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 "2_5compat.h"
  27 #include "mem.h"
  28 #include "mem_kern.h"
  29
  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         unsigned long page;
  40         int err = -EFAULT;
  41
  42         *code_out = SEGV_MAPERR;
  43         down_read(&mm->mmap_sem);
  44         vma = find_vma(mm, address);
  45         if(!vma)
  46                 goto out;
  47         else if(vma->vm_start <= address)
  48                 goto good_area;
  49         else if(!(vma->vm_flags & VM_GROWSDOWN))
  50                 goto out;
  51         else if(is_user && !ARCH_IS_STACKGROW(address))
  52                 goto out;
  53         else if(expand_stack(vma, address))
  54                 goto out;
  55
  56  good_area:
  57         *code_out = SEGV_ACCERR;
  58         if(is_write && !(vma->vm_flags & VM_WRITE))
  59                 goto out;
  60
  61         if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
  62                 goto out;
  63
  64         page = address & PAGE_MASK;
  65         do {
  66  survive:
  67                 switch (handle_mm_fault(mm, vma, address, is_write)){
  68                 case VM_FAULT_MINOR:
  69                         current->min_flt++;
  70                         break;
  71                 case VM_FAULT_MAJOR:
  72                         current->maj_flt++;
  73                         break;
  74                 case VM_FAULT_SIGBUS:
  75                         err = -EACCES;
  76                         goto out;
  77                 case VM_FAULT_OOM:
  78                         err = -ENOMEM;
  79                         goto out_of_memory;
  80                 default:
  81                         BUG();
  82                 }
  83                 pgd = pgd_offset(mm, page);
  84                 pud = pud_offset(pgd, page);
  85                 pmd = pmd_offset(pud, page);
  86                 pte = pte_offset_kernel(pmd, page);
  87         } while(!pte_present(*pte));
  88         err = 0;
  89         *pte = pte_mkyoung(*pte);
  90         if(pte_write(*pte)) *pte = pte_mkdirty(*pte);
  91         flush_tlb_page(vma, page);
  92  out:
  93         up_read(&mm->mmap_sem);
  94         return(err);
  95
  96 /*
  97  * We ran out of memory, or some other thing happened to us that made
  98  * us unable to handle the page fault gracefully.
  99  */
 100 out_of_memory:
 101         if (current->pid == 1) {
 102                 up_read(&mm->mmap_sem);
 103                 yield();
 104                 down_read(&mm->mmap_sem);
 105                 goto survive;
 106         }
 107         goto out;
 108 }
 109
 110 /*
 111  * We give a *copy* of the faultinfo in the regs to segv.
 112  * This must be done, since nesting SEGVs could overwrite
 113  * the info in the regs. A pointer to the info then would
 114  * give us bad data!
 115  */
 116 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 117 {
 118         struct siginfo si;
 119         void *catcher;
 120         int err;
 121         int is_write = FAULT_WRITE(fi);
 122         unsigned long address = FAULT_ADDRESS(fi);
 123
 124         if(!is_user && (address >= start_vm) && (address < end_vm)){
 125                 flush_tlb_kernel_vm();
 126                 return(0);
 127         }
 128         else if(current->mm == NULL)
 129                 panic("Segfault with no mm");
 130         err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 131
 132         catcher = current->thread.fault_catcher;
 133         if(!err)
 134                 return(0);
 135         else if(catcher != NULL){
 136                 current->thread.fault_addr = (void *) address;
 137                 do_longjmp(catcher, 1);
 138         }
 139         else if(current->thread.fault_addr != NULL)
 140                 panic("fault_addr set but no fault catcher");
 141         else if(!is_user && arch_fixup(ip, sc))
 142                 return(0);
 143
 144         if(!is_user)
 145                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 146                       address, ip);
 147
 148         if(err == -EACCES){
 149                 si.si_signo = SIGBUS;
 150                 si.si_errno = 0;
 151                 si.si_code = BUS_ADRERR;
 152                 si.si_addr = (void *)address;
 153                 current->thread.arch.faultinfo = fi;
 154                 force_sig_info(SIGBUS, &si, current);
 155         }
 156         else if(err == -ENOMEM){
 157                 printk("VM: killing process %s\n", current->comm);
 158                 do_exit(SIGKILL);
 159         }
 160         else {
 161                 si.si_signo = SIGSEGV;
 162                 si.si_addr = (void *) address;
 163                 current->thread.arch.faultinfo = fi;
 164                 force_sig_info(SIGSEGV, &si, current);
 165         }
 166         return(0);
 167 }
 168
 169 void bad_segv(struct faultinfo fi, unsigned long ip)
 170 {
 171         struct siginfo si;
 172
 173         si.si_signo = SIGSEGV;
 174         si.si_code = SEGV_ACCERR;
 175         si.si_addr = (void *) FAULT_ADDRESS(fi);
 176         current->thread.arch.faultinfo = fi;
 177         force_sig_info(SIGSEGV, &si, current);
 178 }
 179
 180 void relay_signal(int sig, union uml_pt_regs *regs)
 181 {
 182         if(arch_handle_signal(sig, regs)) return;
 183         if(!UPT_IS_USER(regs))
 184                 panic("Kernel mode signal %d", sig);
 185         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 186         force_sig(sig, current);
 187 }
 188
 189 void bus_handler(int sig, union uml_pt_regs *regs)
 190 {
 191         if(current->thread.fault_catcher != NULL)
 192                 do_longjmp(current->thread.fault_catcher, 1);
 193         else relay_signal(sig, regs);
 194 }
 195
 196 void winch(int sig, union uml_pt_regs *regs)
 197 {
 198         do_IRQ(WINCH_IRQ, regs);
 199 }
 200
 201 void trap_init(void)
 202 {
 203 }
 204
 205 DEFINE_SPINLOCK(trap_lock);
 206
 207 static int trap_index = 0;
 208
 209 int next_trap_index(int limit)
 210 {
 211         int ret;
 212
 213         spin_lock(&trap_lock);
 214         ret = trap_index;
 215         if(++trap_index == limit)
 216                 trap_index = 0;
 217         spin_unlock(&trap_lock);
 218         return(ret);
 219 }
 220
 221 /*
 222  * Overrides for Emacs so that we follow Linus's tabbing style.
 223  * Emacs will notice this stuff at the end of the file and automatically
 224  * adjust the settings for this buffer only.  This must remain at the end
 225  * of the file.
 226  * ---------------------------------------------------------------------------
 227  * Local variables:
 228  * c-file-style: "linux"
 229  * End:
 230  */