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