1 files changed, 104 insertions, 0 deletions
diff --git a/arch/i386/kernel/ldt.c b/arch/i386/kernel/ldt.c
new file mode 100644
index 000000000..bace95f4e
--- /dev/null
+++ b/arch/i386/kernel/ldt.c
@@ -0,0 +1,104 @@
+/*
+ * linux/kernel/ldt.c
+ *
+ * Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <asm/segment.h>
+#include <asm/system.h>
+#include <linux/ldt.h>
+
+static int read_ldt(void * ptr, unsigned long bytecount)
+{
+	int error;
+	void * address = current->ldt;
+	unsigned long size;
+
+	if (!ptr)
+		return -EINVAL;
+	size = LDT_ENTRIES*LDT_ENTRY_SIZE;
+	if (!address) {
+		address = &default_ldt;
+		size = sizeof(default_ldt);
+	}
+	if (size > bytecount)
+		size = bytecount;
+	error = verify_area(VERIFY_WRITE, ptr, size);
+	if (error)
+		return error;
+	memcpy_tofs(ptr, address, size);
+	return size;
+}
+
+static int write_ldt(void * ptr, unsigned long bytecount)
+{
+	struct modify_ldt_ldt_s ldt_info;
+	unsigned long *lp;
+	unsigned long base, limit;
+	int error, i;
+
+	if (bytecount != sizeof(ldt_info))
+		return -EINVAL;
+	error = verify_area(VERIFY_READ, ptr, sizeof(ldt_info));
+	if (error)
+		return error;
+
+	memcpy_fromfs(&ldt_info, ptr, sizeof(ldt_info));
+
+	if (ldt_info.contents == 3 || ldt_info.entry_number >= LDT_ENTRIES)
+		return -EINVAL;
+
+	limit = ldt_info.limit;
+	base = ldt_info.base_addr;
+	if (ldt_info.limit_in_pages)
+		limit *= PAGE_SIZE;
+
+	limit += base;
+	if (limit < base || limit >= 0xC0000000)
+		return -EINVAL;
+
+	if (!current->ldt) {
+		for (i=1 ; i<NR_TASKS ; i++) {
+			if (task[i] == current) {
+				if (!(current->ldt = (struct desc_struct*) vmalloc(LDT_ENTRIES*LDT_ENTRY_SIZE)))
+					return -ENOMEM;
+				memset(current->ldt, 0, LDT_ENTRIES*LDT_ENTRY_SIZE);
+				set_ldt_desc(gdt+(i<<1)+FIRST_LDT_ENTRY, current->ldt, LDT_ENTRIES);
+				load_ldt(i);
+			}
+		}
+	}
+	
+	lp = (unsigned long *) &current->ldt[ldt_info.entry_number];
+   	/* Allow LDTs to be cleared by the user. */
+   	if (ldt_info.base_addr == 0 && ldt_info.limit == 0) {
+		*lp = 0;
+		*(lp+1) = 0;
+		return 0;
+	}
+	*lp = ((ldt_info.base_addr & 0x0000ffff) << 16) |
+		  (ldt_info.limit & 0x0ffff);
+	*(lp+1) = (ldt_info.base_addr & 0xff000000) |
+		  ((ldt_info.base_addr & 0x00ff0000)>>16) |
+		  (ldt_info.limit & 0xf0000) |
+		  (ldt_info.contents << 10) |
+		  ((ldt_info.read_exec_only ^ 1) << 9) |
+		  (ldt_info.seg_32bit << 22) |
+		  (ldt_info.limit_in_pages << 23) |
+		  ((ldt_info.seg_not_present ^1) << 15) |
+		  0x7000;
+	return 0;
+}
+
+asmlinkage int sys_modify_ldt(int func, void *ptr, unsigned long bytecount)
+{
+	if (func == 0)
+		return read_ldt(ptr, bytecount);
+	if (func == 1)
+		return write_ldt(ptr, bytecount);
+	return -ENOSYS;
+}