linux/arch/x86/um/ldt.c
Hans-Werner Hilse 37e81a016c um: Do not rely on libc to provide modify_ldt()
modify_ldt() was declared as an external symbol. Despite the man
page for this syscall telling that there is no wrapper in glibc,
since version 2.1 there actually is, so linking to the glibc
works.

Since modify_ldt() is not a POSIX interface, other libc
implementations do not always provide a wrapper function.
Even glibc headers do not provide a corresponding declaration.

So go the recommended way to call this using syscall().

Signed-off-by: Hans-Werner Hilse <hwhilse@gmail.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
2015-10-19 22:53:37 +02:00

376 lines
8.6 KiB
C

/*
* Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <os.h>
#include <skas.h>
#include <sysdep/tls.h>
static inline int modify_ldt (int func, void *ptr, unsigned long bytecount)
{
return syscall(__NR_modify_ldt, func, ptr, bytecount);
}
static long write_ldt_entry(struct mm_id *mm_idp, int func,
struct user_desc *desc, void **addr, int done)
{
long res;
void *stub_addr;
res = syscall_stub_data(mm_idp, (unsigned long *)desc,
(sizeof(*desc) + sizeof(long) - 1) &
~(sizeof(long) - 1),
addr, &stub_addr);
if (!res) {
unsigned long args[] = { func,
(unsigned long)stub_addr,
sizeof(*desc),
0, 0, 0 };
res = run_syscall_stub(mm_idp, __NR_modify_ldt, args,
0, addr, done);
}
return res;
}
/*
* In skas mode, we hold our own ldt data in UML.
* Thus, the code implementing sys_modify_ldt_skas
* is very similar to (and mostly stolen from) sys_modify_ldt
* for arch/i386/kernel/ldt.c
* The routines copied and modified in part are:
* - read_ldt
* - read_default_ldt
* - write_ldt
* - sys_modify_ldt_skas
*/
static int read_ldt(void __user * ptr, unsigned long bytecount)
{
int i, err = 0;
unsigned long size;
uml_ldt_t *ldt = &current->mm->context.arch.ldt;
if (!ldt->entry_count)
goto out;
if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
err = bytecount;
mutex_lock(&ldt->lock);
if (ldt->entry_count <= LDT_DIRECT_ENTRIES) {
size = LDT_ENTRY_SIZE*LDT_DIRECT_ENTRIES;
if (size > bytecount)
size = bytecount;
if (copy_to_user(ptr, ldt->u.entries, size))
err = -EFAULT;
bytecount -= size;
ptr += size;
}
else {
for (i=0; i<ldt->entry_count/LDT_ENTRIES_PER_PAGE && bytecount;
i++) {
size = PAGE_SIZE;
if (size > bytecount)
size = bytecount;
if (copy_to_user(ptr, ldt->u.pages[i], size)) {
err = -EFAULT;
break;
}
bytecount -= size;
ptr += size;
}
}
mutex_unlock(&ldt->lock);
if (bytecount == 0 || err == -EFAULT)
goto out;
if (clear_user(ptr, bytecount))
err = -EFAULT;
out:
return err;
}
static int read_default_ldt(void __user * ptr, unsigned long bytecount)
{
int err;
if (bytecount > 5*LDT_ENTRY_SIZE)
bytecount = 5*LDT_ENTRY_SIZE;
err = bytecount;
/*
* UML doesn't support lcall7 and lcall27.
* So, we don't really have a default ldt, but emulate
* an empty ldt of common host default ldt size.
*/
if (clear_user(ptr, bytecount))
err = -EFAULT;
return err;
}
static int write_ldt(void __user * ptr, unsigned long bytecount, int func)
{
uml_ldt_t *ldt = &current->mm->context.arch.ldt;
struct mm_id * mm_idp = &current->mm->context.id;
int i, err;
struct user_desc ldt_info;
struct ldt_entry entry0, *ldt_p;
void *addr = NULL;
err = -EINVAL;
if (bytecount != sizeof(ldt_info))
goto out;
err = -EFAULT;
if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
goto out;
err = -EINVAL;
if (ldt_info.entry_number >= LDT_ENTRIES)
goto out;
if (ldt_info.contents == 3) {
if (func == 1)
goto out;
if (ldt_info.seg_not_present == 0)
goto out;
}
mutex_lock(&ldt->lock);
err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
if (err)
goto out_unlock;
if (ldt_info.entry_number >= ldt->entry_count &&
ldt_info.entry_number >= LDT_DIRECT_ENTRIES) {
for (i=ldt->entry_count/LDT_ENTRIES_PER_PAGE;
i*LDT_ENTRIES_PER_PAGE <= ldt_info.entry_number;
i++) {
if (i == 0)
memcpy(&entry0, ldt->u.entries,
sizeof(entry0));
ldt->u.pages[i] = (struct ldt_entry *)
__get_free_page(GFP_KERNEL|__GFP_ZERO);
if (!ldt->u.pages[i]) {
err = -ENOMEM;
/* Undo the change in host */
memset(&ldt_info, 0, sizeof(ldt_info));
write_ldt_entry(mm_idp, 1, &ldt_info, &addr, 1);
goto out_unlock;
}
if (i == 0) {
memcpy(ldt->u.pages[0], &entry0,
sizeof(entry0));
memcpy(ldt->u.pages[0]+1, ldt->u.entries+1,
