2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
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/pgtable.h>
14 #include <asm/tlbflush.h>
16 #include <as-layout.h>
17 #include <kern_util.h>
22 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
25 int handle_page_fault(unsigned long address, unsigned long ip,
26 int is_write, int is_user, int *code_out)
28 struct mm_struct *mm = current->mm;
29 struct vm_area_struct *vma;
35 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
37 *code_out = SEGV_MAPERR;
40 * If the fault was with pagefaults disabled, don't take the fault, just
43 if (faulthandler_disabled())
47 flags |= FAULT_FLAG_USER;
49 down_read(&mm->mmap_sem);
50 vma = find_vma(mm, address);
53 else if (vma->vm_start <= address)
55 else if (!(vma->vm_flags & VM_GROWSDOWN))
57 else if (is_user && !ARCH_IS_STACKGROW(address))
59 else if (expand_stack(vma, address))
63 *code_out = SEGV_ACCERR;
65 if (!(vma->vm_flags & VM_WRITE))
67 flags |= FAULT_FLAG_WRITE;
69 /* Don't require VM_READ|VM_EXEC for write faults! */
70 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
77 fault = handle_mm_fault(vma, address, flags);
79 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
82 if (unlikely(fault & VM_FAULT_ERROR)) {
83 if (fault & VM_FAULT_OOM) {
85 } else if (fault & VM_FAULT_SIGSEGV) {
87 } else if (fault & VM_FAULT_SIGBUS) {
93 if (flags & FAULT_FLAG_ALLOW_RETRY) {
94 if (fault & VM_FAULT_MAJOR)
98 if (fault & VM_FAULT_RETRY) {
99 flags &= ~FAULT_FLAG_ALLOW_RETRY;
100 flags |= FAULT_FLAG_TRIED;
106 pgd = pgd_offset(mm, address);
107 pud = pud_offset(pgd, address);
108 pmd = pmd_offset(pud, address);
109 pte = pte_offset_kernel(pmd, address);
110 } while (!pte_present(*pte));
113 * The below warning was added in place of
114 * pte_mkyoung(); if (is_write) pte_mkdirty();
115 * If it's triggered, we'd see normally a hang here (a clean pte is
116 * marked read-only to emulate the dirty bit).
117 * However, the generic code can mark a PTE writable but clean on a
118 * concurrent read fault, triggering this harmlessly. So comment it out.
121 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
123 flush_tlb_page(vma, address);
125 up_read(&mm->mmap_sem);
131 * We ran out of memory, call the OOM killer, and return the userspace
132 * (which will retry the fault, or kill us if we got oom-killed).
134 up_read(&mm->mmap_sem);
136 goto out_nosemaphore;
137 pagefault_out_of_memory();
140 EXPORT_SYMBOL(handle_page_fault);
142 static void show_segv_info(struct uml_pt_regs *regs)
144 struct task_struct *tsk = current;
145 struct faultinfo *fi = UPT_FAULTINFO(regs);
147 if (!unhandled_signal(tsk, SIGSEGV))
150 if (!printk_ratelimit())
153 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
154 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
155 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
156 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
159 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
160 printk(KERN_CONT "\n");
163 static void bad_segv(struct faultinfo fi, unsigned long ip)
167 si.si_signo = SIGSEGV;
168 si.si_code = SEGV_ACCERR;
169 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
170 current->thread.arch.faultinfo = fi;
171 force_sig_info(SIGSEGV, &si, current);
174 void fatal_sigsegv(void)
176 force_sigsegv(SIGSEGV, current);
177 do_signal(¤t->thread.regs);
179 * This is to tell gcc that we're not returning - do_signal
180 * can, in general, return, but in this case, it's not, since
181 * we just got a fatal SIGSEGV queued.
187 * segv_handler() - the SIGSEGV handler
188 * @sig: the signal number
189 * @unused_si: the signal info struct; unused in this handler
190 * @regs: the ptrace register information
192 * The handler first extracts the faultinfo from the UML ptrace regs struct.
193 * If the userfault did not happen in an UML userspace process, bad_segv is called.
194 * Otherwise the signal did happen in a cloned userspace process, handle it.
196 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
198 struct faultinfo * fi = UPT_FAULTINFO(regs);
200 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
201 show_segv_info(regs);
202 bad_segv(*fi, UPT_IP(regs));
205 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
209 * We give a *copy* of the faultinfo in the regs to segv.
210 * This must be done, since nesting SEGVs could overwrite
211 * the info in the regs. A pointer to the info then would
214 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
215 struct uml_pt_regs *regs)
220 int is_write = FAULT_WRITE(fi);
221 unsigned long address = FAULT_ADDRESS(fi);
223 if (!is_user && regs)
224 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
226 if (!is_user && (address >= start_vm) && (address < end_vm)) {
227 flush_tlb_kernel_vm();
230 else if (current->mm == NULL) {
231 show_regs(container_of(regs, struct pt_regs, regs));
232 panic("Segfault with no mm");
234 else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
235 show_regs(container_of(regs, struct pt_regs, regs));
236 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
240 if (SEGV_IS_FIXABLE(&fi))
241 err = handle_page_fault(address, ip, is_write, is_user,
246 * A thread accessed NULL, we get a fault, but CR2 is invalid.
247 * This code is used in __do_copy_from_user() of TT mode.
248 * XXX tt mode is gone, so maybe this isn't needed any more
253 catcher = current->thread.fault_catcher;
256 else if (catcher != NULL) {
257 current->thread.fault_addr = (void *) address;
258 UML_LONGJMP(catcher, 1);
260 else if (current->thread.fault_addr != NULL)
261 panic("fault_addr set but no fault catcher");
262 else if (!is_user && arch_fixup(ip, regs))
266 show_regs(container_of(regs, struct pt_regs, regs));
267 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
271 show_segv_info(regs);
273 if (err == -EACCES) {
274 si.si_signo = SIGBUS;
276 si.si_code = BUS_ADRERR;
277 si.si_addr = (void __user *)address;
278 current->thread.arch.faultinfo = fi;
279 force_sig_info(SIGBUS, &si, current);
281 BUG_ON(err != -EFAULT);
282 si.si_signo = SIGSEGV;
283 si.si_addr = (void __user *) address;
284 current->thread.arch.faultinfo = fi;
285 force_sig_info(SIGSEGV, &si, current);
290 current->thread.segv_regs = NULL;
295 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
297 struct faultinfo *fi;
298 struct siginfo clean_si;
300 if (!UPT_IS_USER(regs)) {
302 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
303 "mount likely just ran out of space\n");
304 panic("Kernel mode signal %d", sig);
307 arch_examine_signal(sig, regs);
309 memset(&clean_si, 0, sizeof(clean_si));
310 clean_si.si_signo = si->si_signo;
311 clean_si.si_errno = si->si_errno;
312 clean_si.si_code = si->si_code;
319 fi = UPT_FAULTINFO(regs);
320 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
321 current->thread.arch.faultinfo = *fi;
322 #ifdef __ARCH_SI_TRAPNO
323 clean_si.si_trapno = si->si_trapno;
327 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
331 force_sig_info(sig, &clean_si, current);
334 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
336 if (current->thread.fault_catcher != NULL)
337 UML_LONGJMP(current->thread.fault_catcher, 1);
339 relay_signal(sig, si, regs);
342 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
344 do_IRQ(WINCH_IRQ, regs);