2 * Copyright (C) 2005 Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
3 * Licensed under the GPL
6 #include <linux/percpu.h>
7 #include <linux/sched.h>
8 #include <linux/syscalls.h>
9 #include <linux/uaccess.h>
10 #include <asm/ptrace-abi.h>
13 #include <sysdep/tls.h>
16 * If needed we can detect when it's uninitialized.
18 * These are initialized in an initcall and unchanged thereafter.
20 static int host_supports_tls = -1;
21 int host_gdt_entry_tls_min;
23 int do_set_thread_area(struct user_desc *info)
29 ret = os_set_thread_area(info, userspace_pid[cpu]);
33 printk(KERN_ERR "PTRACE_SET_THREAD_AREA failed, err = %d, "
34 "index = %d\n", ret, info->entry_number);
39 int do_get_thread_area(struct user_desc *info)
45 ret = os_get_thread_area(info, userspace_pid[cpu]);
49 printk(KERN_ERR "PTRACE_GET_THREAD_AREA failed, err = %d, "
50 "index = %d\n", ret, info->entry_number);
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 dynamic linking
61 * and running against NPTL.
63 static int get_free_idx(struct task_struct* task)
65 struct thread_struct *t = &task->thread;
68 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
69 if (!t->arch.tls_array[idx].present)
70 return idx + GDT_ENTRY_TLS_MIN;
74 static inline void clear_user_desc(struct user_desc* info)
76 /* Postcondition: LDT_empty(info) returns true. */
77 memset(info, 0, sizeof(*info));
80 * Check the LDT_empty or the i386 sys_get_thread_area code - we obtain
81 * indeed an empty user_desc.
83 info->read_exec_only = 1;
84 info->seg_not_present = 1;
89 static int load_TLS(int flags, struct task_struct *to)
94 for (idx = GDT_ENTRY_TLS_MIN; idx < GDT_ENTRY_TLS_MAX; idx++) {
95 struct uml_tls_struct* curr =
96 &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.
102 if (!curr->present) {
103 if (!curr->flushed) {
104 clear_user_desc(&curr->tls);
105 curr->tls.entry_number = idx;
107 WARN_ON(!LDT_empty(&curr->tls));
112 if (!(flags & O_FORCE) && curr->flushed)
115 ret = do_set_thread_area(&curr->tls);
126 * Verify if we need to do a flush for the new process, i.e. if there are any
127 * present desc's, only if they haven't been flushed.
129 static inline int needs_TLS_update(struct task_struct *task)
134 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
135 struct uml_tls_struct* curr =
136 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
139 * Can't test curr->present, we may need to clear a descriptor
151 * On a newly forked process, the TLS descriptors haven't yet been flushed. So
152 * we mark them as such and the first switch_to will do the job.
154 void clear_flushed_tls(struct task_struct *task)
158 for (i = GDT_ENTRY_TLS_MIN; i < GDT_ENTRY_TLS_MAX; i++) {
159 struct uml_tls_struct* curr =
160 &task->thread.arch.tls_array[i - GDT_ENTRY_TLS_MIN];
163 * Still correct to do this, if it wasn't present on the host it
164 * will remain as flushed as it was.
174 * In SKAS0 mode, currently, multiple guest threads sharing the same ->mm have a
175 * common host process. So this is needed in SKAS0 too.
177 * However, if each thread had a different host process (and this was discussed
178 * for SMP support) this won't be needed.
180 * And this will not need be used when (and if) we'll add support to the host
184 int arch_switch_tls(struct task_struct *to)
186 if (!host_supports_tls)
190 * We have no need whatsoever to switch TLS for kernel threads; beyond
191 * that, that would also result in us calling os_set_thread_area with
192 * userspace_pid[cpu] == 0, which gives an error.
