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fault.c

/* $Id: fault.c,v 1.122 2001/11/17 07:19:26 davem Exp $
 * fault.c:  Page fault handlers for the Sparc.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */

#include <asm/head.h>

#include <linux/string.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/threads.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kdebug.h>

#include <asm/system.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/memreg.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/smp.h>
#include <asm/traps.h>
#include <asm/uaccess.h>

extern int prom_node_root;

/* At boot time we determine these two values necessary for setting
 * up the segment maps and page table entries (pte's).
 */

int num_segmaps, num_contexts;
int invalid_segment;

/* various Virtual Address Cache parameters we find at boot time... */

int vac_size, vac_linesize, vac_do_hw_vac_flushes;
int vac_entries_per_context, vac_entries_per_segment;
int vac_entries_per_page;

/* Nice, simple, prom library does all the sweating for us. ;) */
int prom_probe_memory (void)
{
      register struct linux_mlist_v0 *mlist;
      register unsigned long bytes, base_paddr, tally;
      register int i;

      i = 0;
      mlist= *prom_meminfo()->v0_available;
      bytes = tally = mlist->num_bytes;
      base_paddr = (unsigned long) mlist->start_adr;
  
      sp_banks[0].base_addr = base_paddr;
      sp_banks[0].num_bytes = bytes;

      while (mlist->theres_more != (void *) 0){
            i++;
            mlist = mlist->theres_more;
            bytes = mlist->num_bytes;
            tally += bytes;
            if (i > SPARC_PHYS_BANKS-1) {
                  printk ("The machine has more banks than "
                        "this kernel can support\n"
                        "Increase the SPARC_PHYS_BANKS "
                        "setting (currently %d)\n",
                        SPARC_PHYS_BANKS);
                  i = SPARC_PHYS_BANKS-1;
                  break;
            }
    
            sp_banks[i].base_addr = (unsigned long) mlist->start_adr;
            sp_banks[i].num_bytes = mlist->num_bytes;
      }

      i++;
      sp_banks[i].base_addr = 0xdeadbeef;
      sp_banks[i].num_bytes = 0;

      /* Now mask all bank sizes on a page boundary, it is all we can
       * use anyways.
       */
      for(i=0; sp_banks[i].num_bytes != 0; i++)
            sp_banks[i].num_bytes &= PAGE_MASK;

      return tally;
}

/* Traverse the memory lists in the prom to see how much physical we
 * have.
 */
unsigned long
probe_memory(void)
{
      int total;

      total = prom_probe_memory();

      /* Oh man, much nicer, keep the dirt in promlib. */
      return total;
}

extern void sun4c_complete_all_stores(void);

/* Whee, a level 15 NMI interrupt memory error.  Let's have fun... */
asmlinkage void sparc_lvl15_nmi(struct pt_regs *regs, unsigned long serr,
                        unsigned long svaddr, unsigned long aerr,
                        unsigned long avaddr)
{
      sun4c_complete_all_stores();
      printk("FAULT: NMI received\n");
      printk("SREGS: Synchronous Error %08lx\n", serr);
      printk("       Synchronous Vaddr %08lx\n", svaddr);
      printk("      Asynchronous Error %08lx\n", aerr);
      printk("      Asynchronous Vaddr %08lx\n", avaddr);
      if (sun4c_memerr_reg)
            printk("     Memory Parity Error %08lx\n", *sun4c_memerr_reg);
      printk("REGISTER DUMP:\n");
      show_regs(regs);
      prom_halt();
}

static void unhandled_fault(unsigned long, struct task_struct *,
            struct pt_regs *) __attribute__ ((noreturn));

static void unhandled_fault(unsigned long address, struct task_struct *tsk,
                     struct pt_regs *regs)
{
      if((unsigned long) address < PAGE_SIZE) {
            printk(KERN_ALERT
                "Unable to handle kernel NULL pointer dereference\n");
      } else {
            printk(KERN_ALERT "Unable to handle kernel paging request "
                   "at virtual address %08lx\n", address);
      }
      printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
            (tsk->mm ? tsk->mm->context : tsk->active_mm->context));
      printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
            (tsk->mm ? (unsigned long) tsk->mm->pgd :
                  (unsigned long) tsk->active_mm->pgd));
      die_if_kernel("Oops", regs);
}

asmlinkage int lookup_fault(unsigned long pc, unsigned long ret_pc, 
                      unsigned long address)
{
      struct pt_regs regs;
      unsigned long g2;
      unsigned int insn;
      int i;
      
      i = search_extables_range(ret_pc, &g2);
      switch (i) {
      case 3:
            /* load & store will be handled by fixup */
            return 3;

