2 * Copyright (C) 1995 Linus Torvalds
4 * Pentium III FXSR, SSE support
5 * Gareth Hughes <gareth@valinux.com>, May 2000
9 * This file handles the architecture-dependent parts of process handling..
14 #include <linux/cpu.h>
15 #include <linux/errno.h>
16 #include <linux/sched.h>
18 #include <linux/kernel.h>
20 #include <linux/elfcore.h>
21 #include <linux/smp.h>
22 #include <linux/stddef.h>
23 #include <linux/slab.h>
24 #include <linux/vmalloc.h>
25 #include <linux/user.h>
26 #include <linux/interrupt.h>
27 #include <linux/utsname.h>
28 #include <linux/delay.h>
29 #include <linux/reboot.h>
30 #include <linux/init.h>
31 #include <linux/mc146818rtc.h>
32 #include <linux/module.h>
33 #include <linux/kallsyms.h>
34 #include <linux/ptrace.h>
35 #include <linux/random.h>
36 #include <linux/personality.h>
37 #include <linux/tick.h>
38 #include <linux/percpu.h>
39 #include <linux/prctl.h>
41 #include <asm/uaccess.h>
42 #include <asm/pgtable.h>
43 #include <asm/system.h>
46 #include <asm/processor.h>
49 #ifdef CONFIG_MATH_EMULATION
50 #include <asm/math_emu.h>
53 #include <linux/err.h>
55 #include <asm/tlbflush.h>
57 #include <asm/kdebug.h>
59 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
61 DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
62 EXPORT_PER_CPU_SYMBOL(current_task);
64 DEFINE_PER_CPU(int, cpu_number);
65 EXPORT_PER_CPU_SYMBOL(cpu_number);
68 * Return saved PC of a blocked thread.
70 unsigned long thread_saved_pc(struct task_struct *tsk)
72 return ((unsigned long *)tsk->thread.sp)[3];
76 static inline void play_dead(void)
83 * The idle thread. There's no useful work to be
84 * done, so just try to conserve power and have a
85 * low exit latency (ie sit in a loop waiting for
86 * somebody to say that they'd like to reschedule)
90 int cpu = smp_processor_id();
92 current_thread_info()->status |= TS_POLLING;
94 /* endless idle loop with no priority at all */
96 tick_nohz_stop_sched_tick(1);
97 while (!need_resched()) {
102 if (rcu_pending(cpu))
103 rcu_check_callbacks(cpu, 0);
105 if (cpu_is_offline(cpu))
109 __get_cpu_var(irq_stat).idle_timestamp = jiffies;
110 /* Don't trace irqs off for idle */
111 stop_critical_timings();
113 start_critical_timings();
115 tick_nohz_restart_sched_tick();
116 preempt_enable_no_resched();
122 void __show_registers(struct pt_regs *regs, int all)
124 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
125 unsigned long d0, d1, d2, d3, d6, d7;
127 unsigned short ss, gs;
129 if (user_mode_vm(regs)) {
131 ss = regs->ss & 0xffff;
134 sp = (unsigned long) (®s->sp);
140 printk("Pid: %d, comm: %s %s (%s %.*s)\n",
141 task_pid_nr(current), current->comm,
142 print_tainted(), init_utsname()->release,
143 (int)strcspn(init_utsname()->version, " "),
144 init_utsname()->version);
146 printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
147 (u16)regs->cs, regs->ip, regs->flags,
149 print_symbol("EIP is at %s\n", regs->ip);
151 printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
152 regs->ax, regs->bx, regs->cx, regs->dx);
153 printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
154 regs->si, regs->di, regs->bp, sp);
155 printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
156 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
164 cr4 = read_cr4_safe();
165 printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
172 printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
177 printk("DR6: %08lx DR7: %08lx\n",
181 void show_regs(struct pt_regs *regs)
183 __show_registers(regs, 1);
184 show_trace(NULL, regs, ®s->sp, regs->bp);
188 * This gets run with %bx containing the
189 * function to call, and %dx containing
192 extern void kernel_thread_helper(void);
195 * Create a kernel thread
197 int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
201 memset(®s, 0, sizeof(regs));
203 regs.bx = (unsigned long) fn;
204 regs.dx = (unsigned long) arg;
208 regs.fs = __KERNEL_PERCPU;
210 regs.ip = (unsigned long) kernel_thread_helper;
211 regs.cs = __KERNEL_CS | get_kernel_rpl();
212 regs.flags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
214 /* Ok, create the new process.. */
215 return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
217 EXPORT_SYMBOL(kernel_thread);
220 * Free current thread data structures etc..
