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Vineet Guptafbd70532013-01-18 15:12:20 +05301/* Page Fault Handling for ARC (TLB Miss / ProtV)
2 *
3 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License version 2 as
7 * published by the Free Software Foundation.
8 */
9
10#include <linux/signal.h>
11#include <linux/interrupt.h>
12#include <linux/sched.h>
13#include <linux/errno.h>
14#include <linux/ptrace.h>
Vineet Guptafbd70532013-01-18 15:12:20 +053015#include <linux/uaccess.h>
16#include <linux/kdebug.h>
17#include <asm/pgalloc.h>
Vineet Guptada1677b2013-05-14 13:28:17 +053018#include <asm/mmu.h>
Vineet Guptafbd70532013-01-18 15:12:20 +053019
Vineet Gupta9c41f4e2013-11-02 17:47:49 +053020static int handle_vmalloc_fault(unsigned long address)
Vineet Guptafbd70532013-01-18 15:12:20 +053021{
22 /*
23 * Synchronize this task's top level page-table
24 * with the 'reference' page table.
25 */
26 pgd_t *pgd, *pgd_k;
27 pud_t *pud, *pud_k;
28 pmd_t *pmd, *pmd_k;
29
Vineet Gupta9c41f4e2013-11-02 17:47:49 +053030 pgd = pgd_offset_fast(current->active_mm, address);
Vineet Guptafbd70532013-01-18 15:12:20 +053031 pgd_k = pgd_offset_k(address);
32
33 if (!pgd_present(*pgd_k))
34 goto bad_area;
35
36 pud = pud_offset(pgd, address);
37 pud_k = pud_offset(pgd_k, address);
38 if (!pud_present(*pud_k))
39 goto bad_area;
40
41 pmd = pmd_offset(pud, address);
42 pmd_k = pmd_offset(pud_k, address);
43 if (!pmd_present(*pmd_k))
44 goto bad_area;
45
46 set_pmd(pmd, *pmd_k);
47
48 /* XXX: create the TLB entry here */
49 return 0;
50
51bad_area:
52 return 1;
53}
54
Vineet Gupta38a9ff62013-06-12 15:13:40 +053055void do_page_fault(struct pt_regs *regs, unsigned long address)
Vineet Guptafbd70532013-01-18 15:12:20 +053056{
57 struct vm_area_struct *vma = NULL;
58 struct task_struct *tsk = current;
59 struct mm_struct *mm = tsk->mm;
60 siginfo_t info;
61 int fault, ret;
Vineet Gupta38a9ff62013-06-12 15:13:40 +053062 int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */
Johannes Weiner759496b2013-09-12 15:13:39 -070063 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
Vineet Guptafbd70532013-01-18 15:12:20 +053064
65 /*
66 * We fault-in kernel-space virtual memory on-demand. The
67 * 'reference' page table is init_mm.pgd.
68 *
69 * NOTE! We MUST NOT take any locks for this case. We may
70 * be in an interrupt or a critical region, and should
71 * only copy the information from the master page table,
72 * nothing more.
73 */
74 if (address >= VMALLOC_START && address <= VMALLOC_END) {
Vineet Gupta9c41f4e2013-11-02 17:47:49 +053075 ret = handle_vmalloc_fault(address);
Vineet Guptafbd70532013-01-18 15:12:20 +053076 if (unlikely(ret))
77 goto bad_area_nosemaphore;
78 else
79 return;
80 }
81
82 info.si_code = SEGV_MAPERR;
83
84 /*
85 * If we're in an interrupt or have no user
86 * context, we must not take the fault..
87 */
88 if (in_atomic() || !mm)
89 goto no_context;
90
Johannes Weiner759496b2013-09-12 15:13:39 -070091 if (user_mode(regs))
92 flags |= FAULT_FLAG_USER;
Vineet Guptafbd70532013-01-18 15:12:20 +053093retry:
94 down_read(&mm->mmap_sem);
95 vma = find_vma(mm, address);
96 if (!vma)
97 goto bad_area;
98 if (vma->vm_start <= address)
99 goto good_area;
100 if (!(vma->vm_flags & VM_GROWSDOWN))
101 goto bad_area;
102 if (expand_stack(vma, address))
103 goto bad_area;
104
105 /*
106 * Ok, we have a good vm_area for this memory access, so
107 * we can handle it..
