407 lines
10 KiB
C
407 lines
10 KiB
C
/*
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* Copyright (C) 1995 Linus Torvalds
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*
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* Pentium III FXSR, SSE support
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* Gareth Hughes <gareth@valinux.com>, May 2000
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*/
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/*
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* This file handles the architecture-dependent parts of process handling..
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*/
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#include <linux/stackprotector.h>
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#include <linux/cpu.h>
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/elfcore.h>
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#include <linux/smp.h>
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#include <linux/stddef.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/user.h>
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#include <linux/interrupt.h>
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#include <linux/delay.h>
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#include <linux/reboot.h>
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#include <linux/init.h>
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#include <linux/mc146818rtc.h>
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#include <linux/module.h>
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#include <linux/kallsyms.h>
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#include <linux/ptrace.h>
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#include <linux/personality.h>
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#include <linux/tick.h>
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#include <linux/percpu.h>
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#include <linux/prctl.h>
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#include <linux/ftrace.h>
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#include <linux/uaccess.h>
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#include <linux/io.h>
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#include <linux/kdebug.h>
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#include <asm/pgtable.h>
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#include <asm/system.h>
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#include <asm/ldt.h>
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#include <asm/processor.h>
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#include <asm/i387.h>
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#include <asm/desc.h>
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#ifdef CONFIG_MATH_EMULATION
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#include <asm/math_emu.h>
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#endif
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#include <linux/err.h>
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#include <asm/tlbflush.h>
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#include <asm/cpu.h>
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#include <asm/idle.h>
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#include <asm/syscalls.h>
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#include <asm/debugreg.h>
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asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
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/*
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* Return saved PC of a blocked thread.
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*/
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unsigned long thread_saved_pc(struct task_struct *tsk)
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{
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return ((unsigned long *)tsk->thread.sp)[3];
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}
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#ifndef CONFIG_SMP
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static inline void play_dead(void)
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{
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BUG();
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}
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#endif
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/*
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* The idle thread. There's no useful work to be
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* done, so just try to conserve power and have a
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* low exit latency (ie sit in a loop waiting for
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* somebody to say that they'd like to reschedule)
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*/
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void cpu_idle(void)
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{
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int cpu = smp_processor_id();
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/*
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* If we're the non-boot CPU, nothing set the stack canary up
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* for us. CPU0 already has it initialized but no harm in
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* doing it again. This is a good place for updating it, as
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* we wont ever return from this function (so the invalid
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* canaries already on the stack wont ever trigger).
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*/
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boot_init_stack_canary();
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current_thread_info()->status |= TS_POLLING;
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/* endless idle loop with no priority at all */
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while (1) {
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tick_nohz_stop_sched_tick(1);
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while (!need_resched()) {
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check_pgt_cache();
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rmb();
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if (cpu_is_offline(cpu))
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play_dead();
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local_irq_disable();
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/* Don't trace irqs off for idle */
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stop_critical_timings();
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pm_idle();
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start_critical_timings();
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}
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tick_nohz_restart_sched_tick();
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preempt_enable_no_resched();
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schedule();
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preempt_disable();
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}
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}
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void __show_regs(struct pt_regs *regs, int all)
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{
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unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
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unsigned long d0, d1, d2, d3, d6, d7;
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unsigned long sp;
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unsigned short ss, gs;
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if (user_mode_vm(regs)) {
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sp = regs->sp;
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ss = regs->ss & 0xffff;
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gs = get_user_gs(regs);
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} else {
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sp = kernel_stack_pointer(regs);
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savesegment(ss, ss);
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savesegment(gs, gs);
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}
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show_regs_common();
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printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
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(u16)regs->cs, regs->ip, regs->flags,
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smp_processor_id());
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print_symbol("EIP is at %s\n", regs->ip);
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printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
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regs->ax, regs->bx, regs->cx, regs->dx);
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printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
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regs->si, regs->di, regs->bp, sp);
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printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
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(u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
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if (!all)
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return;
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cr0 = read_cr0();
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cr2 = read_cr2();
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cr3 = read_cr3();
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cr4 = read_cr4_safe();
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printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
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cr0, cr2, cr3, cr4);
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get_debugreg(d0, 0);
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get_debugreg(d1, 1);
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get_debugreg(d2, 2);
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get_debugreg(d3, 3);
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printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
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d0, d1, d2, d3);
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get_debugreg(d6, 6);
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get_debugreg(d7, 7);
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printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
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d6, d7);
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}
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void release_thread(struct task_struct *dead_task)
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{
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BUG_ON(dead_task->mm);
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release_vm86_irqs(dead_task);
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}
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/*
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* This gets called before we allocate a new thread and copy
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* the current task into it.
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*/
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void prepare_to_copy(struct task_struct *tsk)
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{
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unlazy_fpu(tsk);
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}
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int copy_thread(unsigned long clone_flags, unsigned long sp,
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unsigned long unused,
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struct task_struct *p, struct pt_regs *regs)
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{
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struct pt_regs *childregs;
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struct task_struct *tsk;
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int err;
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childregs = task_pt_regs(p);
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*childregs = *regs;
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childregs->ax = 0;
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childregs->sp = sp;
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p->thread.sp = (unsigned long) childregs;
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p->thread.sp0 = (unsigned long) (childregs+1);
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p->thread.ip = (unsigned long) ret_from_fork;
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task_user_gs(p) = get_user_gs(regs);
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p->thread.io_bitmap_ptr = NULL;
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tsk = current;
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err = -ENOMEM;
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memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
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if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
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p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
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IO_BITMAP_BYTES, GFP_KERNEL);
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if (!p->thread.io_bitmap_ptr) {
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p->thread.io_bitmap_max = 0;
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return -ENOMEM;
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}
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set_tsk_thread_flag(p, TIF_IO_BITMAP);
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}
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err = 0;
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/*
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* Set a new TLS for the child thread?
