2 * linux/arch/i386/kernel/process.c
4 * Copyright (C) 1995 Linus Torvalds
6 * Pentium III FXSR, SSE support
7 * Gareth Hughes <gareth@valinux.com>, May 2000
11 * This file handles the architecture-dependent parts of process handling..
16 #include <linux/cpu.h>
17 #include <linux/errno.h>
18 #include <linux/sched.h>
20 #include <linux/kernel.h>
22 #include <linux/elfcore.h>
23 #include <linux/smp.h>
24 #include <linux/smp_lock.h>
25 #include <linux/stddef.h>
26 #include <linux/slab.h>
27 #include <linux/vmalloc.h>
28 #include <linux/user.h>
29 #include <linux/a.out.h>
30 #include <linux/interrupt.h>
31 #include <linux/utsname.h>
32 #include <linux/delay.h>
33 #include <linux/reboot.h>
34 #include <linux/init.h>
35 #include <linux/mc146818rtc.h>
36 #include <linux/module.h>
37 #include <linux/kallsyms.h>
38 #include <linux/ptrace.h>
39 #include <linux/random.h>
40 #include <linux/personality.h>
41 #include <linux/tick.h>
43 #include <asm/uaccess.h>
44 #include <asm/pgtable.h>
45 #include <asm/system.h>
48 #include <asm/processor.h>
52 #ifdef CONFIG_MATH_EMULATION
53 #include <asm/math_emu.h>
56 #include <linux/err.h>
58 #include <asm/tlbflush.h>
62 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
64 static int hlt_counter;
66 unsigned long boot_option_idle_override = 0;
67 EXPORT_SYMBOL(boot_option_idle_override);
70 * Return saved PC of a blocked thread.
72 unsigned long thread_saved_pc(struct task_struct *tsk)
74 return ((unsigned long *)tsk->thread.esp)[3];
78 * Powermanagement idle function, if any..
80 void (*pm_idle)(void);
81 EXPORT_SYMBOL(pm_idle);
82 static DEFINE_PER_CPU(unsigned int, cpu_idle_state);
84 void disable_hlt(void)
89 EXPORT_SYMBOL(disable_hlt);
96 EXPORT_SYMBOL(enable_hlt);
99 * We use this if we don't have any better
102 void default_idle(void)
104 if (!hlt_counter && boot_cpu_data.hlt_works_ok) {
105 current_thread_info()->status &= ~TS_POLLING;
107 * TS_POLLING-cleared state must be visible before we
114 safe_halt(); /* enables interrupts racelessly */
117 current_thread_info()->status |= TS_POLLING;
119 /* loop is done by the caller */
123 #ifdef CONFIG_APM_MODULE
124 EXPORT_SYMBOL(default_idle);
128 * On SMP it's slightly faster (but much more power-consuming!)
129 * to poll the ->work.need_resched flag instead of waiting for the
130 * cross-CPU IPI to arrive. Use this option with caution.
