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fault.c

/* $Id: fault.c,v 1.59 2002/02/09 19:49:31 davem Exp $
 * arch/sparc64/mm/fault.c: Page fault handlers for the 64-bit Sparc.
 *
 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.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/signal.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/kprobes.h>
#include <linux/kallsyms.h>
#include <linux/kdebug.h>

#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/uaccess.h>
#include <asm/asi.h>
#include <asm/lsu.h>
#include <asm/sections.h>
#include <asm/mmu_context.h>

#ifdef CONFIG_KPROBES
static inline int notify_page_fault(struct pt_regs *regs)
{
      int ret = 0;

      /* kprobe_running() needs smp_processor_id() */
      if (!user_mode(regs)) {
            preempt_disable();
            if (kprobe_running() && kprobe_fault_handler(regs, 0))
                  ret = 1;
            preempt_enable();
      }
      return ret;
}
#else
static inline int notify_page_fault(struct pt_regs *regs)
{
      return 0;
}
#endif

/*
 * To debug kernel to catch accesses to certain virtual/physical addresses.
 * Mode = 0 selects physical watchpoints, mode = 1 selects virtual watchpoints.
 * flags = VM_READ watches memread accesses, flags = VM_WRITE watches memwrite accesses.
 * Caller passes in a 64bit aligned addr, with mask set to the bytes that need to be
 * watched. This is only useful on a single cpu machine for now. After the watchpoint
 * is detected, the process causing it will be killed, thus preventing an infinite loop.
 */
void set_brkpt(unsigned long addr, unsigned char mask, int flags, int mode)
{
      unsigned long lsubits;

      __asm__ __volatile__("ldxa [%%g0] %1, %0"
                       : "=r" (lsubits)
                       : "i" (ASI_LSU_CONTROL));
      lsubits &= ~(LSU_CONTROL_PM | LSU_CONTROL_VM |
                 LSU_CONTROL_PR | LSU_CONTROL_VR |
                 LSU_CONTROL_PW | LSU_CONTROL_VW);

      __asm__ __volatile__("stxa    %0, [%1] %2\n\t"
                       "membar      #Sync"
                       : /* no outputs */
                       : "r" (addr), "r" (mode ? VIRT_WATCHPOINT : PHYS_WATCHPOINT),
                         "i" (ASI_DMMU));

      lsubits |= ((unsigned long)mask << (mode ? 25 : 33));
      if (flags & VM_READ)
            lsubits |= (mode ? LSU_CONTROL_VR : LSU_CONTROL_PR);
      if (flags & VM_WRITE)
            lsubits |= (mode ? LSU_CONTROL_VW : LSU_CONTROL_PW);
      __asm__ __volatile__("stxa %0, [%%g0] %1\n\t"
                       "membar #Sync"
                       : /* no outputs */
                       : "r" (lsubits), "i" (ASI_LSU_CONTROL)
                       : "memory");
}

static void __kprobes 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 %016lx\n", (unsigned long)address);
      }
      printk(KERN_ALERT "tsk->{mm,active_mm}->context = %016lx\n",
             (tsk->mm ?
            CTX_HWBITS(tsk->mm->context) :
            CTX_HWBITS(tsk->active_mm->context)));
      printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %016lx\n",
             (tsk->mm ? (unsigned long) tsk->mm->pgd :
                      (unsigned long) tsk->active_mm->pgd));
      die_if_kernel("Oops", regs);
}

static void bad_kernel_pc(struct pt_regs *regs, unsigned long vaddr)
{
      printk(KERN_CRIT "OOPS: Bogus kernel PC [%016lx] in fault handler\n",
             regs->tpc);
      printk(KERN_CRIT "OOPS: RPC [%016lx]\n", regs->u_regs[15]);
      print_symbol("RPC: <%s>\n", regs->u_regs[15]);
      printk(KERN_CRIT "OOPS: Fault was to vaddr[%lx]\n", vaddr);
      dump_stack();
      unhandled_fault(regs->tpc, current, regs);
}

/*
 * We now make sure that mmap_sem is held in all paths that call 
 * this. Additionally, to prevent kswapd from ripping ptes from
 * under us, raise interrupts around the time that we look at the
 * pte, kswapd will have to wait to get his smp ipi response from
 * us. vmtruncate likewise. This saves us having to get pte lock.
 */
static unsigned int get_user_insn(unsigned long tpc)
{
      pgd_t *pgdp = pgd_offset(current->mm, tpc);
      pud_t *pudp;
      pmd_t *pmdp;
      pte_t *ptep, pte;
      unsigned long pa;
      u32 insn = 0;
      unsigned long pstate;

      if (pgd_none(*pgdp))
            goto outret;
      pudp = pud_offset(pgdp, tpc);
      if (pud_none(*pudp))
            goto outret;
      pmdp = pmd_offset(pudp, tpc);
      if (pmd_none(*pmdp))
            goto outret;

