patch-2.4.5 linux/arch/i386/mm/fault.c

• Lines: 77
• Date: Tue May 15 00:16:51 2001
• Orig file: v2.4.4/linux/arch/i386/mm/fault.c
• Orig date: Mon Mar 19 12:35:09 2001

diff -u --recursive --new-file v2.4.4/linux/arch/i386/mm/fault.c linux/arch/i386/mm/fault.c
@@ -117,6 +117,10 @@
 	/* get the address */
 	__asm__("movl %%cr2,%0":"=r" (address));
 
+	/* It's safe to allow irq's after cr2 has been saved */
+	if (regs->eflags & X86_EFLAGS_IF)
+		local_irq_enable();
+
 	tsk = current;
 
 	/*
@@ -127,8 +131,12 @@
 	 * be in an interrupt or a critical region, and should
 	 * only copy the information from the master page table,
 	 * nothing more.
+	 *
+	 * This verifies that the fault happens in kernel space
+	 * (error_code & 4) == 0, and that the fault was not a
+	 * protection error (error_code & 1) == 0.
 	 */
-	if (address >= TASK_SIZE)
+	if (address >= TASK_SIZE && !(error_code & 5))
 		goto vmalloc_fault;
 
 	mm = tsk->mm;
@@ -224,7 +232,6 @@
 bad_area:
 	up_read(&mm->mmap_sem);
 
-bad_area_nosemaphore:
 	/* User mode accesses just cause a SIGSEGV */
 	if (error_code & 4) {
 		tsk->thread.cr2 = address;
@@ -322,27 +329,32 @@
 		/*
 		 * Synchronize this task's top level page-table
 		 * with the 'reference' page table.
+		 *
+		 * Do _not_ use "tsk" here. We might be inside
+		 * an interrupt in the middle of a task switch..
 		 */
 		int offset = __pgd_offset(address);
 		pgd_t *pgd, *pgd_k;
 		pmd_t *pmd, *pmd_k;
+		pte_t *pte_k;
 
-		pgd = tsk->active_mm->pgd + offset;
+		asm("movl %%cr3,%0":"=r" (pgd));
+		pgd = offset + (pgd_t *)__va(pgd);
 		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;
-		}
-
+		if (!pgd_present(*pgd_k))
+			goto no_context;
+		set_pgd(pgd, *pgd_k);
+		
 		pmd = pmd_offset(pgd, address);
 		pmd_k = pmd_offset(pgd_k, address);
-
-		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
-			goto bad_area_nosemaphore;
+		if (!pmd_present(*pmd_k))
+			goto no_context;
 		set_pmd(pmd, *pmd_k);
+
+		pte_k = pte_offset(pmd_k, address);
+		if (!pte_present(*pte_k))
+			goto no_context;
 		return;
 	}
 }