forked from Minki/linux
224101ed69
Impact: fix lazy context switch API Pass the previous and next tasks into the context switch start end calls, so that the called functions can properly access the task state (esp in end_context_switch, in which the next task is not yet completely current). Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
512 lines
13 KiB
C
512 lines
13 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 <stdarg.h>
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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/utsname.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/random.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/dmi.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/ds.h>
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asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
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DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
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EXPORT_PER_CPU_SYMBOL(current_task);
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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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const char *board;
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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 = (unsigned long) (®s->sp);
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savesegment(ss, ss);
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savesegment(gs, gs);
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}
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printk("\n");
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board = dmi_get_system_info(DMI_PRODUCT_NAME);
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if (!board)
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board = "";
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printk("Pid: %d, comm: %s %s (%s %.*s) %s\n",
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task_pid_nr(current), current->comm,
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print_tainted(), init_utsname()->release,
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(int)strcspn(init_utsname()->version, " "),
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init_utsname()->version, board);
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printk("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("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("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(" 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("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("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("DR6: %08lx DR7: %08lx\n",
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d6, d7);
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}
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void show_regs(struct pt_regs *regs)
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{
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__show_regs(regs, 1);
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show_trace(NULL, regs, ®s->sp, regs->bp);
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}
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/*
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* This gets run with %bx containing the
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* function to call, and %dx containing
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* the "args".
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*/
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extern void kernel_thread_helper(void);
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/*
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* Create a kernel thread
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*/
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int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
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{
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struct pt_regs regs;
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memset(®s, 0, sizeof(regs));
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regs.bx = (unsigned long) fn;
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regs.dx = (unsigned long) arg;
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regs.ds = __USER_DS;
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regs.es = __USER_DS;
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regs.fs = __KERNEL_PERCPU;
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regs.gs = __KERNEL_STACK_CANARY;
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regs.orig_ax = -1;
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regs.ip = (unsigned long) kernel_thread_helper;
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regs.cs = __KERNEL_CS | get_kernel_rpl();
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regs.flags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
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/* Ok, create the new process.. */
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return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
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}
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EXPORT_SYMBOL(kernel_thread);
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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(int nr, 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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tsk = current;
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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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ds_copy_thread(p, current);
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clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
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p->thread.debugctlmsr = 0;
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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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/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
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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 (next_p->fpu_counter > 5)
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prefetch(next->xstate);
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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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/*
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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 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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* tsk_used_math() checks prevent calling math_state_restore(),
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* which can sleep in the case of !tsk_used_math()
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*/
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if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
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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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int sys_clone(struct pt_regs *regs)
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{
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unsigned long clone_flags;
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unsigned long newsp;
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int __user *parent_tidptr, *child_tidptr;
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clone_flags = regs->bx;
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newsp = regs->cx;
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parent_tidptr = (int __user *)regs->dx;
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child_tidptr = (int __user *)regs->di;
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if (!newsp)
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newsp = regs->sp;
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return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr);
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}
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/*
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* sys_execve() executes a new program.
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*/
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int sys_execve(struct pt_regs *regs)
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{
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int error;
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char *filename;
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filename = getname((char __user *) regs->bx);
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error = PTR_ERR(filename);
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if (IS_ERR(filename))
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goto out;
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error = do_execve(filename,
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(char __user * __user *) regs->cx,
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(char __user * __user *) regs->dx,
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regs);
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if (error == 0) {
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/* Make sure we don't return using sysenter.. */
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set_thread_flag(TIF_IRET);
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}
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putname(filename);
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out:
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return error;
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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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unsigned long arch_align_stack(unsigned long sp)
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{
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if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
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sp -= get_random_int() % 8192;
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return sp & ~0xf;
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}
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unsigned long arch_randomize_brk(struct mm_struct *mm)
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{
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unsigned long range_end = mm->brk + 0x02000000;
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return randomize_range(mm->brk, range_end, 0) ? : mm->brk;
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}
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