2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3 * Licensed under the GPL
6 #include "linux/config.h"
7 #include "linux/kernel.h"
8 #include "linux/sched.h"
9 #include "linux/slab.h"
10 #include "linux/types.h"
11 #include "asm/uaccess.h"
12 #include "asm/ptrace.h"
13 #include "asm/segment.h"
16 #include "choose-mode.h"
18 #include "kern_util.h"
19 #include "mode_kern.h"
23 #ifdef CONFIG_MODE_SKAS
27 /* If needed we can detect when it's uninitialized. */
28 static int host_supports_tls
= -1;
29 int host_gdt_entry_tls_min
= -1;
31 #ifdef CONFIG_MODE_SKAS
32 int do_set_thread_area_skas(struct user_desc
*info
)
38 ret
= os_set_thread_area(info
, userspace_pid
[cpu
]);
43 int do_get_thread_area_skas(struct user_desc
*info
)
49 ret
= os_get_thread_area(info
, userspace_pid
[cpu
]);
56 * sys_get_thread_area: get a yet unused TLS descriptor index.
57 * XXX: Consider leaving one free slot for glibc usage at first place. This must
58 * be done here (and by changing GDT_ENTRY_TLS_* macros) and nowhere else.
60 * Also, this must be tested when compiling in SKAS mode with dinamic linking
61 * and running against NPTL.
63 static int get_free_idx(struct task_struct
* task
)
65 struct thread_struct
*t
= &task
->thread
;
68 if (!t
->arch
.tls_array
)
69 return GDT_ENTRY_TLS_MIN
;
71 for (idx
= 0; idx
< GDT_ENTRY_TLS_ENTRIES
; idx
++)
72 if (!t
->arch
.tls_array
[idx
].present
)
73 return idx
+ GDT_ENTRY_TLS_MIN
;
77 static inline void clear_user_desc(struct user_desc
* info
)
79 /* Postcondition: LDT_empty(info) returns true. */
80 memset(info
, 0, sizeof(*info
));
82 /* Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
83 * indeed an empty user_desc.
85 info
->read_exec_only
= 1;
86 info
->seg_not_present
= 1;
91 static int load_TLS(int flags
, struct task_struct
*to
)
96 for (idx
= GDT_ENTRY_TLS_MIN
; idx
< GDT_ENTRY_TLS_MAX
; idx
++) {
97 struct uml_tls_struct
* curr
= &to
->thread
.arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
];
99 /* Actually, now if it wasn't flushed it gets cleared and
100 * flushed to the host, which will clear it.*/
101 if (!curr
->present
) {
102 if (!curr
->flushed
) {
103 clear_user_desc(&curr
->tls
);
104 curr
->tls
.entry_number
= idx
;
106 WARN_ON(!LDT_empty(&curr
->tls
));
111 if (!(flags
& O_FORCE
) && curr
->flushed
)
114 ret
= do_set_thread_area(&curr
->tls
);
124 /* Verify if we need to do a flush for the new process, i.e. if there are any
125 * present desc's, only if they haven't been flushed.
127 static inline int needs_TLS_update(struct task_struct
*task
)
132 for (i
= GDT_ENTRY_TLS_MIN
; i
< GDT_ENTRY_TLS_MAX
; i
++) {
133 struct uml_tls_struct
* curr
= &task
->thread
.arch
.tls_array
[i
- GDT_ENTRY_TLS_MIN
];
135 /* Can't test curr->present, we may need to clear a descriptor
136 * which had a value. */
145 /* On a newly forked process, the TLS descriptors haven't yet been flushed. So
146 * we mark them as such and the first switch_to will do the job.
148 void clear_flushed_tls(struct task_struct
*task
)
152 for (i
= GDT_ENTRY_TLS_MIN
; i
< GDT_ENTRY_TLS_MAX
; i
++) {
153 struct uml_tls_struct
* curr
= &task
->thread
.arch
.tls_array
[i
- GDT_ENTRY_TLS_MIN
];
155 /* Still correct to do this, if it wasn't present on the host it
156 * will remain as flushed as it was. */
164 /* In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
165 * common host process. So this is needed in SKAS0 too.
167 * However, if each thread had a different host process (and this was discussed
168 * for SMP support) this won't be needed.
