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..
12 #include <linux/stackprotector.h>
13 #include <linux/cpu.h>
14 #include <linux/errno.h>
15 #include <linux/sched.h>
17 #include <linux/kernel.h>
19 #include <linux/elfcore.h>
20 #include <linux/smp.h>
21 #include <linux/stddef.h>
22 #include <linux/slab.h>
23 #include <linux/vmalloc.h>
24 #include <linux/user.h>
25 #include <linux/interrupt.h>
26 #include <linux/delay.h>
27 #include <linux/reboot.h>
28 #include <linux/init.h>
29 #include <linux/mc146818rtc.h>
30 #include <linux/module.h>
31 #include <linux/kallsyms.h>
32 #include <linux/ptrace.h>
33 #include <linux/personality.h>
34 #include <linux/tick.h>
35 #include <linux/percpu.h>
36 #include <linux/prctl.h>
37 #include <linux/ftrace.h>
38 #include <linux/uaccess.h>
40 #include <linux/kdebug.h>
42 #include <asm/pgtable.h>
43 #include <asm/system.h>
45 #include <asm/processor.h>
48 #ifdef CONFIG_MATH_EMULATION
49 #include <asm/math_emu.h>
52 #include <linux/err.h>
54 #include <asm/tlbflush.h>
57 #include <asm/syscalls.h>
59 #include <asm/debugreg.h>
61 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
64 * Return saved PC of a blocked thread.
66 unsigned long thread_saved_pc(struct task_struct *tsk)
68 return ((unsigned long *)tsk->thread.sp)[3];
72 static inline void play_dead(void)
79 * The idle thread. There's no useful work to be
80 * done, so just try to conserve power and have a
81 * low exit latency (ie sit in a loop waiting for
82 * somebody to say that they'd like to reschedule)
86 int cpu = smp_processor_id();
89 * If we're the non-boot CPU, nothing set the stack canary up
90 * for us. CPU0 already has it initialized but no harm in
91 * doing it again. This is a good place for updating it, as
92 * we wont ever return from this function (so the invalid
93 * canaries already on the stack wont ever trigger).
95 boot_init_stack_canary();
97 current_thread_info()->status |= TS_POLLING;
99 /* endless idle loop with no priority at all */
101 tick_nohz_stop_sched_tick(1);
102 while (!need_resched()) {
107 if (cpu_is_offline(cpu))
111 /* Don't trace irqs off for idle */
112 stop_critical_timings();
114 start_critical_timings();
116 tick_nohz_restart_sched_tick();
117 preempt_enable_no_resched();
123 void __show_regs(struct pt_regs *regs, int all)
125 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
126 unsigned long d0, d1, d2, d3, d6, d7;
128 unsigned short ss, gs;
130 if (user_mode_vm(regs)) {
132 ss = regs->ss & 0xffff;
133 gs = get_user_gs(regs);
135 sp = kernel_stack_pointer(regs);
142 printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
143 (u16)regs->cs, regs->ip, regs->flags,
145 print_symbol("EIP is at %s\n", regs->ip);
147 printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
148 regs->ax, regs->bx, regs->cx, regs->dx);
149 printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
150 regs->si, regs->di, regs->bp, sp);
151 printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
152 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
160 cr4 = read_cr4_safe();
161 printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
168 printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
173 printk("DR6: %08lx DR7: %08lx\n",
177 void show_regs(struct pt_regs *regs)
179 show_registers(regs);
180 show_trace(NULL, regs, ®s->sp, regs->bp);
183 void release_thread(struct task_struct *dead_task)
185 BUG_ON(dead_task->mm);
186 release_vm86_irqs(dead_task);
190 * This gets called before we allocate a new thread and copy
191 * the current task into it.
193 void prepare_to_copy(struct task_struct *tsk)
198 int copy_thread(unsigned long clone_flags, unsigned long sp,
199 unsigned long unused,
200 struct task_struct *p, struct pt_regs *regs)
202 struct pt_regs *childregs;
203 struct task_struct *tsk;
206 childregs = task_pt_regs(p);
211 p->thread.sp = (unsigned long) childregs;
212 p->thread.sp0 = (unsigned long) (childregs+1);
214 p->thread.ip = (unsigned long) ret_from_fork;
216 task_user_gs(p) = get_user_gs(regs);
218 p->thread.io_bitmap_ptr = NULL;
222 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
224 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
225 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
226 IO_BITMAP_BYTES, GFP_KERNEL);
227 if (!p->thread.io_bitmap_ptr) {
228 p->thread.io_bitmap_max = 0;
231 set_tsk_thread_flag(p, TIF_IO_BITMAP);
237 * Set a new TLS for the child thread?
