process_32.c

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/*
 *  Copyright (C) 1995  Linus Torvalds
 *
 *  Pentium III FXSR, SSE support
 *  Gareth Hughes <[email protected]>, May 2000
 */

/*
 * This file handles the architecture-dependent parts of process handling..
 */

#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/user.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/ptrace.h>
#include <linux/personality.h>
#include <linux/percpu.h>
#include <linux/prctl.h>
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/kdebug.h>

#include <asm/pgtable.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/desc.h>
#ifdef CONFIG_MATH_EMULATION
#include <asm/math_emu.h>
#endif

#include <linux/err.h>

#include <asm/tlbflush.h>
#include <asm/cpu.h>
#include <asm/idle.h>
#include <asm/syscalls.h>
#include <asm/debugreg.h>
#include <asm/switch_to.h>

asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");

/*
 * Return saved PC of a blocked thread.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
    return ((unsigned long *)tsk->thread.sp)[3];
}

void __show_regs(struct pt_regs *regs, int all)
{
    unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
    unsigned long d0, d1, d2, d3, d6, d7;
    unsigned long sp;
    unsigned short ss, gs;

    if (user_mode_vm(regs)) {
        sp = regs->sp;
        ss = regs->ss & 0xffff;
        gs = get_user_gs(regs);
    } else {
        sp = kernel_stack_pointer(regs);
        savesegment(ss, ss);
        savesegment(gs, gs);
    }

    show_regs_common();

    printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
            (u16)regs->cs, regs->ip, regs->flags,
            smp_processor_id());
    print_symbol("EIP is at %s\n", regs->ip);

    printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
        regs->ax, regs->bx, regs->cx, regs->dx);
    printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
        regs->si, regs->di, regs->bp, sp);
    printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
           (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);

    if (!all)
        return;

    cr0 = read_cr0();
    cr2 = read_cr2();
    cr3 = read_cr3();
    cr4 = read_cr4_safe();
    printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
            cr0, cr2, cr3, cr4);

    get_debugreg(d0, 0);
    get_debugreg(d1, 1);
    get_debugreg(d2, 2);
    get_debugreg(d3, 3);
    printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
            d0, d1, d2, d3);

    get_debugreg(d6, 6);
    get_debugreg(d7, 7);
    printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
            d6, d7);
}

void release_thread(struct task_struct *dead_task)
{
    BUG_ON(dead_task->mm);
    release_vm86_irqs(dead_task);
}

int copy_thread(unsigned long clone_flags, unsigned long sp,
    unsigned long arg,
    struct task_struct *p, struct pt_regs *regs)
{
    struct pt_regs *childregs = task_pt_regs(p);
    struct task_struct *tsk;
    int err;

    p->thread.sp = (unsigned long) childregs;
    p->thread.sp0 = (unsigned long) (childregs+1);

    if (unlikely(!regs)) {
        /* kernel thread */
        memset(childregs, 0, sizeof(struct pt_regs));
        p->thread.ip = (unsigned long) ret_from_kernel_thread;
        task_user_gs(p) = __KERNEL_STACK_CANARY;
        childregs->ds = __USER_DS;
        childregs->es = __USER_DS;
        childregs->fs = __KERNEL_PERCPU;
        childregs->bx = sp; /* function */
        childregs->bp = arg;
        childregs->orig_ax = -1;
        childregs->cs = __KERNEL_CS | get_kernel_rpl();
        childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_BIT1;
        p->fpu_counter = 0;
        p->thread.io_bitmap_ptr = NULL;
        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
        return 0;
    }
    *childregs = *regs;
    childregs->ax = 0;
    childregs->sp = sp;

    p->thread.ip = (unsigned long) ret_from_fork;
    task_user_gs(p) = get_user_gs(regs);

    p->fpu_counter = 0;
    p->thread.io_bitmap_ptr = NULL;
    tsk = current;
    err = -ENOMEM;

    memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));

    if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
        p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
                        IO_BITMAP_BYTES, GFP_KERNEL);
        if (!p->thread.io_bitmap_ptr) {
            p->thread.io_bitmap_max = 0;
            return -ENOMEM;
        }
        set_tsk_thread_flag(p, TIF_IO_BITMAP);
    }

    err = 0;

