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1/*
2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6#include <linux/mm.h>
7#include <linux/sched.h>
8#include <linux/hardirq.h>
9#include <linux/module.h>
10#include <asm/current.h>
11#include <asm/pgtable.h>
12#include <asm/tlbflush.h>
13#include "arch.h"
14#include "as-layout.h"
15#include "kern_util.h"
16#include "os.h"
17#include "skas.h"
18
19/*
20 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
21 * segv().
22 */
23int handle_page_fault(unsigned long address, unsigned long ip,
24 int is_write, int is_user, int *code_out)
25{
26 struct mm_struct *mm = current->mm;
27 struct vm_area_struct *vma;
28 pgd_t *pgd;
29 pud_t *pud;
30 pmd_t *pmd;
31 pte_t *pte;
32 int err = -EFAULT;
33 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
34 (is_write ? FAULT_FLAG_WRITE : 0);
35
36 *code_out = SEGV_MAPERR;
37
38 /*
39 * If the fault was during atomic operation, don't take the fault, just
40 * fail.
41 */
42 if (in_atomic())
43 goto out_nosemaphore;
44
45retry:
46 down_read(&mm->mmap_sem);
47 vma = find_vma(mm, address);
48 if (!vma)
49 goto out;
50 else if (vma->vm_start <= address)
51 goto good_area;
52 else if (!(vma->vm_flags & VM_GROWSDOWN))
53 goto out;
54 else if (is_user && !ARCH_IS_STACKGROW(address))
55 goto out;
56 else if (expand_stack(vma, address))
57 goto out;
58
59good_area:
60 *code_out = SEGV_ACCERR;
61 if (is_write && !(vma->vm_flags & VM_WRITE))
62 goto out;
63
64 /* Don't require VM_READ|VM_EXEC for write faults! */
65 if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
66 goto out;
67
68 do {
69 int fault;
70
71 fault = handle_mm_fault(mm, vma, address, flags);
72
73 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
74 goto out_nosemaphore;
75
76 if (unlikely(fault & VM_FAULT_ERROR)) {
77 if (fault & VM_FAULT_OOM) {
78 goto out_of_memory;
79 } else if (fault & VM_FAULT_SIGBUS) {
80 err = -EACCES;
81 goto out;
82 }
83 BUG();
84 }
85 if (flags & FAULT_FLAG_ALLOW_RETRY) {
86 if (fault & VM_FAULT_MAJOR)
87 current->maj_flt++;
88 else
89 current->min_flt++;
90 if (fault & VM_FAULT_RETRY) {
91 flags &= ~FAULT_FLAG_ALLOW_RETRY;
92
93 goto retry;
94 }
95 }
96
97 pgd = pgd_offset(mm, address);
98 pud = pud_offset(pgd, address);
99 pmd = pmd_offset(pud, address);
100 pte = pte_offset_kernel(pmd, address);
101 } while (!pte_present(*pte));
102 err = 0;
103 /*
104 * The below warning was added in place of
105 * pte_mkyoung(); if (is_write) pte_mkdirty();
106 * If it's triggered, we'd see normally a hang here (a clean pte is
107 * marked read-only to emulate the dirty bit).
108 * However, the generic code can mark a PTE writable but clean on a
109 * concurrent read fault, triggering this harmlessly. So comment it out.
110 */
111#if 0
112 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
113#endif
114 flush_tlb_page(vma, address);
115out:
116 up_read(&mm->mmap_sem);
117out_nosemaphore:
118 return err;
119
120out_of_memory:
121 /*
122 * We ran out of memory, call the OOM killer, and return the userspace
123 * (which will retry the fault, or kill us if we got oom-killed).
124 */
125 up_read(&mm->mmap_sem);
126 pagefault_out_of_memory();
127 return 0;
128}
129EXPORT_SYMBOL(handle_page_fault);
130
131static void show_segv_info(struct uml_pt_regs *regs)
132{
133 struct task_struct *tsk = current;
134 struct faultinfo *fi = UPT_FAULTINFO(regs);
135
136 if (!unhandled_signal(tsk, SIGSEGV))
137 return;
138
139 if (!printk_ratelimit())
140 return;
141
142 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
143 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
144 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
145 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
146 fi->error_code);
147
148 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
149 printk(KERN_CONT "\n");
150}
151
152static void bad_segv(struct faultinfo fi, unsigned long ip)
153{
154 struct siginfo si;
155
156 si.si_signo = SIGSEGV;
157 si.si_code = SEGV_ACCERR;
158 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
159 current->thread.arch.faultinfo = fi;
160 force_sig_info(SIGSEGV, &si, current);
161}
162
163void fatal_sigsegv(void)
164{
165 force_sigsegv(SIGSEGV, current);
166 do_signal();
167 /*
168 * This is to tell gcc that we're not returning - do_signal
169 * can, in general, return, but in this case, it's not, since
170 * we just got a fatal SIGSEGV queued.
