patch-2.4.2 linux/arch/cris/mm/fault.c

• Lines: 391
• Date: Thu Feb 8 16:32:44 2001
• Orig file: v2.4.1/linux/arch/cris/mm/fault.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.1/linux/arch/cris/mm/fault.c linux/arch/cris/mm/fault.c
@@ -0,0 +1,390 @@
+/*
+ *  linux/arch/cris/mm/fault.c
+ *
+ *  Copyright (C) 2000  Axis Communications AB
+ *
+ *  Authors:  Bjorn Wesen 
+ * 
+ *  $Log: fault.c,v $
+ *  Revision 1.8  2000/11/22 14:45:31  bjornw
+ *  * 2.4.0-test10 removed the set_pgdir instantaneous kernel global mapping
+ *    into all processes. Instead we fill in the missing PTE entries on demand.
+ *
+ *  Revision 1.7  2000/11/21 16:39:09  bjornw
+ *  fixup switches frametype
+ *
+ *  Revision 1.6  2000/11/17 16:54:08  bjornw
+ *  More detailed siginfo reporting
+ *
+ *
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+
+#include <asm/system.h>
+#include <asm/segment.h>
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/svinto.h>
+
+extern void die_if_kernel(const char *,struct pt_regs *,long);
+
+asmlinkage void do_invalid_op (struct pt_regs *, unsigned long);
+asmlinkage void do_page_fault(unsigned long address, struct pt_regs *regs,
+			      int error_code);
+
+/* debug of low-level TLB reload */
+#define D(x)
+/* debug of higher-level faults */
+#define DPG(x)
+
+/* fast TLB-fill fault handler */
+
+void
+handle_mmu_bus_fault(struct pt_regs *regs)
+{
+	int cause, select;
+	int index;
+	int page_id;
+	int miss, we, acc, inv;  
+	struct mm_struct *mm = current->active_mm;
+	pmd_t *pmd;
+	pte_t pte;
+	int errcode = 0;
+	unsigned long address;
+
+	cause = *R_MMU_CAUSE;
+	select = *R_TLB_SELECT;
+
+	address = cause & PAGE_MASK; /* get faulting address */
+	
+	page_id = IO_EXTRACT(R_MMU_CAUSE,  page_id,   cause);
+	miss    = IO_EXTRACT(R_MMU_CAUSE,  miss_excp, cause);
+	we      = IO_EXTRACT(R_MMU_CAUSE,  we_excp,   cause);
+	acc     = IO_EXTRACT(R_MMU_CAUSE,  acc_excp,  cause);
+	inv     = IO_EXTRACT(R_MMU_CAUSE,  inv_excp,  cause);  
+	index  =  IO_EXTRACT(R_TLB_SELECT, index,     select);
+	
+	D(printk("bus_fault from IRP 0x%x: addr 0x%x, miss %d, inv %d, we %d, acc %d, "
+		 "idx %d pid %d\n",
+		 regs->irp, address, miss, inv, we, acc, index, page_id));
+
+	/* for a miss, we need to reload the TLB entry */
+
+	if(miss) {
+
+		/* see if the pte exists at all */
+		
+		pmd = (pmd_t *)pgd_offset(mm, address);
+		if(pmd_none(*pmd))
+			goto dofault;
+		if(pmd_bad(*pmd)) {
+			printk("bad pgdir entry 0x%x at 0x%x\n", *pmd, pmd);
+			pmd_clear(pmd);
+			return;
+		}
+		pte = *pte_offset(pmd, address);
+		if(!pte_present(pte))
+			goto dofault;
+		
+		D(printk(" found pte %x pg %x ", pte_val(pte), pte_page(pte)));
+		D(
+		  {
+			  if(pte_val(pte) & _PAGE_SILENT_WRITE)
+				  printk("Silent-W ");
+			  if(pte_val(pte) & _PAGE_KERNEL)
+				  printk("Kernel ");
+			  if(pte_val(pte) & _PAGE_SILENT_READ)
+				  printk("Silent-R ");
+			  if(pte_val(pte) & _PAGE_GLOBAL)
+				  printk("Global ");
+			  if(pte_val(pte) & _PAGE_PRESENT)
+				  printk("Present ");
+			  if(pte_val(pte) & _PAGE_ACCESSED)
+				  printk("Accessed ");
+			  if(pte_val(pte) & _PAGE_MODIFIED)
+				  printk("Modified ");
+			  if(pte_val(pte) & _PAGE_READ)
+				  printk("Readable ");
+			  if(pte_val(pte) & _PAGE_WRITE)
+				  printk("Writeable ");
+			  printk("\n");
+		  });
+
+		/* load up the chosen TLB entry
+		 * this assumes the pte format is the same as the TLB_LO layout.
+		 *
+		 * the write to R_TLB_LO also writes the vpn and page_id fields from
+		 * R_MMU_CAUSE, which we in this case obviously want to keep
+		 */
+		
+		*R_TLB_LO = pte_val(pte);
+
+		return;
+	} 
+
+	errcode = 0x01 | (we << 1);
+
+ dofault:
+	/* leave it to the MM system fault handler below */
+	D(printk("do_page_fault %p errcode %d\n", address, errcode));
+	do_page_fault(address, regs, errcode);
+}
+
+/*
+ * This routine handles page faults.  It determines the address,
+ * and the problem, and then passes it off to one of the appropriate
+ * routines.