      case 1:
            /* store will be handled by fixup, load will bump out */
            /* for _to_ macros */
            insn = *((unsigned int *) pc);
            if ((insn >> 21) & 1)
                  return 1;
            break;

      case 2:
            /* load will be handled by fixup, store will bump out */
            /* for _from_ macros */
            insn = *((unsigned int *) pc);
            if (!((insn >> 21) & 1) || ((insn>>19)&0x3f) == 15)
                  return 2; 
            break; 

      default:
            break;
      };

      memset(&regs, 0, sizeof (regs));
      regs.pc = pc;
      regs.npc = pc + 4;
      __asm__ __volatile__(
            "rd %%psr, %0\n\t"
            "nop\n\t"
            "nop\n\t"
            "nop\n" : "=r" (regs.psr));
      unhandled_fault(address, current, &regs);

      /* Not reached */
      return 0;
}

extern unsigned long safe_compute_effective_address(struct pt_regs *,
                                        unsigned int);

static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
{
      unsigned int insn;

      if (text_fault)
            return regs->pc;

      if (regs->psr & PSR_PS) {
            insn = *(unsigned int *) regs->pc;
      } else {
            __get_user(insn, (unsigned int *) regs->pc);
      }

      return safe_compute_effective_address(regs, insn);
}

asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
                         unsigned long address)
{
      struct vm_area_struct *vma;
      struct task_struct *tsk = current;
      struct mm_struct *mm = tsk->mm;
      unsigned int fixup;
      unsigned long g2;
      siginfo_t info;
      int from_user = !(regs->psr & PSR_PS);
      int fault;

      if(text_fault)
            address = regs->pc;

      /*
       * We fault-in kernel-space virtual memory on-demand. The
       * 'reference' page table is init_mm.pgd.
       *
       * NOTE! We MUST NOT take any locks for this case. We may
       * be in an interrupt or a critical region, and should
       * only copy the information from the master page table,
       * nothing more.
       */
      if (!ARCH_SUN4C_SUN4 && address >= TASK_SIZE)
            goto vmalloc_fault;

      info.si_code = SEGV_MAPERR;

      /*
       * If we're in an interrupt or have no user
       * context, we must not take the fault..
       */
        if (in_atomic() || !mm)
                goto no_context;

      down_read(&mm->mmap_sem);

      /*
       * The kernel referencing a bad kernel pointer can lock up
       * a sun4c machine completely, so we must attempt recovery.
       */
      if(!from_user && address >= PAGE_OFFSET)
            goto bad_area;

      vma = find_vma(mm, address);
      if(!vma)
            goto bad_area;
      if(vma->vm_start <= address)
            goto good_area;
      if(!(vma->vm_flags & VM_GROWSDOWN))
            goto bad_area;
      if(expand_stack(vma, address))
            goto bad_area;
      /*
       * Ok, we have a good vm_area for this memory access, so
       * we can handle it..
       */
good_area:
      info.si_code = SEGV_ACCERR;
      if(write) {
            if(!(vma->vm_flags & VM_WRITE))
                  goto bad_area;
      } else {
            /* Allow reads even for write-only mappings */
            if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
                  goto bad_area;
      }

      /*
       * If for any reason at all we couldn't handle the fault,
       * make sure we exit gracefully rather than endlessly redo
       * the fault.
       */
      fault = handle_mm_fault(mm, vma, address, write);
      if (unlikely(fault & VM_FAULT_ERROR)) {
            if (fault & VM_FAULT_OOM)
                  goto out_of_memory;
            else if (fault & VM_FAULT_SIGBUS)
                  goto do_sigbus;
            BUG();
      }
      if (fault & VM_FAULT_MAJOR)
            current->maj_flt++;
      else
            current->min_flt++;
      up_read(&mm->mmap_sem);
      return;

      /*
       * Something tried to access memory that isn't in our memory map..
       * Fix it, but check if it's kernel or user first..
       */
bad_area:
      up_read(&mm->mmap_sem);

bad_area_nosemaphore:
      /* User mode accesses just cause a SIGSEGV */
      if(from_user) {
#if 0
            printk("Fault whee %s [%d]: segfaults at %08lx pc=%08lx\n",
                   tsk->comm, tsk->pid, address, regs->pc);
#endif
            info.si_signo = SIGSEGV;
            info.si_errno = 0;
            /* info.si_code set above to make clear whether
               this was a SEGV_MAPERR or SEGV_ACCERR fault.  */
            info.si_addr = (void __user *)compute_si_addr(regs, text_fault);
            info.si_trapno = 0;
            force_sig_info (SIGSEGV, &info, tsk);
            return;
      }

