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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
4 * Lennox Wu <lennox.wu@sunplusct.com>
5 * Chen Liqin <liqin.chen@sunplusct.com>
6 * Copyright (C) 2012 Regents of the University of California
7 */
8
9
10#include <linux/mm.h>
11#include <linux/kernel.h>
12#include <linux/interrupt.h>
13#include <linux/perf_event.h>
14#include <linux/signal.h>
15#include <linux/uaccess.h>
16
17#include <asm/ptrace.h>
18#include <asm/tlbflush.h>
19
20#include "../kernel/head.h"
21
22/*
23 * This routine handles page faults. It determines the address and the
24 * problem, and then passes it off to one of the appropriate routines.
25 */
26asmlinkage void do_page_fault(struct pt_regs *regs)
27{
28 struct task_struct *tsk;
29 struct vm_area_struct *vma;
30 struct mm_struct *mm;
31 unsigned long addr, cause;
32 unsigned int flags = FAULT_FLAG_DEFAULT;
33 int code = SEGV_MAPERR;
34 vm_fault_t fault;
35
36 cause = regs->cause;
37 addr = regs->badaddr;
38
39 tsk = current;
40 mm = tsk->mm;
41
42 /*
43 * Fault-in kernel-space virtual memory on-demand.
44 * The 'reference' page table is init_mm.pgd.
45 *
46 * NOTE! We MUST NOT take any locks for this case. We may
47 * be in an interrupt or a critical region, and should
48 * only copy the information from the master page table,
49 * nothing more.
50 */
51 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END)))
52 goto vmalloc_fault;
53
54 /* Enable interrupts if they were enabled in the parent context. */
55 if (likely(regs->status & SR_PIE))
56 local_irq_enable();
57
58 /*
59 * If we're in an interrupt, have no user context, or are running
60 * in an atomic region, then we must not take the fault.
61 */
62 if (unlikely(faulthandler_disabled() || !mm))
63 goto no_context;
64
65 if (user_mode(regs))
66 flags |= FAULT_FLAG_USER;
67
68 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
69
70retry:
71 mmap_read_lock(mm);
72 vma = find_vma(mm, addr);
73 if (unlikely(!vma))
74 goto bad_area;
75 if (likely(vma->vm_start <= addr))
76 goto good_area;
77 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
78 goto bad_area;
79 if (unlikely(expand_stack(vma, addr)))
80 goto bad_area;
81
82 /*
83 * Ok, we have a good vm_area for this memory access, so
84 * we can handle it.
85 */
86good_area:
87 code = SEGV_ACCERR;
88
89 switch (cause) {
90 case EXC_INST_PAGE_FAULT:
91 if (!(vma->vm_flags & VM_EXEC))
92 goto bad_area;
93 break;
94 case EXC_LOAD_PAGE_FAULT:
95 if (!(vma->vm_flags & VM_READ))
96 goto bad_area;
97 break;
98 case EXC_STORE_PAGE_FAULT:
99 if (!(vma->vm_flags & VM_WRITE))
100 goto bad_area;
101 flags |= FAULT_FLAG_WRITE;
102 break;
103 default:
104 panic("%s: unhandled cause %lu", __func__, cause);
105 }
106
107 /*
108 * If for any reason at all we could not handle the fault,
109 * make sure we exit gracefully rather than endlessly redo
110 * the fault.
111 */
112 fault = handle_mm_fault(vma, addr, flags, regs);
113
114 /*
115 * If we need to retry but a fatal signal is pending, handle the
116 * signal first. We do not need to release the mmap_lock because it
117 * would already be released in __lock_page_or_retry in mm/filemap.c.
118 */
119 if (fault_signal_pending(fault, regs))
120 return;
121
122 if (unlikely(fault & VM_FAULT_ERROR)) {
123 if (fault & VM_FAULT_OOM)
124 goto out_of_memory;
125 else if (fault & VM_FAULT_SIGBUS)
126 goto do_sigbus;
127 BUG();
128 }
129
130 if (flags & FAULT_FLAG_ALLOW_RETRY) {
131 if (fault & VM_FAULT_RETRY) {
132 flags |= FAULT_FLAG_TRIED;
133
134 /*
135 * No need to mmap_read_unlock(mm) as we would
136 * have already released it in __lock_page_or_retry
137 * in mm/filemap.c.