132 static void poll_idle (void)
137 #ifdef CONFIG_HOTPLUG_CPU
139 /* We don't actually take CPU down, just spin without interrupts. */
140 static inline void play_dead(void)
142 /* This must be done before dead CPU ack */
147 __get_cpu_var(cpu_state) = CPU_DEAD;
150 * With physical CPU hotplug, we should halt the cpu
157 static inline void play_dead(void)
161 #endif /* CONFIG_HOTPLUG_CPU */
164 * The idle thread. There's no useful work to be
165 * done, so just try to conserve power and have a
166 * low exit latency (ie sit in a loop waiting for
167 * somebody to say that they'd like to reschedule)
171 int cpu = smp_processor_id();
173 current_thread_info()->status |= TS_POLLING;
175 /* endless idle loop with no priority at all */
177 tick_nohz_stop_sched_tick();
178 while (!need_resched()) {
181 if (__get_cpu_var(cpu_idle_state))
182 __get_cpu_var(cpu_idle_state) = 0;
190 if (cpu_is_offline(cpu))
193 __get_cpu_var(irq_stat).idle_timestamp = jiffies;
196 tick_nohz_restart_sched_tick();
197 preempt_enable_no_resched();
203 void cpu_idle_wait(void)
205 unsigned int cpu, this_cpu = get_cpu();
206 cpumask_t map, tmp = current->cpus_allowed;
208 set_cpus_allowed(current, cpumask_of_cpu(this_cpu));
212 for_each_online_cpu(cpu) {
213 per_cpu(cpu_idle_state, cpu) = 1;
217 __get_cpu_var(cpu_idle_state) = 0;
222 for_each_online_cpu(cpu) {
223 if (cpu_isset(cpu, map) && !per_cpu(cpu_idle_state, cpu))
226 cpus_and(map, map, cpu_online_map);
227 } while (!cpus_empty(map));
229 set_cpus_allowed(current, tmp);
231 EXPORT_SYMBOL_GPL(cpu_idle_wait);
234 * This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
235 * which can obviate IPI to trigger checking of need_resched.
236 * We execute MONITOR against need_resched and enter optimized wait state
237 * through MWAIT. Whenever someone changes need_resched, we would be woken
238 * up from MWAIT (without an IPI).
240 * New with Core Duo processors, MWAIT can take some hints based on CPU
243 void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
245 if (!need_resched()) {
246 __monitor((void *)¤t_thread_info()->flags, 0, 0);
253 /* Default MONITOR/MWAIT with no hints, used for default C1 state */
254 static void mwait_idle(void)
257 mwait_idle_with_hints(0, 0);
260 void __devinit select_idle_routine(const struct cpuinfo_x86 *c)
262 if (cpu_has(c, X86_FEATURE_MWAIT)) {
263 printk("monitor/mwait feature present.\n");
265 * Skip, if setup has overridden idle.
266 * One CPU supports mwait => All CPUs supports mwait
269 printk("using mwait in idle threads.\n");
270 pm_idle = mwait_idle;
275 static int __init idle_setup(char *str)
277 if (!strcmp(str, "poll")) {
278 printk("using polling idle threads.\n");
280 #ifdef CONFIG_X86_SMP
281 if (smp_num_siblings > 1)
282 printk("WARNING: polling idle and HT enabled, performance may degrade.\n");
284 } else if (!strcmp(str, "mwait"))
289 boot_option_idle_override = 1;
292 early_param("idle", idle_setup);
294 void show_regs(struct pt_regs * regs)
296 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
299 printk("Pid: %d, comm: %20s\n", current->pid, current->comm);
300 printk("EIP: %04x:[<%08lx>] CPU: %d\n",0xffff & regs->xcs,regs->eip, smp_processor_id());
301 print_symbol("EIP is at %s\n", regs->eip);
303 if (user_mode_vm(regs))
304 printk(" ESP: %04x:%08lx",0xffff & regs->xss,regs->esp);
305 printk(" EFLAGS: %08lx %s (%s %.*s)\n",
306 regs->eflags, print_tainted(), init_utsname()->release,
307 (int)strcspn(init_utsname()->version, " "),
308 init_utsname()->version);
309 printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
310 regs->eax,regs->ebx,regs->ecx,regs->edx);
311 printk("ESI: %08lx EDI: %08lx EBP: %08lx",
312 regs->esi, regs->edi, regs->ebp);
313 printk(" DS: %04x ES: %04x FS: %04x\n",
314 0xffff & regs->xds,0xffff & regs->xes, 0xffff & regs->xfs);
319 cr4 = read_cr4_safe();
320 printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
321 show_trace(NULL, regs, ®s->esp);
325 * This gets run with %ebx containing the
326 * function to call, and %edx containing
329 extern void kernel_thread_helper(void);
332 * Create a kernel thread
334 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
338 memset(®s, 0, sizeof(regs));
340 regs.ebx = (unsigned long) fn;
341 regs.edx = (unsigned long) arg;
343 regs.xds = __USER_DS;
344 regs.xes = __USER_DS;
345 regs.xfs = __KERNEL_PDA;
347 regs.eip = (unsigned long) kernel_thread_helper;
348 regs.xcs = __KERNEL_CS | get_kernel_rpl();
349 regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
351 /* Ok, create the new process.. */
352 return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
354 EXPORT_SYMBOL(kernel_thread);
357 * Free current thread data structures etc..
