uml: kernel segfaults should dump proper registers
[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 #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 survive:
80                 switch (handle_mm_fault(mm, vma, address, is_write)){
81                 case VM_FAULT_MINOR:
82                         current->min_flt++;
83                         break;
84                 case VM_FAULT_MAJOR:
85                         current->maj_flt++;
86                         break;
87                 case VM_FAULT_SIGBUS:
88                         err = -EACCES;
89                         goto out;
90                 case VM_FAULT_OOM:
91                         err = -ENOMEM;
92                         goto out_of_memory;
93                 default:
94                         BUG();
95                 }
96                 pgd = pgd_offset(mm, address);
97                 pud = pud_offset(pgd, address);
98                 pmd = pmd_offset(pud, address);
99                 pte = pte_offset_kernel(pmd, address);
100         } while(!pte_present(*pte));
101         err = 0;
102         /* The below warning was added in place of
103          *      pte_mkyoung(); if (is_write) pte_mkdirty();
104          * If it's triggered, we'd see normally a hang here (a clean pte is
105          * marked read-only to emulate the dirty bit).
106          * However, the generic code can mark a PTE writable but clean on a
107          * concurrent read fault, triggering this harmlessly. So comment it out.
108          */
109 #if 0
110         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
111 #endif
112         flush_tlb_page(vma, address);
113 out:
114         up_read(&mm->mmap_sem);
115 out_nosemaphore:
116         return(err);
117
118 /*
119  * We ran out of memory, or some other thing happened to us that made
120  * us unable to handle the page fault gracefully.
121  */
122 out_of_memory:
123         if (is_init(current)) {
124                 up_read(&mm->mmap_sem);
125                 yield();
126                 down_read(&mm->mmap_sem);
127                 goto survive;
128         }
129         goto out;
130 }
131
132 static void bad_segv(struct faultinfo fi, unsigned long ip)
133 {
134         struct siginfo si;
135
136         si.si_signo = SIGSEGV;
137         si.si_code = SEGV_ACCERR;
138         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
139         current->thread.arch.faultinfo = fi;
140         force_sig_info(SIGSEGV, &si, current);
141 }
142
143 static void segv_handler(int sig, union uml_pt_regs *regs)
144 {
145         struct faultinfo * fi = UPT_FAULTINFO(regs);
146
147         if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
148                 bad_segv(*fi, UPT_IP(regs));
149                 return;
150         }
151         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
152 }
153
154 /*
155  * We give a *copy* of the faultinfo in the regs to segv.
156  * This must be done, since nesting SEGVs could overwrite
157  * the info in the regs. A pointer to the info then would
158  * give us bad data!
159  */
160 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
161                    union uml_pt_regs *regs)
162 {
163         struct siginfo si;
164         void *catcher;
165         int err;
166         int is_write = FAULT_WRITE(fi);
167         unsigned long address = FAULT_ADDRESS(fi);
168
169         if(!is_user && (address >= start_vm) && (address < end_vm)){
170                 flush_tlb_kernel_vm();
171                 return 0;
172         }
173         else if(current->mm == NULL) {
174                 show_regs(container_of(regs, struct pt_regs, regs));
175                 panic("Segfault with no mm");
176         }
177
178         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
179                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
180         else {
181                 err = -EFAULT;
182                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
183                  * This code is used in __do_copy_from_user() of TT mode. */
184                 address = 0;
185         }
186
187         catcher = current->thread.fault_catcher;
188         if(!err)
189                 return 0;
190         else if(catcher != NULL){
191                 current->thread.fault_addr = (void *) address;
192                 do_longjmp(catcher, 1);
193         }
194         else if(current->thread.fault_addr != NULL)
195                 panic("fault_addr set but no fault catcher");
196         else if(!is_user && arch_fixup(ip, regs))
197                 return 0;
198
199         if(!is_user) {
200                 show_regs(container_of(regs, struct pt_regs, regs));
201                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
202                       address, ip);
203         }
204
205         if (err == -EACCES) {
206                 si.si_signo = SIGBUS;
207                 si.si_errno = 0;
208                 si.si_code = BUS_ADRERR;
209                 si.si_addr = (void __user *)address;
210                 current->thread.arch.faultinfo = fi;
211                 force_sig_info(SIGBUS, &si, current);
212         } else if (err == -ENOMEM) {
213                 printk("VM: killing process %s\n", current->comm);
214                 do_exit(SIGKILL);
215         } else {
216                 BUG_ON(err != -EFAULT);
217                 si.si_signo = SIGSEGV;
218                 si.si_addr = (void __user *) address;
219                 current->thread.arch.faultinfo = fi;
220                 force_sig_info(SIGSEGV, &si, current);
221         }
222         return 0;
223 }
224
225 void relay_signal(int sig, union uml_pt_regs *regs)
226 {
227         if(arch_handle_signal(sig, regs))
228                 return;
229
230         if(!UPT_IS_USER(regs)){
231                 if(sig == SIGBUS)
232                         printk("Bus error - the /dev/shm or /tmp mount likely "
233                                "just ran out of space\n");
234                 panic("Kernel mode signal %d", sig);
235         }
236
237         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
238         force_sig(sig, current);
239 }
240
241 static void bus_handler(int sig, union uml_pt_regs *regs)
242 {
243         if(current->thread.fault_catcher != NULL)
244                 do_longjmp(current->thread.fault_catcher, 1);
245         else relay_signal(sig, regs);
246 }
247
248 static void winch(int sig, union uml_pt_regs *regs)
249 {
250         do_IRQ(WINCH_IRQ, regs);
251 }
252
253 const struct kern_handlers handlinfo_kern = {
254         .relay_signal = relay_signal,
255         .winch = winch,
256         .bus_handler = bus_handler,
257         .page_fault = segv_handler,
258         .sigio_handler = sigio_handler,
259         .timer_handler = timer_handler
260 };
261
262 void trap_init(void)
263 {
264 }