138 */
139 goto retry;
140 }
141 }
142
143 mmap_read_unlock(mm);
144 return;
145
146 /*
147 * Something tried to access memory that isn't in our memory map.
148 * Fix it, but check if it's kernel or user first.
149 */
150bad_area:
151 mmap_read_unlock(mm);
152 /* User mode accesses just cause a SIGSEGV */
153 if (user_mode(regs)) {
154 do_trap(regs, SIGSEGV, code, addr);
155 return;
156 }
157
158no_context:
159 /* Are we prepared to handle this kernel fault? */
160 if (fixup_exception(regs))
161 return;
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 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n",
169 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
170 "paging request", addr);
171 die(regs, "Oops");
172 do_exit(SIGKILL);
173
174 /*
175 * We ran out of memory, call the OOM killer, and return the userspace
176 * (which will retry the fault, or kill us if we got oom-killed).
177 */
178out_of_memory:
179 mmap_read_unlock(mm);
180 if (!user_mode(regs))
181 goto no_context;
182 pagefault_out_of_memory();
183 return;
184
185do_sigbus:
186 mmap_read_unlock(mm);
187 /* Kernel mode? Handle exceptions or die */
188 if (!user_mode(regs))
189 goto no_context;
190 do_trap(regs, SIGBUS, BUS_ADRERR, addr);
191 return;
192
193vmalloc_fault:
194 {
195 pgd_t *pgd, *pgd_k;
196 pud_t *pud, *pud_k;
197 p4d_t *p4d, *p4d_k;
198 pmd_t *pmd, *pmd_k;
199 pte_t *pte_k;
200 int index;
201
202 /* User mode accesses just cause a SIGSEGV */
203 if (user_mode(regs))
204 return do_trap(regs, SIGSEGV, code, addr);
205
206 /*
207 * Synchronize this task's top level page-table
208 * with the 'reference' page table.
209 *
210 * Do _not_ use "tsk->active_mm->pgd" here.
211 * We might be inside an interrupt in the middle
212 * of a task switch.
213 */
214 index = pgd_index(addr);
215 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index;
216 pgd_k = init_mm.pgd + index;
217
218 if (!pgd_present(*pgd_k))
219 goto no_context;
220 set_pgd(pgd, *pgd_k);
221
222 p4d = p4d_offset(pgd, addr);
223 p4d_k = p4d_offset(pgd_k, addr);
224 if (!p4d_present(*p4d_k))
225 goto no_context;
226
227 pud = pud_offset(p4d, addr);
228 pud_k = pud_offset(p4d_k, addr);
229 if (!pud_present(*pud_k))
230 goto no_context;
231
232 /*
233 * Since the vmalloc area is global, it is unnecessary
234 * to copy individual PTEs
235 */
236 pmd = pmd_offset(pud, addr);
237 pmd_k = pmd_offset(pud_k, addr);
238 if (!pmd_present(*pmd_k))
239 goto no_context;
240 set_pmd(pmd, *pmd_k);
241
242 /*
243 * Make sure the actual PTE exists as well to
244 * catch kernel vmalloc-area accesses to non-mapped
245 * addresses. If we don't do this, this will just
246 * silently loop forever.
247 */
248 pte_k = pte_offset_kernel(pmd_k, addr);
249 if (!pte_present(*pte_k))
250 goto no_context;
251
252 /*
253 * The kernel assumes that TLBs don't cache invalid
254 * entries, but in RISC-V, SFENCE.VMA specifies an
255 * ordering constraint, not a cache flush; it is
256 * necessary even after writing invalid entries.
