process.c

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/*
 *  linux/arch/alpha/kernel/process.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 */

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

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/time.h>
#include <linux/major.h>
#include <linux/stat.h>
#include <linux/vt.h>
#include <linux/mman.h>
#include <linux/elfcore.h>
#include <linux/reboot.h>
#include <linux/tty.h>
#include <linux/console.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>

#include <asm/reg.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/pgtable.h>
#include <asm/hwrpb.h>
#include <asm/fpu.h>

#include "proto.h"
#include "pci_impl.h"

/*
 * Power off function, if any
 */
void (*pm_power_off)(void) = machine_power_off;
EXPORT_SYMBOL(pm_power_off);

void
cpu_idle(void)
{
    current_thread_info()->status |= TS_POLLING;

    while (1) {
        /* FIXME -- EV6 and LCA45 know how to power down
           the CPU.  */

        rcu_idle_enter();
        while (!need_resched())
            cpu_relax();

        rcu_idle_exit();
        schedule_preempt_disabled();
    }
}


struct halt_info {
    int mode;
    char *restart_cmd;
};

static void
common_shutdown_1(void *generic_ptr)
{
    struct halt_info *how = (struct halt_info *)generic_ptr;
    struct percpu_struct *cpup;
    unsigned long *pflags, flags;
    int cpuid = smp_processor_id();

    /* No point in taking interrupts anymore. */
    local_irq_disable();

    cpup = (struct percpu_struct *)
            ((unsigned long)hwrpb + hwrpb->processor_offset
             + hwrpb->processor_size * cpuid);
    pflags = &cpup->flags;
    flags = *pflags;

    /* Clear reason to "default"; clear "bootstrap in progress". */
    flags &= ~0x00ff0001UL;

#ifdef CONFIG_SMP
    /* Secondaries halt here. */
    if (cpuid != boot_cpuid) {
        flags |= 0x00040000UL; /* "remain halted" */
        *pflags = flags;
        set_cpu_present(cpuid, false);
        set_cpu_possible(cpuid, false);
        halt();
    }
#endif

    if (how->mode == LINUX_REBOOT_CMD_RESTART) {
        if (!how->restart_cmd) {
            flags |= 0x00020000UL; /* "cold bootstrap" */
        } else {
            /* For SRM, we could probably set environment
               variables to get this to work.  We'd have to
               delay this until after srm_paging_stop unless
               we ever got srm_fixup working.

               At the moment, SRM will use the last boot device,
               but the file and flags will be the defaults, when
               doing a "warm" bootstrap.  */
            flags |= 0x00030000UL; /* "warm bootstrap" */
        }
    } else {
        flags |= 0x00040000UL; /* "remain halted" */
    }
    *pflags = flags;

#ifdef CONFIG_SMP
    /* Wait for the secondaries to halt. */
    set_cpu_present(boot_cpuid, false);
    set_cpu_possible(boot_cpuid, false);
    while (cpumask_weight(cpu_present_mask))
        barrier();
#endif

    /* If booted from SRM, reset some of the original environment. */
    if (alpha_using_srm) {
#ifdef CONFIG_DUMMY_CONSOLE
        /* If we've gotten here after SysRq-b, leave interrupt
           context before taking over the console. */
        if (in_interrupt())
            irq_exit();
        /* This has the effect of resetting the VGA video origin.  */
        take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);
#endif
        pci_restore_srm_config();
        set_hae(srm_hae);
    }

    if (alpha_mv.kill_arch)
        alpha_mv.kill_arch(how->mode);

    if (! alpha_using_srm && how->mode != LINUX_REBOOT_CMD_RESTART) {
        /* Unfortunately, since MILO doesn't currently understand
           the hwrpb bits above, we can't reliably halt the 
           processor and keep it halted.  So just loop.  */
        return;
    }

    if (alpha_using_srm)
        srm_paging_stop();

    halt();
}

static void
common_shutdown(int mode, char *restart_cmd)
{
    struct halt_info args;
    args.mode = mode;
    args.restart_cmd = restart_cmd;
    on_each_cpu(common_shutdown_1, &args, 0);
}

void
machine_restart(char *restart_cmd)
{
    common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
}


void
machine_halt(void)
{
    common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
}


void
machine_power_off(void)
{
    common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
}


