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 */
handle_page_fault(unsigned long address,unsigned long ip,int is_write,int is_user,int * code_out)23 int 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
34 *code_out = SEGV_MAPERR;
35
36 /*
37 * If the fault was during atomic operation, don't take the fault, just
38 * fail.
39 */
40 if (in_atomic())
41 goto out_nosemaphore;
42
43 down_read(&mm->mmap_sem);
44 vma = find_vma(mm, address);
45 if (!vma)
46 goto out;
47 else if (vma->vm_start <= address)
48 goto good_area;
49 else if (!(vma->vm_flags & VM_GROWSDOWN))
50 goto out;
51 else if (is_user && !ARCH_IS_STACKGROW(address))
52 goto out;
53 else if (expand_stack(vma, address))
54 goto out;
55
56 good_area:
57 *code_out = SEGV_ACCERR;
58 if (is_write && !(vma->vm_flags & VM_WRITE))
59 goto out;
60
61 /* Don't require VM_READ|VM_EXEC for write faults! */
62 if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
63 goto out;
64
65 do {
66 int fault;
67
68 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
69 if (unlikely(fault & VM_FAULT_ERROR)) {
70 if (fault & VM_FAULT_OOM) {
71 goto out_of_memory;
72 } else if (fault & VM_FAULT_SIGBUS) {
73 err = -EACCES;
74 goto out;
75 }
76 BUG();
77 }
78 if (fault & VM_FAULT_MAJOR)
79 current->maj_flt++;
80 else
81 current->min_flt++;
82
83 pgd = pgd_offset(mm, address);
84 pud = pud_offset(pgd, address);
85 pmd = pmd_offset(pud, address);
86 pte = pte_offset_kernel(pmd, address);
87 } while (!pte_present(*pte));
88 err = 0;
89 /*
90 * The below warning was added in place of
91 * pte_mkyoung(); if (is_write) pte_mkdirty();
92 * If it's triggered, we'd see normally a hang here (a clean pte is
93 * marked read-only to emulate the dirty bit).
94 * However, the generic code can mark a PTE writable but clean on a
95 * concurrent read fault, triggering this harmlessly. So comment it out.
96 */
97 #if 0
98 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
99 #endif
100 flush_tlb_page(vma, address);
101 out:
102 up_read(&mm->mmap_sem);
103 out_nosemaphore:
104 return err;
105
106 out_of_memory:
107 /*
108 * We ran out of memory, call the OOM killer, and return the userspace
109 * (which will retry the fault, or kill us if we got oom-killed).
110 */
111 up_read(&mm->mmap_sem);
112 pagefault_out_of_memory();
113 return 0;
114 }
115 EXPORT_SYMBOL(handle_page_fault);
116
show_segv_info(struct uml_pt_regs * regs)117 static void show_segv_info(struct uml_pt_regs *regs)
118 {
119 struct task_struct *tsk = current;
120 struct faultinfo *fi = UPT_FAULTINFO(regs);
121
122 if (!unhandled_signal(tsk, SIGSEGV))
123 return;
124
125 if (!printk_ratelimit())
126 return;
127
128 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
129 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
130 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
131 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
132 fi->error_code);
133
134 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
135 printk(KERN_CONT "\n");
136 }
137
bad_segv(struct faultinfo fi,unsigned long ip)138 static void bad_segv(struct faultinfo fi, unsigned long ip)
139 {
140 struct siginfo si;
141
142 si.si_signo = SIGSEGV;
143 si.si_code = SEGV_ACCERR;
144 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
145 current->thread.arch.faultinfo = fi;
146 force_sig_info(SIGSEGV, &si, current);
147 }
148
fatal_sigsegv(void)149 void fatal_sigsegv(void)
150 {
151 force_sigsegv(SIGSEGV, current);
152 do_signal();
153 /*
154 * This is to tell gcc that we're not returning - do_signal
155 * can, in general, return, but in this case, it's not, since
156 * we just got a fatal SIGSEGV queued.
