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