Merge branch 'for-linus' of git://git.o-hand.com/linux-rpurdie-backlight
[linux-2.6] / arch / um / kernel / trap.c
1 /*
2  * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
3  * Licensed under the GPL
4  */
5
6 #include "linux/kernel.h"
7 #include "asm/errno.h"
8 #include "linux/sched.h"
9 #include "linux/mm.h"
10 #include "linux/spinlock.h"
11 #include "linux/init.h"
12 #include "linux/ptrace.h"
13 #include "asm/semaphore.h"
14 #include "asm/pgtable.h"
15 #include "asm/pgalloc.h"
16 #include "asm/tlbflush.h"
17 #include "asm/a.out.h"
18 #include "asm/current.h"
19 #include "asm/irq.h"
20 #include "sysdep/sigcontext.h"
21 #include "kern_util.h"
22 #include "as-layout.h"
23 #include "arch.h"
24 #include "kern.h"
25 #include "chan_kern.h"
26 #include "mconsole_kern.h"
27 #include "mem.h"
28 #include "mem_kern.h"
29 #include "sysdep/sigcontext.h"
30 #include "sysdep/ptrace.h"
31 #include "os.h"
32 #ifdef CONFIG_MODE_SKAS
33 #include "skas.h"
34 #endif
35 #include "os.h"
36
37 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
38 int handle_page_fault(unsigned long address, unsigned long ip,
39                       int is_write, int is_user, int *code_out)
40 {
41         struct mm_struct *mm = current->mm;
42         struct vm_area_struct *vma;
43         pgd_t *pgd;
44         pud_t *pud;
45         pmd_t *pmd;
46         pte_t *pte;
47         int err = -EFAULT;
48
49         *code_out = SEGV_MAPERR;
50
51         /* If the fault was during atomic operation, don't take the fault, just
52          * fail. */
53         if (in_atomic())
54                 goto out_nosemaphore;
55
56         down_read(&mm->mmap_sem);
57         vma = find_vma(mm, address);
58         if(!vma)
59                 goto out;
60         else if(vma->vm_start <= address)
61                 goto good_area;
62         else if(!(vma->vm_flags & VM_GROWSDOWN))
63                 goto out;
64         else if(is_user && !ARCH_IS_STACKGROW(address))
65                 goto out;
66         else if(expand_stack(vma, address))
67                 goto out;
68
69 good_area:
70         *code_out = SEGV_ACCERR;
71         if(is_write && !(vma->vm_flags & VM_WRITE))
72                 goto out;
73
74         /* Don't require VM_READ|VM_EXEC for write faults! */
75         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
76                 goto out;
77
78         do {
79                 int fault;
80 survive:
81                 fault = handle_mm_fault(mm, vma, address, is_write);
82                 if (unlikely(fault & VM_FAULT_ERROR)) {
83                         if (fault & VM_FAULT_OOM) {
84                                 err = -ENOMEM;
85                                 goto out_of_memory;
86                         } else if (fault & VM_FAULT_SIGBUS) {
87                                 err = -EACCES;
88                                 goto out;
89                         }
90                         BUG();
91                 }
92                 if (fault & VM_FAULT_MAJOR)
93                         current->maj_flt++;
94                 else
95                         current->min_flt++;
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         /* 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);
114 out:
115         up_read(&mm->mmap_sem);
116 out_nosemaphore:
117         return(err);
118
119 /*
120  * We ran out of memory, or some other thing happened to us that made
121  * us unable to handle the page fault gracefully.