      /* This disables preemption for us as well. */
      __asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
      __asm__ __volatile__("wrpr %0, %1, %%pstate"
                        : : "r" (pstate), "i" (PSTATE_IE));
      ptep = pte_offset_map(pmdp, tpc);
      pte = *ptep;
      if (!pte_present(pte))
            goto out;

      pa  = (pte_pfn(pte) << PAGE_SHIFT);
      pa += (tpc & ~PAGE_MASK);

      /* Use phys bypass so we don't pollute dtlb/dcache. */
      __asm__ __volatile__("lduwa [%1] %2, %0"
                       : "=r" (insn)
                       : "r" (pa), "i" (ASI_PHYS_USE_EC));

out:
      pte_unmap(ptep);
      __asm__ __volatile__("wrpr %0, 0x0, %%pstate" : : "r" (pstate));
outret:
      return insn;
}

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

static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
                       unsigned int insn, int fault_code)
{
      siginfo_t info;

      info.si_code = code;
      info.si_signo = sig;
      info.si_errno = 0;
      if (fault_code & FAULT_CODE_ITLB)
            info.si_addr = (void __user *) regs->tpc;
      else
            info.si_addr = (void __user *)
                  compute_effective_address(regs, insn, 0);
      info.si_trapno = 0;
      force_sig_info(sig, &info, current);
}

extern int handle_ldf_stq(u32, struct pt_regs *);
extern int handle_ld_nf(u32, struct pt_regs *);

static unsigned int get_fault_insn(struct pt_regs *regs, unsigned int insn)
{
      if (!insn) {
            if (!regs->tpc || (regs->tpc & 0x3))
                  return 0;
            if (regs->tstate & TSTATE_PRIV) {
                  insn = *(unsigned int *) regs->tpc;
            } else {
                  insn = get_user_insn(regs->tpc);
            }
      }
      return insn;
}

static void do_kernel_fault(struct pt_regs *regs, int si_code, int fault_code,
                      unsigned int insn, unsigned long address)
{
      unsigned char asi = ASI_P;
 
      if ((!insn) && (regs->tstate & TSTATE_PRIV))
            goto cannot_handle;

      /* If user insn could be read (thus insn is zero), that
       * is fine.  We will just gun down the process with a signal
       * in that case.
       */

      if (!(fault_code & (FAULT_CODE_WRITE|FAULT_CODE_ITLB)) &&
          (insn & 0xc0800000) == 0xc0800000) {
            if (insn & 0x2000)
                  asi = (regs->tstate >> 24);
            else
                  asi = (insn >> 5);
            if ((asi & 0xf2) == 0x82) {
                  if (insn & 0x1000000) {
                        handle_ldf_stq(insn, regs);
                  } else {
                        /* This was a non-faulting load. Just clear the
                         * destination register(s) and continue with the next
                         * instruction. -jj
                         */
                        handle_ld_nf(insn, regs);
                  }
                  return;
            }
      }
            
      /* Is this in ex_table? */
      if (regs->tstate & TSTATE_PRIV) {
            const struct exception_table_entry *entry;

            if (asi == ASI_P && (insn & 0xc0800000) == 0xc0800000) {
                  if (insn & 0x2000)
                        asi = (regs->tstate >> 24);
                  else
                        asi = (insn >> 5);
            }
      
            /* Look in asi.h: All _S asis have LS bit set */
            if ((asi & 0x1) &&
                (entry = search_exception_tables(regs->tpc))) {
                  regs->tpc = entry->fixup;
                  regs->tnpc = regs->tpc + 4;
                  return;
            }
      } else {
            /* The si_code was set to make clear whether
             * this was a SEGV_MAPERR or SEGV_ACCERR fault.
             */
            do_fault_siginfo(si_code, SIGSEGV, regs, insn, fault_code);
            return;
      }

cannot_handle:
      unhandled_fault (address, current, regs);
}

asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
{
      struct mm_struct *mm = current->mm;
      struct vm_area_struct *vma;
      unsigned int insn = 0;
      int si_code, fault_code, fault;
      unsigned long address, mm_rss;

      fault_code = get_thread_fault_code();

      if (notify_page_fault(regs))
            return;

      si_code = SEGV_MAPERR;
      address = current_thread_info()->fault_address;

      if ((fault_code & FAULT_CODE_ITLB) &&
          (fault_code & FAULT_CODE_DTLB))
            BUG();

      if (regs->tstate & TSTATE_PRIV) {
            unsigned long tpc = regs->tpc;

            /* Sanity check the PC. */
            if ((tpc >= KERNBASE && tpc < (unsigned long) _etext) ||
                (tpc >= MODULES_VADDR && tpc < MODULES_END)) {
                  /* Valid, no problems... */
            } else {
                  bad_kernel_pc(regs, address);
                  return;
            }
      }

