arch/um/kernel/trap.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/init.h"
  12 #include "linux/ptrace.h"
  13 #include "asm/semaphore.h"
  14 #include "asm/pgtable.h"
  15 #include "asm/pgalloc.h"
  16 #include "asm/tlbflush.h"
  17 #include "asm/a.out.h"
  18 #include "asm/current.h"
  19 #include "asm/irq.h"
  20 #include "sysdep/sigcontext.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 #include "sysdep/sigcontext.h"
  29 #include "sysdep/ptrace.h"
  30 #include "os.h"
  31 #ifdef CONFIG_MODE_SKAS
  32 #include "skas.h"
  33 #endif
  34 #include "os.h"
  35
  36 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
  37 int handle_page_fault(unsigned long address, unsigned long ip,
  38                       int is_write, int is_user, int *code_out)
  39 {
  40         struct mm_struct *mm = current->mm;
  41         struct vm_area_struct *vma;
  42         pgd_t *pgd;
  43         pud_t *pud;
  44         pmd_t *pmd;
  45         pte_t *pte;
  46         int err = -EFAULT;
  47
  48         *code_out = SEGV_MAPERR;
  49
  50         /* If the fault was during atomic operation, don't take the fault, just
  51          * fail. */
  52         if (in_atomic())
  53                 goto out_nosemaphore;
  54
  55         down_read(&mm->mmap_sem);
  56         vma = find_vma(mm, address);
  57         if(!vma)
  58                 goto out;
  59         else if(vma->vm_start <= address)
  60                 goto good_area;
  61         else if(!(vma->vm_flags & VM_GROWSDOWN))
  62                 goto out;
  63         else if(is_user && !ARCH_IS_STACKGROW(address))
  64                 goto out;
  65         else if(expand_stack(vma, address))
  66                 goto out;
  67
  68 good_area:
  69         *code_out = SEGV_ACCERR;
  70         if(is_write && !(vma->vm_flags & VM_WRITE))
  71                 goto out;
  72
  73         /* Don't require VM_READ|VM_EXEC for write faults! */
  74         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
  75                 goto out;
  76
  77         do {
  78 survive:
  79                 switch (handle_mm_fault(mm, vma, address, is_write)){
  80                 case VM_FAULT_MINOR:
  81                         current->min_flt++;
  82                         break;
  83                 case VM_FAULT_MAJOR:
  84                         current->maj_flt++;
  85                         break;
  86                 case VM_FAULT_SIGBUS:
  87                         err = -EACCES;
  88                         goto out;
  89                 case VM_FAULT_OOM:
  90                         err = -ENOMEM;
  91                         goto out_of_memory;
  92                 default:
  93                         BUG();
  94                 }
  95                 pgd = pgd_offset(mm, address);
  96                 pud = pud_offset(pgd, address);
  97                 pmd = pmd_offset(pud, address);
  98                 pte = pte_offset_kernel(pmd, address);
  99         } while(!pte_present(*pte));
 100         err = 0;
 101         /* The below warning was added in place of
 102          *      pte_mkyoung(); if (is_write) pte_mkdirty();
 103          * If it's triggered, we'd see normally a hang here (a clean pte is
 104          * marked read-only to emulate the dirty bit).
 105          * However, the generic code can mark a PTE writable but clean on a
 106          * concurrent read fault, triggering this harmlessly. So comment it out.
 107          */
 108 #if 0
 109         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
 110 #endif
 111         flush_tlb_page(vma, address);
 112 out:
 113         up_read(&mm->mmap_sem);
 114 out_nosemaphore:
 115         return(err);
 116
 117 /*
 118  * We ran out of memory, or some other thing happened to us that made
 119  * us unable to handle the page fault gracefully.
 120  */
 121 out_of_memory:
 122         if (is_init(current)) {
 123                 up_read(&mm->mmap_sem);
 124                 yield();
 125                 down_read(&mm->mmap_sem);
 126                 goto survive;
 127         }
 128         goto out;
 129 }
 130
 131 void segv_handler(int sig, union uml_pt_regs *regs)
 132 {
 133         struct faultinfo * fi = UPT_FAULTINFO(regs);
 134
 135         if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
 136                 bad_segv(*fi, UPT_IP(regs));
 137                 return;
 138         }
 139         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
 140 }
 141
 142 /*
 143  * We give a *copy* of the faultinfo in the regs to segv.
