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 "user_util.h"
  22 #include "kern_util.h"
  23 #include "kern.h"
  24 #include "chan_kern.h"
  25 #include "mconsole_kern.h"
  26 #include "mem.h"
  27 #include "mem_kern.h"
  28
  29 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
  30 int handle_page_fault(unsigned long address, unsigned long ip,
  31                       int is_write, int is_user, int *code_out)
  32 {
  33         struct mm_struct *mm = current->mm;
  34         struct vm_area_struct *vma;
  35         pgd_t *pgd;
  36         pud_t *pud;
  37         pmd_t *pmd;
  38         pte_t *pte;
  39         int err = -EFAULT;
  40
  41         *code_out = SEGV_MAPERR;
  42         down_read(&mm->mmap_sem);
  43         vma = find_vma(mm, address);
  44         if(!vma)
  45                 goto out;
  46         else if(vma->vm_start <= address)
  47                 goto good_area;
  48         else if(!(vma->vm_flags & VM_GROWSDOWN))
  49                 goto out;
  50         else if(is_user && !ARCH_IS_STACKGROW(address))
  51                 goto out;
  52         else if(expand_stack(vma, address))
  53                 goto out;
  54
  55 good_area:
  56         *code_out = SEGV_ACCERR;
  57         if(is_write && !(vma->vm_flags & VM_WRITE))
  58                 goto out;
  59
  60         /* Don't require VM_READ|VM_EXEC for write faults! */
  61         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
  62                 goto out;
  63
  64         do {
  65 survive:
  66                 switch (handle_mm_fault(mm, vma, address, is_write)){
  67                 case VM_FAULT_MINOR:
  68                         current->min_flt++;
  69                         break;
  70                 case VM_FAULT_MAJOR:
  71                         current->maj_flt++;
  72                         break;
  73                 case VM_FAULT_SIGBUS:
  74                         err = -EACCES;
  75                         goto out;
  76                 case VM_FAULT_OOM:
  77                         err = -ENOMEM;
  78                         goto out_of_memory;
  79                 default:
  80                         BUG();
  81                 }
  82                 pgd = pgd_offset(mm, address);
  83                 pud = pud_offset(pgd, address);
  84                 pmd = pmd_offset(pud, address);
  85                 pte = pte_offset_kernel(pmd, address);
  86         } while(!pte_present(*pte));
  87         err = 0;
  88         *pte = pte_mkyoung(*pte);
  89         if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
  90         flush_tlb_page(vma, address);
  91 out:
  92         up_read(&mm->mmap_sem);
  93         return(err);
  94
  95 /*
  96  * We ran out of memory, or some other thing happened to us that made
  97  * us unable to handle the page fault gracefully.
  98  */
  99 out_of_memory:
 100         if (current->pid == 1) {
 101                 up_read(&mm->mmap_sem);
 102                 yield();
 103                 down_read(&mm->mmap_sem);
 104                 goto survive;
 105         }
 106         goto out;
 107 }
 108
 109 /*
 110  * We give a *copy* of the faultinfo in the regs to segv.
 111  * This must be done, since nesting SEGVs could overwrite
 112  * the info in the regs. A pointer to the info then would
 113  * give us bad data!
 114  */
 115 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 116 {
 117         struct siginfo si;
 118         void *catcher;
 119         int err;
 120         int is_write = FAULT_WRITE(fi);
 121         unsigned long address = FAULT_ADDRESS(fi);
 122
 123         if(!is_user && (address >= start_vm) && (address < end_vm)){
 124                 flush_tlb_kernel_vm();
 125                 return(0);
 126         }
 127         else if(current->mm == NULL)
 128                 panic("Segfault with no mm");
 129         err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 130
 131         catcher = current->thread.fault_catcher;
 132         if(!err)
 133                 return(0);
 134         else if(catcher != NULL){
 135                 current->thread.fault_addr = (void *) address;
 136                 do_longjmp(catcher, 1);
 137         }
 138         else if(current->thread.fault_addr != NULL)
 139                 panic("fault_addr set but no fault catcher");
 140         else if(!is_user && arch_fixup(ip, sc))
 141                 return(0);
 142
 143         if(!is_user)
 144                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 145                       address, ip);
 146
 147         if (err == -EACCES) {
 148                 si.si_signo = SIGBUS;
 149                 si.si_errno = 0;
 150                 si.si_code = BUS_ADRERR;
 151                 si.si_addr = (void *)address;
 152                 current->thread.arch.faultinfo = fi;
 153                 force_sig_info(SIGBUS, &si, current);
 154         } else if (err == -ENOMEM) {
 155                 printk("VM: killing process %s\n", current->comm);
 156                 do_exit(SIGKILL);
 157         } else {
 158                 BUG_ON(err != -EFAULT);
 159                 si.si_signo = SIGSEGV;
 160                 si.si_addr = (void *) address;
 161                 current->thread.arch.faultinfo = fi;
 162                 force_sig_info(SIGSEGV, &si, current);
 163         }
 164         return(0);
 165 }
 166
 167 void bad_segv(struct faultinfo fi, unsigned long ip)
 168 {
 169         struct siginfo si;
 170
 171         si.si_signo = SIGSEGV;
 172         si.si_code = SEGV_ACCERR;
 173         si.si_addr = (void *) FAULT_ADDRESS(fi);
 174         current->thread.arch.faultinfo = fi;
 175         force_sig_info(SIGSEGV, &si, current);
 176 }
 177
 178 void relay_signal(int sig, union uml_pt_regs *regs)
 179 {
 180         if(arch_handle_signal(sig, regs)) return;
 181         if(!UPT_IS_USER(regs))
 182                 panic("Kernel mode signal %d", sig);
 183         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 184         force_sig(sig, current);
 185 }
 186
 187 void bus_handler(int sig, union uml_pt_regs *regs)
 188 {
 189         if(current->thread.fault_catcher != NULL)
 190                 do_longjmp(current->thread.fault_catcher, 1);
 191         else relay_signal(sig, regs);
 192 }
 193
 194 void winch(int sig, union uml_pt_regs *regs)
 195 {
 196         do_IRQ(WINCH_IRQ, regs);
 197 }
 198
 199 void trap_init(void)
 200 {
 201 }