257 */
258 local_flush_tlb_page(addr);
259
260 return;
261 }
262}
1/*
2 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
3 * Lennox Wu <lennox.wu@sunplusct.com>
4 * Chen Liqin <liqin.chen@sunplusct.com>
5 * Copyright (C) 2012 Regents of the University of California
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, see the file COPYING, or write
19 * to the Free Software Foundation, Inc.,
20 */
21
22
23#include <linux/mm.h>
24#include <linux/kernel.h>
25#include <linux/interrupt.h>
26#include <linux/perf_event.h>
27#include <linux/signal.h>
28#include <linux/uaccess.h>
29
30#include <asm/pgalloc.h>
31#include <asm/ptrace.h>
32
33/*
34 * This routine handles page faults. It determines the address and the
35 * problem, and then passes it off to one of the appropriate routines.
36 */
37asmlinkage void do_page_fault(struct pt_regs *regs)
38{
39 struct task_struct *tsk;
40 struct vm_area_struct *vma;
41 struct mm_struct *mm;
42 unsigned long addr, cause;
43 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
44 int fault, code = SEGV_MAPERR;
45
46 cause = regs->scause;
47 addr = regs->sbadaddr;
48
49 tsk = current;
50 mm = tsk->mm;
51
52 /*
53 * Fault-in kernel-space virtual memory on-demand.
54 * The '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((addr >= VMALLOC_START) && (addr <= VMALLOC_END)))
62 goto vmalloc_fault;
63
64 /* Enable interrupts if they were enabled in the parent context. */
65 if (likely(regs->sstatus & SR_SPIE))
66 local_irq_enable();
67
68 /*
69 * If we're in an interrupt, have no user context, or are running
70 * in an atomic region, then we must not take the fault.
71 */
72 if (unlikely(faulthandler_disabled() || !mm))
73 goto no_context;
74
75 if (user_mode(regs))
76 flags |= FAULT_FLAG_USER;
77
78 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
79
80retry:
81 down_read(&mm->mmap_sem);
82 vma = find_vma(mm, addr);
83 if (unlikely(!vma))
84 goto bad_area;
85 if (likely(vma->vm_start <= addr))
86 goto good_area;
87 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
88 goto bad_area;
89 if (unlikely(expand_stack(vma, addr)))
90 goto bad_area;
91
92 /*
93 * Ok, we have a good vm_area for this memory access, so
94 * we can handle it.
95 */
96good_area:
97 code = SEGV_ACCERR;
98
99 switch (cause) {
100 case EXC_INST_PAGE_FAULT:
101 if (!(vma->vm_flags & VM_EXEC))
102 goto bad_area;
103 break;
104 case EXC_LOAD_PAGE_FAULT:
105 if (!(vma->vm_flags & VM_READ))
106 goto bad_area;
107 break;
108 case EXC_STORE_PAGE_FAULT:
109 if (!(vma->vm_flags & VM_WRITE))
110 goto bad_area;
111 flags |= FAULT_FLAG_WRITE;
112 break;
113 default:
114 panic("%s: unhandled cause %lu", __func__, cause);
115 }
116
117 /*
118 * If for any reason at all we could not handle the fault,
119 * make sure we exit gracefully rather than endlessly redo
120 * the fault.
121 */
122 fault = handle_mm_fault(vma, addr, flags);
123
124 /*
125 * If we need to retry but a fatal signal is pending, handle the
126 * signal first. We do not need to release the mmap_sem because it
127 * would already be released in __lock_page_or_retry in mm/filemap.c.
128 */
129 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk))
130 return;
131
132 if (unlikely(fault & VM_FAULT_ERROR)) {
133 if (fault & VM_FAULT_OOM)
134 goto out_of_memory;
135 else if (fault & VM_FAULT_SIGBUS)
136 goto do_sigbus;
137 BUG();
138 }
139
140 /*
141 * Major/minor page fault accounting is only done on the
142 * initial attempt. If we go through a retry, it is extremely
143 * likely that the page will be found in page cache at that point.
144 */
145 if (flags & FAULT_FLAG_ALLOW_RETRY) {
146 if (fault & VM_FAULT_MAJOR) {
147 tsk->maj_flt++;
148 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
149 1, regs, addr);
150 } else {
151 tsk->min_flt++;
152 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
153 1, regs, addr);
154 }
155 if (fault & VM_FAULT_RETRY) {
156 /*
157 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
158 * of starvation.
