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1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Page Fault Handling for ARC (TLB Miss / ProtV)
3  *
4  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
5  */
6
7 #include <linux/signal.h>
8 #include <linux/interrupt.h>
9 #include <linux/sched/signal.h>
10 #include <linux/errno.h>
11 #include <linux/ptrace.h>
12 #include <linux/uaccess.h>
13 #include <linux/kdebug.h>
14 #include <linux/perf_event.h>
15 #include <linux/mm_types.h>
16 #include <asm/pgalloc.h>
17 #include <asm/mmu.h>
18
19 /*
20  * kernel virtual address is required to implement vmalloc/pkmap/fixmap
21  * Refer to asm/processor.h for System Memory Map
22  *
23  * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
24  * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
25  */
26 noinline static int handle_kernel_vaddr_fault(unsigned long address)
27 {
28         /*
29          * Synchronize this task's top level page-table
30          * with the 'reference' page table.
31          */
32         pgd_t *pgd, *pgd_k;
33         p4d_t *p4d, *p4d_k;
34         pud_t *pud, *pud_k;
35         pmd_t *pmd, *pmd_k;
36
37         pgd = pgd_offset_fast(current->active_mm, address);
38         pgd_k = pgd_offset_k(address);
39
40         if (!pgd_present(*pgd_k))
41                 goto bad_area;
42
43         p4d = p4d_offset(pgd, address);
44         p4d_k = p4d_offset(pgd_k, address);
45         if (!p4d_present(*p4d_k))
46                 goto bad_area;
47
48         pud = pud_offset(p4d, address);
49         pud_k = pud_offset(p4d_k, address);
50         if (!pud_present(*pud_k))
51                 goto bad_area;
52
53         pmd = pmd_offset(pud, address);
54         pmd_k = pmd_offset(pud_k, address);
55         if (!pmd_present(*pmd_k))
56                 goto bad_area;
57
58         set_pmd(pmd, *pmd_k);
59
60         /* XXX: create the TLB entry here */
61         return 0;
62
63 bad_area:
64         return 1;
65 }
66
67 void do_page_fault(unsigned long address, struct pt_regs *regs)
68 {
69         struct vm_area_struct *vma = NULL;
70         struct task_struct *tsk = current;
71         struct mm_struct *mm = tsk->mm;
72         int sig, si_code = SEGV_MAPERR;
73         unsigned int write = 0, exec = 0, mask;
74         vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
75         unsigned int flags;                     /* handle_mm_fault() input */
76
77         /*
78          * NOTE! We MUST NOT take any locks for this case. We may
79          * be in an interrupt or a critical region, and should
80          * only copy the information from the master page table,
81          * nothing more.
82          */
83         if (address >= VMALLOC_START && !user_mode(regs)) {
84                 if (unlikely(handle_kernel_vaddr_fault(address)))
85                         goto no_context;
86                 else
87                         return;
88         }
89
90         /*
91          * If we're in an interrupt or have no user
92          * context, we must not take the fault..
93          */
94         if (faulthandler_disabled() || !mm)
95                 goto no_context;
96
97         if (regs->ecr_cause & ECR_C_PROTV_STORE)        /* ST/EX */
98                 write = 1;
99         else if ((regs->ecr_vec == ECR_V_PROTV) &&
100                  (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
101                 exec = 1;
102
103         flags = FAULT_FLAG_DEFAULT;
104         if (user_mode(regs))
105                 flags |= FAULT_FLAG_USER;
106         if (write)
107                 flags |= FAULT_FLAG_WRITE;
108
109 retry:
110         down_read(&mm->mmap_sem);
111
112         vma = find_vma(mm, address);
113         if (!vma)
114                 goto bad_area;
115         if (unlikely(address < vma->vm_start)) {
116                 if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
117                         goto bad_area;
118         }
119
120         /*
121          * vm_area is good, now check permissions for this memory access
122          */
123         mask = VM_READ;
124         if (write)
125                 mask = VM_WRITE;
126         if (exec)
127                 mask = VM_EXEC;
128
129         if (!(vma->vm_flags & mask)) {
130                 si_code = SEGV_ACCERR;
131                 goto bad_area;
132         }
133
134         fault = handle_mm_fault(vma, address, flags);
135
136         /* Quick path to respond to signals */
137         if (fault_signal_pending(fault, regs)) {
138                 if (!user_mode(regs))
139                         goto no_context;
140                 return;
141         }
142
143         /*
144          * Fault retry nuances, mmap_sem already relinquished by core mm
145          */
146         if (unlikely((fault & VM_FAULT_RETRY) &&
147                      (flags & FAULT_FLAG_ALLOW_RETRY))) {
148                 flags |= FAULT_FLAG_TRIED;
149                 goto retry;
150         }
151
152 bad_area:
153         up_read(&mm->mmap_sem);
154
155         /*
156          * Major/minor page fault accounting
157          * (in case of retry we only land here once)
158          */
159         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
160
161         if (likely(!(fault & VM_FAULT_ERROR))) {
162                 if (fault & VM_FAULT_MAJOR) {
163                         tsk->maj_flt++;
164                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
165                                       regs, address);
166                 } else {
167                         tsk->min_flt++;
168                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
169                                       regs, address);
170                 }
171
172                 /* Normal return path: fault Handled Gracefully */
173                 return;
174         }
175
176         if (!user_mode(regs))
177                 goto no_context;
178
179         if (fault & VM_FAULT_OOM) {
180                 pagefault_out_of_memory();
181                 return;
182         }
183
184         if (fault & VM_FAULT_SIGBUS) {
185                 sig = SIGBUS;
186                 si_code = BUS_ADRERR;
187         }
188         else {
189                 sig = SIGSEGV;
190         }
191
192         tsk->thread.fault_address = address;
193         force_sig_fault(sig, si_code, (void __user *)address);
194         return;
195
196 no_context:
197         if (fixup_exception(regs))
198                 return;
199
200         die("Oops", regs, address);
201 }
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