157 */
158 os_dump_core();
159 }
160
segv_handler(int sig,struct uml_pt_regs * regs)161 void segv_handler(int sig, struct uml_pt_regs *regs)
162 {
163 struct faultinfo * fi = UPT_FAULTINFO(regs);
164
165 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
166 show_segv_info(regs);
167 bad_segv(*fi, UPT_IP(regs));
168 return;
169 }
170 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
171 }
172
173 /*
174 * We give a *copy* of the faultinfo in the regs to segv.
175 * This must be done, since nesting SEGVs could overwrite
176 * the info in the regs. A pointer to the info then would
177 * give us bad data!
178 */
segv(struct faultinfo fi,unsigned long ip,int is_user,struct uml_pt_regs * regs)179 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
180 struct uml_pt_regs *regs)
181 {
182 struct siginfo si;
183 jmp_buf *catcher;
184 int err;
185 int is_write = FAULT_WRITE(fi);
186 unsigned long address = FAULT_ADDRESS(fi);
187
188 if (!is_user && (address >= start_vm) && (address < end_vm)) {
189 flush_tlb_kernel_vm();
190 return 0;
191 }
192 else if (current->mm == NULL) {
193 show_regs(container_of(regs, struct pt_regs, regs));
194 panic("Segfault with no mm");
195 }
196
197 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
198 err = handle_page_fault(address, ip, is_write, is_user,
199 &si.si_code);
200 else {
201 err = -EFAULT;
202 /*
203 * A thread accessed NULL, we get a fault, but CR2 is invalid.
204 * This code is used in __do_copy_from_user() of TT mode.
205 * XXX tt mode is gone, so maybe this isn't needed any more
206 */
207 address = 0;
208 }
209
210 catcher = current->thread.fault_catcher;
211 if (!err)
212 return 0;
213 else if (catcher != NULL) {
214 current->thread.fault_addr = (void *) address;
215 UML_LONGJMP(catcher, 1);
216 }
217 else if (current->thread.fault_addr != NULL)
218 panic("fault_addr set but no fault catcher");
219 else if (!is_user && arch_fixup(ip, regs))
220 return 0;
221
222 if (!is_user) {
223 show_regs(container_of(regs, struct pt_regs, regs));
224 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
225 address, ip);
226 }
227
228 show_segv_info(regs);
229
230 if (err == -EACCES) {
231 si.si_signo = SIGBUS;
232 si.si_errno = 0;
233 si.si_code = BUS_ADRERR;
234 si.si_addr = (void __user *)address;
235 current->thread.arch.faultinfo = fi;
236 force_sig_info(SIGBUS, &si, current);
237 } else {
238 BUG_ON(err != -EFAULT);
239 si.si_signo = SIGSEGV;
240 si.si_addr = (void __user *) address;
241 current->thread.arch.faultinfo = fi;
242 force_sig_info(SIGSEGV, &si, current);
243 }
244 return 0;
245 }
246
relay_signal(int sig,struct uml_pt_regs * regs)247 void relay_signal(int sig, struct uml_pt_regs *regs)
248 {
249 if (!UPT_IS_USER(regs)) {
250 if (sig == SIGBUS)
251 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
252 "mount likely just ran out of space\n");
253 panic("Kernel mode signal %d", sig);
254 }
255
256 arch_examine_signal(sig, regs);
257
258 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
259 force_sig(sig, current);
260 }
261
bus_handler(int sig,struct uml_pt_regs * regs)262 void bus_handler(int sig, struct uml_pt_regs *regs)
263 {
264 if (current->thread.fault_catcher != NULL)
265 UML_LONGJMP(current->thread.fault_catcher, 1);
266 else relay_signal(sig, regs);
267 }
268
winch(int sig,struct uml_pt_regs * regs)269 void winch(int sig, struct uml_pt_regs *regs)
270 {
271 do_IRQ(WINCH_IRQ, regs);
272 }
273
trap_init(void)274 void trap_init(void)
275 {
276 }
277