/* Used by sysrq-p, among others.  I don't believe r9-r15 are ever
   saved in the context it's used.  */

void
show_regs(struct pt_regs *regs)
{
    dik_show_regs(regs, NULL);
}

/*
 * Re-start a thread when doing execve()
 */
void
start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
    regs->pc = pc;
    regs->ps = 8;
    wrusp(sp);
}
EXPORT_SYMBOL(start_thread);

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

void
flush_thread(void)
{
    /* Arrange for each exec'ed process to start off with a clean slate
       with respect to the FPU.  This is all exceptions disabled.  */
    current_thread_info()->ieee_state = 0;
    wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));

    /* Clean slate for TLS.  */
    current_thread_info()->pcb.unique = 0;
}

void
release_thread(struct task_struct *dead_task)
{
}

/*
 * "alpha_clone()".. By the time we get here, the
 * non-volatile registers have also been saved on the
 * stack. We do some ugly pointer stuff here.. (see
 * also copy_thread)
 *
 * Notice that "fork()" is implemented in terms of clone,
 * with parameters (SIGCHLD, 0).
 */
int
alpha_clone(unsigned long clone_flags, unsigned long usp,
        int __user *parent_tid, int __user *child_tid,
        unsigned long tls_value, struct pt_regs *regs)
{
    if (!usp)
        usp = rdusp();

    return do_fork(clone_flags, usp, regs, 0, parent_tid, child_tid);
}

int
alpha_vfork(struct pt_regs *regs)
{
    return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, rdusp(),
               regs, 0, NULL, NULL);
}

/*
 * Copy an alpha thread..
 */

int
copy_thread(unsigned long clone_flags, unsigned long usp,
        unsigned long arg,
        struct task_struct * p, struct pt_regs * regs)
{
    extern void ret_from_fork(void);
    extern void ret_from_kernel_thread(void);

    struct thread_info *childti = task_thread_info(p);
    struct pt_regs *childregs = task_pt_regs(p);
    struct switch_stack *childstack, *stack;
    unsigned long settls;

    childstack = ((struct switch_stack *) childregs) - 1;
    if (unlikely(!regs)) {
        /* kernel thread */
        memset(childstack, 0,
            sizeof(struct switch_stack) + sizeof(struct pt_regs));
        childstack->r26 = (unsigned long) ret_from_kernel_thread;
        childstack->r9 = usp;   /* function */
        childstack->r10 = arg;
        childregs->hae = alpha_mv.hae_cache,
        childti->pcb.usp = 0;
        childti->pcb.ksp = (unsigned long) childstack;
        childti->pcb.flags = 1; /* set FEN, clear everything else */
        return 0;
    }
    *childregs = *regs;
    settls = regs->r20;
    childregs->r0 = 0;
    childregs->r19 = 0;
    childregs->r20 = 1; /* OSF/1 has some strange fork() semantics.  */
    regs->r20 = 0;
    stack = ((struct switch_stack *) regs) - 1;
    *childstack = *stack;
    childstack->r26 = (unsigned long) ret_from_fork;
    childti->pcb.usp = usp;
    childti->pcb.ksp = (unsigned long) childstack;
    childti->pcb.flags = 1; /* set FEN, clear everything else */