171 */
172 os_dump_core();
173}
174
175void segv_handler(int sig, struct uml_pt_regs *regs)
176{
177 struct faultinfo * fi = UPT_FAULTINFO(regs);
178
179 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
180 show_segv_info(regs);
181 bad_segv(*fi, UPT_IP(regs));
182 return;
183 }
184 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
185}
186
187/*
188 * We give a *copy* of the faultinfo in the regs to segv.
189 * This must be done, since nesting SEGVs could overwrite
190 * the info in the regs. A pointer to the info then would
191 * give us bad data!
192 */
193unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
194 struct uml_pt_regs *regs)
195{
196 struct siginfo si;
197 jmp_buf *catcher;
198 int err;
199 int is_write = FAULT_WRITE(fi);
200 unsigned long address = FAULT_ADDRESS(fi);
201
202 if (!is_user && (address >= start_vm) && (address < end_vm)) {
203 flush_tlb_kernel_vm();
204 return 0;
205 }
206 else if (current->mm == NULL) {
207 show_regs(container_of(regs, struct pt_regs, regs));
208 panic("Segfault with no mm");
209 }
210
211 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
212 err = handle_page_fault(address, ip, is_write, is_user,
213 &si.si_code);
214 else {
215 err = -EFAULT;
216 /*
217 * A thread accessed NULL, we get a fault, but CR2 is invalid.
218 * This code is used in __do_copy_from_user() of TT mode.
219 * XXX tt mode is gone, so maybe this isn't needed any more
220 */
221 address = 0;
222 }
223
224 catcher = current->thread.fault_catcher;
225 if (!err)
226 return 0;
227 else if (catcher != NULL) {
228 current->thread.fault_addr = (void *) address;
229 UML_LONGJMP(catcher, 1);
230 }
231 else if (current->thread.fault_addr != NULL)
232 panic("fault_addr set but no fault catcher");
233 else if (!is_user && arch_fixup(ip, regs))
234 return 0;
235
236 if (!is_user) {
237 show_regs(container_of(regs, struct pt_regs, regs));
238 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
239 address, ip);
240 }
241
242 show_segv_info(regs);
243
244 if (err == -EACCES) {
245 si.si_signo = SIGBUS;
246 si.si_errno = 0;
247 si.si_code = BUS_ADRERR;
248 si.si_addr = (void __user *)address;
249 current->thread.arch.faultinfo = fi;
250 force_sig_info(SIGBUS, &si, current);
251 } else {
252 BUG_ON(err != -EFAULT);
253 si.si_signo = SIGSEGV;
254 si.si_addr = (void __user *) address;
255 current->thread.arch.faultinfo = fi;
256 force_sig_info(SIGSEGV, &si, current);
257 }
258 return 0;
259}
260
261void relay_signal(int sig, struct uml_pt_regs *regs)
262{
263 if (!UPT_IS_USER(regs)) {
264 if (sig == SIGBUS)
265 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
266 "mount likely just ran out of space\n");
267 panic("Kernel mode signal %d", sig);
268 }
269
270 arch_examine_signal(sig, regs);
271
272 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
273 force_sig(sig, current);
274}
275
276void bus_handler(int sig, struct uml_pt_regs *regs)
277{
278 if (current->thread.fault_catcher != NULL)
279 UML_LONGJMP(current->thread.fault_catcher, 1);
280 else relay_signal(sig, regs);
281}
282
283void winch(int sig, struct uml_pt_regs *regs)
284{
285 do_IRQ(WINCH_IRQ, regs);
286}
287
288void trap_init(void)
289{
290}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4 */
5
6#include <linux/mm.h>
7#include <linux/sched/signal.h>
8#include <linux/hardirq.h>
9#include <linux/module.h>
10#include <linux/uaccess.h>
11#include <linux/sched/debug.h>
12#include <asm/current.h>
13#include <asm/tlbflush.h>
14#include <arch.h>
15#include <as-layout.h>
16#include <kern_util.h>
17#include <os.h>
18#include <skas.h>
19
20/*
21 * Note this is constrained to return 0, -EFAULT, -EACCES, -ENOMEM by
22 * segv().