sizeof(entry0)*(LDT_DIRECT_ENTRIES-1));
}
ldt->entry_count = (i + 1) * LDT_ENTRIES_PER_PAGE;
}
}
if (ldt->entry_count <= ldt_info.entry_number)
ldt->entry_count = ldt_info.entry_number + 1;
if (ldt->entry_count <= LDT_DIRECT_ENTRIES)
ldt_p = ldt->u.entries + ldt_info.entry_number;
else
ldt_p = ldt->u.pages[ldt_info.entry_number/LDT_ENTRIES_PER_PAGE] +
ldt_info.entry_number%LDT_ENTRIES_PER_PAGE;
if (ldt_info.base_addr == 0 && ldt_info.limit == 0 &&
(func == 1 || LDT_empty(&ldt_info))) {
ldt_p->a = 0;
ldt_p->b = 0;
}
else{
if (func == 1)
ldt_info.useable = 0;
ldt_p->a = LDT_entry_a(&ldt_info);
ldt_p->b = LDT_entry_b(&ldt_info);
}
err = 0;
out_unlock:
mutex_unlock(&ldt->lock);
out:
return err;
}
static long do_modify_ldt_skas(int func, void __user *ptr,
unsigned long bytecount)
{
int ret = -ENOSYS;
switch (func) {
case 0:
ret = read_ldt(ptr, bytecount);
break;
case 1:
case 0x11:
ret = write_ldt(ptr, bytecount, func);
break;
case 2:
ret = read_default_ldt(ptr, bytecount);
break;
}
return ret;
}
static DEFINE_SPINLOCK(host_ldt_lock);
static short dummy_list[9] = {0, -1};
static short * host_ldt_entries = NULL;
static void ldt_get_host_info(void)
{
long ret;
struct ldt_entry * ldt;
short *tmp;
int i, size, k, order;
spin_lock(&host_ldt_lock);
if (host_ldt_entries != NULL) {
spin_unlock(&host_ldt_lock);
return;
}
host_ldt_entries = dummy_list+1;
spin_unlock(&host_ldt_lock);
for (i = LDT_PAGES_MAX-1, order=0; i; i>>=1, order++)
;
ldt = (struct ldt_entry *)
__get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
if (ldt == NULL) {
printk(KERN_ERR "ldt_get_host_info: couldn't allocate buffer "
"for host ldt\n");
return;
}
ret = modify_ldt(0, ldt, (1<<order)*PAGE_SIZE);
if (ret < 0) {
printk(KERN_ERR "ldt_get_host_info: couldn't read host ldt\n");
goto out_free;
}
if (ret == 0) {
/* default_ldt is active, simply write an empty entry 0 */
host_ldt_entries = dummy_list;
goto out_free;
}
for (i=0, size=0; i<ret/LDT_ENTRY_SIZE; i++) {
if (ldt[i].a != 0 || ldt[i].b != 0)
size++;
}
if (size < ARRAY_SIZE(dummy_list))
host_ldt_entries = dummy_list;
else {
size = (size + 1) * sizeof(dummy_list[0]);
tmp = kmalloc(size, GFP_KERNEL);
if (tmp == NULL) {
printk(KERN_ERR "ldt_get_host_info: couldn't allocate "
"host ldt list\n");
goto out_free;
}
host_ldt_entries = tmp;
}
for (i=0, k=0; i<ret/LDT_ENTRY_SIZE; i++) {
if (ldt[i].a != 0 || ldt[i].b != 0)
host_ldt_entries[k++] = i;
}
host_ldt_entries[k] = -1;
out_free:
free_pages((unsigned long)ldt, order);
}
long init_new_ldt(struct mm_context *new_mm, struct mm_context *from_mm)
{
struct user_desc desc;
short * num_p;
int i;
long page, err=0;
void *addr = NULL;
mutex_init(&new_mm->arch.ldt.lock);
if (!from_mm) {
memset(&desc, 0, sizeof(desc));
/*
* Now we try to retrieve info about the ldt, we
* inherited from the host. All ldt-entries found
* will be reset in the following loop
*/
ldt_get_host_info();
for (num_p=host_ldt_entries; *num_p != -1; num_p++) {
desc.entry_number = *num_p;
err = write_ldt_entry(&new_mm->id, 1, &desc,
&addr, *(num_p + 1) == -1);
if (err)
break;
}
new_mm->arch.ldt.entry_count = 0;
goto out;
}
/*
* Our local LDT is used to supply the data for
* modify_ldt(READLDT), if PTRACE_LDT isn't available,
* i.e., we have to use the stub for modify_ldt, which
* can't handle the big read buffer of up to 64kB.
*/
mutex_lock(&from_mm->arch.ldt.lock);
if (from_mm->arch.ldt.entry_count <= LDT_DIRECT_ENTRIES)
memcpy(new_mm->arch.ldt.u.entries, from_mm->arch.ldt.u.entries,
sizeof(new_mm->arch.ldt.u.entries));
else {
i = from_mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
while (i-->0) {
page = __get_free_page(GFP_KERNEL|__GFP_ZERO);
if (!page) {
err = -ENOMEM;
break;
}
new_mm->arch.ldt.u.pages[i] =
(struct ldt_entry *) page;
memcpy(new_mm->arch.ldt.u.pages[i],
from_mm->arch.ldt.u.pages[i], PAGE_SIZE);
}
}
new_mm->arch.ldt.entry_count = from_mm->arch.ldt.entry_count;
mutex_unlock(&from_mm->arch.ldt.lock);
out:
return err;
}
void free_ldt(struct mm_context *mm)
{
int i;
if (mm->arch.ldt.entry_count > LDT_DIRECT_ENTRIES) {
i = mm->arch.ldt.entry_count / LDT_ENTRIES_PER_PAGE;
while (i-- > 0)
free_page((long) mm->arch.ldt.u.pages[i]);
}
mm->arch.ldt.entry_count = 0;
}
int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
{
return do_modify_ldt_skas(func, ptr, bytecount);
}