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/tlbflush.h"
  17 #include "asm/a.out.h"
  18 #include "asm/current.h"
  19 #include "user_util.h"
  20 #include "kern_util.h"
  21 #include "kern.h"
  22 #include "chan_kern.h"
  23 #include "mconsole_kern.h"
  24 #include "2_5compat.h"
  25
  26 int handle_page_fault(unsigned long address, unsigned long ip,
  27                       int is_write, int is_user, int *code_out)
  28 {
  29         struct mm_struct *mm = current->mm;
  30         struct vm_area_struct *vma;
  31         pgd_t *pgd;
  32         pmd_t *pmd;
  33         pte_t *pte;
  34         unsigned long page;
  35         int err = -EFAULT;
  36
  37         *code_out = SEGV_MAPERR;
  38         down_read(&mm->mmap_sem);
  39         vma = find_vma(mm, address);
  40         if(!vma)
  41                 goto out;
  42         else if(vma->vm_start <= address)
  43                 goto good_area;
  44         else if(!(vma->vm_flags & VM_GROWSDOWN))
  45                 goto out;
  46         else if(expand_stack(vma, address))
  47                 goto out;
  48
  49  good_area:
  50         *code_out = SEGV_ACCERR;
  51         if(is_write && !(vma->vm_flags & VM_WRITE))
  52                 goto out;
  53         page = address & PAGE_MASK;
  54         if(page == (unsigned long) current->thread_info + PAGE_SIZE)
  55                 panic("Kernel stack overflow");
  56         pgd = pgd_offset(mm, page);
  57         pmd = pmd_offset(pgd, page);
  58  survive:
  59         do {
  60                 switch (handle_mm_fault(mm, vma, address, is_write)){
  61                 case VM_FAULT_MINOR:
  62                         current->min_flt++;
  63                         break;
  64                 case VM_FAULT_MAJOR:
  65                         current->maj_flt++;
  66                         break;
  67                 case VM_FAULT_SIGBUS:
  68                         err = -EACCES;
  69                         goto out;
  70                 case VM_FAULT_OOM:
  71                         err = -ENOMEM;
  72                         goto out_of_memory;
  73                 default:
  74                         BUG();
  75                 }
  76                 pte = pte_offset_kernel(pmd, page);
  77         } while(!pte_present(*pte));
  78         *pte = pte_mkyoung(*pte);
  79         if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
  80         flush_tlb_page(vma, page);
  81         err = 0;
  82  out:
  83         up_read(&mm->mmap_sem);
  84         return(err);
  85
  86 /*
  87  * We ran out of memory, or some other thing happened to us that made
  88  * us unable to handle the page fault gracefully.
  89  */
  90 out_of_memory:
  91         if (current->pid == 1) {
  92                 up_read(&mm->mmap_sem);
  93                 yield();
  94                 down_read(&mm->mmap_sem);
  95                 goto survive;
  96         }
  97         err = -ENOMEM;
  98         goto out;
  99 }
 100
 101 unsigned long segv(unsigned long address, unsigned long ip, int is_write,
 102                    int is_user, void *sc)
 103 {
 104         struct siginfo si;
 105         void *catcher;
 106         int err;
 107
 108         if(!is_user && (address >= start_vm) && (address < end_vm)){
 109                 flush_tlb_kernel_vm();
 110                 return(0);
 111         }
 112         if(current->mm == NULL)
 113                 panic("Segfault with no mm");
 114         err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 115
 116         catcher = current->thread.fault_catcher;
 117         if(!err)
 118                 return(0);
 119         else if(catcher != NULL){
 120                 current->thread.fault_addr = (void *) address;
 121                 do_longjmp(catcher, 1);
 122         }
 123         else if(current->thread.fault_addr != NULL){
 124                 panic("fault_addr set but no fault catcher");
 125         }
 126         else if(arch_fixup(ip, sc))
 127                 return(0);
 128
 129         if(!is_user)
 130                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 131                       address, ip);
 132
 133         if(err == -EACCES){
 134                 si.si_signo = SIGBUS;
 135                 si.si_errno = 0;
 136                 si.si_code = BUS_ADRERR;
 137                 si.si_addr = (void *)address;
 138                 force_sig_info(SIGBUS, &si, current);
 139         }
 140         else if(err == -ENOMEM){
 141                 printk("VM: killing process %s\n", current->comm);
 142                 do_exit(SIGKILL);
 143         }
 144         else {
 145                 si.si_signo = SIGSEGV;
 146                 si.si_addr = (void *) address;
 147                 current->thread.cr2 = address;
 148                 current->thread.err = is_write;
 149                 force_sig_info(SIGSEGV, &si, current);
 150         }
 151         return(0);
 152 }
 153
 154 void bad_segv(unsigned long address, unsigned long ip, int is_write)
 155 {
 156         struct siginfo si;
 157
 158         printk(KERN_ERR "Unfixable SEGV in '%s' (pid %d) at 0x%lx "
 159                "(ip 0x%lx)\n", current->comm, current->pid, address, ip);
 160         si.si_signo = SIGSEGV;
 161         si.si_code = SEGV_ACCERR;
 162         si.si_addr = (void *) address;
 163         current->thread.cr2 = address;
 164         current->thread.err = is_write;
 165         force_sig_info(SIGSEGV, &si, current);
 166 }
 167
 168 void relay_signal(int sig, union uml_pt_regs *regs)
 169 {
 170         if(arch_handle_signal(sig, regs)) return;
 171         if(!UPT_IS_USER(regs))
 172                 panic("Kernel mode signal %d", sig);
 173         force_sig(sig, current);
 174 }
 175
 176 void bus_handler(int sig, union uml_pt_regs *regs)
 177 {
 178         if(current->thread.fault_catcher != NULL)
 179                 do_longjmp(current->thread.fault_catcher, 1);
 180         else relay_signal(sig, regs);
 181 }
 182
 183 void trap_init(void)
 184 {
 185 }
 186
 187 spinlock_t trap_lock = SPIN_LOCK_UNLOCKED;
 188
 189 static int trap_index = 0;
 190
 191 int next_trap_index(int limit)
 192 {
 193         int ret;
 194
 195         spin_lock(&trap_lock);
 196         ret = trap_index;
 197         if(++trap_index == limit)
 198                 trap_index = 0;
 199         spin_unlock(&trap_lock);
 200         return(ret);
 201 }
 202
 203 /*
 204  * Overrides for Emacs so that we follow Linus's tabbing style.
 205  * Emacs will notice this stuff at the end of the file and automatically
 206  * adjust the settings for this buffer only.  This must remain at the end
 207  * of the file.
 208  * ---------------------------------------------------------------------------
 209  * Local variables:
 210  * c-file-style: "linux"
 211  * End:
 212  */