- 根目录:
- arch
- um
- sys-i386
- tls.c
/*
* Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
* Licensed under the GPL
*/
#include "linux/percpu.h"
#include "linux/sched.h"
#include "asm/uaccess.h"
#include "os.h"
#include "skas.h"
#include "sysdep/tls.h"
/*
* If needed we can detect when it's uninitialized.
*
* These are initialized in an initcall and unchanged thereafter.
*/
static int host_supports_tls = -1;
int host_gdt_entry_tls_min;
int do_set_thread_area(struct user_desc *info)
{
int ret;
u32 cpu;
cpu = get_cpu();
ret = os_set_thread_area(info, userspace_pid[cpu]);
put_cpu();
if (ret)
printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
"index = %d\n", ret, info->entry_number);
return ret;
}
int do_get_thread_area(struct user_desc *info)
{
int ret;
u32 cpu;
cpu = get_cpu();
ret = os_get_thread_area(info, userspace_pid[cpu]);
put_cpu();
if (ret)
printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, "
"index = %d\n", ret, info->entry_number);
return ret;
}
/*
* sys_get_thread_area: get a yet unused TLS descriptor index.
* XXX: Consider leaving one free slot for glibc usage at first place. This must
* be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
*
* Also, this must be tested when compiling in SKAS mode with dynamic linking
* and running against NPTL.
*/
static int get_free_idx(struct task_struct* task)
{
struct thread_struct *t = &task->thread;
int idx;
if (!t->arch.tls_array)
return GDT_ENTRY_TLS_MIN;
for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
if (!t->arch.tls_array[idx].present)
return idx + GDT_ENTRY_TLS_MIN;
return -ESRCH;
}
static inline void clear_user_desc(struct user_desc* info)
{
/* Postcondition: LDT_empty(info) returns true. */
memset(info, 0, sizeof(*info));
/*
* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
* indeed an empty user_desc.
*/
info->read_exec_only = 1;
info->seg_not_present = 1;
}
#define O_FORCE 1
static int load_TLS(int flags, struct task_struct *to)
{
int ret = 0;
int idx;
for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
struct uml_tls_struct* curr =
&to->thread.arch.tls_array[idx - GDT_ENTRY_TLS_MIN];
/*
* Actually, now if it wasn't flushed it gets cleared and
* flushed to the host, which will clear it.
*/
if (!curr->present) {
if (!curr->flushed) {
clear_user_desc(&curr->tls);
curr->tls.entry_number = idx;
} else {
WARN_ON(!LDT_empty(&curr->tls));
continue;
}
}
if (!(flags & O_FORCE) && curr->flushed)
continue;
ret = do_set_thread_area(&curr->tls);
if (ret)
goto out;
curr->flushed = 1;
}
out:
return ret;
}
/*
* Verify if we need to do a flush for the new process, i.e. if there are any
* present desc's, only if they haven't been flushed.
*/
static inline int needs_TLS_update(struct task_struct *task)
{
int i;
int ret = 0;
for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
struct uml_tls_struct* curr =
&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
/*
* Can't test curr->present, we may need to clear a descriptor
* which had a value.
*/
if (curr->flushed)
continue;
ret = 1;
break;
}
return ret;
}
/*
* On a newly forked process, the TLS descriptors haven't yet been flushed. So
* we mark them as such and the first switch_to will do the job.
*/
void clear_flushed_tls(struct task_struct *task)
{
int i;
for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
struct uml_tls_struct* curr =
&task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
/*
* Still correct to do this, if it wasn't present on the host it
* will remain as flushed as it was.
*/
if (!curr->present)
continue;
curr->flushed = 0;
}
}
/*
* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
* common host process. So this is needed in SKAS0 too.
*
* However, if each thread had a different host process (and this was discussed
* for SMP support) this won't be needed.
*
* And this will not need be used when (and if) we'll add support to the host
* SKAS patch.
*/
int arch_switch_tls(struct task_struct *to)
{
if (!host_supports_tls)
return 0;
/*
* We have no need whatsoever to switch TLS for kernel threads; beyond
* that, that would also result in us calling os_set_thread_area with
* userspace_pid[cpu] == 0, which gives an error.