222 void exit_thread(void)
224 /* The process may have allocated an io port bitmap... nuke it. */
225 if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
226 struct task_struct *tsk = current;
227 struct thread_struct *t = &tsk->thread;
229 struct tss_struct *tss = &per_cpu(init_tss, cpu);
231 kfree(t->io_bitmap_ptr);
232 t->io_bitmap_ptr = NULL;
233 clear_thread_flag(TIF_IO_BITMAP);
235 * Careful, clear this in the TSS too:
237 memset(tss->io_bitmap, 0xff, tss->io_bitmap_max);
238 t->io_bitmap_max = 0;
239 tss->io_bitmap_owner = NULL;
240 tss->io_bitmap_max = 0;
241 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
246 void flush_thread(void)
248 struct task_struct *tsk = current;
250 tsk->thread.debugreg0 = 0;
251 tsk->thread.debugreg1 = 0;
252 tsk->thread.debugreg2 = 0;
253 tsk->thread.debugreg3 = 0;
254 tsk->thread.debugreg6 = 0;
255 tsk->thread.debugreg7 = 0;
256 memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
257 clear_tsk_thread_flag(tsk, TIF_DEBUG);
259 * Forget coprocessor state..
261 tsk->fpu_counter = 0;
266 void release_thread(struct task_struct *dead_task)
268 BUG_ON(dead_task->mm);
269 release_vm86_irqs(dead_task);
273 * This gets called before we allocate a new thread and copy
274 * the current task into it.
276 void prepare_to_copy(struct task_struct *tsk)
281 int copy_thread(int nr, unsigned long clone_flags, unsigned long sp,
282 unsigned long unused,
283 struct task_struct * p, struct pt_regs * regs)
285 struct pt_regs * childregs;
286 struct task_struct *tsk;
289 childregs = task_pt_regs(p);
294 p->thread.sp = (unsigned long) childregs;
295 p->thread.sp0 = (unsigned long) (childregs+1);
297 p->thread.ip = (unsigned long) ret_from_fork;
299 savesegment(gs, p->thread.gs);
302 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
303 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
304 IO_BITMAP_BYTES, GFP_KERNEL);
305 if (!p->thread.io_bitmap_ptr) {
306 p->thread.io_bitmap_max = 0;
309 set_tsk_thread_flag(p, TIF_IO_BITMAP);
315 * Set a new TLS for the child thread?
317 if (clone_flags & CLONE_SETTLS)
318 err = do_set_thread_area(p, -1,
319 (struct user_desc __user *)childregs->si, 0);
321 if (err && p->thread.io_bitmap_ptr) {
322 kfree(p->thread.io_bitmap_ptr);
323 p->thread.io_bitmap_max = 0;
329 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
331 __asm__("movl %0, %%gs" :: "r"(0));
334 regs->ds = __USER_DS;
335 regs->es = __USER_DS;
336 regs->ss = __USER_DS;
337 regs->cs = __USER_CS;
341 * Free the old FP and other extended state
343 free_thread_xstate(current);
345 EXPORT_SYMBOL_GPL(start_thread);
347 static void hard_disable_TSC(void)
349 write_cr4(read_cr4() | X86_CR4_TSD);
352 void disable_TSC(void)
355 if (!test_and_set_thread_flag(TIF_NOTSC))
357 * Must flip the CPU state synchronously with
358 * TIF_NOTSC in the current running context.
364 static void hard_enable_TSC(void)
366 write_cr4(read_cr4() & ~X86_CR4_TSD);
369 static void enable_TSC(void)
372 if (test_and_clear_thread_flag(TIF_NOTSC))
374 * Must flip the CPU state synchronously with
375 * TIF_NOTSC in the current running context.
