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