+ *
+ * Notice that the address we're given is aligned to the page the fault
+ * occured in, since we only get the PFN in R_MMU_CAUSE not the complete
+ * address.
+ *
+ * error_code:
+ *	bit 0 == 0 means no page found, 1 means protection fault
+ *	bit 1 == 0 means read, 1 means write
+ *
+ * If this routine detects a bad access, it returns 1, otherwise it
+ * returns 0.
+ */
+
+asmlinkage void
+do_page_fault(unsigned long address, struct pt_regs *regs,
+	      int error_code)
+{
+	struct task_struct *tsk;
+	struct mm_struct *mm;
+	struct vm_area_struct * vma;
+	int writeaccess;
+	int fault;
+	unsigned long fixup;
+	siginfo_t info;
+
+	tsk = current;
+
+        /*
+         * 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.
+	 *
+	 * NOTE2: This is done so that, when updating the vmalloc
+	 * mappings we don't have to walk all processes pgdirs and
+	 * add the high mappings all at once. Instead we do it as they
+	 * are used.
+	 *
+	 * TODO: On CRIS, we have a PTE Global bit which should be set in
+	 * all the PTE's related to vmalloc in all processes - that means if
+	 * we switch process and a vmalloc PTE is still in the TLB, it won't
+	 * need to be reloaded. It's an optimization.
+	 *
+	 * Linux/CRIS's kernel is not page-mapped, so the comparision below
+	 * should really be >= VMALLOC_START, however, kernel fixup errors
+	 * will be handled more quickly by going through vmalloc_fault and then
+	 * into bad_area_nosemaphore than falling through the find_vma user-mode
+	 * tests.
+         */
+
+        if (address >= TASK_SIZE)
+                goto vmalloc_fault;
+
+	mm = tsk->mm;
+	writeaccess = error_code & 2;
+	info.si_code = SEGV_MAPERR;
+
+	/*
+	 * If we're in an interrupt or have no user
+	 * context, we must not take the fault..
+	 */
+
+	if (in_interrupt() || !mm)
+		goto no_context;
+
+	down(&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 (user_mode(regs)) {
+		/*
+		 * accessing the stack below usp is always a bug.
+		 * we get page-aligned addresses so we can only check
+		 * if we're within a page from usp, but that might be
+		 * enough to catch brutal errors at least.
+		 */
+		if (address + PAGE_SIZE < rdusp())
+			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;
+
+	/* first do some preliminary protection checks */
+
+	if (writeaccess) {
+		if (!(vma->vm_flags & VM_WRITE))
+			goto bad_area;
+	} else {
+		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.
+	 */
+
+	switch (handle_mm_fault(mm, vma, address, writeaccess)) {
+        case 1:
+                tsk->min_flt++;
+                break;
+        case 2:
+                tsk->maj_flt++;
+                break;
+        case 0:
+                goto do_sigbus;
+        default:
+                goto out_of_memory;
+	}
+
+	up(&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(&mm->mmap_sem);
+
+ bad_area_nosemaphore:
+	DPG(show_registers(regs));
+
+	/* User mode accesses just cause a SIGSEGV */
+
+	if (user_mode(regs)) {
+		info.si_signo = SIGSEGV;
+		info.si_errno = 0;
+		/* info.si_code has been set above */
+		info.si_addr = (void *)address;
+		force_sig_info(SIGSEGV, &info, tsk);
+		return;
+	}
+
+ no_context:
+
+	/* Are we prepared to handle this kernel fault?
+	 *
+	 * (The kernel has valid exception-points in the source 
+	 *  when it acesses user-memory. When it fails in one
+	 *  of those points, we find it in a table and do a jump
+	 *  to some fixup code that loads an appropriate error
+	 *  code)
+	 */
+
+        if ((fixup = search_exception_table(regs->irp)) != 0) {
+                regs->irp = fixup;
+		regs->frametype = CRIS_FRAME_FIXUP;
+		D(printk("doing fixup to 0x%x\n", fixup));
+                return;
+        }
+
+/*
+ * Oops. The kernel tried to access some bad page. We'll have to
+ * terminate things with extreme prejudice.
+ */
+	if ((unsigned long) (address) < PAGE_SIZE)
+		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
+	else
+		printk(KERN_ALERT "Unable to handle kernel access");
+	printk(" at virtual address %08lx\n",address);
+
+	die_if_kernel("Oops", regs, error_code);
+
+	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(&mm->mmap_sem);
+	printk("VM: killing process %s\n", tsk->comm);
+	if(user_mode(regs))
+		do_exit(SIGKILL);
+	goto no_context;
+
+ do_sigbus:
+	up(&mm->mmap_sem);
+
+	/*
+         * Send a sigbus, regardless of whether we were in kernel
+         * or user mode.
+         */
+	info.si_code = SIGBUS;
+	info.si_errno = 0;
+	info.si_code = BUS_ADRERR;
+	info.si_addr = (void *)address;
+	force_sig_info(SIGBUS, &info, tsk);
+	
+        /* Kernel mode? Handle exceptions or die */
+        if (!user_mode(regs))
+                goto no_context;
+        return;
+
+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;
+                        set_pgd(pgd, *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;
+                set_pmd(pmd, *pmd_k);
+                return;
+        }
+
+}