381 int get_tsc_mode(unsigned long adr)
385 if (test_thread_flag(TIF_NOTSC))
386 val = PR_TSC_SIGSEGV;
390 return put_user(val, (unsigned int __user *)adr);
393 int set_tsc_mode(unsigned int val)
395 if (val == PR_TSC_SIGSEGV)
397 else if (val == PR_TSC_ENABLE)
406 __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
407 struct tss_struct *tss)
409 struct thread_struct *prev, *next;
410 unsigned long debugctl;
412 prev = &prev_p->thread;
413 next = &next_p->thread;
415 debugctl = prev->debugctlmsr;
416 if (next->ds_area_msr != prev->ds_area_msr) {
417 /* we clear debugctl to make sure DS
418 * is not in use when we change it */
420 update_debugctlmsr(0);
421 wrmsr(MSR_IA32_DS_AREA, next->ds_area_msr, 0);
424 if (next->debugctlmsr != debugctl)
425 update_debugctlmsr(next->debugctlmsr);
427 if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
428 set_debugreg(next->debugreg0, 0);
429 set_debugreg(next->debugreg1, 1);
430 set_debugreg(next->debugreg2, 2);
431 set_debugreg(next->debugreg3, 3);
433 set_debugreg(next->debugreg6, 6);
434 set_debugreg(next->debugreg7, 7);
437 if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
438 test_tsk_thread_flag(next_p, TIF_NOTSC)) {
439 /* prev and next are different */
440 if (test_tsk_thread_flag(next_p, TIF_NOTSC))
447 if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
448 ptrace_bts_take_timestamp(prev_p, BTS_TASK_DEPARTS);
450 if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
451 ptrace_bts_take_timestamp(next_p, BTS_TASK_ARRIVES);
455 if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
457 * Disable the bitmap via an invalid offset. We still cache
458 * the previous bitmap owner and the IO bitmap contents:
460 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
464 if (likely(next == tss->io_bitmap_owner)) {
466 * Previous owner of the bitmap (hence the bitmap content)
467 * matches the next task, we dont have to do anything but
468 * to set a valid offset in the TSS:
470 tss->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
474 * Lazy TSS's I/O bitmap copy. We set an invalid offset here
475 * and we let the task to get a GPF in case an I/O instruction
476 * is performed. The handler of the GPF will verify that the
477 * faulting task has a valid I/O bitmap and, it true, does the
478 * real copy and restart the instruction. This will save us
479 * redundant copies when the currently switched task does not
480 * perform any I/O during its timeslice.
482 tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET_LAZY;
486 * switch_to(x,yn) should switch tasks from x to y.
488 * We fsave/fwait so that an exception goes off at the right time
489 * (as a call from the fsave or fwait in effect) rather than to
490 * the wrong process. Lazy FP saving no longer makes any sense
491 * with modern CPU's, and this simplifies a lot of things (SMP
492 * and UP become the same).
494 * NOTE! We used to use the x86 hardware context switching. The
495 * reason for not using it any more becomes apparent when you
496 * try to recover gracefully from saved state that is no longer
497 * valid (stale segment register values in particular). With the
498 * hardware task-switch, there is no way to fix up bad state in
499 * a reasonable manner.
501 * The fact that Intel documents the hardware task-switching to
502 * be slow is a fairly red herring - this code is not noticeably
503 * faster. However, there _is_ some room for improvement here,
504 * so the performance issues may eventually be a valid point.
505 * More important, however, is the fact that this allows us much
508 * The return value (in %ax) will be the "prev" task after
509 * the task-switch, and shows up in ret_from_fork in entry.S,
512 struct task_struct * __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
514 struct thread_struct *prev = &prev_p->thread,
515 *next = &next_p->thread;
516 int cpu = smp_processor_id();
517 struct tss_struct *tss = &per_cpu(init_tss, cpu);
519 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
521 __unlazy_fpu(prev_p);
524 /* we're going to use this soon, after a few expensive things */
525 if (next_p->fpu_counter > 5)
526 prefetch(next->xstate);
534 * Save away %gs. No need to save %fs, as it was saved on the
535 * stack on entry. No need to save %es and %ds, as those are
536 * always kernel segments while inside the kernel. Doing this
537 * before setting the new TLS descriptors avoids the situation
538 * where we temporarily have non-reloadable segments in %fs
539 * and %gs. This could be an issue if the NMI handler ever
540 * used %fs or %gs (it does not today), or if the kernel is
541 * running inside of a hypervisor layer.
