patch-2.4.20 linux-2.4.20/arch/x86_64/kernel/ldt.c

• Lines: 177
• Date: Thu Nov 28 15:53:12 2002
• Orig file: linux-2.4.19/arch/x86_64/kernel/ldt.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/x86_64/kernel/ldt.c linux-2.4.20/arch/x86_64/kernel/ldt.c
@@ -0,0 +1,176 @@
+/*
+ * linux/arch/x86_64/kernel/ldt.c
+ *
+ * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
+ * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
+ * Copyright (C) 2002 Andi Kleen
+ * 
+ * Manage the local descriptor table for user processes.
+ * This handles calls from both 32bit and 64bit mode.
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/smp_lock.h>
+#include <linux/vmalloc.h>
+
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/ldt.h>
+#include <asm/desc.h>
+
+/*
+ * read_ldt() is not really atomic - this is not a problem since
+ * synchronization of reads and writes done to the LDT has to be
+ * assured by user-space anyway. Writes are atomic, to protect
+ * the security checks done on new descriptors.
+ */
+static int read_ldt(void * ptr, unsigned long bytecount)
+{
+	int err;
+	unsigned long size;
+	struct mm_struct * mm = current->mm;
+
+	err = 0;
+	if (!mm->context.segments)
+		goto out;
+
+	size = LDT_ENTRIES*LDT_ENTRY_SIZE;
+	if (size > bytecount)
+		size = bytecount;
+
+	err = size;
+	if (copy_to_user(ptr, mm->context.segments, size))
+		err = -EFAULT;
+out:
+	return err;
+}
+
+static int read_default_ldt(void * ptr, unsigned long bytecount)
+{
+	/* Arbitary number */ 
+	if (bytecount > 128) 
+		bytecount = 128; 	
+	if (clear_user(ptr, bytecount))
+		return -EFAULT;
+	return bytecount; 
+}
+
+static int write_ldt(void * ptr, unsigned long bytecount, int oldmode)
+{
+	struct task_struct *me = current;
+	struct mm_struct * mm = me->mm;
+	__u32 entry_1, entry_2, *lp;
+	int error;
+	struct modify_ldt_ldt_s ldt_info;
+
+	error = -EINVAL;
+
+	if (bytecount != sizeof(ldt_info))
+		goto out;
+	error = -EFAULT; 	
+	if (copy_from_user(&ldt_info, ptr, bytecount))
+		goto out;
+
+	error = -EINVAL;
+	if (ldt_info.entry_number >= LDT_ENTRIES)
+		goto out;
+	if (ldt_info.contents == 3) {
+		if (oldmode)
+			goto out;
+		if (ldt_info.seg_not_present == 0)
+			goto out;
+	}
+
+	me->thread.fsindex = 0; 
+	me->thread.gsindex = 0; 
+	me->thread.gs = 0; 
+	me->thread.fs = 0; 
+
+	/*
+	 * the GDT index of the LDT is allocated dynamically, and is
+	 * limited by MAX_LDT_DESCRIPTORS.
+	 */
+	down_write(&mm->mmap_sem);
+	if (!mm->context.segments) {
+		void * segments = vmalloc(LDT_ENTRIES*LDT_ENTRY_SIZE);
+		error = -ENOMEM;
+		if (!segments)
+			goto out_unlock;
+		memset(segments, 0, LDT_ENTRIES*LDT_ENTRY_SIZE);
+		wmb();
+		mm->context.segments = segments;
+		mm->context.cpuvalid = 1UL << smp_processor_id();
+		load_LDT(mm);
+	}
+
+	lp = (__u32 *) ((ldt_info.entry_number << 3) + (char *) mm->context.segments);
+
+   	/* Allow LDTs to be cleared by the user. */
+   	if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
+		if (oldmode ||
+		    (ldt_info.contents == 0		&&
+		     ldt_info.read_exec_only == 1	&&
+		     ldt_info.seg_32bit == 0		&&
+		     ldt_info.limit_in_pages == 0	&&
+		     ldt_info.seg_not_present == 1	&&
+		     ldt_info.useable == 0 && 
+		     ldt_info.lm == 0)) {
+			entry_1 = 0;
+			entry_2 = 0;
+			goto install;
+		}
+	}
+
+	entry_1 = ((ldt_info.base_addr & 0x0000ffff) << 16) |
+		  (ldt_info.limit & 0x0ffff);
+	entry_2 = (ldt_info.base_addr & 0xff000000) |
+		  ((ldt_info.base_addr & 0x00ff0000) >> 16) |
+		  (ldt_info.limit & 0xf0000) |
+		  ((ldt_info.read_exec_only ^ 1) << 9) |
+		  (ldt_info.contents << 10) |
+		  ((ldt_info.seg_not_present ^ 1) << 15) |
+		  (ldt_info.seg_32bit << 22) |
+		  (ldt_info.limit_in_pages << 23) |
+		  (ldt_info.lm << 21) |
+		  0x7000;
+	if (!oldmode)
+		entry_2 |= (ldt_info.useable << 20);
+
+	/* Install the new entry ...  */
+install:
+	write_lock(&mm->context.ldtlock);
+	*lp	= entry_1;
+	*(lp+1)	= entry_2;
+	write_unlock(&mm->context.ldtlock);
+	error = 0;
+
+out_unlock:
+	up_write(&mm->mmap_sem);
+out:
+	return error;
+}
+
+asmlinkage long sys_modify_ldt(int func, void *ptr, unsigned long bytecount)
+{
+	int ret = -ENOSYS;
+
+	switch (func) {
+	case 0:
+		ret = read_ldt(ptr, bytecount);
+		break;
+	case 1:
+		ret = write_ldt(ptr, bytecount, 1);
+		break;
+	case 2:
+		ret = read_default_ldt(ptr, bytecount);
+		break;
+	case 0x11:
+		ret = write_ldt(ptr, bytecount, 0);
+		break;
+	}
+	return ret;
+}