FAULT_OOM:
112 		goto out_of_memory;
113 	default:
114 		BUG();
115 	}
116 
117 	up_read(&mm->mmap_sem);
118 	return;
119 
120 /*
121  * Something tried to access memory that isn't in our memory map..
122  * Fix it, but check if it's kernel or user first..
123  */
124 bad_area:
125 	up_read(&mm->mmap_sem);
126 
127 bad_area_nosemaphore:
128 	/* User mode accesses just cause a SIGSEGV */
129 	if (user_mode(regs)) {
130 		tsk->thread.cp0_badvaddr = address;
131 		tsk->thread.error_code = write;
132 #if 0
133 		printk("do_page_fault() #2: sending SIGSEGV to %s for "
134 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
135 		       tsk->comm,
136 		       write ? "write access to" : "read access from",
137 		       field, address,
138 		       field, (unsigned long) regs->cp0_epc,
139 		       field, (unsigned long) regs->regs[31]);
140 #endif
141 		info.si_signo = SIGSEGV;
142 		info.si_errno = 0;
143 		/* info.si_code has been set above */
144 		info.si_addr = (void __user *) address;
145 		force_sig_info(SIGSEGV, &info, tsk);
146 		return;
147 	}
148 
149 no_context:
150 	/* Are we prepared to handle this kernel fault?  */
151 	if (fixup_exception(regs)) {
152 		current->thread.cp0_baduaddr = address;
153 		return;
154 	}
155 
156 	/*
157 	 * Oops. The kernel tried to access some bad page. We'll have to
158 	 * terminate things with extreme prejudice.
159 	 */
160 
161 	bust_spinlocks(1);
162 
163 	printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
164 	       "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
165 	       smp_processor_id(), field, address, field, regs->cp0_epc,
166 	       field,  regs->regs[31]);
167 	die("Oops", regs);
168 
169 /*
170  * We ran out of memory, or some other thing happened to us that made
171  * us unable to handle the page fault gracefully.
172  */
173 out_of_memory:
174 	up_read(&mm->mmap_sem);
175 	if (tsk->pid == 1) {
176 		yield();
177 		down_read(&mm->mmap_sem);
178 		goto survive;
179 	}
180 	printk("VM: killing process %s\n", tsk->comm);
181 	if (user_mode(regs))
182 		do_exit(SIGKILL);
183 	goto no_context;
184 
185 do_sigbus:
186 	up_read(&mm->mmap_sem);
187 
188 	/* Kernel mode? Handle exceptions or die */
189 	if (!user_mode(regs))
190 		goto no_context;
191 
192 	/*
193 	 * Send a sigbus, regardless of whether we were in kernel
194 	 * or user mode.
195 	 */
196 	tsk->thread.cp0_badvaddr = address;
197 	info.si_signo = SIGBUS;
198 	info.si_errno = 0;
199 	info.si_code = BUS_ADRERR;
200 	info.si_addr = (void __user *) address;
201 	force_sig_info(SIGBUS, &info, tsk);
202 
203 	return;
204 
205 vmalloc_fault:
206 	{
207 		/*
208 		 * Synchronize this task's top level page-table
209 		 * with the 'reference' page table.
210 		 *
211 		 * Do _not_ use "tsk" here. We might be inside
212 		 * an interrupt in the middle of a task switch..
213 		 */
214 		int offset = __pgd_offset(address);
215 		pgd_t *pgd, *pgd_k;
216 		pud_t *pud, *pud_k;
217 		pmd_t *pmd, *pmd_k;
218 		pte_t *pte_k;
219 
220 		pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset;
221 		pgd_k = init_mm.pgd + offset;
222 
223 		if (!pgd_present(*pgd_k))
224 			goto no_context;
225 		set_pgd(pgd, *pgd_k);
226 
227 		pud = pud_offset(pgd, address);
228 		pud_k = pud_offset(pgd_k, address);
229 		if (!pud_present(*pud_k))
230 			goto no_context;
231 
232 		pmd = pmd_offset(pud, address);
233 		pmd_k = pmd_offset(pud_k, address);
234 		if (!pmd_present(*pmd_k))
235 			goto no_context;
236 		set_pmd(pmd, *pmd_k);
237 
238 		pte_k = pte_offset_kernel(pmd_k, address);
239 		if (!pte_present(*pte_k))
240 			goto no_context;
241 		return;
242 	}
243 }
244