c517c449d0dd3570d9f7fb8b80da200808d7cdb1
[linux-2.6.git] / 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 #include "skas.h"
33 #include "os.h"
34
35 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
36 int handle_page_fault(unsigned long address, unsigned long ip,
37                       int is_write, int is_user, int *code_out)
38 {
39         struct mm_struct *mm = current->mm;
40         struct vm_area_struct *vma;
41         pgd_t *pgd;
42         pud_t *pud;
43         pmd_t *pmd;
44         pte_t *pte;
45         int err = -EFAULT;
46
47         *code_out = SEGV_MAPERR;
48
49         /* If the fault was during atomic operation, don't take the fault, just
50          * fail. */
51         if (in_atomic())
52                 goto out_nosemaphore;
53
54         down_read(&mm->mmap_sem);
55         vma = find_vma(mm, address);
56         if(!vma)
57                 goto out;
58         else if(vma->vm_start <= address)
59                 goto good_area;
60         else if(!(vma->vm_flags & VM_GROWSDOWN))
61                 goto out;
62         else if(is_user && !ARCH_IS_STACKGROW(address))
63                 goto out;
64         else if(expand_stack(vma, address))
65                 goto out;
66
67 good_area:
68         *code_out = SEGV_ACCERR;
69         if(is_write && !(vma->vm_flags & VM_WRITE))
70                 goto out;
71
72         /* Don't require VM_READ|VM_EXEC for write faults! */
73         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
74                 goto out;
75
76         do {
77                 int fault;
78 survive:
79                 fault = handle_mm_fault(mm, vma, address, is_write);
80                 if (unlikely(fault & VM_FAULT_ERROR)) {
81                         if (fault & VM_FAULT_OOM) {
82                                 err = -ENOMEM;
83                                 goto out_of_memory;
84                         } else if (fault & VM_FAULT_SIGBUS) {
85                                 err = -EACCES;
86                                 goto out;
87                         }
88                         BUG();
89                 }
90                 if (fault & VM_FAULT_MAJOR)
91                         current->maj_flt++;
92                 else
93                         current->min_flt++;
94
95                 pgd = pgd_offset(mm, address);
96                 pud = pud_offset(pgd, address);
97                 pmd = pmd_offset(pud, address);
98                 pte = pte_offset_kernel(pmd, address);
99         } while(!pte_present(*pte));
100         err = 0;
101         /* The below warning was added in place of
102          *      pte_mkyoung(); if (is_write) pte_mkdirty();
103          * If it's triggered, we'd see normally a hang here (a clean pte is
104          * marked read-only to emulate the dirty bit).
105          * However, the generic code can mark a PTE writable but clean on a
106          * concurrent read fault, triggering this harmlessly. So comment it out.
107          */
108 #if 0
109         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
110 #endif
111         flush_tlb_page(vma, address);
112 out:
113         up_read(&mm->mmap_sem);
114 out_nosemaphore:
115         return(err);
116
117 /*
118  * We ran out of memory, or some other thing happened to us that made
119  * us unable to handle the page fault gracefully.
120  */
121 out_of_memory:
122         if (is_init(current)) {
123                 up_read(&mm->mmap_sem);
124                 yield();
125                 down_read(&mm->mmap_sem);
126                 goto survive;
127         }
128         goto out;
129 }
130
131 static void bad_segv(struct faultinfo fi, unsigned long ip)
132 {
133         struct siginfo si;
134
135         si.si_signo = SIGSEGV;
136         si.si_code = SEGV_ACCERR;
137         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
138         current->thread.arch.faultinfo = fi;
139         force_sig_info(SIGSEGV, &si, current);
140 }
141
142 static void segv_handler(int sig, union uml_pt_regs *regs)
143 {
144         struct faultinfo * fi = UPT_FAULTINFO(regs);
145
146         if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
147                 bad_segv(*fi, UPT_IP(regs));
148                 return;
149         }
150         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
151 }
152
153 /*
154  * We give a *copy* of the faultinfo in the regs to segv.
155  * This must be done, since nesting SEGVs could overwrite
156  * the info in the regs. A pointer to the info then would
157  * give us bad data!
158  */
159 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
160                    union uml_pt_regs *regs)
161 {
162         struct siginfo si;
163         void *catcher;
164         int err;
165         int is_write = FAULT_WRITE(fi);
166         unsigned long address = FAULT_ADDRESS(fi);
167
168         if(!is_user && (address >= start_vm) && (address < end_vm)){
169                 flush_tlb_kernel_vm();
170                 return 0;
171         }
172         else if(current->mm == NULL) {
173                 show_regs(container_of(regs, struct pt_regs, regs));
174                 panic("Segfault with no mm");
175         }
176
177         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
178                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
179         else {
180                 err = -EFAULT;
181                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
182                  * This code is used in __do_copy_from_user() of TT mode. */
183                 address = 0;
184         }
185
186         catcher = current->thread.fault_catcher;
187         if(!err)
188                 return 0;
189         else if(catcher != NULL){
190                 current->thread.fault_addr = (void *) address;
191                 do_longjmp(catcher, 1);
192         }
193         else if(current->thread.fault_addr != NULL)
194                 panic("fault_addr set but no fault catcher");
195         else if(!is_user && arch_fixup(ip, regs))
196                 return 0;
197
198         if(!is_user) {
199                 show_regs(container_of(regs, struct pt_regs, regs));
200                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
201                       address, ip);
202         }
203
204         if (err == -EACCES) {
205                 si.si_signo = SIGBUS;
206                 si.si_errno = 0;
207                 si.si_code = BUS_ADRERR;
208                 si.si_addr = (void __user *)address;
209                 current->thread.arch.faultinfo = fi;
210                 force_sig_info(SIGBUS, &si, current);
211         } else if (err == -ENOMEM) {
212                 printk("VM: killing process %s\n", current->comm);
213                 do_exit(SIGKILL);
214         } else {
215                 BUG_ON(err != -EFAULT);
216                 si.si_signo = SIGSEGV;
217                 si.si_addr = (void __user *) address;
218                 current->thread.arch.faultinfo = fi;
219                 force_sig_info(SIGSEGV, &si, current);
220         }
221         return 0;
222 }
223
224 void relay_signal(int sig, union uml_pt_regs *regs)
225 {
226         if(arch_handle_signal(sig, regs))
227                 return;
228
229         if(!UPT_IS_USER(regs)){
230                 if(sig == SIGBUS)
231                         printk("Bus error - the host /dev/shm or /tmp mount "
232                                "likely just ran out of space\n");
233                 panic("Kernel mode signal %d", sig);
234         }
235
236         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
237         force_sig(sig, current);
238 }
239
240 static void bus_handler(int sig, union uml_pt_regs *regs)
241 {
242         if(current->thread.fault_catcher != NULL)
243                 do_longjmp(current->thread.fault_catcher, 1);
244         else relay_signal(sig, regs);
245 }
246
247 static void winch(int sig, union uml_pt_regs *regs)
248 {
249         do_IRQ(WINCH_IRQ, regs);
250 }
251
252 const struct kern_handlers handlinfo_kern = {
253         .relay_signal = relay_signal,
254         .winch = winch,
255         .bus_handler = bus_handler,
256         .page_fault = segv_handler,
257         .sigio_handler = sigio_handler,
258         .timer_handler = timer_handler
259 };
260
261 void trap_init(void)
262 {
263 }