/*
 * PPC64 code to handle Linux booting another kernel.
 *
 * Copyright (C) 2004-2005, IBM Corp.
 *
 * Created by: Milton D Miller II
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 */


#include <linux/kexec.h>
#include <linux/smp.h>
#include <linux/thread_info.h>
#include <linux/init_task.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/cpu.h>
#include <linux/hardirq.h>

#include <asm/page.h>
#include <asm/current.h>
#include <asm/machdep.h>
#include <asm/cacheflush.h>
#include <asm/paca.h>
#include <asm/mmu.h>
#include <asm/sections.h>       /* _end */
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/hw_breakpoint.h>

int default_machine_kexec_prepare(struct kimage *image)
{
        int i;
        unsigned long begin, end;       /* limits of segment */
        unsigned long low, high;        /* limits of blocked memory range */
        struct device_node *node;
        const unsigned long *basep;
        const unsigned int *sizep;

        if (!ppc_md.hpte_clear_all)
                return -ENOENT;

        /*
         * Since we use the kernel fault handlers and paging code to
         * handle the virtual mode, we must make sure no destination
         * overlaps kernel static data or bss.
         */
        for (i = 0; i < image->nr_segments; i++)
                if (image->segment[i].mem < __pa(_end))
                        return -ETXTBSY;

        /*
         * For non-LPAR, we absolutely can not overwrite the mmu hash
         * table, since we are still using the bolted entries in it to
         * do the copy.  Check that here.
         *
         * It is safe if the end is below the start of the blocked
         * region (end <= low), or if the beginning is after the
         * end of the blocked region (begin >= high).  Use the
         * boolean identity !(a || b)  === (!a && !b).
         */
        if (htab_address) {
                low = __pa(htab_address);
                high = low + htab_size_bytes;

                for (i = 0; i < image->nr_segments; i++) {
                        begin = image->segment[i].mem;
                        end = begin + image->segment[i].memsz;

                        if ((begin < high) && (end > low))
                                return -ETXTBSY;
                }
        }

        /* We also should not overwrite the tce tables */
        for_each_node_by_type(node, "pci") {
                basep = of_get_property(node, "linux,tce-base", NULL);
                sizep = of_get_property(node, "linux,tce-size", NULL);
                if (basep == NULL || sizep == NULL)
                        continue;

                low = *basep;
                high = low + (*sizep);

                for (i = 0; i < image->nr_segments; i++) {
                        begin = image->segment[i].mem;
                        end = begin + image->segment[i].memsz;

                        if ((begin < high) && (end > low))
                                return -ETXTBSY;
                }
        }

        return 0;
}

#define IND_FLAGS (IND_DESTINATION | IND_INDIRECTION | IND_DONE | IND_SOURCE)

static void copy_segments(unsigned long ind)
{
        unsigned long entry;
        unsigned long *ptr;
        void *dest;
        void *addr;

        /*
         * We rely on kexec_load to create a lists that properly
         * initializes these pointers before they are used.
         * We will still crash if the list is wrong, but at least
         * the compiler will be quiet.
         */
        ptr = NULL;
        dest = NULL;

        for (entry = ind; !(entry & IND_DONE); entry = *ptr++) {
                addr = __va(entry & PAGE_MASK);

                switch (entry & IND_FLAGS) {
                case IND_DESTINATION:
                        dest = addr;
                        break;
                case IND_INDIRECTION:
                        ptr = addr;
                        break;
                case IND_SOURCE:
                        copy_page(dest, addr);
                        dest += PAGE_SIZE;
                }
        }
}

void kexec_copy_flush(struct kimage *image)
{
        long i, nr_segments = image->nr_segments;
        struct  kexec_segment ranges[KEXEC_SEGMENT_MAX];

        /* save the ranges on the stack to efficiently flush the icache */
        memcpy(ranges, image->segment, sizeof(ranges));

        /*
         * After this call we may not use anything allocated in dynamic
         * memory, including *image.
         *
         * Only globals and the stack are allowed.
         */
        copy_segments(image->head);

        /*
         * we need to clear the icache for all dest pages sometime,
         * including ones that were in place on the original copy
         */
        for (i = 0; i < nr_segments; i++)
                flush_icache_range((unsigned long)__va(ranges[i].mem),
                        (unsigned long)__va(ranges[i].mem + ranges[i].memsz));
}

#ifdef CONFIG_SMP

static int kexec_all_irq_disabled = 0;

static void kexec_smp_down(void *arg)
{
        local_irq_disable();
        hard_irq_disable();

        mb(); /* make sure our irqs are disabled before we say they are */
        get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;
        while(kexec_all_irq_disabled == 0)
                cpu_relax();
        mb(); /* make sure all irqs are disabled before this */
        hw_breakpoint_disable();
        /*
         * Now every CPU has IRQs off, we can clear out any pending
         * IPIs and be sure that no more will come in after this.
         */
        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(0, 1);

        kexec_smp_wait();
        /* NOTREACHED */
}

static void kexec_prepare_cpus_wait(int wait_state)
{
        int my_cpu, i, notified=-1;