 144  * This must be done, since nesting SEGVs could overwrite
 145  * the info in the regs. A pointer to the info then would
 146  * give us bad data!
 147  */
 148 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 149 {
 150         struct siginfo si;
 151         void *catcher;
 152         int err;
 153         int is_write = FAULT_WRITE(fi);
 154         unsigned long address = FAULT_ADDRESS(fi);
 155
 156         if(!is_user && (address >= start_vm) && (address < end_vm)){
 157                 flush_tlb_kernel_vm();
 158                 return(0);
 159         }
 160         else if(current->mm == NULL)
 161                 panic("Segfault with no mm");
 162
 163         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
 164                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 165         else {
 166                 err = -EFAULT;
 167                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
 168                  * This code is used in __do_copy_from_user() of TT mode. */
 169                 address = 0;
 170         }
 171
 172         catcher = current->thread.fault_catcher;
 173         if(!err)
 174                 return(0);
 175         else if(catcher != NULL){
 176                 current->thread.fault_addr = (void *) address;
 177                 do_longjmp(catcher, 1);
 178         }
 179         else if(current->thread.fault_addr != NULL)
 180                 panic("fault_addr set but no fault catcher");
 181         else if(!is_user && arch_fixup(ip, sc))
 182                 return(0);
 183
 184         if(!is_user)
 185                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 186                       address, ip);
 187
 188         if (err == -EACCES) {
 189                 si.si_signo = SIGBUS;
 190                 si.si_errno = 0;
 191                 si.si_code = BUS_ADRERR;
 192                 si.si_addr = (void __user *)address;
 193                 current->thread.arch.faultinfo = fi;
 194                 force_sig_info(SIGBUS, &si, current);
 195         } else if (err == -ENOMEM) {
 196                 printk("VM: killing process %s\n", current->comm);
 197                 do_exit(SIGKILL);
 198         } else {
 199                 BUG_ON(err != -EFAULT);
 200                 si.si_signo = SIGSEGV;
 201                 si.si_addr = (void __user *) address;
 202                 current->thread.arch.faultinfo = fi;
 203                 force_sig_info(SIGSEGV, &si, current);
 204         }
 205         return(0);
 206 }
 207
 208 void bad_segv(struct faultinfo fi, unsigned long ip)
 209 {
 210         struct siginfo si;
 211
 212         si.si_signo = SIGSEGV;
 213         si.si_code = SEGV_ACCERR;
 214         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
 215         current->thread.arch.faultinfo = fi;
 216         force_sig_info(SIGSEGV, &si, current);
 217 }
 218
 219 void relay_signal(int sig, union uml_pt_regs *regs)
 220 {
 221         if(arch_handle_signal(sig, regs))
 222                 return;
 223
 224         if(!UPT_IS_USER(regs)){
 225                 if(sig == SIGBUS)
 226                         printk("Bus error - the /dev/shm or /tmp mount likely "
 227                                "just ran out of space\n");
 228                 panic("Kernel mode signal %d", sig);
 229         }
 230
 231         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 232         force_sig(sig, current);
 233 }
 234
 235 void bus_handler(int sig, union uml_pt_regs *regs)
 236 {
 237         if(current->thread.fault_catcher != NULL)
 238                 do_longjmp(current->thread.fault_catcher, 1);
 239         else relay_signal(sig, regs);
 240 }
 241
 242 void winch(int sig, union uml_pt_regs *regs)
 243 {
 244         do_IRQ(WINCH_IRQ, regs);
 245 }
 246
 247 const struct kern_handlers handlinfo_kern = {
 248         .relay_signal = relay_signal,
 249         .winch = winch,
 250         .bus_handler = bus_handler,
 251         .page_fault = segv_handler,
 252         .sigio_handler = sigio_handler,
 253         .timer_handler = timer_handler
 254 };
 255
 256 void trap_init(void)
 257 {
 258 }