159 */
160 flags &= ~(FAULT_FLAG_ALLOW_RETRY);
161 flags |= FAULT_FLAG_TRIED;
162
163 /*
164 * No need to up_read(&mm->mmap_sem) as we would
165 * have already released it in __lock_page_or_retry
166 * in mm/filemap.c.
167 */
168 goto retry;
169 }
170 }
171
172 up_read(&mm->mmap_sem);
173 return;
174
175 /*
176 * Something tried to access memory that isn't in our memory map.
177 * Fix it, but check if it's kernel or user first.
178 */
179bad_area:
180 up_read(&mm->mmap_sem);
181 /* User mode accesses just cause a SIGSEGV */
182 if (user_mode(regs)) {
183 do_trap(regs, SIGSEGV, code, addr, tsk);
184 return;
185 }
186
187no_context:
188 /* Are we prepared to handle this kernel fault? */
189 if (fixup_exception(regs))
190 return;
191
192 /*
193 * Oops. The kernel tried to access some bad page. We'll have to
194 * terminate things with extreme prejudice.
195 */
196 bust_spinlocks(1);
197 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n",
198 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
199 "paging request", addr);
200 die(regs, "Oops");
201 do_exit(SIGKILL);
202
203 /*
204 * We ran out of memory, call the OOM killer, and return the userspace
205 * (which will retry the fault, or kill us if we got oom-killed).
206 */
207out_of_memory:
208 up_read(&mm->mmap_sem);
209 if (!user_mode(regs))
210 goto no_context;
211 pagefault_out_of_memory();
212 return;
213
214do_sigbus:
215 up_read(&mm->mmap_sem);
216 /* Kernel mode? Handle exceptions or die */
217 if (!user_mode(regs))
218 goto no_context;
219 do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk);
220 return;
221
222vmalloc_fault:
223 {
224 pgd_t *pgd, *pgd_k;
225 pud_t *pud, *pud_k;
226 p4d_t *p4d, *p4d_k;
227 pmd_t *pmd, *pmd_k;
228 pte_t *pte_k;
229 int index;
230
231 if (user_mode(regs))
232 goto bad_area;
233
234 /*
235 * Synchronize this task's top level page-table
236 * with the 'reference' page table.
237 *
238 * Do _not_ use "tsk->active_mm->pgd" here.
239 * We might be inside an interrupt in the middle
240 * of a task switch.
241 *
242 * Note: Use the old spbtr name instead of using the current
243 * satp name to support binutils 2.29 which doesn't know about
244 * the privileged ISA 1.10 yet.
245 */
246 index = pgd_index(addr);
247 pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index;
248 pgd_k = init_mm.pgd + index;
249
250 if (!pgd_present(*pgd_k))
251 goto no_context;
252 set_pgd(pgd, *pgd_k);
253
254 p4d = p4d_offset(pgd, addr);
255 p4d_k = p4d_offset(pgd_k, addr);
256 if (!p4d_present(*p4d_k))
257 goto no_context;
258
259 pud = pud_offset(p4d, addr);
260 pud_k = pud_offset(p4d_k, addr);
261 if (!pud_present(*pud_k))
262 goto no_context;
263
264 /*
265 * Since the vmalloc area is global, it is unnecessary
266 * to copy individual PTEs
267 */
268 pmd = pmd_offset(pud, addr);
269 pmd_k = pmd_offset(pud_k, addr);
270 if (!pmd_present(*pmd_k))
271 goto no_context;
272 set_pmd(pmd, *pmd_k);
273
274 /*
275 * Make sure the actual PTE exists as well to
276 * catch kernel vmalloc-area accesses to non-mapped
277 * addresses. If we don't do this, this will just
278 * silently loop forever.
279 */
280 pte_k = pte_offset_kernel(pmd_k, addr);
281 if (!pte_present(*pte_k))
282 goto no_context;
283 return;
284 }
285}