1 /*
2 * Meta page fault handling.
3 *
4 * Copyright (C) 2005-2012 Imagination Technologies Ltd.
5 */
6
7 #include <linux/mman.h>
8 #include <linux/mm.h>
9 #include <linux/kernel.h>
10 #include <linux/ptrace.h>
11 #include <linux/interrupt.h>
12 #include <linux/uaccess.h>
13
14 #include <asm/tlbflush.h>
15 #include <asm/mmu.h>
16 #include <asm/traps.h>
17
18 /* Clear any pending catch buffer state. */
clear_cbuf_entry(struct pt_regs * regs,unsigned long addr,unsigned int trapno)19 static void clear_cbuf_entry(struct pt_regs *regs, unsigned long addr,
20 unsigned int trapno)
21 {
22 PTBICTXEXTCB0 cbuf = regs->extcb0;
23
24 switch (trapno) {
25 /* Instruction fetch faults leave no catch buffer state. */
26 case TBIXXF_SIGNUM_IGF:
27 case TBIXXF_SIGNUM_IPF:
28 return;
29 default:
30 if (cbuf[0].CBAddr == addr) {
31 cbuf[0].CBAddr = 0;
32 cbuf[0].CBFlags &= ~TXCATCH0_FAULT_BITS;
33
34 /* And, as this is the ONLY catch entry, we
35 * need to clear the cbuf bit from the context!
36 */
37 regs->ctx.SaveMask &= ~(TBICTX_CBUF_BIT |
38 TBICTX_XCBF_BIT);
39
40 return;
41 }
42 pr_err("Failed to clear cbuf entry!\n");
43 }
44 }
45
46 int show_unhandled_signals = 1;
47
do_page_fault(struct pt_regs * regs,unsigned long address,unsigned int write_access,unsigned int trapno)48 int do_page_fault(struct pt_regs *regs, unsigned long address,
49 unsigned int write_access, unsigned int trapno)
50 {
51 struct task_struct *tsk;
52 struct mm_struct *mm;
53 struct vm_area_struct *vma, *prev_vma;
54 siginfo_t info;
55 int fault;
56 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
57
58 tsk = current;
59
60 if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
61 /*
62 * Synchronize this task's top level page-table
63 * with the 'reference' page table.
64 *
65 * Do _not_ use "tsk" here. We might be inside
66 * an interrupt in the middle of a task switch..
67 */
68 int offset = pgd_index(address);
69 pgd_t *pgd, *pgd_k;
70 pud_t *pud, *pud_k;
71 pmd_t *pmd, *pmd_k;
72 pte_t *pte_k;
73
74 pgd = ((pgd_t *)mmu_get_base()) + offset;
75 pgd_k = swapper_pg_dir + offset;
76
77 /* This will never happen with the folded page table. */
78 if (!pgd_present(*pgd)) {
79 if (!pgd_present(*pgd_k))
80 goto bad_area_nosemaphore;
81 set_pgd(pgd, *pgd_k);
82 return 0;
83 }
84
85 pud = pud_offset(pgd, address);
86 pud_k = pud_offset(pgd_k, address);
87 if (!pud_present(*pud_k))
88 goto bad_area_nosemaphore;
89 set_pud(pud, *pud_k);
90
91 pmd = pmd_offset(pud, address);
92 pmd_k = pmd_offset(pud_k, address);
93 if (!pmd_present(*pmd_k))
94 goto bad_area_nosemaphore;
95 set_pmd(pmd, *pmd_k);
96
97 pte_k = pte_offset_kernel(pmd_k, address);
98 if (!pte_present(*pte_k))
99 goto bad_area_nosemaphore;
100
101 /* May only be needed on Chorus2 */
102 flush_tlb_all();
103 return 0;
104 }
105
106 mm = tsk->mm;
107
108 if (faulthandler_disabled() || !mm)
109 goto no_context;
110
111 if (user_mode(regs))
112 flags |= FAULT_FLAG_USER;
113 retry:
114 down_read(&mm->mmap_sem);
115
116 vma = find_vma_prev(mm, address, &prev_vma);
117
118 if (!vma || address < vma->vm_start)
119 goto check_expansion;
120
121 good_area:
122 if (write_access) {
123 if (!(vma->vm_flags & VM_WRITE))
124 goto bad_area;
125 flags |= FAULT_FLAG_WRITE;
126 } else {
127 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
128 goto bad_area;
129 }
130
131 /*
132 * If for any reason at all we couldn't handle the fault,
133 * make sure we exit gracefully rather than endlessly redo
134 * the fault.
