git.oblomov.eu Git - linux-2.6/blob - arch/um/kernel/trap_kern.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/config.h"
  12 #include "linux/init.h"
  13 #include "linux/ptrace.h"
  14 #include "asm/semaphore.h"
  15 #include "asm/pgtable.h"
  16 #include "asm/pgalloc.h"
  17 #include "asm/tlbflush.h"
  18 #include "asm/a.out.h"
  19 #include "asm/current.h"
  20 #include "asm/irq.h"
  21 #include "sysdep/sigcontext.h"
  22 #include "user_util.h"
  23 #include "kern_util.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 #ifdef CONFIG_MODE_SKAS
  30 #include "skas.h"
  31 #endif
  32
  33 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
  34 int handle_page_fault(unsigned long address, unsigned long ip,
  35                       int is_write, int is_user, int *code_out)
  36 {
  37         struct mm_struct *mm = current->mm;
  38         struct vm_area_struct *vma;
  39         pgd_t *pgd;
  40         pud_t *pud;
  41         pmd_t *pmd;
  42         pte_t *pte;
  43         int err = -EFAULT;
  44
  45         *code_out = SEGV_MAPERR;
  46
  47         /* If the fault was during atomic operation, don't take the fault, just
  48          * fail. */
  49         if (in_atomic())
  50                 goto out_nosemaphore;
  51
  52         down_read(&mm->mmap_sem);
  53         vma = find_vma(mm, address);
  54         if(!vma)
  55                 goto out;
  56         else if(vma->vm_start <= address)
  57                 goto good_area;
  58         else if(!(vma->vm_flags & VM_GROWSDOWN))
  59                 goto out;
  60         else if(is_user && !ARCH_IS_STACKGROW(address))
  61                 goto out;
  62         else if(expand_stack(vma, address))
  63                 goto out;
  64
  65 good_area:
  66         *code_out = SEGV_ACCERR;
  67         if(is_write && !(vma->vm_flags & VM_WRITE))
  68                 goto out;
  69
  70         /* Don't require VM_READ|VM_EXEC for write faults! */
  71         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
  72                 goto out;
  73
  74         do {
  75 survive:
  76                 switch (handle_mm_fault(mm, vma, address, is_write)){
  77                 case VM_FAULT_MINOR:
  78                         current->min_flt++;
  79                         break;
  80                 case VM_FAULT_MAJOR:
  81                         current->maj_flt++;
  82                         break;
  83                 case VM_FAULT_SIGBUS:
  84                         err = -EACCES;
  85                         goto out;
  86                 case VM_FAULT_OOM:
  87                         err = -ENOMEM;
  88                         goto out_of_memory;
  89                 default:
  90                         BUG();
  91                 }
  92                 pgd = pgd_offset(mm, address);
  93                 pud = pud_offset(pgd, address);
  94                 pmd = pmd_offset(pud, address);
  95                 pte = pte_offset_kernel(pmd, address);
  96         } while(!pte_present(*pte));
  97         err = 0;
  98         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
  99         flush_tlb_page(vma, address);
 100 out:
 101         up_read(&mm->mmap_sem);
 102 out_nosemaphore:
 103         return(err);
 104
 105 /*
 106  * We ran out of memory, or some other thing happened to us that made
 107  * us unable to handle the page fault gracefully.
 108  */
 109 out_of_memory:
 110         if (current->pid == 1) {
 111                 up_read(&mm->mmap_sem);
 112                 yield();
 113                 down_read(&mm->mmap_sem);
 114                 goto survive;
 115         }
 116         goto out;
 117 }
 118
 119 /*
 120  * We give a *copy* of the faultinfo in the regs to segv.
 121  * This must be done, since nesting SEGVs could overwrite
 122  * the info in the regs. A pointer to the info then would
 123  * give us bad data!
 124  */
 125 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 126 {
 127         struct siginfo si;
 128         void *catcher;
 129         int err;
 130         int is_write = FAULT_WRITE(fi);
 131         unsigned long address = FAULT_ADDRESS(fi);
 132
 133         if(!is_user && (address >= start_vm) && (address < end_vm)){
 134                 flush_tlb_kernel_vm();
 135                 return(0);
 136         }
 137         else if(current->mm == NULL)
 138                 panic("Segfault with no mm");
 139
 140         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
 141                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 142         else {
 143                 err = -EFAULT;
 144                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
 145                  * This code is used in __do_copy_from_user() of TT mode. */
 146                 address = 0;
 147         }
 148
 149         catcher = current->thread.fault_catcher;
 150         if(!err)
 151                 return(0);
 152         else if(catcher != NULL){
 153                 current->thread.fault_addr = (void *) address;
 154                 do_longjmp(catcher, 1);
 155         }
 156         else if(current->thread.fault_addr != NULL)
 157                 panic("fault_addr set but no fault catcher");
 158         else if(!is_user && arch_fixup(ip, sc))
 159                 return(0);
 160
 161         if(!is_user)
 162                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 163                       address, ip);
 164
 165         if (err == -EACCES) {
 166                 si.si_signo = SIGBUS;
 167                 si.si_errno = 0;
 168                 si.si_code = BUS_ADRERR;
 169                 si.si_addr = (void *)address;
 170                 current->thread.arch.faultinfo = fi;
 171                 force_sig_info(SIGBUS, &si, current);
 172         } else if (err == -ENOMEM) {
 173                 printk("VM: killing process %s\n", current->comm);
 174                 do_exit(SIGKILL);
 175         } else {
 176                 BUG_ON(err != -EFAULT);
 177                 si.si_signo = SIGSEGV;
 178                 si.si_addr = (void *) address;
 179                 current->thread.arch.faultinfo = fi;
 180                 force_sig_info(SIGSEGV, &si, current);
 181         }
 182         return(0);
 183 }
 184
 185 void bad_segv(struct faultinfo fi, unsigned long ip)
 186 {
 187         struct siginfo si;
 188
 189         si.si_signo = SIGSEGV;
 190         si.si_code = SEGV_ACCERR;
 191         si.si_addr = (void *) FAULT_ADDRESS(fi);
 192         current->thread.arch.faultinfo = fi;
 193         force_sig_info(SIGSEGV, &si, current);
 194 }
 195
 196 void relay_signal(int sig, union uml_pt_regs *regs)
 197 {
 198         if(arch_handle_signal(sig, regs)) return;
 199         if(!UPT_IS_USER(regs))
 200                 panic("Kernel mode signal %d", sig);
 201         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 202         force_sig(sig, current);
 203 }
 204
 205 void bus_handler(int sig, union uml_pt_regs *regs)
 206 {
 207         if(current->thread.fault_catcher != NULL)
 208                 do_longjmp(current->thread.fault_catcher, 1);
 209         else relay_signal(sig, regs);
 210 }
 211
 212 void winch(int sig, union uml_pt_regs *regs)
 213 {
 214         do_IRQ(WINCH_IRQ, regs);
 215 }
 216
 217 void trap_init(void)
 218 {
 219 }