195 return load_TLS(O_FORCE, to);
200 static int set_tls_entry(struct task_struct* task, struct user_desc *info,
201 int idx, int flushed)
203 struct thread_struct *t = &task->thread;
205 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
208 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].tls = *info;
209 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].present = 1;
210 t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed = flushed;
215 int arch_copy_tls(struct task_struct *new)
217 struct user_desc info;
218 int idx, ret = -EFAULT;
220 if (copy_from_user(&info,
221 (void __user *) UPT_SI(&new->thread.regs.regs),
226 if (LDT_empty(&info))
229 idx = info.entry_number;
231 ret = set_tls_entry(new, &info, idx, 0);
236 /* XXX: use do_get_thread_area to read the host value? I'm not at all sure! */
237 static int get_tls_entry(struct task_struct *task, struct user_desc *info,
240 struct thread_struct *t = &task->thread;
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;
252 * Temporary debugging check, to make sure that things have been
253 * flushed. This could be triggered if load_TLS() failed.
255 if (unlikely(task == current &&
256 !t->arch.tls_array[idx - GDT_ENTRY_TLS_MIN].flushed)) {
257 printk(KERN_ERR "get_tls_entry: task with pid %d got here "
258 "without flushed TLS.", current->pid);
264 * When the TLS entry has not been set, the values read to user in the
265 * tls_array are 0 (because it's cleared at boot, see
266 * arch/i386/kernel/head.S:cpu_gdt_table). Emulate that.
268 clear_user_desc(info);
269 info->entry_number = idx;
273 SYSCALL_DEFINE1(set_thread_area, struct user_desc __user *, user_desc)
275 struct user_desc info;
278 if (!host_supports_tls)
281 if (copy_from_user(&info, user_desc, sizeof(info)))
284 idx = info.entry_number;
287 idx = get_free_idx(current);
290 info.entry_number = idx;
291 /* Tell the user which slot we chose for him.*/
292 if (put_user(idx, &user_desc->entry_number))
296 ret = do_set_thread_area(&info);
299 return set_tls_entry(current, &info, idx, 1);
303 * Perform set_thread_area on behalf of the traced child.
304 * Note: error handling is not done on the deferred load, and this differ from
305 * i386. However the only possible error are caused by bugs.
307 int ptrace_set_thread_area(struct task_struct *child, int idx,
308 struct user_desc __user *user_desc)
310 struct user_desc info;
312 if (!host_supports_tls)
315 if (copy_from_user(&info, user_desc, sizeof(info)))
318 return set_tls_entry(child, &info, idx, 0);
321 SYSCALL_DEFINE1(get_thread_area, struct user_desc __user *, user_desc)
323 struct user_desc info;
326 if (!host_supports_tls)
329 if (get_user(idx, &user_desc->entry_number))
332 ret = get_tls_entry(current, &info, idx);
336 if (copy_to_user(user_desc, &info, sizeof(info)))
344 * Perform get_thread_area on behalf of the traced child.
346 int ptrace_get_thread_area(struct task_struct *child, int idx,
347 struct user_desc __user *user_desc)
349 struct user_desc info;
352 if (!host_supports_tls)
355 ret = get_tls_entry(child, &info, idx);
359 if (copy_to_user(user_desc, &info, sizeof(info)))
366 * This code is really i386-only, but it detects and logs x86_64 GDT indexes
367 * if a 32-bit UML is running on a 64-bit host.
369 static int __init __setup_host_supports_tls(void)
371 check_host_supports_tls(&host_supports_tls, &host_gdt_entry_tls_min);
372 if (host_supports_tls) {
373 printk(KERN_INFO "Host TLS support detected\n");
374 printk(KERN_INFO "Detected host type: ");
375 switch (host_gdt_entry_tls_min) {
376 case GDT_ENTRY_TLS_MIN_I386:
377 printk(KERN_CONT "i386");
379 case GDT_ENTRY_TLS_MIN_X86_64:
380 printk(KERN_CONT "x86_64");
383 printk(KERN_CONT " (GDT indexes %d to %d)\n",
384 host_gdt_entry_tls_min,
385 host_gdt_entry_tls_min + GDT_ENTRY_TLS_ENTRIES);
387 printk(KERN_ERR " Host TLS support NOT detected! "
388 "TLS support inside UML will not work\n");
392 __initcall(__setup_host_supports_tls);