239 if (clone_flags & CLONE_SETTLS)
240 err = do_set_thread_area(p, -1,
241 (struct user_desc __user *)childregs->si, 0);
243 if (err && p->thread.io_bitmap_ptr) {
244 kfree(p->thread.io_bitmap_ptr);
245 p->thread.io_bitmap_max = 0;
248 clear_tsk_thread_flag(p, TIF_DS_AREA_MSR);
249 p->thread.ds_ctx = NULL;
251 clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
252 p->thread.debugctlmsr = 0;
258 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
260 set_user_gs(regs, 0);
263 regs->ds = __USER_DS;
264 regs->es = __USER_DS;
265 regs->ss = __USER_DS;
266 regs->cs = __USER_CS;
270 * Free the old FP and other extended state
272 free_thread_xstate(current);
274 EXPORT_SYMBOL_GPL(start_thread);
278 * switch_to(x,yn) should switch tasks from x to y.
280 * We fsave/fwait so that an exception goes off at the right time
281 * (as a call from the fsave or fwait in effect) rather than to
282 * the wrong process. Lazy FP saving no longer makes any sense
283 * with modern CPU's, and this simplifies a lot of things (SMP
284 * and UP become the same).
286 * NOTE! We used to use the x86 hardware context switching. The
287 * reason for not using it any more becomes apparent when you
288 * try to recover gracefully from saved state that is no longer
289 * valid (stale segment register values in particular). With the
290 * hardware task-switch, there is no way to fix up bad state in
291 * a reasonable manner.
293 * The fact that Intel documents the hardware task-switching to
294 * be slow is a fairly red herring - this code is not noticeably
295 * faster. However, there _is_ some room for improvement here,
296 * so the performance issues may eventually be a valid point.
297 * More important, however, is the fact that this allows us much
300 * The return value (in %ax) will be the "prev" task after
301 * the task-switch, and shows up in ret_from_fork in entry.S,
304 __notrace_funcgraph struct task_struct *
305 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
307 struct thread_struct *prev = &prev_p->thread,
308 *next = &next_p->thread;
309 int cpu = smp_processor_id();
310 struct tss_struct *tss = &per_cpu(init_tss, cpu);
313 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
316 * If the task has used fpu the last 5 timeslices, just do a full
317 * restore of the math state immediately to avoid the trap; the
318 * chances of needing FPU soon are obviously high now
320 preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
322 __unlazy_fpu(prev_p);
324 /* we're going to use this soon, after a few expensive things */
326 prefetch(next->xstate);
334 * Save away %gs. No need to save %fs, as it was saved on the
335 * stack on entry. No need to save %es and %ds, as those are
336 * always kernel segments while inside the kernel. Doing this
337 * before setting the new TLS descriptors avoids the situation
338 * where we temporarily have non-reloadable segments in %fs
339 * and %gs. This could be an issue if the NMI handler ever
340 * used %fs or %gs (it does not today), or if the kernel is
341 * running inside of a hypervisor layer.
343 lazy_save_gs(prev->gs);
346 * Load the per-thread Thread-Local Storage descriptor.
351 * Restore IOPL if needed. In normal use, the flags restore
352 * in the switch assembly will handle this. But if the kernel
353 * is running virtualized at a non-zero CPL, the popf will
354 * not restore flags, so it must be done in a separate step.
356 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
357 set_iopl_mask(next->iopl);
360 * Now maybe handle debug registers and/or IO bitmaps
362 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
363 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
364 __switch_to_xtra(prev_p, next_p, tss);
366 /* If we're going to preload the fpu context, make sure clts
367 is run while we're batching the cpu state updates. */
372 * Leave lazy mode, flushing any hypercalls made here.
373 * This must be done before restoring TLS segments so
374 * the GDT and LDT are properly updated, and must be
375 * done before math_state_restore, so the TS bit is up
378 arch_end_context_switch(next_p);
381 __math_state_restore();
384 * Restore %gs if needed (which is common)
386 if (prev->gs | next->gs)
387 lazy_load_gs(next->gs);
389 percpu_write(current_task, next_p);
394 #define top_esp (THREAD_SIZE - sizeof(unsigned long))
395 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
397 unsigned long get_wchan(struct task_struct *p)
399 unsigned long bp, sp, ip;
400 unsigned long stack_page;
402 if (!p || p == current || p->state == TASK_RUNNING)
404 stack_page = (unsigned long)task_stack_page(p);
406 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
408 /* include/asm-i386/system.h:switch_to() pushes bp last. */
409 bp = *(unsigned long *) sp;
411 if (bp < stack_page || bp > top_ebp+stack_page)
413 ip = *(unsigned long *) (bp+4);
414 if (!in_sched_functions(ip))
416 bp = *(unsigned long *) bp;
417 } while (count++ < 16);