543 savesegment(gs, prev->gs);
546 * Load the per-thread Thread-Local Storage descriptor.
551 * Restore IOPL if needed. In normal use, the flags restore
552 * in the switch assembly will handle this. But if the kernel
553 * is running virtualized at a non-zero CPL, the popf will
554 * not restore flags, so it must be done in a separate step.
556 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
557 set_iopl_mask(next->iopl);
560 * Now maybe handle debug registers and/or IO bitmaps
562 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
563 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
564 __switch_to_xtra(prev_p, next_p, tss);
567 * Leave lazy mode, flushing any hypercalls made here.
568 * This must be done before restoring TLS segments so
569 * the GDT and LDT are properly updated, and must be
570 * done before math_state_restore, so the TS bit is up
573 arch_leave_lazy_cpu_mode();
575 /* If the task has used fpu the last 5 timeslices, just do a full
576 * restore of the math state immediately to avoid the trap; the
577 * chances of needing FPU soon are obviously high now
579 * tsk_used_math() checks prevent calling math_state_restore(),
580 * which can sleep in the case of !tsk_used_math()
582 if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
583 math_state_restore();
586 * Restore %gs if needed (which is common)
588 if (prev->gs | next->gs)
589 loadsegment(gs, next->gs);
591 x86_write_percpu(current_task, next_p);
596 asmlinkage int sys_fork(struct pt_regs regs)
598 return do_fork(SIGCHLD, regs.sp, ®s, 0, NULL, NULL);
601 asmlinkage int sys_clone(struct pt_regs regs)
603 unsigned long clone_flags;
605 int __user *parent_tidptr, *child_tidptr;
607 clone_flags = regs.bx;
609 parent_tidptr = (int __user *)regs.dx;
610 child_tidptr = (int __user *)regs.di;
613 return do_fork(clone_flags, newsp, ®s, 0, parent_tidptr, child_tidptr);
617 * This is trivial, and on the face of it looks like it
618 * could equally well be done in user mode.
620 * Not so, for quite unobvious reasons - register pressure.
621 * In user mode vfork() cannot have a stack frame, and if
622 * done by calling the "clone()" system call directly, you
623 * do not have enough call-clobbered registers to hold all
624 * the information you need.
626 asmlinkage int sys_vfork(struct pt_regs regs)
628 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.sp, ®s, 0, NULL, NULL);
632 * sys_execve() executes a new program.
634 asmlinkage int sys_execve(struct pt_regs regs)
639 filename = getname((char __user *) regs.bx);
640 error = PTR_ERR(filename);
641 if (IS_ERR(filename))
643 error = do_execve(filename,
644 (char __user * __user *) regs.cx,
645 (char __user * __user *) regs.dx,
648 /* Make sure we don't return using sysenter.. */
649 set_thread_flag(TIF_IRET);
656 #define top_esp (THREAD_SIZE - sizeof(unsigned long))
657 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
659 unsigned long get_wchan(struct task_struct *p)
661 unsigned long bp, sp, ip;
662 unsigned long stack_page;
664 if (!p || p == current || p->state == TASK_RUNNING)
666 stack_page = (unsigned long)task_stack_page(p);
668 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
670 /* include/asm-i386/system.h:switch_to() pushes bp last. */
671 bp = *(unsigned long *) sp;
673 if (bp < stack_page || bp > top_ebp+stack_page)
675 ip = *(unsigned long *) (bp+4);
676 if (!in_sched_functions(ip))
678 bp = *(unsigned long *) bp;
679 } while (count++ < 16);
683 unsigned long arch_align_stack(unsigned long sp)
685 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
686 sp -= get_random_int() % 8192;
690 unsigned long arch_randomize_brk(struct mm_struct *mm)
692 unsigned long range_end = mm->brk + 0x02000000;
693 return randomize_range(mm->brk, range_end, 0) ? : mm->brk;