patch-2.4.0-test10 linux/arch/i386/mm/fault.c

• Lines: 110
• Date: Mon Oct 16 12:26:52 2000
• Orig file: v2.4.0-test9/linux/arch/i386/mm/fault.c
• Orig date: Wed May 24 18:38:26 2000

diff -u --recursive --new-file v2.4.0-test9/linux/arch/i386/mm/fault.c linux/arch/i386/mm/fault.c
@@ -77,31 +77,6 @@
 	return 0;
 }
 
-static void __init handle_wp_test (void)
-{
-	const unsigned long vaddr = PAGE_OFFSET;
-	pgd_t *pgd;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	/*
-	 * make it read/writable temporarily, so that the fault
-	 * can be handled.
-	 */
-	pgd = swapper_pg_dir + __pgd_offset(vaddr);
-	pmd = pmd_offset(pgd, vaddr);
-	pte = pte_offset(pmd, vaddr);
-	*pte = mk_pte_phys(0, PAGE_KERNEL);
-	__flush_tlb_all();
-
-	boot_cpu_data.wp_works_ok = 1;
-	/*
-	 * Beware: Black magic here. The printk is needed here to flush
-	 * CPU state on certain buggy processors.
-	 */
-	printk("Ok");
-}
-
 asmlinkage void do_invalid_op(struct pt_regs *, unsigned long);
 extern unsigned long idt;
 
@@ -130,6 +105,19 @@
 	__asm__("movl %%cr2,%0":"=r" (address));
 
 	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.
+	 */
+	if (address >= TASK_SIZE)
+		goto vmalloc_fault;
+
 	mm = tsk->mm;
 	info.si_code = SEGV_MAPERR;
 
@@ -223,6 +211,7 @@
 bad_area:
 	up(&mm->mmap_sem);
 
+bad_area_nosemaphore:
 	/* User mode accesses just cause a SIGSEGV */
 	if (error_code & 4) {
 		tsk->thread.cr2 = address;
@@ -260,14 +249,7 @@
 /*
  * Oops. The kernel tried to access some bad page. We'll have to
  * terminate things with extreme prejudice.
- *
- * First we check if it was the bootup rw-test, though..
  */
-	if (boot_cpu_data.wp_works_ok < 0 &&
-			address == PAGE_OFFSET && (error_code & 1)) {
-		handle_wp_test();
-		return;
-	}
 
 	if (address < PAGE_SIZE)
 		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
@@ -318,4 +300,34 @@
 	/* Kernel mode? Handle exceptions or die */
 	if (!(error_code & 4))
 		goto no_context;
+	return;
+
+vmalloc_fault:
+	{
+		/*
+		 * Synchronize this task's top level page-table
+		 * with the 'reference' page table.
+		 */
+		int offset = __pgd_offset(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;
+	}
 }