2 * Copyright (C) 2001 Hewlett-Packard Co
3 * David Mosberger-Tang <davidm@hpl.hp.com>
5 * Adapted from arch/i386/kernel/ldt.c
8 #include <linux/errno.h>
9 #include <linux/sched.h>
10 #include <linux/string.h>
12 #include <linux/smp.h>
13 #include <linux/smp_lock.h>
14 #include <linux/vmalloc.h>
16 #include <asm/uaccess.h>
20 #define P(p) ((void *) (unsigned long) (p))
23 * read_ldt() is not really atomic - this is not a problem since synchronization of reads
24 * and writes done to the LDT has to be assured by user-space anyway. Writes are atomic,
25 * to protect the security checks done on new descriptors.
28 read_ldt (void *ptr, unsigned long bytecount)
30 char *src, *dst, buf[256]; /* temporary buffer (don't overflow kernel stack!) */
31 unsigned long bytes_left, n;
33 if (bytecount > IA32_LDT_ENTRIES*IA32_LDT_ENTRY_SIZE)
34 bytecount = IA32_LDT_ENTRIES*IA32_LDT_ENTRY_SIZE;
36 bytes_left = bytecount;
38 src = (void *) IA32_LDT_OFFSET;
47 * We know we're reading valid memory, but we still must guard against
48 * running out of memory.
50 if (__copy_from_user(buf, src, n))
53 if (copy_to_user(dst, buf, n))
64 read_default_ldt (void * ptr, unsigned long bytecount)
69 /* XXX fix me: should return equivalent of default_ldt[0] */
76 if (clear_user(ptr, size))
83 write_ldt (void * ptr, unsigned long bytecount, int oldmode)
85 struct ia32_user_desc ldt_info;
89 if (bytecount != sizeof(ldt_info))
91 if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
94 if (ldt_info.entry_number >= IA32_LDT_ENTRIES)
96 if (ldt_info.contents == 3) {
99 if (ldt_info.seg_not_present == 0)
103 if (ldt_info.base_addr == 0 && ldt_info.limit == 0
104 && (oldmode || (ldt_info.contents == 0 && ldt_info.read_exec_only == 1
105 && ldt_info.seg_32bit == 0 && ldt_info.limit_in_pages == 0
106 && ldt_info.seg_not_present == 1 && ldt_info.useable == 0)))
107 /* allow LDTs to be cleared by the user */
110 /* we must set the "Accessed" bit as IVE doesn't emulate it */
111 entry = IA32_SEG_DESCRIPTOR(ldt_info.base_addr, ldt_info.limit,
112 (((ldt_info.read_exec_only ^ 1) << 1)
113 | (ldt_info.contents << 2)) | 1,
114 1, 3, ldt_info.seg_not_present ^ 1,
115 (oldmode ? 0 : ldt_info.useable),
117 ldt_info.limit_in_pages);
119 * Install the new entry. We know we're accessing valid (mapped) user-level
120 * memory, but we still need to guard against out-of-memory, hence we must use
123 ret = __put_user(entry, (__u64 *) IA32_LDT_OFFSET + ldt_info.entry_number);
124 ia32_load_segment_descriptors(current);
129 sys32_modify_ldt (int func, unsigned int ptr, unsigned int bytecount)
135 ret = read_ldt(P(ptr), bytecount);
138 ret = write_ldt(P(ptr), bytecount, 1);
141 ret = read_default_ldt(P(ptr), bytecount);
144 ret = write_ldt(P(ptr), bytecount, 0);