    /* Set a new TLS for the child thread?  Peek back into the
       syscall arguments that we saved on syscall entry.  Oops,
       except we'd have clobbered it with the parent/child set
       of r20.  Read the saved copy.  */
    /* Note: if CLONE_SETTLS is not set, then we must inherit the
       value from the parent, which will have been set by the block
       copy in dup_task_struct.  This is non-intuitive, but is
       required for proper operation in the case of a threaded
       application calling fork.  */
    if (clone_flags & CLONE_SETTLS)
        childti->pcb.unique = settls;

    return 0;
}

/*
 * Fill in the user structure for a ELF core dump.
 */
void
dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
{
    /* switch stack follows right below pt_regs: */
    struct switch_stack * sw = ((struct switch_stack *) pt) - 1;

    dest[ 0] = pt->r0;
    dest[ 1] = pt->r1;
    dest[ 2] = pt->r2;
    dest[ 3] = pt->r3;
    dest[ 4] = pt->r4;
    dest[ 5] = pt->r5;
    dest[ 6] = pt->r6;
    dest[ 7] = pt->r7;
    dest[ 8] = pt->r8;
    dest[ 9] = sw->r9;
    dest[10] = sw->r10;
    dest[11] = sw->r11;
    dest[12] = sw->r12;
    dest[13] = sw->r13;
    dest[14] = sw->r14;
    dest[15] = sw->r15;
    dest[16] = pt->r16;
    dest[17] = pt->r17;
    dest[18] = pt->r18;
    dest[19] = pt->r19;
    dest[20] = pt->r20;
    dest[21] = pt->r21;
    dest[22] = pt->r22;
    dest[23] = pt->r23;
    dest[24] = pt->r24;
    dest[25] = pt->r25;
    dest[26] = pt->r26;
    dest[27] = pt->r27;
    dest[28] = pt->r28;
    dest[29] = pt->gp;
    dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
    dest[31] = pt->pc;

    /* Once upon a time this was the PS value.  Which is stupid
       since that is always 8 for usermode.  Usurped for the more
       useful value of the thread's UNIQUE field.  */
    dest[32] = ti->pcb.unique;
}
EXPORT_SYMBOL(dump_elf_thread);

int
dump_elf_task(elf_greg_t *dest, struct task_struct *task)
{
    dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
    return 1;
}
EXPORT_SYMBOL(dump_elf_task);

int
dump_elf_task_fp(elf_fpreg_t *dest, struct task_struct *task)
{
    struct switch_stack *sw = (struct switch_stack *)task_pt_regs(task) - 1;
    memcpy(dest, sw->fp, 32 * 8);
    return 1;
}
EXPORT_SYMBOL(dump_elf_task_fp);

/*
 * Return saved PC of a blocked thread.  This assumes the frame
 * pointer is the 6th saved long on the kernel stack and that the
 * saved return address is the first long in the frame.  This all
 * holds provided the thread blocked through a call to schedule() ($15
 * is the frame pointer in schedule() and $15 is saved at offset 48 by
 * entry.S:do_switch_stack).
 *
 * Under heavy swap load I've seen this lose in an ugly way.  So do
 * some extra sanity checking on the ranges we expect these pointers
 * to be in so that we can fail gracefully.  This is just for ps after
 * all.  -- r~
 */

unsigned long
thread_saved_pc(struct task_struct *t)
{
    unsigned long base = (unsigned long)task_stack_page(t);
    unsigned long fp, sp = task_thread_info(t)->pcb.ksp;

    if (sp > base && sp+6*8 < base + 16*1024) {
        fp = ((unsigned long*)sp)[6];
        if (fp > sp && fp < base + 16*1024)
            return *(unsigned long *)fp;
    }

    return 0;
}

unsigned long
get_wchan(struct task_struct *p)
{
    unsigned long schedule_frame;
    unsigned long pc;
    if (!p || p == current || p->state == TASK_RUNNING)
        return 0;
    /*
     * This one depends on the frame size of schedule().  Do a
     * "disass schedule" in gdb to find the frame size.  Also, the
     * code assumes that sleep_on() follows immediately after
     * interruptible_sleep_on() and that add_timer() follows
     * immediately after interruptible_sleep().  Ugly, isn't it?
     * Maybe adding a wchan field to task_struct would be better,
     * after all...
     */

    pc = thread_saved_pc(p);
    if (in_sched_functions(pc)) {
        schedule_frame = ((unsigned long *)task_thread_info(p)->pcb.ksp)[6];
        return ((unsigned long *)schedule_frame)[12];
    }
    return pc;
}