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 "kern_util.h"
  22 #include "as-layout.h"
  23 #include "arch.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 #include "sysdep/sigcontext.h"
  30 #include "sysdep/ptrace.h"
  31 #include "os.h"
  32 #ifdef CONFIG_MODE_SKAS
  33 #include "skas.h"
  34 #endif
  35 #include "os.h"
  36
  37 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
  38 int handle_page_fault(unsigned long address, unsigned long ip,
  39                       int is_write, int is_user, int *code_out)
  40 {
  41         struct mm_struct *mm = current->mm;
  42         struct vm_area_struct *vma;
  43         pgd_t *pgd;
  44         pud_t *pud;
  45         pmd_t *pmd;
  46         pte_t *pte;
  47         int err = -EFAULT;
  48
  49         *code_out = SEGV_MAPERR;
  50
  51         /* If the fault was during atomic operation, don't take the fault, just
  52          * fail. */
  53         if (in_atomic())
  54                 goto out_nosemaphore;
  55
  56         down_read(&mm->mmap_sem);
  57         vma = find_vma(mm, address);
  58         if(!vma)
  59                 goto out;
  60         else if(vma->vm_start <= address)
  61                 goto good_area;
  62         else if(!(vma->vm_flags & VM_GROWSDOWN))
  63                 goto out;
  64         else if(is_user && !ARCH_IS_STACKGROW(address))
  65                 goto out;
  66         else if(expand_stack(vma, address))
  67                 goto out;
  68
  69 good_area:
  70         *code_out = SEGV_ACCERR;
  71         if(is_write && !(vma->vm_flags & VM_WRITE))
  72                 goto out;
  73
  74         /* Don't require VM_READ|VM_EXEC for write faults! */
  75         if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
  76                 goto out;
  77
  78         do {
  79                 int fault;
  80 survive:
  81                 fault = handle_mm_fault(mm, vma, address, is_write);
  82                 if (unlikely(fault & VM_FAULT_ERROR)) {
  83                         if (fault & VM_FAULT_OOM) {
  84                                 err = -ENOMEM;
  85                                 goto out_of_memory;
  86                         } else if (fault & VM_FAULT_SIGBUS) {
  87                                 err = -EACCES;
  88                                 goto out;
  89                         }
  90                         BUG();
  91                 }
  92                 if (fault & VM_FAULT_MAJOR)
  93                         current->maj_flt++;
  94                 else
  95                         current->min_flt++;
  96
  97                 pgd = pgd_offset(mm, address);
  98                 pud = pud_offset(pgd, address);
  99                 pmd = pmd_offset(pud, address);
 100                 pte = pte_offset_kernel(pmd, address);
 101         } while(!pte_present(*pte));
 102         err = 0;
 103         /* The below warning was added in place of
 104          *      pte_mkyoung(); if (is_write) pte_mkdirty();
 105          * If it's triggered, we'd see normally a hang here (a clean pte is
 106          * marked read-only to emulate the dirty bit).
 107          * However, the generic code can mark a PTE writable but clean on a
 108          * concurrent read fault, triggering this harmlessly. So comment it out.
 109          */
 110 #if 0
 111         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
 112 #endif
 113         flush_tlb_page(vma, address);
 114 out:
 115         up_read(&mm->mmap_sem);
 116 out_nosemaphore:
 117         return(err);
 118
 119 /*
 120  * We ran out of memory, or some other thing happened to us that made
 121  * us unable to handle the page fault gracefully.
 122  */
 123 out_of_memory:
 124         if (is_init(current)) {
 125                 up_read(&mm->mmap_sem);
 126                 yield();
 127                 down_read(&mm->mmap_sem);
 128                 goto survive;
 129         }
 130         goto out;
 131 }
 132
 133 static void bad_segv(struct faultinfo fi, unsigned long ip)
 134 {
 135         struct siginfo si;
 136
 137         si.si_signo = SIGSEGV;
 138         si.si_code = SEGV_ACCERR;
 139         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
 140         current->thread.arch.faultinfo = fi;
 141         force_sig_info(SIGSEGV, &si, current);
 142 }
 143
 144 static void segv_handler(int sig, union uml_pt_regs *regs)
 145 {
 146         struct faultinfo * fi = UPT_FAULTINFO(regs);
 147
 148         if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){
 149                 bad_segv(*fi, UPT_IP(regs));
 150                 return;
 151         }
 152         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
 153 }
 154
 155 /*
 156  * We give a *copy* of the faultinfo in the regs to segv.
