process.c

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/*
 * This file handles the architecture dependent parts of process handling.
 *
 *    Copyright IBM Corp. 1999, 2009
 *    Author(s): Martin Schwidefsky <[email protected]>,
 *       Hartmut Penner <[email protected]>,
 *       Denis Joseph Barrow,
 */

#include <linux/compiler.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/elfcore.h>
#include <linux/smp.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
#include <linux/personality.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <linux/kprobes.h>
#include <linux/random.h>
#include <linux/module.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/vtimer.h>
#include <asm/exec.h>
#include <asm/irq.h>
#include <asm/nmi.h>
#include <asm/smp.h>
#include <asm/switch_to.h>
#include <asm/runtime_instr.h>
#include "entry.h"

asmlinkage void ret_from_fork(void) asm ("ret_from_fork");

/*
 * Return saved PC of a blocked thread. used in kernel/sched.
 * resume in entry.S does not create a new stack frame, it
 * just stores the registers %r6-%r15 to the frame given by
 * schedule. We want to return the address of the caller of
 * schedule, so we have to walk the backchain one time to
 * find the frame schedule() store its return address.
 */
unsigned long thread_saved_pc(struct task_struct *tsk)
{
    struct stack_frame *sf, *low, *high;

    if (!tsk || !task_stack_page(tsk))
        return 0;
    low = task_stack_page(tsk);
    high = (struct stack_frame *) task_pt_regs(tsk);
    sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
    if (sf <= low || sf > high)
        return 0;
    sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
    if (sf <= low || sf > high)
        return 0;
    return sf->gprs[8];
}

/*
 * The idle loop on a S390...
 */
static void default_idle(void)
{
    if (cpu_is_offline(smp_processor_id()))
        cpu_die();
    local_irq_disable();
    if (need_resched()) {
        local_irq_enable();
        return;
    }
    local_mcck_disable();
    if (test_thread_flag(TIF_MCCK_PENDING)) {
        local_mcck_enable();
        local_irq_enable();
        return;
    }
    /* Halt the cpu and keep track of cpu time accounting. */
    vtime_stop_cpu();
}

void cpu_idle(void)
{
    for (;;) {
        tick_nohz_idle_enter();
        rcu_idle_enter();
        while (!need_resched() && !test_thread_flag(TIF_MCCK_PENDING))
            default_idle();
        rcu_idle_exit();
        tick_nohz_idle_exit();
        if (test_thread_flag(TIF_MCCK_PENDING))
            s390_handle_mcck();
        schedule_preempt_disabled();
    }
}

extern void __kprobes kernel_thread_starter(void);

/*
 * Free current thread data structures etc..
 */
void exit_thread(void)
{
    exit_thread_runtime_instr();
}

void flush_thread(void)
{
}

void release_thread(struct task_struct *dead_task)
{
}

int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
        unsigned long arg,
        struct task_struct *p, struct pt_regs *regs)
{
    struct thread_info *ti;
    struct fake_frame
    {
        struct stack_frame sf;
        struct pt_regs childregs;
    } *frame;

    frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
    p->thread.ksp = (unsigned long) frame;
    /* Save access registers to new thread structure. */
    save_access_regs(&p->thread.acrs[0]);
    /* start new process with ar4 pointing to the correct address space */
    p->thread.mm_segment = get_fs();
    /* Don't copy debug registers */
    memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
    memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
    clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
    clear_tsk_thread_flag(p, TIF_PER_TRAP);
    /* Initialize per thread user and system timer values */
    ti = task_thread_info(p);
    ti->user_timer = 0;
    ti->system_timer = 0;

    frame->sf.back_chain = 0;
    /* new return point is ret_from_fork */
    frame->sf.gprs[8] = (unsigned long) ret_from_fork;
    /* fake return stack for resume(), don't go back to schedule */
    frame->sf.gprs[9] = (unsigned long) frame;

    /* Store access registers to kernel stack of new process. */
    if (unlikely(!regs)) {
        /* kernel thread */
        memset(&frame->childregs, 0, sizeof(struct pt_regs));
        frame->childregs.psw.mask = psw_kernel_bits | PSW_MASK_DAT |
                PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
        frame->childregs.psw.addr = PSW_ADDR_AMODE |
                (unsigned long) kernel_thread_starter;
        frame->childregs.gprs[9] = new_stackp; /* function */
        frame->childregs.gprs[10] = arg;
        frame->childregs.gprs[11] = (unsigned long) do_exit;
        frame->childregs.orig_gpr2 = -1;

        return 0;
    }
    frame->childregs = *regs;
    frame->childregs.gprs[2] = 0;   /* child returns 0 on fork. */
    frame->childregs.gprs[15] = new_stackp;

