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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/*
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 <linux/uaccess.h>
11#include <asm/current.h>
12#include <asm/pgtable.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, -EACCESS, -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 pgd_t *pgd;
30 pud_t *pud;
31 pmd_t *pmd;
32 pte_t *pte;
33 int err = -EFAULT;
34 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
35
36 *code_out = SEGV_MAPERR;
37
38 /*
39 * If the fault was with pagefaults disabled, don't take the fault, just
40 * fail.
41 */
42 if (faulthandler_disabled())
43 goto out_nosemaphore;
44
45 if (is_user)
46 flags |= FAULT_FLAG_USER;
47retry:
48 down_read(&mm->mmap_sem);
49 vma = find_vma(mm, address);
50 if (!vma)
51 goto out;
52 else if (vma->vm_start <= address)
53 goto good_area;
54 else if (!(vma->vm_flags & VM_GROWSDOWN))
55 goto out;
56 else if (is_user && !ARCH_IS_STACKGROW(address))
57 goto out;
58 else if (expand_stack(vma, address))
59 goto out;
60
61good_area:
62 *code_out = SEGV_ACCERR;
63 if (is_write) {
64 if (!(vma->vm_flags & VM_WRITE))
65 goto out;
66 flags |= FAULT_FLAG_WRITE;
67 } else {
68 /* Don't require VM_READ|VM_EXEC for write faults! */
69 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
70 goto out;
71 }
72
73 do {
74 int fault;
75
76 fault = handle_mm_fault(mm, vma, address, flags);
77
78 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
79 goto out_nosemaphore;
80
81 if (unlikely(fault & VM_FAULT_ERROR)) {
82 if (fault & VM_FAULT_OOM) {
83 goto out_of_memory;
84 } else if (fault & VM_FAULT_SIGSEGV) {
85 goto out;
86 } else if (fault & VM_FAULT_SIGBUS) {
87 err = -EACCES;
88 goto out;
89 }
90 BUG();
91 }
92 if (flags & FAULT_FLAG_ALLOW_RETRY) {
93 if (fault & VM_FAULT_MAJOR)
94 current->maj_flt++;
95 else
96 current->min_flt++;
97 if (fault & VM_FAULT_RETRY) {
98 flags &= ~FAULT_FLAG_ALLOW_RETRY;
99 flags |= FAULT_FLAG_TRIED;
100
101 goto retry;
102 }
103 }
104
105 pgd = pgd_offset(mm, address);
106 pud = pud_offset(pgd, address);
107 pmd = pmd_offset(pud, address);
108 pte = pte_offset_kernel(pmd, address);
109 } while (!pte_present(*pte));
110 err = 0;
111 /*
112 * The below warning was added in place of
113 * pte_mkyoung(); if (is_write) pte_mkdirty();
114 * If it's triggered, we'd see normally a hang here (a clean pte is
115 * marked read-only to emulate the dirty bit).
116 * However, the generic code can mark a PTE writable but clean on a
117 * concurrent read fault, triggering this harmlessly. So comment it out.
118 */
119#if 0
120 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
121#endif
122 flush_tlb_page(vma, address);
123out:
124 up_read(&mm->mmap_sem);
125out_nosemaphore:
126 return err;
127
128out_of_memory:
129 /*
130 * We ran out of memory, call the OOM killer, and return the userspace
131 * (which will retry the fault, or kill us if we got oom-killed).
132 */
133 up_read(&mm->mmap_sem);
134 if (!is_user)
135 goto out_nosemaphore;
136 pagefault_out_of_memory();
137 return 0;
138}
139EXPORT_SYMBOL(handle_page_fault);
140
141static void show_segv_info(struct uml_pt_regs *regs)
142{
143 struct task_struct *tsk = current;
144 struct faultinfo *fi = UPT_FAULTINFO(regs);
145
146 if (!unhandled_signal(tsk, SIGSEGV))
147 return;
148
149 if (!printk_ratelimit())
150 return;
151
152 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
153 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
154 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
155 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
156 fi->error_code);
157
158 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
159 printk(KERN_CONT "\n");
160}
161
162static void bad_segv(struct faultinfo fi, unsigned long ip)
163{
164 struct siginfo si;
165
166 si.si_signo = SIGSEGV;
167 si.si_code = SEGV_ACCERR;
168 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
169 current->thread.arch.faultinfo = fi;
170 force_sig_info(SIGSEGV, &si, current);
171}
172
173void fatal_sigsegv(void)
174{
175 force_sigsegv(SIGSEGV, current);
176 do_signal(¤t->thread.regs);
177 /*
178 * This is to tell gcc that we're not returning - do_signal
179 * can, in general, return, but in this case, it's not, since
180 * we just got a fatal SIGSEGV queued.