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*/
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if (clone_flags & CLONE_SETTLS)
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err = do_set_thread_area(p, -1,
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(struct user_desc __user *)childregs->si, 0);
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if (err && p->thread.io_bitmap_ptr) {
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kfree(p->thread.io_bitmap_ptr);
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p->thread.io_bitmap_max = 0;
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}
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return err;
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}
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void
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start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
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{
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set_user_gs(regs, 0);
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regs->fs = 0;
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set_fs(USER_DS);
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regs->ds = __USER_DS;
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regs->es = __USER_DS;
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regs->ss = __USER_DS;
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regs->cs = __USER_CS;
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regs->ip = new_ip;
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regs->sp = new_sp;
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/*
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* Free the old FP and other extended state
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*/
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free_thread_xstate(current);
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}
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EXPORT_SYMBOL_GPL(start_thread);
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/*
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* switch_to(x,yn) should switch tasks from x to y.
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*
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* We fsave/fwait so that an exception goes off at the right time
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* (as a call from the fsave or fwait in effect) rather than to
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* the wrong process. Lazy FP saving no longer makes any sense
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* with modern CPU's, and this simplifies a lot of things (SMP
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* and UP become the same).
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*
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* NOTE! We used to use the x86 hardware context switching. The
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* reason for not using it any more becomes apparent when you
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* try to recover gracefully from saved state that is no longer
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* valid (stale segment register values in particular). With the
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* hardware task-switch, there is no way to fix up bad state in
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* a reasonable manner.
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*
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* The fact that Intel documents the hardware task-switching to
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* be slow is a fairly red herring - this code is not noticeably
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* faster. However, there _is_ some room for improvement here,
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* so the performance issues may eventually be a valid point.
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* More important, however, is the fact that this allows us much
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* more flexibility.
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*
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* The return value (in %ax) will be the "prev" task after
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* the task-switch, and shows up in ret_from_fork in entry.S,
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* for example.
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*/
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__notrace_funcgraph struct task_struct *
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__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
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{
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struct thread_struct *prev = &prev_p->thread,
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*next = &next_p->thread;
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int cpu = smp_processor_id();
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struct tss_struct *tss = &per_cpu(init_tss, cpu);
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bool preload_fpu;
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/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
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/*
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* If the task has used fpu the last 5 timeslices, just do a full
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* restore of the math state immediately to avoid the trap; the
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* chances of needing FPU soon are obviously high now
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*/
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preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
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__unlazy_fpu(prev_p);
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/* we're going to use this soon, after a few expensive things */
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if (preload_fpu)
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prefetch(next->fpu.state);
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/*
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* Reload esp0.
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*/
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load_sp0(tss, next);
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/*
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* Save away %gs. No need to save %fs, as it was saved on the
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* stack on entry. No need to save %es and %ds, as those are
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* always kernel segments while inside the kernel. Doing this
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* before setting the new TLS descriptors avoids the situation
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* where we temporarily have non-reloadable segments in %fs
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* and %gs. This could be an issue if the NMI handler ever
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* used %fs or %gs (it does not today), or if the kernel is
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* running inside of a hypervisor layer.
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*/
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lazy_save_gs(prev->gs);
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/*
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* Load the per-thread Thread-Local Storage descriptor.
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*/
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load_TLS(next, cpu);
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/*
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* Restore IOPL if needed. In normal use, the flags restore
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* in the switch assembly will handle this. But if the kernel
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* is running virtualized at a non-zero CPL, the popf will
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* not restore flags, so it must be done in a separate step.
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*/
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if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
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set_iopl_mask(next->iopl);
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/*
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* Now maybe handle debug registers and/or IO bitmaps
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*/
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if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
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task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
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__switch_to_xtra(prev_p, next_p, tss);
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/* If we're going to preload the fpu context, make sure clts
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is run while we're batching the cpu state updates. */
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if (preload_fpu)
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clts();
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/*
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* Leave lazy mode, flushing any hypercalls made here.
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* This must be done before restoring TLS segments so
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* the GDT and LDT are properly updated, and must be
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* done before math_state_restore, so the TS bit is up
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* to date.
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*/
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arch_end_context_switch(next_p);
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if (preload_fpu)
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__math_state_restore();
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/*
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* Restore %gs if needed (which is common)
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*/
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if (prev->gs | next->gs)
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lazy_load_gs(next->gs);
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percpu_write(current_task, next_p);
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return prev_p;
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}
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#define top_esp (THREAD_SIZE - sizeof(unsigned long))
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#define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
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unsigned long get_wchan(struct task_struct *p)
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{
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unsigned long bp, sp, ip;
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unsigned long stack_page;
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int count = 0;
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if (!p || p == current || p->state == TASK_RUNNING)
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return 0;
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stack_page = (unsigned long)task_stack_page(p);
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sp = p->thread.sp;
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if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
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return 0;
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/* include/asm-i386/system.h:switch_to() pushes bp last. */
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bp = *(unsigned long *) sp;
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do {
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if (bp < stack_page || bp > top_ebp+stack_page)
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return 0;
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ip = *(unsigned long *) (bp+4);
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if (!in_sched_functions(ip))
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return ip;
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bp = *(unsigned long *) bp;
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} while (count++ < 16);
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return 0;
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}
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