*/
if (likely(to->mm))
return load_TLS(O_FORCE, to);
return 0;
}
static int set_tls_entry(struct task_struct* task, struct user_desc *info,
int idx, int flushed)
{
struct thread_struct *t = &task->thread;
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;
t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
return 0;
}
int arch_copy_tls(struct task_struct *new)
{
struct user_desc info;
int idx, ret = -EFAULT;
if (copy_from_user(&info,
(void __user *) UPT_ESI(&new->thread.regs.regs),
sizeof(info)))
goto out;
ret = -EINVAL;
if (LDT_empty(&info))
goto out;
idx = info.entry_number;
ret = set_tls_entry(new, &info, idx, 0);
out:
return ret;
}
/* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
static int get_tls_entry(struct task_struct *task, struct user_desc *info,
int idx)
{
struct thread_struct *t = &task->thread;
if (!t->arch.tls_array)
goto clear;
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;
if (!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present)
goto clear;
*info = t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls;
out:
/*
* Temporary debugging check, to make sure that things have been
* flushed. This could be triggered if load_TLS() failed.
*/
if (unlikely(task == current &&
!t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
printk(KERN_ERR "get_tls_entry: task with pid %d got here "
"without flushed TLS.", current->pid);
}
return 0;
clear:
/*
* When the TLS entry has not been set, the values read to user in the
* tls_array are 0 (because it's cleared at boot, see
* arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
*/
clear_user_desc(info);
info->entry_number = idx;
goto out;
}
int sys_set_thread_area(struct user_desc __user *user_desc)
{
struct user_desc info;
int idx, ret;
if (!host_supports_tls)
return -ENOSYS;
if (copy_from_user(&info, user_desc, sizeof(info)))
return -EFAULT;
idx = info.entry_number;
if (idx == -1) {
idx = get_free_idx(current);
if (idx < 0)
return idx;
info.entry_number = idx;
/* Tell the user which slot we chose for him.*/
if (put_user(idx, &user_desc->entry_number))
return -EFAULT;
}
ret = do_set_thread_area(&info);
if (ret)
return ret;
return set_tls_entry(current, &info, idx, 1);
}
/*
* Perform set_thread_area on behalf of the traced child.
* Note: error handling is not done on the deferred load, and this differ from
* i386. However the only possible error are caused by bugs.
*/
int ptrace_set_thread_area(struct task_struct *child, int idx,
struct user_desc __user *user_desc)
{
struct user_desc info;
if (!host_supports_tls)
return -EIO;
if (copy_from_user(&info, user_desc, sizeof(info)))
return -EFAULT;
return set_tls_entry(child, &info, idx, 0);
}
int sys_get_thread_area(struct user_desc __user *user_desc)
{
struct user_desc info;
int idx, ret;
if (!host_supports_tls)
return -ENOSYS;
if (get_user(idx, &user_desc->entry_number))
return -EFAULT;
ret = get_tls_entry(current, &info, idx);
if (ret < 0)
goto out;
if (copy_to_user(user_desc, &info, sizeof(info)))
ret = -EFAULT;
out:
return ret;
}
/*
* Perform get_thread_area on behalf of the traced child.
*/
int ptrace_get_thread_area(struct task_struct *child, int idx,
struct user_desc __user *user_desc)
{
struct user_desc info;
int ret;
if (!host_supports_tls)
return -EIO;
ret = get_tls_entry(child, &info, idx);
if (ret < 0)
goto out;
if (copy_to_user(user_desc, &info, sizeof(info)))
ret = -EFAULT;
out:
return ret;
}
/*
* This code is really i386-only, but it detects and logs x86_64 GDT indexes
* if a 32-bit UML is running on a 64-bit host.
*/
static int __init __setup_host_supports_tls(void)
{
check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
if (host_supports_tls) {
printk(KERN_INFO "Host TLS support detected\n");
printk(KERN_INFO "Detected host type: ");
switch (host_gdt_entry_tls_min) {
case GDT_ENTRY_TLS_MIN_I386:
printk(KERN_CONT "i386");
break;
case GDT_ENTRY_TLS_MIN_X86_64:
printk(KERN_CONT "x86_64");
break;
}
printk(KERN_CONT " (GDT indexes %d to %d)\n",
host_gdt_entry_tls_min,
host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
} else
printk(KERN_ERR " Host TLS support NOT detected! "
"TLS support inside UML will not work\n");
return 0;
}
__initcall(__setup_host_supports_tls);