359 void exit_thread(void)
361 /* The process may have allocated an io port bitmap... nuke it. */
362 if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
363 struct task_struct *tsk = current;
364 struct thread_struct *t = &tsk->thread;
366 struct tss_struct *tss = &per_cpu(init_tss, cpu);
368 kfree(t->io_bitmap_ptr);
369 t->io_bitmap_ptr = NULL;
370 clear_thread_flag(TIF_IO_BITMAP);
372 * Careful, clear this in the TSS too:
374 memset(tss->io_bitmap, 0xff, tss->io_bitmap_max);
375 t->io_bitmap_max = 0;
376 tss->io_bitmap_owner = NULL;
377 tss->io_bitmap_max = 0;
378 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
383 void flush_thread(void)
385 struct task_struct *tsk = current;
387 memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
388 memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
389 clear_tsk_thread_flag(tsk, TIF_DEBUG);
391 * Forget coprocessor state..
397 void release_thread(struct task_struct *dead_task)
399 BUG_ON(dead_task->mm);
400 release_vm86_irqs(dead_task);
404 * This gets called before we allocate a new thread and copy
405 * the current task into it.
407 void prepare_to_copy(struct task_struct *tsk)
412 int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
413 unsigned long unused,
414 struct task_struct * p, struct pt_regs * regs)
416 struct pt_regs * childregs;
417 struct task_struct *tsk;
420 childregs = task_pt_regs(p);
423 childregs->esp = esp;
425 p->thread.esp = (unsigned long) childregs;
426 p->thread.esp0 = (unsigned long) (childregs+1);
428 p->thread.eip = (unsigned long) ret_from_fork;
430 savesegment(gs,p->thread.gs);
433 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
434 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
435 IO_BITMAP_BYTES, GFP_KERNEL);
436 if (!p->thread.io_bitmap_ptr) {
437 p->thread.io_bitmap_max = 0;
440 set_tsk_thread_flag(p, TIF_IO_BITMAP);
444 * Set a new TLS for the child thread?
446 if (clone_flags & CLONE_SETTLS) {
447 struct desc_struct *desc;
448 struct user_desc info;
452 if (copy_from_user(&info, (void __user *)childregs->esi, sizeof(info)))
455 if (LDT_empty(&info))
458 idx = info.entry_number;
459 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
462 desc = p->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
463 desc->a = LDT_entry_a(&info);
464 desc->b = LDT_entry_b(&info);
469 if (err && p->thread.io_bitmap_ptr) {
470 kfree(p->thread.io_bitmap_ptr);
471 p->thread.io_bitmap_max = 0;
477 * fill in the user structure for a core dump..