181 */
182 os_dump_core();
183}
184
185void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
186{
187 struct faultinfo * fi = UPT_FAULTINFO(regs);
188
189 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
190 show_segv_info(regs);
191 bad_segv(*fi, UPT_IP(regs));
192 return;
193 }
194 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
195}
196
197/*
198 * We give a *copy* of the faultinfo in the regs to segv.
199 * This must be done, since nesting SEGVs could overwrite
200 * the info in the regs. A pointer to the info then would
201 * give us bad data!
202 */
203unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
204 struct uml_pt_regs *regs)
205{
206 struct siginfo si;
207 jmp_buf *catcher;
208 int err;
209 int is_write = FAULT_WRITE(fi);
210 unsigned long address = FAULT_ADDRESS(fi);
211
212 if (!is_user && regs)
213 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
214
215 if (!is_user && (address >= start_vm) && (address < end_vm)) {
216 flush_tlb_kernel_vm();
217 goto out;
218 }
219 else if (current->mm == NULL) {
220 show_regs(container_of(regs, struct pt_regs, regs));
221 panic("Segfault with no mm");
222 }
223 else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
224 show_regs(container_of(regs, struct pt_regs, regs));
225 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
226 address, ip);
227 }
228
229 if (SEGV_IS_FIXABLE(&fi))
230 err = handle_page_fault(address, ip, is_write, is_user,
231 &si.si_code);
232 else {
233 err = -EFAULT;
234 /*
235 * A thread accessed NULL, we get a fault, but CR2 is invalid.
236 * This code is used in __do_copy_from_user() of TT mode.
237 * XXX tt mode is gone, so maybe this isn't needed any more
238 */
239 address = 0;
240 }
241
242 catcher = current->thread.fault_catcher;
243 if (!err)
244 goto out;
245 else if (catcher != NULL) {
246 current->thread.fault_addr = (void *) address;
247 UML_LONGJMP(catcher, 1);
248 }
249 else if (current->thread.fault_addr != NULL)
250 panic("fault_addr set but no fault catcher");
251 else if (!is_user && arch_fixup(ip, regs))
252 goto out;
253
254 if (!is_user) {
255 show_regs(container_of(regs, struct pt_regs, regs));
256 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
257 address, ip);
258 }
259
260 show_segv_info(regs);
261
262 if (err == -EACCES) {
263 si.si_signo = SIGBUS;
264 si.si_errno = 0;
265 si.si_code = BUS_ADRERR;
266 si.si_addr = (void __user *)address;
267 current->thread.arch.faultinfo = fi;
268 force_sig_info(SIGBUS, &si, current);
269 } else {
270 BUG_ON(err != -EFAULT);
271 si.si_signo = SIGSEGV;
272 si.si_addr = (void __user *) address;
273 current->thread.arch.faultinfo = fi;
274 force_sig_info(SIGSEGV, &si, current);
275 }
276
277out:
278 if (regs)
279 current->thread.segv_regs = NULL;
280
281 return 0;
282}
283
284void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
285{
286 struct faultinfo *fi;
287 struct siginfo clean_si;
288
289 if (!UPT_IS_USER(regs)) {
290 if (sig == SIGBUS)
291 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
292 "mount likely just ran out of space\n");
293 panic("Kernel mode signal %d", sig);
294 }
295
296 arch_examine_signal(sig, regs);
297
298 memset(&clean_si, 0, sizeof(clean_si));
299 clean_si.si_signo = si->si_signo;
300 clean_si.si_errno = si->si_errno;
301 clean_si.si_code = si->si_code;
302 switch (sig) {
303 case SIGILL:
304 case SIGFPE:
305 case SIGSEGV:
306 case SIGBUS:
307 case SIGTRAP:
308 fi = UPT_FAULTINFO(regs);
309 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
310 current->thread.arch.faultinfo = *fi;
311#ifdef __ARCH_SI_TRAPNO
312 clean_si.si_trapno = si->si_trapno;
313#endif
314 break;
315 default:
316 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
317 sig, si->si_code);
318 }
319
320 force_sig_info(sig, &clean_si, current);
321}
322
323void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
324{
325 if (current->thread.fault_catcher != NULL)
326 UML_LONGJMP(current->thread.fault_catcher, 1);
327 else
328 relay_signal(sig, si, regs);
329}
330
331void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
332{
333 do_IRQ(WINCH_IRQ, regs);
334}
335
336void trap_init(void)
337{
338}