108 */
109good_area:
110 info.si_code = SEGV_ACCERR;
111
112 /* Handle protection violation, execute on heap or stack */
113
Vineet Gupta38a9ff62013-06-12 15:13:40 +0530114 if ((regs->ecr_vec == ECR_V_PROTV) &&
115 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
Vineet Guptafbd70532013-01-18 15:12:20 +0530116 goto bad_area;
117
118 if (write) {
119 if (!(vma->vm_flags & VM_WRITE))
120 goto bad_area;
Johannes Weiner759496b2013-09-12 15:13:39 -0700121 flags |= FAULT_FLAG_WRITE;
Vineet Guptafbd70532013-01-18 15:12:20 +0530122 } else {
123 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
124 goto bad_area;
125 }
126
Vineet Guptafbd70532013-01-18 15:12:20 +0530127 /*
128 * If for any reason at all we couldn't handle the fault,
129 * make sure we exit gracefully rather than endlessly redo
130 * the fault.
131 */
132 fault = handle_mm_fault(mm, vma, address, flags);
133
134 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
135 if (unlikely(fatal_signal_pending(current))) {
136 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
137 up_read(&mm->mmap_sem);
138 if (user_mode(regs))
139 return;
140 }
141
142 if (likely(!(fault & VM_FAULT_ERROR))) {
143 if (flags & FAULT_FLAG_ALLOW_RETRY) {
144 /* To avoid updating stats twice for retry case */
145 if (fault & VM_FAULT_MAJOR)
146 tsk->maj_flt++;
147 else
148 tsk->min_flt++;
149
150 if (fault & VM_FAULT_RETRY) {
151 flags &= ~FAULT_FLAG_ALLOW_RETRY;
152 flags |= FAULT_FLAG_TRIED;
153 goto retry;
154 }
155 }
156
157 /* Fault Handled Gracefully */
158 up_read(&mm->mmap_sem);
159 return;
160 }
161
162 /* TBD: switch to pagefault_out_of_memory() */
163 if (fault & VM_FAULT_OOM)
164 goto out_of_memory;
165 else if (fault & VM_FAULT_SIGBUS)
166 goto do_sigbus;
167
168 /* no man's land */
169 BUG();
170
171 /*
172 * Something tried to access memory that isn't in our memory map..
173 * Fix it, but check if it's kernel or user first..
174 */
175bad_area:
176 up_read(&mm->mmap_sem);
177
178bad_area_nosemaphore:
179 /* User mode accesses just cause a SIGSEGV */
180 if (user_mode(regs)) {
181 tsk->thread.fault_address = address;
Vineet Guptafbd70532013-01-18 15:12:20 +0530182 info.si_signo = SIGSEGV;
183 info.si_errno = 0;
184 /* info.si_code has been set above */
185 info.si_addr = (void __user *)address;
186 force_sig_info(SIGSEGV, &info, tsk);
187 return;
188 }
189
190no_context:
191 /* Are we prepared to handle this kernel fault?
192 *
193 * (The kernel has valid exception-points in the source
194 * when it acesses user-memory. When it fails in one
195 * of those points, we find it in a table and do a jump
196 * to some fixup code that loads an appropriate error
197 * code)
198 */
199 if (fixup_exception(regs))
200 return;
201
Vineet Gupta38a9ff62013-06-12 15:13:40 +0530202 die("Oops", regs, address);
Vineet Guptafbd70532013-01-18 15:12:20 +0530203
204out_of_memory:
Vineet Guptafbd70532013-01-18 15:12:20 +0530205 up_read(&mm->mmap_sem);
206
Johannes Weiner609838c2013-07-08 15:59:50 -0700207 if (user_mode(regs)) {
208 pagefault_out_of_memory();
209 return;
210 }
Vineet Guptafbd70532013-01-18 15:12:20 +0530211
212 goto no_context;
213
214do_sigbus:
215 up_read(&mm->mmap_sem);
216
217 if (!user_mode(regs))
218 goto no_context;
219
220 tsk->thread.fault_address = address;
Vineet Guptafbd70532013-01-18 15:12:20 +0530221 info.si_signo = SIGBUS;
222 info.si_errno = 0;
223 info.si_code = BUS_ADRERR;
224 info.si_addr = (void __user *)address;
225 force_sig_info(SIGBUS, &info, tsk);
226}