 157  * This must be done, since nesting SEGVs could overwrite
 158  * the info in the regs. A pointer to the info then would
 159  * give us bad data!
 160  */
 161 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
 162                    union uml_pt_regs *regs)
 163 {
 164         struct siginfo si;
 165         void *catcher;
 166         int err;
 167         int is_write = FAULT_WRITE(fi);
 168         unsigned long address = FAULT_ADDRESS(fi);
 169
 170         if(!is_user && (address >= start_vm) && (address < end_vm)){
 171                 flush_tlb_kernel_vm();
 172                 return 0;
 173         }
 174         else if(current->mm == NULL) {
 175                 show_regs(container_of(regs, struct pt_regs, regs));
 176                 panic("Segfault with no mm");
 177         }
 178
 179         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
 180                 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
 181         else {
 182                 err = -EFAULT;
 183                 /* A thread accessed NULL, we get a fault, but CR2 is invalid.
 184                  * This code is used in __do_copy_from_user() of TT mode. */
 185                 address = 0;
 186         }
 187
 188         catcher = current->thread.fault_catcher;
 189         if(!err)
 190                 return 0;
 191         else if(catcher != NULL){
 192                 current->thread.fault_addr = (void *) address;
 193                 do_longjmp(catcher, 1);
 194         }
 195         else if(current->thread.fault_addr != NULL)
 196                 panic("fault_addr set but no fault catcher");
 197         else if(!is_user && arch_fixup(ip, regs))
 198                 return 0;
 199
 200         if(!is_user) {
 201                 show_regs(container_of(regs, struct pt_regs, regs));
 202                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
 203                       address, ip);
 204         }
 205
 206         if (err == -EACCES) {
 207                 si.si_signo = SIGBUS;
 208                 si.si_errno = 0;
 209                 si.si_code = BUS_ADRERR;
 210                 si.si_addr = (void __user *)address;
 211                 current->thread.arch.faultinfo = fi;
 212                 force_sig_info(SIGBUS, &si, current);
 213         } else if (err == -ENOMEM) {
 214                 printk("VM: killing process %s\n", current->comm);
 215                 do_exit(SIGKILL);
 216         } else {
 217                 BUG_ON(err != -EFAULT);
 218                 si.si_signo = SIGSEGV;
 219                 si.si_addr = (void __user *) address;
 220                 current->thread.arch.faultinfo = fi;
 221                 force_sig_info(SIGSEGV, &si, current);
 222         }
 223         return 0;
 224 }
 225
 226 void relay_signal(int sig, union uml_pt_regs *regs)
 227 {
 228         if(arch_handle_signal(sig, regs))
 229                 return;
 230
 231         if(!UPT_IS_USER(regs)){
 232                 if(sig == SIGBUS)
 233                         printk("Bus error - the host /dev/shm or /tmp mount "
 234                                "likely just ran out of space\n");
 235                 panic("Kernel mode signal %d", sig);
 236         }
 237
 238         current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
 239         force_sig(sig, current);
 240 }
 241
 242 static void bus_handler(int sig, union uml_pt_regs *regs)
 243 {
 244         if(current->thread.fault_catcher != NULL)
 245                 do_longjmp(current->thread.fault_catcher, 1);
 246         else relay_signal(sig, regs);
 247 }
 248
 249 static void winch(int sig, union uml_pt_regs *regs)
 250 {
 251         do_IRQ(WINCH_IRQ, regs);
 252 }
 253
 254 const struct kern_handlers handlinfo_kern = {
 255         .relay_signal = relay_signal,
 256         .winch = winch,
 257         .bus_handler = bus_handler,
 258         .page_fault = segv_handler,
 259         .sigio_handler = sigio_handler,
 260         .timer_handler = timer_handler
 261 };
 262
 263 void trap_init(void)
 264 {
 265 }