    /*
     * Set a new TLS for the child thread?
     */
    if (clone_flags & CLONE_SETTLS)
        err = do_set_thread_area(p, -1,
            (struct user_desc __user *)childregs->si, 0);

    if (err && p->thread.io_bitmap_ptr) {
        kfree(p->thread.io_bitmap_ptr);
        p->thread.io_bitmap_max = 0;
    }
    return err;
}

void
start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
{
    set_user_gs(regs, 0);
    regs->fs        = 0;
    regs->ds        = __USER_DS;
    regs->es        = __USER_DS;
    regs->ss        = __USER_DS;
    regs->cs        = __USER_CS;
    regs->ip        = new_ip;
    regs->sp        = new_sp;
    regs->flags     = X86_EFLAGS_IF;
    /*
     * force it to the iret return path by making it look as if there was
     * some work pending.
     */
    set_thread_flag(TIF_NOTIFY_RESUME);
}
EXPORT_SYMBOL_GPL(start_thread);


/*
 *  switch_to(x,y) should switch tasks from x to y.
 *
 * We fsave/fwait so that an exception goes off at the right time
 * (as a call from the fsave or fwait in effect) rather than to
 * the wrong process. Lazy FP saving no longer makes any sense
 * with modern CPU's, and this simplifies a lot of things (SMP
 * and UP become the same).
 *
 * NOTE! We used to use the x86 hardware context switching. The
 * reason for not using it any more becomes apparent when you
 * try to recover gracefully from saved state that is no longer
 * valid (stale segment register values in particular). With the
 * hardware task-switch, there is no way to fix up bad state in
 * a reasonable manner.
 *
 * The fact that Intel documents the hardware task-switching to
 * be slow is a fairly red herring - this code is not noticeably
 * faster. However, there _is_ some room for improvement here,
 * so the performance issues may eventually be a valid point.
 * More important, however, is the fact that this allows us much
 * more flexibility.
 *
 * The return value (in %ax) will be the "prev" task after
 * the task-switch, and shows up in ret_from_fork in entry.S,
 * for example.
 */
__notrace_funcgraph struct task_struct *
__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
{
    struct thread_struct *prev = &prev_p->thread,
                 *next = &next_p->thread;
    int cpu = smp_processor_id();
    struct tss_struct *tss = &per_cpu(init_tss, cpu);
    fpu_switch_t fpu;

    /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */

    fpu = switch_fpu_prepare(prev_p, next_p, cpu);

    /*
     * Reload esp0.
     */
    load_sp0(tss, next);

    /*
     * Save away %gs. No need to save %fs, as it was saved on the
     * stack on entry.  No need to save %es and %ds, as those are
     * always kernel segments while inside the kernel.  Doing this
     * before setting the new TLS descriptors avoids the situation
     * where we temporarily have non-reloadable segments in %fs
     * and %gs.  This could be an issue if the NMI handler ever
     * used %fs or %gs (it does not today), or if the kernel is
     * running inside of a hypervisor layer.
     */
    lazy_save_gs(prev->gs);

    /*
     * Load the per-thread Thread-Local Storage descriptor.
     */
    load_TLS(next, cpu);

    /*
     * Restore IOPL if needed.  In normal use, the flags restore
     * in the switch assembly will handle this.  But if the kernel
     * is running virtualized at a non-zero CPL, the popf will
     * not restore flags, so it must be done in a separate step.
     */
    if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
        set_iopl_mask(next->iopl);

    /*
     * Now maybe handle debug registers and/or IO bitmaps
     */
    if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
             task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
        __switch_to_xtra(prev_p, next_p, tss);

    /*
     * Leave lazy mode, flushing any hypercalls made here.
     * This must be done before restoring TLS segments so
     * the GDT and LDT are properly updated, and must be
     * done before math_state_restore, so the TS bit is up
     * to date.
     */
    arch_end_context_switch(next_p);

    /*
     * Restore %gs if needed (which is common)
     */
    if (prev->gs | next->gs)
        lazy_load_gs(next->gs);

    switch_fpu_finish(next_p, fpu);

    this_cpu_write(current_task, next_p);

    return prev_p;
}

#define top_esp                (THREAD_SIZE - sizeof(unsigned long))
#define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))

unsigned long get_wchan(struct task_struct *p)
{
    unsigned long bp, sp, ip;
    unsigned long stack_page;
    int count = 0;
    if (!p || p == current || p->state == TASK_RUNNING)
        return 0;
    stack_page = (unsigned long)task_stack_page(p);
    sp = p->thread.sp;
    if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
        return 0;
    /* include/asm-i386/system.h:switch_to() pushes bp last. */
    bp = *(unsigned long *) sp;
    do {
        if (bp < stack_page || bp > top_ebp+stack_page)
            return 0;
        ip = *(unsigned long *) (bp+4);
        if (!in_sched_functions(ip))
            return ip;
        bp = *(unsigned long *) bp;
    } while (count++ < 16);
    return 0;
}