      /* Is this in ex_table? */
no_context:
      g2 = regs->u_regs[UREG_G2];
      if (!from_user && (fixup = search_extables_range(regs->pc, &g2))) {
            if (fixup > 10) { /* Values below are reserved for other things */
                  extern const unsigned __memset_start[];
                  extern const unsigned __memset_end[];
                  extern const unsigned __csum_partial_copy_start[];
                  extern const unsigned __csum_partial_copy_end[];

#ifdef DEBUG_EXCEPTIONS
                  printk("Exception: PC<%08lx> faddr<%08lx>\n", regs->pc, address);
                  printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
                        regs->pc, fixup, g2);
#endif
                  if ((regs->pc >= (unsigned long)__memset_start &&
                       regs->pc < (unsigned long)__memset_end) ||
                      (regs->pc >= (unsigned long)__csum_partial_copy_start &&
                       regs->pc < (unsigned long)__csum_partial_copy_end)) {
                          regs->u_regs[UREG_I4] = address;
                        regs->u_regs[UREG_I5] = regs->pc;
                  }
                  regs->u_regs[UREG_G2] = g2;
                  regs->pc = fixup;
                  regs->npc = regs->pc + 4;
                  return;
            }
      }
      
      unhandled_fault (address, tsk, regs);
      do_exit(SIGKILL);

/*
 * We ran out of memory, or some other thing happened to us that made
 * us unable to handle the page fault gracefully.
 */
out_of_memory:
      up_read(&mm->mmap_sem);
      printk("VM: killing process %s\n", tsk->comm);
      if (from_user)
            do_group_exit(SIGKILL);
      goto no_context;

do_sigbus:
      up_read(&mm->mmap_sem);
      info.si_signo = SIGBUS;
      info.si_errno = 0;
      info.si_code = BUS_ADRERR;
      info.si_addr = (void __user *) compute_si_addr(regs, text_fault);
      info.si_trapno = 0;
      force_sig_info (SIGBUS, &info, tsk);
      if (!from_user)
            goto no_context;

vmalloc_fault:
      {
            /*
             * Synchronize this task's top level page-table
             * with the 'reference' page table.
             */
            int offset = pgd_index(address);
            pgd_t *pgd, *pgd_k;
            pmd_t *pmd, *pmd_k;

            pgd = tsk->active_mm->pgd + offset;
            pgd_k = init_mm.pgd + offset;

            if (!pgd_present(*pgd)) {
                  if (!pgd_present(*pgd_k))
                        goto bad_area_nosemaphore;
                  pgd_val(*pgd) = pgd_val(*pgd_k);
                  return;
            }

            pmd = pmd_offset(pgd, address);
            pmd_k = pmd_offset(pgd_k, address);

            if (pmd_present(*pmd) || !pmd_present(*pmd_k))
                  goto bad_area_nosemaphore;
            *pmd = *pmd_k;
            return;
      }
}

asmlinkage void do_sun4c_fault(struct pt_regs *regs, int text_fault, int write,
                         unsigned long address)
{
      extern void sun4c_update_mmu_cache(struct vm_area_struct *,
                                 unsigned long,pte_t);
      extern pte_t *sun4c_pte_offset_kernel(pmd_t *,unsigned long);
      struct task_struct *tsk = current;
      struct mm_struct *mm = tsk->mm;
      pgd_t *pgdp;
      pte_t *ptep;

      if (text_fault) {
            address = regs->pc;
      } else if (!write &&
               !(regs->psr & PSR_PS)) {
            unsigned int insn, __user *ip;

            ip = (unsigned int __user *)regs->pc;
            if (!get_user(insn, ip)) {
                  if ((insn & 0xc1680000) == 0xc0680000)
                        write = 1;
            }
      }

      if (!mm) {
            /* We are oopsing. */
            do_sparc_fault(regs, text_fault, write, address);
            BUG();      /* P3 Oops already, you bitch */
      }

      pgdp = pgd_offset(mm, address);
      ptep = sun4c_pte_offset_kernel((pmd_t *) pgdp, address);

      if (pgd_val(*pgdp)) {
          if (write) {
            if ((pte_val(*ptep) & (_SUN4C_PAGE_WRITE|_SUN4C_PAGE_PRESENT))
                           == (_SUN4C_PAGE_WRITE|_SUN4C_PAGE_PRESENT)) {
                  unsigned long flags;