135 */
136 fault = handle_mm_fault(mm, vma, address, flags);
137
138 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
139 return 0;
140
141 if (unlikely(fault & VM_FAULT_ERROR)) {
142 if (fault & VM_FAULT_OOM)
143 goto out_of_memory;
144 else if (fault & VM_FAULT_SIGSEGV)
145 goto bad_area;
146 else if (fault & VM_FAULT_SIGBUS)
147 goto do_sigbus;
148 BUG();
149 }
150 if (flags & FAULT_FLAG_ALLOW_RETRY) {
151 if (fault & VM_FAULT_MAJOR)
152 tsk->maj_flt++;
153 else
154 tsk->min_flt++;
155 if (fault & VM_FAULT_RETRY) {
156 flags &= ~FAULT_FLAG_ALLOW_RETRY;
157 flags |= FAULT_FLAG_TRIED;
158
159 /*
160 * No need to up_read(&mm->mmap_sem) as we would
161 * have already released it in __lock_page_or_retry
162 * in mm/filemap.c.
163 */
164
165 goto retry;
166 }
167 }
168
169 up_read(&mm->mmap_sem);
170 return 0;
171
172 check_expansion:
173 vma = prev_vma;
174 if (vma && (expand_stack(vma, address) == 0))
175 goto good_area;
176
177 bad_area:
178 up_read(&mm->mmap_sem);
179
180 bad_area_nosemaphore:
181 if (user_mode(regs)) {
182 info.si_signo = SIGSEGV;
183 info.si_errno = 0;
184 info.si_code = SEGV_MAPERR;
185 info.si_addr = (__force void __user *)address;
186 info.si_trapno = trapno;
187
188 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
189 printk_ratelimit()) {
190 pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
191 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
192 tsk->comm, task_pid_nr(tsk), address,
193 regs->ctx.CurrPC, regs->ctx.AX[0].U0,
194 write_access, trapno, trap_name(trapno));
195 print_vma_addr(" in ", regs->ctx.CurrPC);
196 print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
197 printk("\n");
198 show_regs(regs);
199 }
200 force_sig_info(SIGSEGV, &info, tsk);
201 return 1;
202 }
203 goto no_context;
204
205 do_sigbus:
206 up_read(&mm->mmap_sem);
207
208 /*
209 * Send a sigbus, regardless of whether we were in kernel
210 * or user mode.
211 */
212 info.si_signo = SIGBUS;
213 info.si_errno = 0;
214 info.si_code = BUS_ADRERR;
215 info.si_addr = (__force void __user *)address;
216 info.si_trapno = trapno;
217 force_sig_info(SIGBUS, &info, tsk);
218
219 /* Kernel mode? Handle exceptions or die */
220 if (!user_mode(regs))
221 goto no_context;
222
223 return 1;
224
225 /*
226 * We ran out of memory, or some other thing happened to us that made
227 * us unable to handle the page fault gracefully.
228 */
229 out_of_memory:
230 up_read(&mm->mmap_sem);
231 if (user_mode(regs)) {
232 pagefault_out_of_memory();
233 return 1;
234 }
235
236 no_context:
237 /* Are we prepared to handle this kernel fault? */
238 if (fixup_exception(regs)) {
239 clear_cbuf_entry(regs, address, trapno);
240 return 1;
241 }
242
243 die("Oops", regs, (write_access << 15) | trapno, address);
244 do_exit(SIGKILL);
245 }
246