- 根目录:
- arch
- x86
- um
- ldt.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 <asm/unistd.h>
#include "os.h"
#include "proc_mm.h"
#include "skas.h"
#include "skas_ptrace.h"
#include "sysdep/tls.h"
extern int modify_ldt(int func, void *ptr, unsigned long bytecount);
static long write_ldt_entry(struct mm_id *mm_idp, int func,
struct user_desc *desc, void **addr, int done)
{
long res;
if (proc_mm) {
/*
* This is a special handling for the case, that the mm to
* modify isn't current->active_mm.
* If this is called directly by modify_ldt,
* (current->active_mm->context.skas.u == mm_idp)
* will be true. So no call to __switch_mm(mm_idp) is done.
* If this is called in case of init_new_ldt or PTRACE_LDT,
* mm_idp won't belong to current->active_mm, but child->mm.
* So we need to switch child's mm into our userspace, then
* later switch back.
*
* Note: I'm unsure: should interrupts be disabled here?
*/
if (!current->active_mm || current->active_mm == &init_mm ||
mm_idp != ¤t->active_mm->context.id)
__switch_mm(mm_idp);
}
if (ptrace_ldt) {
struct ptrace_ldt ldt_op = (struct ptrace_ldt) {
.func = func,
.ptr = desc,
.bytecount = sizeof(*desc)};
u32 cpu;
int pid;
if (!proc_mm)
pid = mm_idp->u.pid;
else {
cpu = get_cpu();
pid = userspace_pid[cpu];
}
res = os_ptrace_ldt(pid, 0, (unsigned long) &ldt_op);
if (proc_mm)
put_cpu();
}
else {
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);
}
}
if (proc_mm) {
/*
* This is the second part of special handling, that makes
* PTRACE_LDT possible to implement.
*/
if (current->active_mm && current->active_mm != &init_mm &&
mm_idp != ¤t->active_mm->context.id)
__switch_mm(¤t->active_mm->context.id);
}
return res;
}
static long read_ldt_from_host(void __user * ptr, unsigned long bytecount)
{
int res, n;
struct ptrace_ldt ptrace_ldt = (struct ptrace_ldt) {
.func = 0,
.bytecount = bytecount,
.ptr = kmalloc(bytecount, GFP_KERNEL)};
u32 cpu;
if (ptrace_ldt.ptr == NULL)
return -ENOMEM;
/*
* This is called from sys_modify_ldt only, so userspace_pid gives
* us the right number
*/
cpu = get_cpu();
res = os_ptrace_ldt(userspace_pid[cpu], 0, (unsigned long) &ptrace_ldt);
put_cpu();
if (res < 0)
goto out;
n = copy_to_user(ptr, ptrace_ldt.ptr, res);
if (n != 0)
res = -EFAULT;
out:
kfree(ptrace_ldt.ptr);
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 = ¤t->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;
if (ptrace_ldt)
return read_ldt_from_host(ptr, 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 = ¤t->mm->context.arch.ldt;
struct mm_id * mm_idp = ¤t->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;
}
if (!ptrace_ldt)
mutex_lock(&ldt->lock);
err = write_ldt_entry(mm_idp, func, &ldt_info, &addr, 1);
if (err)
goto out_unlock;
else if (ptrace_ldt) {
/* With PTRACE_LDT available, this is used as a flag only */
ldt->entry_count = 1;
goto out;
}
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;
struct proc_mm_op copy;
if (!ptrace_ldt)
mutex_init(&new_mm->arch.ldt.lock);
if (!from_mm) {
memset(&desc, 0, sizeof(desc));
/*
* We have to initialize a clean ldt.
*/
if (proc_mm) {
/*
* If the new mm was created using proc_mm, host's
* default-ldt currently is assigned, which normally
* contains the call-gates for lcall7 and lcall27.
* To remove these gates, we simply write an empty
* entry as number 0 to the host.
*/
err = write_ldt_entry(&new_mm->id, 1, &desc, &addr, 1);
}
else{
/*
* 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;
}
if (proc_mm) {
/*
* We have a valid from_mm, so we now have to copy the LDT of
* from_mm to new_mm, because using proc_mm an new mm with
* an empty/default LDT was created in new_mm()
*/
copy = ((struct proc_mm_op) { .op = MM_COPY_SEGMENTS,
.u =
{ .copy_segments =
from_mm->id.u.mm_fd } } );
i = os_write_file(new_mm->id.u.mm_fd, ©, sizeof(copy));
if (i != sizeof(copy))
printk(KERN_ERR "new_mm : /proc/mm copy_segments "
"failed, err = %d\n", -i);
}
if (!ptrace_ldt) {
/*
* 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 (!ptrace_ldt && 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);
}