xref: /openbmc/linux/arch/mips/mm/fault.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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/vt_kern.h>		/* For unblank_screen() */
20 #include <linux/module.h>
21 
22 #include <asm/branch.h>
23 #include <asm/mmu_context.h>
24 #include <asm/system.h>
25 #include <asm/uaccess.h>
26 #include <asm/ptrace.h>
27 #include <asm/highmem.h>		/* For VMALLOC_END */
28 
29 /*
30  * This routine handles page faults.  It determines the address,
31  * and the problem, and then passes it off to one of the appropriate
32  * routines.
33  */
34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
35 			      unsigned long address)
36 {
37 	struct vm_area_struct * vma = NULL;
38 	struct task_struct *tsk = current;
39 	struct mm_struct *mm = tsk->mm;
40 	const int field = sizeof(unsigned long) * 2;
41 	siginfo_t info;
42 	int fault;
43 
44 #if 0
45 	printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_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 #ifdef CONFIG_64BIT
62 # define VMALLOC_FAULT_TARGET no_context
63 #else
64 # define VMALLOC_FAULT_TARGET vmalloc_fault
65 #endif
66 
67 	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
68 		goto VMALLOC_FAULT_TARGET;
69 #ifdef MODULE_START
70 	if (unlikely(address >= MODULE_START && address < MODULE_END))
71 		goto VMALLOC_FAULT_TARGET;
72 #endif
73 
74 	/*
75 	 * If we're in an interrupt or have no user
76 	 * context, we must not take the fault..
77 	 */
78 	if (in_atomic() || !mm)
79 		goto bad_area_nosemaphore;
80 
81 	down_read(&mm->mmap_sem);
82 	vma = find_vma(mm, address);
83 	if (!vma)
84 		goto bad_area;
85 	if (vma->vm_start <= address)
86 		goto good_area;
87 	if (!(vma->vm_flags & VM_GROWSDOWN))
88 		goto bad_area;
89 	if (expand_stack(vma, address))
90 		goto bad_area;
91 /*
92  * Ok, we have a good vm_area for this memory access, so
93  * we can handle it..
94  */
95 good_area:
96 	info.si_code = SEGV_ACCERR;
97 
98 	if (write) {
99 		if (!(vma->vm_flags & VM_WRITE))
100 			goto bad_area;
101 	} else {
102 		if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
103 			goto bad_area;
104 	}
105 
106 	/*
107 	 * If for any reason at all we couldn't handle the fault,
108 	 * make sure we exit gracefully rather than endlessly redo
109 	 * the fault.
110 	 */
111 	fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
112 	if (unlikely(fault & VM_FAULT_ERROR)) {
113 		if (fault & VM_FAULT_OOM)
114 			goto out_of_memory;
115 		else if (fault & VM_FAULT_SIGBUS)
116 			goto do_sigbus;
117 		BUG();
118 	}
119 	if (fault & VM_FAULT_MAJOR)
120 		tsk->maj_flt++;
121 	else
122 		tsk->min_flt++;
123 
124 	up_read(&mm->mmap_sem);
125 	return;
126 
127 /*
128  * Something tried to access memory that isn't in our memory map..
129  * Fix it, but check if it's kernel or user first..
130  */
131 bad_area:
132 	up_read(&mm->mmap_sem);
133 
134 bad_area_nosemaphore:
135 	/* User mode accesses just cause a SIGSEGV */
136 	if (user_mode(regs)) {
137 		tsk->thread.cp0_badvaddr = address;
138 		tsk->thread.error_code = write;
139 #if 0
140 		printk("do_page_fault() #2: sending SIGSEGV to %s for "
141 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
142 		       tsk->comm,
143 		       write ? "write access to" : "read access from",
144 		       field, address,
145 		       field, (unsigned long) regs->cp0_epc,
146 		       field, (unsigned long) regs->regs[31]);
147 #endif
148 		info.si_signo = SIGSEGV;
149 		info.si_errno = 0;
150 		/* info.si_code has been set above */
151 		info.si_addr = (void __user *) address;
152 		force_sig_info(SIGSEGV, &info, tsk);
153 		return;
154 	}
155 
156 no_context:
157 	/* Are we prepared to handle this kernel fault?  */
158 	if (fixup_exception(regs)) {
159 		current->thread.cp0_baduaddr = address;
160 		return;
161 	}
162 
163 	/*
164 	 * Oops. The kernel tried to access some bad page. We'll have to
165 	 * terminate things with extreme prejudice.
166 	 */
167 	bust_spinlocks(1);
168 
169 	printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
170 	       "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
171 	       raw_smp_processor_id(), field, address, field, regs->cp0_epc,
172 	       field,  regs->regs[31]);
173 	die("Oops", regs);
174 
175 out_of_memory:
176 	/*
177 	 * We ran out of memory, call the OOM killer, and return the userspace
178 	 * (which will retry the fault, or kill us if we got oom-killed).
179 	 */
180 	up_read(&mm->mmap_sem);
181 	pagefault_out_of_memory();
182 	return;
183 
184 do_sigbus:
185 	up_read(&mm->mmap_sem);
186 
187 	/* Kernel mode? Handle exceptions or die */
188 	if (!user_mode(regs))
189 		goto no_context;
190 	else
191 	/*
192 	 * Send a sigbus, regardless of whether we were in kernel
193 	 * or user mode.
194 	 */
195 #if 0
196 		printk("do_page_fault() #3: sending SIGBUS to %s for "
197 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
198 		       tsk->comm,
199 		       write ? "write access to" : "read access from",
200 		       field, address,
201 		       field, (unsigned long) regs->cp0_epc,
202 		       field, (unsigned long) regs->regs[31]);
203 #endif
204 	tsk->thread.cp0_badvaddr = address;
205 	info.si_signo = SIGBUS;
206 	info.si_errno = 0;
207 	info.si_code = BUS_ADRERR;
208 	info.si_addr = (void __user *) address;
209 	force_sig_info(SIGBUS, &info, tsk);
210 
211 	return;
212 #ifndef CONFIG_64BIT
213 vmalloc_fault:
214 	{
215 		/*
216 		 * Synchronize this task's top level page-table
217 		 * with the 'reference' page table.
218 		 *
219 		 * Do _not_ use "tsk" here. We might be inside
220 		 * an interrupt in the middle of a task switch..
221 		 */
222 		int offset = __pgd_offset(address);
223 		pgd_t *pgd, *pgd_k;
224 		pud_t *pud, *pud_k;
225 		pmd_t *pmd, *pmd_k;
226 		pte_t *pte_k;
227 
228 		pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
229 		pgd_k = init_mm.pgd + offset;
230 
231 		if (!pgd_present(*pgd_k))
232 			goto no_context;
233 		set_pgd(pgd, *pgd_k);
234 
235 		pud = pud_offset(pgd, address);
236 		pud_k = pud_offset(pgd_k, address);
237 		if (!pud_present(*pud_k))
238 			goto no_context;
239 
240 		pmd = pmd_offset(pud, address);
241 		pmd_k = pmd_offset(pud_k, address);
242 		if (!pmd_present(*pmd_k))
243 			goto no_context;
244 		set_pmd(pmd, *pmd_k);
245 
246 		pte_k = pte_offset_kernel(pmd_k, address);
247 		if (!pte_present(*pte_k))
248 			goto no_context;
249 		return;
250 	}
251 #endif
252 }
253