                  *ptep = __pte(pte_val(*ptep) | _SUN4C_PAGE_ACCESSED |
                              _SUN4C_PAGE_MODIFIED |
                              _SUN4C_PAGE_VALID |
                              _SUN4C_PAGE_DIRTY);

                  local_irq_save(flags);
                  if (sun4c_get_segmap(address) != invalid_segment) {
                        sun4c_put_pte(address, pte_val(*ptep));
                        local_irq_restore(flags);
                        return;
                  }
                  local_irq_restore(flags);
            }
          } else {
            if ((pte_val(*ptep) & (_SUN4C_PAGE_READ|_SUN4C_PAGE_PRESENT))
                           == (_SUN4C_PAGE_READ|_SUN4C_PAGE_PRESENT)) {
                  unsigned long flags;

                  *ptep = __pte(pte_val(*ptep) | _SUN4C_PAGE_ACCESSED |
                              _SUN4C_PAGE_VALID);

                  local_irq_save(flags);
                  if (sun4c_get_segmap(address) != invalid_segment) {
                        sun4c_put_pte(address, pte_val(*ptep));
                        local_irq_restore(flags);
                        return;
                  }
                  local_irq_restore(flags);
            }
          }
      }

      /* This conditional is 'interesting'. */
      if (pgd_val(*pgdp) && !(write && !(pte_val(*ptep) & _SUN4C_PAGE_WRITE))
          && (pte_val(*ptep) & _SUN4C_PAGE_VALID))
            /* Note: It is safe to not grab the MMAP semaphore here because
             *       we know that update_mmu_cache() will not sleep for
             *       any reason (at least not in the current implementation)
             *       and therefore there is no danger of another thread getting
             *       on the CPU and doing a shrink_mmap() on this vma.
             */
            sun4c_update_mmu_cache (find_vma(current->mm, address), address,
                              *ptep);
      else
            do_sparc_fault(regs, text_fault, write, address);
}

/* This always deals with user addresses. */
inline void force_user_fault(unsigned long address, int write)
{
      struct vm_area_struct *vma;
      struct task_struct *tsk = current;
      struct mm_struct *mm = tsk->mm;
      siginfo_t info;

      info.si_code = SEGV_MAPERR;

#if 0
      printk("wf<pid=%d,wr=%d,addr=%08lx>\n",
             tsk->pid, write, address);
#endif
      down_read(&mm->mmap_sem);
      vma = find_vma(mm, address);
      if(!vma)
            goto bad_area;
      if(vma->vm_start <= address)
            goto good_area;
      if(!(vma->vm_flags & VM_GROWSDOWN))
            goto bad_area;
      if(expand_stack(vma, address))
            goto bad_area;
good_area:
      info.si_code = SEGV_ACCERR;
      if(write) {
            if(!(vma->vm_flags & VM_WRITE))
                  goto bad_area;
      } else {
            if(!(vma->vm_flags & (VM_READ | VM_EXEC)))
                  goto bad_area;
      }
      switch (handle_mm_fault(mm, vma, address, write)) {
      case VM_FAULT_SIGBUS:
      case VM_FAULT_OOM:
            goto do_sigbus;
      }
      up_read(&mm->mmap_sem);
      return;
bad_area:
      up_read(&mm->mmap_sem);
#if 0
      printk("Window whee %s [%d]: segfaults at %08lx\n",
             tsk->comm, tsk->pid, address);
#endif
      info.si_signo = SIGSEGV;
      info.si_errno = 0;
      /* info.si_code set above to make clear whether
         this was a SEGV_MAPERR or SEGV_ACCERR fault.  */
      info.si_addr = (void __user *) address;
      info.si_trapno = 0;
      force_sig_info (SIGSEGV, &info, tsk);
      return;

do_sigbus:
      up_read(&mm->mmap_sem);
      info.si_signo = SIGBUS;
      info.si_errno = 0;
      info.si_code = BUS_ADRERR;
      info.si_addr = (void __user *) address;
      info.si_trapno = 0;
      force_sig_info (SIGBUS, &info, tsk);
}

void window_overflow_fault(void)
{
      unsigned long sp;

      sp = current_thread_info()->rwbuf_stkptrs[0];
      if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
            force_user_fault(sp + 0x38, 1);
      force_user_fault(sp, 1);
}

void window_underflow_fault(unsigned long sp)
{
      if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
            force_user_fault(sp + 0x38, 0);
      force_user_fault(sp, 0);
}

void window_ret_fault(struct pt_regs *regs)
{
      unsigned long sp;

      sp = regs->u_regs[UREG_FP];
      if(((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
            force_user_fault(sp + 0x38, 0);
      force_user_fault(sp, 0);
}

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