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 (current->pid == 1) {
 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 struct kern_handlers handlinfo_kern = {
 143         .relay_signal = relay_signal,
 144         .winch = winch,
 145         .bus_handler = relay_signal,
 146         .page_fault = segv_handler,
 147         .sigio_handler = sigio_handler,
 148         .timer_handler = timer_handler
 149 };
 150 /*
 151  * We give a *copy* of the faultinfo in the regs to segv.
 152  * This must be done, since nesting SEGVs could overwrite
 153  * the info in the regs. A pointer to the info then would
 154  * give us bad data!
 155  */
 156 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
 157 {
 158         struct siginfo si;
 159         void *catcher;
 160         int err;
 161         int is_write = FAULT_WRITE(fi);
 162         unsigned long address = FAULT_ADDRESS(fi);
 163
 164         if(!is_user && (address >= start_vm) && (address < end_vm)){
 165                 flush_tlb_kernel_vm();
 166                 return(0);
 167         }
 168         else if(current->mm == NULL)
 169                 panic("Segfault with no mm");
 170
 171         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
 172                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 173         else {
 174                 err = -EFAULT;
 175                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
 176                  * This code is used in __do_copy_from_user() of TT mode. */
 177                 address = 0;
 178         }
 179
 180         catcher = current->thread.fault_catcher;
 181         if(!err)
 182                 return(0);
 183         else if(catcher != NULL){
 184                 current->thread.fault_addr = (void *) address;
 185                 do_longjmp(catcher, 1);
 186         }
 187         else if(current->thread.fault_addr != NULL)
 188                 panic("fault_addr set but no fault catcher");
 189         else if(!is_user && arch_fixup(ip, sc))
 190                 return(0);
 191
 192         if(!is_user)
 193                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 194                       address, ip);
 195
 196         if (err == -EACCES) {
 197                 si.si_signo = SIGBUS;
 198                 si.si_errno = 0;
 199                 si.si_code = BUS_ADRERR;
 200                 si.si_addr = (void __user *)address;
 201                 current->thread.arch.faultinfo = fi;
 202                 force_sig_info(SIGBUS, &si, current);
 203         } else if (err == -ENOMEM) {
 204                 printk("VM: killing process %s\n", current->comm);
 205                 do_exit(SIGKILL);
 206         } else {
 207                 BUG_ON(err != -EFAULT);
 208                 si.si_signo = SIGSEGV;
 209                 si.si_addr = (void __user *) address;
 210                 current->thread.arch.faultinfo = fi;
 211                 force_sig_info(SIGSEGV, &si, current);
 212         }
 213         return(0);
 214 }
 215
 216 void bad_segv(struct faultinfo fi, unsigned long ip)
 217 {
 218         struct siginfo si;
 219
 220         si.si_signo = SIGSEGV;
 221         si.si_code = SEGV_ACCERR;
 222         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
 223         current->thread.arch.faultinfo = fi;
 224         force_sig_info(SIGSEGV, &si, current);
 225 }
 226
 227 void relay_signal(int sig, union uml_pt_regs *regs)
 228 {
 229         if(arch_handle_signal(sig, regs)) return;
 230         if(!UPT_IS_USER(regs))
 231                 panic("Kernel mode signal %d", sig);
 232         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 233         force_sig(sig, current);
 234 }
 235
 236 void bus_handler(int sig, union uml_pt_regs *regs)
 237 {
 238         if(current->thread.fault_catcher != NULL)
 239                 do_longjmp(current->thread.fault_catcher, 1);
 240         else relay_signal(sig, regs);
 241 }
 242
 243 void winch(int sig, union uml_pt_regs *regs)
 244 {
 245         do_IRQ(WINCH_IRQ, regs);
 246 }
 247
 248 void trap_init(void)
 249 {
 250 }