    /* Don't copy runtime instrumentation info */
    p->thread.ri_cb = NULL;
    p->thread.ri_signum = 0;
    frame->childregs.psw.mask &= ~PSW_MASK_RI;

#ifndef CONFIG_64BIT
    /*
     * save fprs to current->thread.fp_regs to merge them with
     * the emulated registers and then copy the result to the child.
     */
    save_fp_regs(&current->thread.fp_regs);
    memcpy(&p->thread.fp_regs, &current->thread.fp_regs,
           sizeof(s390_fp_regs));
    /* Set a new TLS ?  */
    if (clone_flags & CLONE_SETTLS)
        p->thread.acrs[0] = regs->gprs[6];
#else /* CONFIG_64BIT */
    /* Save the fpu registers to new thread structure. */
    save_fp_regs(&p->thread.fp_regs);
    /* Set a new TLS ?  */
    if (clone_flags & CLONE_SETTLS) {
        if (is_compat_task()) {
            p->thread.acrs[0] = (unsigned int) regs->gprs[6];
        } else {
            p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);
            p->thread.acrs[1] = (unsigned int) regs->gprs[6];
        }
    }
#endif /* CONFIG_64BIT */
    return 0;
}

SYSCALL_DEFINE0(fork)
{
    struct pt_regs *regs = task_pt_regs(current);
    return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
}

SYSCALL_DEFINE4(clone, unsigned long, newsp, unsigned long, clone_flags,
        int __user *, parent_tidptr, int __user *, child_tidptr)
{
    struct pt_regs *regs = task_pt_regs(current);

    if (!newsp)
        newsp = regs->gprs[15];
    return do_fork(clone_flags, newsp, regs, 0,
               parent_tidptr, child_tidptr);
}

/*
 * This is trivial, and on the face of it looks like it
 * could equally well be done in user mode.
 *
 * Not so, for quite unobvious reasons - register pressure.
 * In user mode vfork() cannot have a stack frame, and if
 * done by calling the "clone()" system call directly, you
 * do not have enough call-clobbered registers to hold all
 * the information you need.
 */
SYSCALL_DEFINE0(vfork)
{
    struct pt_regs *regs = task_pt_regs(current);
    return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
               regs->gprs[15], regs, 0, NULL, NULL);
}

asmlinkage void execve_tail(void)
{
    current->thread.fp_regs.fpc = 0;
    if (MACHINE_HAS_IEEE)
        asm volatile("sfpc %0,%0" : : "d" (0));
}

/*
 * fill in the FPU structure for a core dump.
 */
int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
{
#ifndef CONFIG_64BIT
    /*
     * save fprs to current->thread.fp_regs to merge them with
     * the emulated registers and then copy the result to the dump.
     */
    save_fp_regs(&current->thread.fp_regs);
    memcpy(fpregs, &current->thread.fp_regs, sizeof(s390_fp_regs));
#else /* CONFIG_64BIT */
    save_fp_regs(fpregs);
#endif /* CONFIG_64BIT */
    return 1;
}
EXPORT_SYMBOL(dump_fpu);

unsigned long get_wchan(struct task_struct *p)
{
    struct stack_frame *sf, *low, *high;
    unsigned long return_address;
    int count;

    if (!p || p == current || p->state == TASK_RUNNING || !task_stack_page(p))
        return 0;
    low = task_stack_page(p);
    high = (struct stack_frame *) task_pt_regs(p);
    sf = (struct stack_frame *) (p->thread.ksp & PSW_ADDR_INSN);
    if (sf <= low || sf > high)
        return 0;
    for (count = 0; count < 16; count++) {
        sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
        if (sf <= low || sf > high)
            return 0;
        return_address = sf->gprs[8] & PSW_ADDR_INSN;
        if (!in_sched_functions(return_address))
            return return_address;
    }
    return 0;
}

unsigned long arch_align_stack(unsigned long sp)
{
    if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
        sp -= get_random_int() & ~PAGE_MASK;
    return sp & ~0xf;
}

static inline unsigned long brk_rnd(void)
{
    /* 8MB for 32bit, 1GB for 64bit */
    if (is_32bit_task())
        return (get_random_int() & 0x7ffUL) << PAGE_SHIFT;
    else
        return (get_random_int() & 0x3ffffUL) << PAGE_SHIFT;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
    unsigned long ret = PAGE_ALIGN(mm->brk + brk_rnd());

    if (ret < mm->brk)
        return mm->brk;
    return ret;
}

unsigned long randomize_et_dyn(unsigned long base)
{
    unsigned long ret = PAGE_ALIGN(base + brk_rnd());

    if (!(current->flags & PF_RANDOMIZE))
        return base;
    if (ret < base)
        return base;
    return ret;
}