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

      if (test_thread_flag(TIF_32BIT)) {
            if (!(regs->tstate & TSTATE_PRIV))
                  regs->tpc &= 0xffffffff;
            address &= 0xffffffff;
      }

      if (!down_read_trylock(&mm->mmap_sem)) {
            if ((regs->tstate & TSTATE_PRIV) &&
                !search_exception_tables(regs->tpc)) {
                  insn = get_fault_insn(regs, insn);
                  goto handle_kernel_fault;
            }
            down_read(&mm->mmap_sem);
      }

      vma = find_vma(mm, address);
      if (!vma)
            goto bad_area;

      /* Pure DTLB misses do not tell us whether the fault causing
       * load/store/atomic was a write or not, it only says that there
       * was no match.  So in such a case we (carefully) read the
       * instruction to try and figure this out.  It's an optimization
       * so it's ok if we can't do this.
       *
       * Special hack, window spill/fill knows the exact fault type.
       */
      if (((fault_code &
            (FAULT_CODE_DTLB | FAULT_CODE_WRITE | FAULT_CODE_WINFIXUP)) == FAULT_CODE_DTLB) &&
          (vma->vm_flags & VM_WRITE) != 0) {
            insn = get_fault_insn(regs, 0);
            if (!insn)
                  goto continue_fault;
            /* All loads, stores and atomics have bits 30 and 31 both set
             * in the instruction.  Bit 21 is set in all stores, but we
             * have to avoid prefetches which also have bit 21 set.
             */
            if ((insn & 0xc0200000) == 0xc0200000 &&
                (insn & 0x01780000) != 0x01680000) {
                  /* Don't bother updating thread struct value,
                   * because update_mmu_cache only cares which tlb
                   * the access came from.
                   */
                  fault_code |= FAULT_CODE_WRITE;
            }
      }
continue_fault:

      if (vma->vm_start <= address)
            goto good_area;
      if (!(vma->vm_flags & VM_GROWSDOWN))
            goto bad_area;
      if (!(fault_code & FAULT_CODE_WRITE)) {
            /* Non-faulting loads shouldn't expand stack. */
            insn = get_fault_insn(regs, insn);
            if ((insn & 0xc0800000) == 0xc0800000) {
                  unsigned char asi;

                  if (insn & 0x2000)
                        asi = (regs->tstate >> 24);
                  else
                        asi = (insn >> 5);
                  if ((asi & 0xf2) == 0x82)
                        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:
      si_code = SEGV_ACCERR;

      /* If we took a ITLB miss on a non-executable page, catch
       * that here.
       */
      if ((fault_code & FAULT_CODE_ITLB) && !(vma->vm_flags & VM_EXEC)) {
            BUG_ON(address != regs->tpc);
            BUG_ON(regs->tstate & TSTATE_PRIV);
            goto bad_area;
      }

      if (fault_code & FAULT_CODE_WRITE) {
            if (!(vma->vm_flags & VM_WRITE))
                  goto bad_area;

            /* Spitfire has an icache which does not snoop
             * processor stores.  Later processors do...
             */
            if (tlb_type == spitfire &&
                (vma->vm_flags & VM_EXEC) != 0 &&
                vma->vm_file != NULL)
                  set_thread_fault_code(fault_code |
                                    FAULT_CODE_BLKCOMMIT);
      } else {
            /* Allow reads even for write-only mappings */
            if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                  goto bad_area;
      }

      fault = handle_mm_fault(mm, vma, address, (fault_code & FAULT_CODE_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);

      mm_rss = get_mm_rss(mm);
#ifdef CONFIG_HUGETLB_PAGE
      mm_rss -= (mm->context.huge_pte_count * (HPAGE_SIZE / PAGE_SIZE));
#endif
      if (unlikely(mm_rss >
                 mm->context.tsb_block[MM_TSB_BASE].tsb_rss_limit))
            tsb_grow(mm, MM_TSB_BASE, mm_rss);
#ifdef CONFIG_HUGETLB_PAGE
      mm_rss = mm->context.huge_pte_count;
      if (unlikely(mm_rss >
                 mm->context.tsb_block[MM_TSB_HUGE].tsb_rss_limit))
            tsb_grow(mm, MM_TSB_HUGE, mm_rss);
#endif
      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:
      insn = get_fault_insn(regs, insn);
      up_read(&mm->mmap_sem);

handle_kernel_fault:
      do_kernel_fault(regs, si_code, fault_code, insn, address);
      return;

/*
 * 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:
      insn = get_fault_insn(regs, insn);
      up_read(&mm->mmap_sem);
      printk("VM: killing process %s\n", current->comm);
      if (!(regs->tstate & TSTATE_PRIV))
            do_group_exit(SIGKILL);
      goto handle_kernel_fault;

intr_or_no_mm:
      insn = get_fault_insn(regs, 0);
      goto handle_kernel_fault;

do_sigbus:
      insn = get_fault_insn(regs, insn);
      up_read(&mm->mmap_sem);

      /*
       * Send a sigbus, regardless of whether we were in kernel
       * or user mode.
       */
      do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, insn, fault_code);

      /* Kernel mode? Handle exceptions or die */
      if (regs->tstate & TSTATE_PRIV)
            goto handle_kernel_fault;
}

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