23 */
24int handle_page_fault(unsigned long address, unsigned long ip,
25 int is_write, int is_user, int *code_out)
26{
27 struct mm_struct *mm = current->mm;
28 struct vm_area_struct *vma;
29 pmd_t *pmd;
30 pte_t *pte;
31 int err = -EFAULT;
32 unsigned int flags = FAULT_FLAG_DEFAULT;
33
34 *code_out = SEGV_MAPERR;
35
36 /*
37 * If the fault was with pagefaults disabled, don't take the fault, just
38 * fail.
39 */
40 if (faulthandler_disabled())
41 goto out_nosemaphore;
42
43 if (is_user)
44 flags |= FAULT_FLAG_USER;
45retry:
46 mmap_read_lock(mm);
47 vma = find_vma(mm, address);
48 if (!vma)
49 goto out;
50 else if (vma->vm_start <= address)
51 goto good_area;
52 else if (!(vma->vm_flags & VM_GROWSDOWN))
53 goto out;
54 else if (is_user && !ARCH_IS_STACKGROW(address))
55 goto out;
56 else if (expand_stack(vma, address))
57 goto out;
58
59good_area:
60 *code_out = SEGV_ACCERR;
61 if (is_write) {
62 if (!(vma->vm_flags & VM_WRITE))
63 goto out;
64 flags |= FAULT_FLAG_WRITE;
65 } else {
66 /* Don't require VM_READ|VM_EXEC for write faults! */
67 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
68 goto out;
69 }
70
71 do {
72 vm_fault_t fault;
73
74 fault = handle_mm_fault(vma, address, flags, NULL);
75
76 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
77 goto out_nosemaphore;
78
79 if (unlikely(fault & VM_FAULT_ERROR)) {
80 if (fault & VM_FAULT_OOM) {
81 goto out_of_memory;
82 } else if (fault & VM_FAULT_SIGSEGV) {
83 goto out;
84 } else if (fault & VM_FAULT_SIGBUS) {
85 err = -EACCES;
86 goto out;
87 }
88 BUG();
89 }
90 if (flags & FAULT_FLAG_ALLOW_RETRY) {
91 if (fault & VM_FAULT_RETRY) {
92 flags |= FAULT_FLAG_TRIED;
93
94 goto retry;
95 }
96 }
97
98 pmd = pmd_off(mm, address);
99 pte = pte_offset_kernel(pmd, address);
100 } while (!pte_present(*pte));
101 err = 0;
102 /*
103 * The below warning was added in place of
104 * pte_mkyoung(); if (is_write) pte_mkdirty();
105 * If it's triggered, we'd see normally a hang here (a clean pte is
106 * marked read-only to emulate the dirty bit).
107 * However, the generic code can mark a PTE writable but clean on a
108 * concurrent read fault, triggering this harmlessly. So comment it out.
109 */
110#if 0
111 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
112#endif
113 flush_tlb_page(vma, address);
114out:
115 mmap_read_unlock(mm);
116out_nosemaphore:
117 return err;
118
119out_of_memory:
120 /*
121 * We ran out of memory, call the OOM killer, and return the userspace
122 * (which will retry the fault, or kill us if we got oom-killed).
123 */
124 mmap_read_unlock(mm);
125 if (!is_user)
126 goto out_nosemaphore;
127 pagefault_out_of_memory();
128 return 0;
129}
130EXPORT_SYMBOL(handle_page_fault);
131
132static void show_segv_info(struct uml_pt_regs *regs)
133{
134 struct task_struct *tsk = current;
135 struct faultinfo *fi = UPT_FAULTINFO(regs);
136
137 if (!unhandled_signal(tsk, SIGSEGV))
138 return;
139
140 if (!printk_ratelimit())
141 return;
142
143 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %x",
144 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
145 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
146 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
147 fi->error_code);
148
149 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
150 printk(KERN_CONT "\n");
151}
152
153static void bad_segv(struct faultinfo fi, unsigned long ip)
154{
155 current->thread.arch.faultinfo = fi;
156 force_sig_fault(SIGSEGV, SEGV_ACCERR, (void __user *) FAULT_ADDRESS(fi));
157}
158
159void fatal_sigsegv(void)
160{
161 force_sigsegv(SIGSEGV);
162 do_signal(¤t->thread.regs);
163 /*
164 * This is to tell gcc that we're not returning - do_signal
165 * can, in general, return, but in this case, it's not, since
166 * we just got a fatal SIGSEGV queued.