479 void dump_thread(struct pt_regs * regs, struct user * dump)
483 /* changed the size calculations - should hopefully work better. lbt */
484 dump->magic = CMAGIC;
485 dump->start_code = 0;
486 dump->start_stack = regs->esp & ~(PAGE_SIZE - 1);
487 dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
488 dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
489 dump->u_dsize -= dump->u_tsize;
491 for (i = 0; i < 8; i++)
492 dump->u_debugreg[i] = current->thread.debugreg[i];
494 if (dump->start_stack < TASK_SIZE)
495 dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
497 dump->regs.ebx = regs->ebx;
498 dump->regs.ecx = regs->ecx;
499 dump->regs.edx = regs->edx;
500 dump->regs.esi = regs->esi;
501 dump->regs.edi = regs->edi;
502 dump->regs.ebp = regs->ebp;
503 dump->regs.eax = regs->eax;
504 dump->regs.ds = regs->xds;
505 dump->regs.es = regs->xes;
506 dump->regs.fs = regs->xfs;
507 savesegment(gs,dump->regs.gs);
508 dump->regs.orig_eax = regs->orig_eax;
509 dump->regs.eip = regs->eip;
510 dump->regs.cs = regs->xcs;
511 dump->regs.eflags = regs->eflags;
512 dump->regs.esp = regs->esp;
513 dump->regs.ss = regs->xss;
515 dump->u_fpvalid = dump_fpu (regs, &dump->i387);
517 EXPORT_SYMBOL(dump_thread);
520 * Capture the user space registers if the task is not running (in user space)
522 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
524 struct pt_regs ptregs = *task_pt_regs(tsk);
525 ptregs.xcs &= 0xffff;
526 ptregs.xds &= 0xffff;
527 ptregs.xes &= 0xffff;
528 ptregs.xss &= 0xffff;
530 elf_core_copy_regs(regs, &ptregs);
535 static noinline void __switch_to_xtra(struct task_struct *next_p,
536 struct tss_struct *tss)
538 struct thread_struct *next;
540 next = &next_p->thread;
542 if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
543 set_debugreg(next->debugreg[0], 0);
544 set_debugreg(next->debugreg[1], 1);
545 set_debugreg(next->debugreg[2], 2);
546 set_debugreg(next->debugreg[3], 3);
548 set_debugreg(next->debugreg[6], 6);
549 set_debugreg(next->debugreg[7], 7);
552 if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
554 * Disable the bitmap via an invalid offset. We still cache
555 * the previous bitmap owner and the IO bitmap contents:
557 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
561 if (likely(next == tss->io_bitmap_owner)) {
563 * Previous owner of the bitmap (hence the bitmap content)
564 * matches the next task, we dont have to do anything but
565 * to set a valid offset in the TSS:
567 tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
571 * Lazy TSS's I/O bitmap copy. We set an invalid offset here
572 * and we let the task to get a GPF in case an I/O instruction
573 * is performed. The handler of the GPF will verify that the
574 * faulting task has a valid I/O bitmap and, it true, does the
575 * real copy and restart the instruction. This will save us
576 * redundant copies when the currently switched task does not
577 * perform any I/O during its timeslice.
579 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
583 * This function selects if the context switch from prev to next
584 * has to tweak the TSC disable bit in the cr4.
586 static inline void disable_tsc(struct task_struct *prev_p,
587 struct task_struct *next_p)
589 struct thread_info *prev, *next;
592 * gcc should eliminate the ->thread_info dereference if
593 * has_secure_computing returns 0 at compile time (SECCOMP=n).
595 prev = task_thread_info(prev_p);
596 next = task_thread_info(next_p);
598 if (has_secure_computing(prev) || has_secure_computing(next)) {
600 if (has_secure_computing(prev) &&
601 !has_secure_computing(next)) {
602 write_cr4(read_cr4() & ~X86_CR4_TSD);
603 } else if (!has_secure_computing(prev) &&
604 has_secure_computing(next))
605 write_cr4(read_cr4() | X86_CR4_TSD);
610 * switch_to(x,yn) should switch tasks from x to y.
612 * We fsave/fwait so that an exception goes off at the right time
613 * (as a call from the fsave or fwait in effect) rather than to
614 * the wrong process. Lazy FP saving no longer makes any sense
615 * with modern CPU's, and this simplifies a lot of things (SMP
616 * and UP become the same).
618 * NOTE! We used to use the x86 hardware context switching. The
619 * reason for not using it any more becomes apparent when you
620 * try to recover gracefully from saved state that is no longer
621 * valid (stale segment register values in particular). With the
622 * hardware task-switch, there is no way to fix up bad state in
623 * a reasonable manner.