122  */
123 out_of_memory:
124         if (is_init(current)) {
125                 up_read(&mm->mmap_sem);
126                 yield();
127                 down_read(&mm->mmap_sem);
128                 goto survive;
129         }
130         goto out;
131 }
132
133 static void bad_segv(struct faultinfo fi, unsigned long ip)
134 {
135         struct siginfo si;
136
137         si.si_signo = SIGSEGV;
138         si.si_code = SEGV_ACCERR;
139         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
140         current->thread.arch.faultinfo = fi;
141         force_sig_info(SIGSEGV, &si, current);
142 }
143
144 static void segv_handler(int sig, union uml_pt_regs *regs)
145 {
146         struct faultinfo * fi = UPT_FAULTINFO(regs);
147
148         if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
149                 bad_segv(*fi, UPT_IP(regs));
150                 return;
151         }
152         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
153 }
154
155 /*
156  * We give a *copy* of the faultinfo in the regs to segv.
157  * This must be done, since nesting SEGVs could overwrite
158  * the info in the regs. A pointer to the info then would
159  * give us bad data!
160  */
161 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
162                    union uml_pt_regs *regs)
163 {
164         struct siginfo si;
165         void *catcher;
166         int err;
167         int is_write = FAULT_WRITE(fi);
168         unsigned long address = FAULT_ADDRESS(fi);
169
170         if(!is_user && (address >= start_vm) && (address < end_vm)){
171                 flush_tlb_kernel_vm();
172                 return 0;
173         }
174         else if(current->mm == NULL) {
175                 show_regs(container_of(regs, struct pt_regs, regs));
176                 panic("Segfault with no mm");
177         }
178
179         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
180                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
181         else {
182                 err = -EFAULT;
183                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
184                  * This code is used in __do_copy_from_user() of TT mode. */
185                 address = 0;
186         }
187
188         catcher = current->thread.fault_catcher;
189         if(!err)
190                 return 0;
191         else if(catcher != NULL){
192                 current->thread.fault_addr = (void *) address;
193                 do_longjmp(catcher, 1);
194         }
195         else if(current->thread.fault_addr != NULL)
196                 panic("fault_addr set but no fault catcher");
197         else if(!is_user && arch_fixup(ip, regs))
198                 return 0;
199
200         if(!is_user) {
201                 show_regs(container_of(regs, struct pt_regs, regs));
202                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
203                       address, ip);
204         }
205
206         if (err == -EACCES) {
207                 si.si_signo = SIGBUS;
208                 si.si_errno = 0;
209                 si.si_code = BUS_ADRERR;
210                 si.si_addr = (void __user *)address;
211                 current->thread.arch.faultinfo = fi;
212                 force_sig_info(SIGBUS, &si, current);
213         } else if (err == -ENOMEM) {
214                 printk("VM: killing process %s\n", current->comm);
215                 do_exit(SIGKILL);
216         } else {
217                 BUG_ON(err != -EFAULT);
218                 si.si_signo = SIGSEGV;
219                 si.si_addr = (void __user *) address;
220                 current->thread.arch.faultinfo = fi;
221                 force_sig_info(SIGSEGV, &si, current);
222         }
223         return 0;
224 }
225
226 void relay_signal(int sig, union uml_pt_regs *regs)
227 {
228         if(arch_handle_signal(sig, regs))
229                 return;
230
231         if(!UPT_IS_USER(regs)){
232                 if(sig == SIGBUS)
233                         printk("Bus error - the host /dev/shm or /tmp mount "
234                                "likely just ran out of space\n");
235                 panic("Kernel mode signal %d", sig);
236         }
237
238         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
239         force_sig(sig, current);
240 }
241
242 static void bus_handler(int sig, union uml_pt_regs *regs)
243 {
244         if(current->thread.fault_catcher != NULL)
245                 do_longjmp(current->thread.fault_catcher, 1);
246         else relay_signal(sig, regs);
247 }
248
249 static void winch(int sig, union uml_pt_regs *regs)
250 {
251         do_IRQ(WINCH_IRQ, regs);
252 }
253
254 const struct kern_handlers handlinfo_kern = {
255         .relay_signal = relay_signal,
256         .winch = winch,
257         .bus_handler = bus_handler,
258         .page_fault = segv_handler,
259         .sigio_handler = sigio_handler,
260         .timer_handler = timer_handler
261 };
262
263 void trap_init(void)
264 {
265 }