167 */
168 os_dump_core();
169}
170
171/**
172 * segv_handler() - the SIGSEGV handler
173 * @sig: the signal number
174 * @unused_si: the signal info struct; unused in this handler
175 * @regs: the ptrace register information
176 *
177 * The handler first extracts the faultinfo from the UML ptrace regs struct.
178 * If the userfault did not happen in an UML userspace process, bad_segv is called.
179 * Otherwise the signal did happen in a cloned userspace process, handle it.
180 */
181void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
182{
183 struct faultinfo * fi = UPT_FAULTINFO(regs);
184
185 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
186 show_segv_info(regs);
187 bad_segv(*fi, UPT_IP(regs));
188 return;
189 }
190 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
191}
192
193/*
194 * We give a *copy* of the faultinfo in the regs to segv.
195 * This must be done, since nesting SEGVs could overwrite
196 * the info in the regs. A pointer to the info then would
197 * give us bad data!
198 */
199unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
200 struct uml_pt_regs *regs)
201{
202 jmp_buf *catcher;
203 int si_code;
204 int err;
205 int is_write = FAULT_WRITE(fi);
206 unsigned long address = FAULT_ADDRESS(fi);
207
208 if (!is_user && regs)
209 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
210
211 if (!is_user && (address >= start_vm) && (address < end_vm)) {
212 flush_tlb_kernel_vm();
213 goto out;
214 }
215 else if (current->mm == NULL) {
216 show_regs(container_of(regs, struct pt_regs, regs));
217 panic("Segfault with no mm");
218 }
219 else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
220 show_regs(container_of(regs, struct pt_regs, regs));
221 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
222 address, ip);
223 }
224
225 if (SEGV_IS_FIXABLE(&fi))
226 err = handle_page_fault(address, ip, is_write, is_user,
227 &si_code);
228 else {
229 err = -EFAULT;
230 /*
231 * A thread accessed NULL, we get a fault, but CR2 is invalid.
232 * This code is used in __do_copy_from_user() of TT mode.
233 * XXX tt mode is gone, so maybe this isn't needed any more
234 */
235 address = 0;
236 }
237
238 catcher = current->thread.fault_catcher;
239 if (!err)
240 goto out;
241 else if (catcher != NULL) {
242 current->thread.fault_addr = (void *) address;
243 UML_LONGJMP(catcher, 1);
244 }
245 else if (current->thread.fault_addr != NULL)
246 panic("fault_addr set but no fault catcher");
247 else if (!is_user && arch_fixup(ip, regs))
248 goto out;
249
250 if (!is_user) {
251 show_regs(container_of(regs, struct pt_regs, regs));
252 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
253 address, ip);
254 }
255
256 show_segv_info(regs);
257
258 if (err == -EACCES) {
259 current->thread.arch.faultinfo = fi;
260 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
261 } else {
262 BUG_ON(err != -EFAULT);
263 current->thread.arch.faultinfo = fi;
264 force_sig_fault(SIGSEGV, si_code, (void __user *) address);
265 }
266
267out:
268 if (regs)
269 current->thread.segv_regs = NULL;
270
271 return 0;
272}
273
274void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
275{
276 int code, err;
277 if (!UPT_IS_USER(regs)) {
278 if (sig == SIGBUS)
279 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
280 "mount likely just ran out of space\n");
281 panic("Kernel mode signal %d", sig);
282 }
283
284 arch_examine_signal(sig, regs);
285
286 /* Is the signal layout for the signal known?
287 * Signal data must be scrubbed to prevent information leaks.
288 */
289 code = si->si_code;
290 err = si->si_errno;
291 if ((err == 0) && (siginfo_layout(sig, code) == SIL_FAULT)) {
292 struct faultinfo *fi = UPT_FAULTINFO(regs);
293 current->thread.arch.faultinfo = *fi;
294 force_sig_fault(sig, code, (void __user *)FAULT_ADDRESS(*fi));
295 } else {
296 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
297 sig, code, err);
298 force_sig(sig);
299 }
300}
301
302void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
303{
304 if (current->thread.fault_catcher != NULL)
305 UML_LONGJMP(current->thread.fault_catcher, 1);
306 else
307 relay_signal(sig, si, regs);
308}
309
310void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
311{
312 do_IRQ(WINCH_IRQ, regs);
313}
314
315void trap_init(void)
316{
317}