170 * And this will not need be used when (and if) we'll add support to the host
173 int arch_switch_tls_skas(struct task_struct
*from
, struct task_struct
*to
)
175 if (!host_supports_tls
)
178 /* We have no need whatsoever to switch TLS for kernel threads; beyond
179 * that, that would also result in us calling os_set_thread_area with
180 * userspace_pid[cpu] == 0, which gives an error. */
182 return load_TLS(O_FORCE
, to
);
187 int arch_switch_tls_tt(struct task_struct
*from
, struct task_struct
*to
)
189 if (!host_supports_tls
)
192 if (needs_TLS_update(to
))
193 return load_TLS(0, to
);
198 static int set_tls_entry(struct task_struct
* task
, struct user_desc
*info
,
199 int idx
, int flushed
)
201 struct thread_struct
*t
= &task
->thread
;
203 if (idx
< GDT_ENTRY_TLS_MIN
|| idx
> GDT_ENTRY_TLS_MAX
)
206 t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].tls
= *info
;
207 t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].present
= 1;
208 t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].flushed
= flushed
;
213 int arch_copy_tls(struct task_struct
*new)
215 struct user_desc info
;
216 int idx
, ret
= -EFAULT
;
218 if (copy_from_user(&info
,
219 (void __user
*) UPT_ESI(&new->thread
.regs
.regs
),
224 if (LDT_empty(&info
))
227 idx
= info
.entry_number
;
229 ret
= set_tls_entry(new, &info
, idx
, 0);
234 /* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
235 static int get_tls_entry(struct task_struct
* task
, struct user_desc
*info
, int idx
)
237 struct thread_struct
*t
= &task
->thread
;
239 if (!t
->arch
.tls_array
)
242 if (idx
< GDT_ENTRY_TLS_MIN
|| idx
> GDT_ENTRY_TLS_MAX
)
245 if (!t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].present
)
248 *info
= t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].tls
;
251 /* Temporary debugging check, to make sure that things have been
252 * flushed. This could be triggered if load_TLS() failed.
254 if (unlikely(task
== current
&& !t
->arch
.tls_array
[idx
- GDT_ENTRY_TLS_MIN
].flushed
)) {
255 printk(KERN_ERR
"get_tls_entry: task with pid %d got here "
256 "without flushed TLS.", current
->pid
);
261 /* When the TLS entry has not been set, the values read to user in the
262 * tls_array are 0 (because it's cleared at boot, see
263 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
265 clear_user_desc(info
);
266 info
->entry_number
= idx
;
270 asmlinkage
int sys_set_thread_area(struct user_desc __user
*user_desc
)
272 struct user_desc info
;
275 if (!host_supports_tls
)
278 if (copy_from_user(&info
, user_desc
, sizeof(info
)))
281 idx
= info
.entry_number
;
284 idx
= get_free_idx(current
);
287 info
.entry_number
= idx
;
288 /* Tell the user which slot we chose for him.*/
289 if (put_user(idx
, &user_desc
->entry_number
))
293 ret
= CHOOSE_MODE_PROC(do_set_thread_area_tt
, do_set_thread_area_skas
, &info
);
296 return set_tls_entry(current
, &info
, idx
, 1);
300 * Perform set_thread_area on behalf of the traced child.
301 * Note: error handling is not done on the deferred load, and this differ from
302 * i386. However the only possible error are caused by bugs.
304 int ptrace_set_thread_area(struct task_struct
*child
, int idx
,
305 struct user_desc __user
*user_desc
)
307 struct user_desc info
;
309 if (!host_supports_tls
)
312 if (copy_from_user(&info
, user_desc
, sizeof(info
)))
315 return set_tls_entry(child
, &info
, idx
, 0);
318 asmlinkage
int sys_get_thread_area(struct user_desc __user
*user_desc
)
320 struct user_desc info
;
323 if (!host_supports_tls
)
326 if (get_user(idx
, &user_desc
->entry_number
))
329 ret
= get_tls_entry(current
, &info
, idx
);
333 if (copy_to_user(user_desc
, &info
, sizeof(info
)))
341 * Perform get_thread_area on behalf of the traced child.
343 int ptrace_get_thread_area(struct task_struct
*child
, int idx
,
344 struct user_desc __user
*user_desc
)
346 struct user_desc info
;
349 if (!host_supports_tls
)
352 ret
= get_tls_entry(child
, &info
, idx
);
356 if (copy_to_user(user_desc
, &info
, sizeof(info
)))
363 /* XXX: This part is probably common to i386 and x86-64. Don't create a common
364 * file for now, do that when implementing x86-64 support.*/
365 static int __init
__setup_host_supports_tls(void) {
366 check_host_supports_tls(&host_supports_tls
, &host_gdt_entry_tls_min
);
367 if (host_supports_tls
) {
368 printk(KERN_INFO
"Host TLS support detected\n");
369 printk(KERN_INFO
"Detected host type: ");
370 switch (host_gdt_entry_tls_min
) {
371 case GDT_ENTRY_TLS_MIN_I386
:
374 case GDT_ENTRY_TLS_MIN_X86_64
:
379 printk(KERN_ERR
" Host TLS support NOT detected! "
380 "TLS support inside UML will not work\n");
384 __initcall(__setup_host_supports_tls
);