625 * The fact that Intel documents the hardware task-switching to
626 * be slow is a fairly red herring - this code is not noticeably
627 * faster. However, there _is_ some room for improvement here,
628 * so the performance issues may eventually be a valid point.
629 * More important, however, is the fact that this allows us much
632 * The return value (in %eax) will be the "prev" task after
633 * the task-switch, and shows up in ret_from_fork in entry.S,
636 struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
638 struct thread_struct *prev = &prev_p->thread,
639 *next = &next_p->thread;
640 int cpu = smp_processor_id();
641 struct tss_struct *tss = &per_cpu(init_tss, cpu);
643 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
645 __unlazy_fpu(prev_p);
648 /* we're going to use this soon, after a few expensive things */
649 if (next_p->fpu_counter > 5)
650 prefetch(&next->i387.fxsave);
655 load_esp0(tss, next);
658 * Save away %gs. No need to save %fs, as it was saved on the
659 * stack on entry. No need to save %es and %ds, as those are
660 * always kernel segments while inside the kernel. Doing this
661 * before setting the new TLS descriptors avoids the situation
662 * where we temporarily have non-reloadable segments in %fs
663 * and %gs. This could be an issue if the NMI handler ever
664 * used %fs or %gs (it does not today), or if the kernel is
665 * running inside of a hypervisor layer.
667 savesegment(gs, prev->gs);
670 * Load the per-thread Thread-Local Storage descriptor.
675 * Restore IOPL if needed. In normal use, the flags restore
676 * in the switch assembly will handle this. But if the kernel
677 * is running virtualized at a non-zero CPL, the popf will
678 * not restore flags, so it must be done in a separate step.
680 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
681 set_iopl_mask(next->iopl);
684 * Now maybe handle debug registers and/or IO bitmaps
686 if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW)
687 || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)))
688 __switch_to_xtra(next_p, tss);
690 disable_tsc(prev_p, next_p);
693 * Leave lazy mode, flushing any hypercalls made here.
694 * This must be done before restoring TLS segments so
695 * the GDT and LDT are properly updated, and must be
696 * done before math_state_restore, so the TS bit is up
699 arch_leave_lazy_cpu_mode();
701 /* If the task has used fpu the last 5 timeslices, just do a full
702 * restore of the math state immediately to avoid the trap; the
703 * chances of needing FPU soon are obviously high now
705 if (next_p->fpu_counter > 5)
706 math_state_restore();
709 * Restore %gs if needed (which is common)
711 if (prev->gs | next->gs)
712 loadsegment(gs, next->gs);
714 write_pda(pcurrent, next_p);
719 asmlinkage int sys_fork(struct pt_regs regs)
721 return do_fork(SIGCHLD, regs.esp, ®s, 0, NULL, NULL);
724 asmlinkage int sys_clone(struct pt_regs regs)
726 unsigned long clone_flags;
728 int __user *parent_tidptr, *child_tidptr;
730 clone_flags = regs.ebx;
732 parent_tidptr = (int __user *)regs.edx;
733 child_tidptr = (int __user *)regs.edi;
736 return do_fork(clone_flags, newsp, ®s, 0, parent_tidptr, child_tidptr);
740 * This is trivial, and on the face of it looks like it
741 * could equally well be done in user mode.
743 * Not so, for quite unobvious reasons - register pressure.
744 * In user mode vfork() cannot have a stack frame, and if
745 * done by calling the "clone()" system call directly, you
746 * do not have enough call-clobbered registers to hold all
747 * the information you need.
749 asmlinkage int sys_vfork(struct pt_regs regs)
751 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, ®s, 0, NULL, NULL);
755 * sys_execve() executes a new program.
