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 #include "os.h"
  33
  34 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
  35 int handle_page_fault(unsigned long address, unsigned long ip,
  36                       int is_write, int is_user, int *code_out)
  37 {
  38         struct mm_struct *mm = current->mm;
  39         struct vm_area_struct *vma;
  40         pgd_t *pgd;
  41         pud_t *pud;
  42         pmd_t *pmd;
  43         pte_t *pte;
  44         int err = -EFAULT;
  45
  46         *code_out = SEGV_MAPERR;
  47
  48         /* If the fault was during atomic operation, don't take the fault, just
  49          * fail. */
  50         if (in_atomic())
  51                 goto out_nosemaphore;
  52
  53         down_read(&mm->mmap_sem);
  54         vma = find_vma(mm, address);
  55         if(!vma)
  56                 goto out;
  57         else if(vma->vm_start <= address)
  58                 goto good_area;
  59         else if(!(vma->vm_flags & VM_GROWSDOWN))
  60                 goto out;
  61         else if(is_user && !ARCH_IS_STACKGROW(address))
  62                 goto out;
  63         else if(expand_stack(vma, address))
  64                 goto out;
  65
  66 good_area:
  67         *code_out = SEGV_ACCERR;
  68         if(is_write && !(vma->vm_flags & VM_WRITE))
  69                 goto out;
  70
  71         /* Don't require VM_READ|VM_EXEC for write faults! */
  72         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
  73                 goto out;
  74
  75         do {
  76 survive:
  77                 switch (handle_mm_fault(mm, vma, address, is_write)){
  78                 case VM_FAULT_MINOR:
  79                         current->min_flt++;
  80                         break;
  81                 case VM_FAULT_MAJOR:
  82                         current->maj_flt++;
  83                         break;
  84                 case VM_FAULT_SIGBUS:
  85                         err = -EACCES;
  86                         goto out;
  87                 case VM_FAULT_OOM:
  88                         err = -ENOMEM;
  89                         goto out_of_memory;
  90                 default:
  91                         BUG();
  92                 }
  93                 pgd = pgd_offset(mm, address);
  94                 pud = pud_offset(pgd, address);
  95                 pmd = pmd_offset(pud, address);
  96                 pte = pte_offset_kernel(pmd, address);
  97         } while(!pte_present(*pte));
  98         err = 0;
  99         /* The below warning was added in place of
 100          *      pte_mkyoung(); if (is_write) pte_mkdirty();
 101          * If it's triggered, we'd see normally a hang here (a clean pte is
 102          * marked read-only to emulate the dirty bit).
 103          * However, the generic code can mark a PTE writable but clean on a
 104          * concurrent read fault, triggering this harmlessly. So comment it out.
 105          */
 106 #if 0
 107         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
 108 #endif
 109         flush_tlb_page(vma, address);
 110 out:
 111         up_read(&mm->mmap_sem);
 112 out_nosemaphore:
 113         return(err);
 114
 115 /*
 116  * We ran out of memory, or some other thing happened to us that made
 117  * us unable to handle the page fault gracefully.
 118  */
 119 out_of_memory:
 120         if (current->pid == 1) {
 121                 up_read(&mm->mmap_sem);
 122                 yield();
 123                 down_read(&mm->mmap_sem);
 124                 goto survive;
 125         }
 126         goto out;
 127 }
 128
 129 struct kern_handlers handlinfo_kern = {
 130         .relay_signal = relay_signal,
 131         .winch = winch,
 132         .bus_handler = relay_signal,
 133         .page_fault = segv_handler,
 134         .sigio_handler = sigio_handler,
 135         .timer_handler = timer_handler
 136 };
 137 /*
 138  * We give a *copy* of the faultinfo in the regs to segv.
 139  * This must be done, since nesting SEGVs could overwrite
 140  * the info in the regs. A pointer to the info then would
 141  * give us bad data!
 142  */
 143 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 144 {
 145         struct siginfo si;
 146         void *catcher;
 147         int err;
 148         int is_write = FAULT_WRITE(fi);
 149         unsigned long address = FAULT_ADDRESS(fi);
 150
 151         if(!is_user && (address >= start_vm) && (address < end_vm)){
 152                 flush_tlb_kernel_vm();
 153                 return(0);
 154         }
 155         else if(current->mm == NULL)
 156                 panic("Segfault with no mm");
 157
 158         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
 159                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 160         else {
 161                 err = -EFAULT;
 162                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
 163                  * This code is used in __do_copy_from_user() of TT mode. */
 164                 address = 0;
 165         }
 166
 167         catcher = current->thread.fault_catcher;
 168         if(!err)
 169                 return(0);
 170         else if(catcher != NULL){
 171                 current->thread.fault_addr = (void *) address;
 172                 do_longjmp(catcher, 1);
 173         }
 174         else if(current->thread.fault_addr != NULL)
 175                 panic("fault_addr set but no fault catcher");
 176         else if(!is_user && arch_fixup(ip, sc))
 177                 return(0);
 178
 179         if(!is_user)
 180                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 181                       address, ip);
 182
 183         if (err == -EACCES) {
 184                 si.si_signo = SIGBUS;
 185                 si.si_errno = 0;
 186                 si.si_code = BUS_ADRERR;
 187                 si.si_addr = (void *)address;
 188                 current->thread.arch.faultinfo = fi;
 189                 force_sig_info(SIGBUS, &si, current);
 190         } else if (err == -ENOMEM) {
 191                 printk("VM: killing process %s\n", current->comm);
 192                 do_exit(SIGKILL);
 193         } else {
 194                 BUG_ON(err != -EFAULT);
 195                 si.si_signo = SIGSEGV;
 196                 si.si_addr = (void *) address;
 197                 current->thread.arch.faultinfo = fi;
 198                 force_sig_info(SIGSEGV, &si, current);
 199         }
 200         return(0);
 201 }
 202
 203 void bad_segv(struct faultinfo fi, unsigned long ip)
 204 {
 205         struct siginfo si;
 206
 207         si.si_signo = SIGSEGV;
 208         si.si_code = SEGV_ACCERR;
 209         si.si_addr = (void *) FAULT_ADDRESS(fi);
 210         current->thread.arch.faultinfo = fi;
 211         force_sig_info(SIGSEGV, &si, current);
 212 }
 213
 214 void relay_signal(int sig, union uml_pt_regs *regs)
 215 {
 216         if(arch_handle_signal(sig, regs)) return;
 217         if(!UPT_IS_USER(regs))
 218                 panic("Kernel mode signal %d", sig);
 219         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 220         force_sig(sig, current);
 221 }
 222
 223 void bus_handler(int sig, union uml_pt_regs *regs)
 224 {
 225         if(current->thread.fault_catcher != NULL)
 226                 do_longjmp(current->thread.fault_catcher, 1);
 227         else relay_signal(sig, regs);
 228 }
 229
 230 void winch(int sig, union uml_pt_regs *regs)
 231 {
 232         do_IRQ(WINCH_IRQ, regs);
 233 }
 234
 235 void trap_init(void)
 236 {
 237 }