757 asmlinkage int sys_execve(struct pt_regs regs)
762 filename = getname((char __user *) regs.ebx);
763 error = PTR_ERR(filename);
764 if (IS_ERR(filename))
766 error = do_execve(filename,
767 (char __user * __user *) regs.ecx,
768 (char __user * __user *) regs.edx,
772 current->ptrace &= ~PT_DTRACE;
773 task_unlock(current);
774 /* Make sure we don't return using sysenter.. */
775 set_thread_flag(TIF_IRET);
782 #define top_esp (THREAD_SIZE - sizeof(unsigned long))
783 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
785 unsigned long get_wchan(struct task_struct *p)
787 unsigned long ebp, esp, eip;
788 unsigned long stack_page;
790 if (!p || p == current || p->state == TASK_RUNNING)
792 stack_page = (unsigned long)task_stack_page(p);
794 if (!stack_page || esp < stack_page || esp > top_esp+stack_page)
796 /* include/asm-i386/system.h:switch_to() pushes ebp last. */
797 ebp = *(unsigned long *) esp;
799 if (ebp < stack_page || ebp > top_ebp+stack_page)
801 eip = *(unsigned long *) (ebp+4);
802 if (!in_sched_functions(eip))
804 ebp = *(unsigned long *) ebp;
805 } while (count++ < 16);
810 * sys_alloc_thread_area: get a yet unused TLS descriptor index.
812 static int get_free_idx(void)
814 struct thread_struct *t = ¤t->thread;
817 for (idx = 0; idx < GDT_ENTRY_TLS_ENTRIES; idx++)
818 if (desc_empty(t->tls_array + idx))
819 return idx + GDT_ENTRY_TLS_MIN;
824 * Set a given TLS descriptor:
826 asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
828 struct thread_struct *t = ¤t->thread;
829 struct user_desc info;
830 struct desc_struct *desc;
833 if (copy_from_user(&info, u_info, sizeof(info)))
835 idx = info.entry_number;
838 * index -1 means the kernel should try to find and
839 * allocate an empty descriptor:
842 idx = get_free_idx();
845 if (put_user(idx, &u_info->entry_number))
849 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
852 desc = t->tls_array + idx - GDT_ENTRY_TLS_MIN;
855 * We must not get preempted while modifying the TLS.
859 if (LDT_empty(&info)) {
863 desc->a = LDT_entry_a(&info);
864 desc->b = LDT_entry_b(&info);
874 * Get the current Thread-Local Storage area:
877 #define GET_BASE(desc) ( \
878 (((desc)->a >> 16) & 0x0000ffff) | \
879 (((desc)->b << 16) & 0x00ff0000) | \
880 ( (desc)->b & 0xff000000) )
882 #define GET_LIMIT(desc) ( \
883 ((desc)->a & 0x0ffff) | \
884 ((desc)->b & 0xf0000) )
886 #define GET_32BIT(desc) (((desc)->b >> 22) & 1)
887 #define GET_CONTENTS(desc) (((desc)->b >> 10) & 3)
888 #define GET_WRITABLE(desc) (((desc)->b >> 9) & 1)
889 #define GET_LIMIT_PAGES(desc) (((desc)->b >> 23) & 1)
890 #define GET_PRESENT(desc) (((desc)->b >> 15) & 1)
891 #define GET_USEABLE(desc) (((desc)->b >> 20) & 1)
893 asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
895 struct user_desc info;
896 struct desc_struct *desc;
899 if (get_user(idx, &u_info->entry_number))
901 if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
904 memset(&info, 0, sizeof(info));
906 desc = current->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
908 info.entry_number = idx;
909 info.base_addr = GET_BASE(desc);
910 info.limit = GET_LIMIT(desc);
911 info.seg_32bit = GET_32BIT(desc);
912 info.contents = GET_CONTENTS(desc);
913 info.read_exec_only = !GET_WRITABLE(desc);
914 info.limit_in_pages = GET_LIMIT_PAGES(desc);
915 info.seg_not_present = !GET_PRESENT(desc);
916 info.useable = GET_USEABLE(desc);
918 if (copy_to_user(u_info, &info, sizeof(info)))
923 unsigned long arch_align_stack(unsigned long sp)
925 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
926 sp -= get_random_int() % 8192;