        hw_breakpoint_disable();
        my_cpu = get_cpu();
        /* Make sure each CPU has at least made it to the state we need.
         *
         * FIXME: There is a (slim) chance of a problem if not all of the CPUs
         * are correctly onlined.  If somehow we start a CPU on boot with RTAS
         * start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
         * time, the boot CPU will timeout.  If it does eventually execute
         * stuff, the secondary will start up (paca[].cpu_start was written) and
         * get into a peculiar state.  If the platform supports
         * smp_ops->take_timebase(), the secondary CPU will probably be spinning
         * in there.  If not (i.e. pseries), the secondary will continue on and
         * try to online itself/idle/etc. If it survives that, we need to find
         * these possible-but-not-online-but-should-be CPUs and chaperone them
         * into kexec_smp_wait().
         */
        for_each_online_cpu(i) {
                if (i == my_cpu)
                        continue;

                while (paca[i].kexec_state < wait_state) {
                        barrier();
                        if (i != notified) {
                                printk(KERN_INFO "kexec: waiting for cpu %d "
                                       "(physical %d) to enter %i state\n",
                                       i, paca[i].hw_cpu_id, wait_state);
                                notified = i;
                        }
                }
        }
        mb();
}

/*
 * We need to make sure each present CPU is online.  The next kernel will scan
 * the device tree and assume primary threads are online and query secondary
 * threads via RTAS to online them if required.  If we don't online primary
 * threads, they will be stuck.  However, we also online secondary threads as we
 * may be using 'cede offline'.  In this case RTAS doesn't see the secondary
 * threads as offline -- and again, these CPUs will be stuck.
 *
 * So, we online all CPUs that should be running, including secondary threads.
 */
static void wake_offline_cpus(void)
{
        int cpu = 0;

        for_each_present_cpu(cpu) {
                if (!cpu_online(cpu)) {
                        printk(KERN_INFO "kexec: Waking offline cpu %d.\n",
                               cpu);
                        cpu_up(cpu);
                }
        }
}

static void kexec_prepare_cpus(void)
{
        wake_offline_cpus();
        smp_call_function(kexec_smp_down, NULL, /* wait */0);
        local_irq_disable();
        hard_irq_disable();

        mb(); /* make sure IRQs are disabled before we say they are */
        get_paca()->kexec_state = KEXEC_STATE_IRQS_OFF;

        kexec_prepare_cpus_wait(KEXEC_STATE_IRQS_OFF);
        /* we are sure every CPU has IRQs off at this point */
        kexec_all_irq_disabled = 1;

        /* after we tell the others to go down */
        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(0, 0);

        /*
         * Before removing MMU mappings make sure all CPUs have entered real
         * mode:
         */
        kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);

        put_cpu();
}

#else /* ! SMP */

static void kexec_prepare_cpus(void)
{
        /*
         * move the secondarys to us so that we can copy
         * the new kernel 0-0x100 safely
         *
         * do this if kexec in setup.c ?
         *
         * We need to release the cpus if we are ever going from an
         * UP to an SMP kernel.
         */
        smp_release_cpus();
        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(0, 0);
        local_irq_disable();
        hard_irq_disable();
}

#endif /* SMP */

/*
 * kexec thread structure and stack.
 *
 * We need to make sure that this is 16384-byte aligned due to the
 * way process stacks are handled.  It also must be statically allocated
 * or allocated as part of the kimage, because everything else may be
 * overwritten when we copy the kexec image.  We piggyback on the
 * "init_task" linker section here to statically allocate a stack.
 *
 * We could use a smaller stack if we don't care about anything using
 * current, but that audit has not been performed.
 */
static union thread_union kexec_stack __init_task_data =
        { };

/*
 * For similar reasons to the stack above, the kexecing CPU needs to be on a
 * static PACA; we switch to kexec_paca.
 */
struct paca_struct kexec_paca;

/* Our assembly helper, in kexec_stub.S */
extern void kexec_sequence(void *newstack, unsigned long start,
                           void *image, void *control,
                           void (*clear_all)(void)) __noreturn;

/* too late to fail here */
void default_machine_kexec(struct kimage *image)
{
        /* prepare control code if any */

        /*
        * If the kexec boot is the normal one, need to shutdown other cpus
        * into our wait loop and quiesce interrupts.
        * Otherwise, in the case of crashed mode (crashing_cpu >= 0),
        * stopping other CPUs and collecting their pt_regs is done before
        * using debugger IPI.
        */

        if (crashing_cpu == -1)
                kexec_prepare_cpus();

        pr_debug("kexec: Starting switchover sequence.\n");

        /* switch to a staticly allocated stack.  Based on irq stack code.
         * We setup preempt_count to avoid using VMX in memcpy.
         * XXX: the task struct will likely be invalid once we do the copy!
         */
        kexec_stack.thread_info.task = current_thread_info()->task;
        kexec_stack.thread_info.flags = 0;
        kexec_stack.thread_info.preempt_count = HARDIRQ_OFFSET;
        kexec_stack.thread_info.cpu = current_thread_info()->cpu;

        /* We need a static PACA, too; copy this CPU's PACA over and switch to
         * it.  Also poison per_cpu_offset to catch anyone using non-static
         * data.
         */
        memcpy(&kexec_paca, get_paca(), sizeof(struct paca_struct));
        kexec_paca.data_offset = 0xedeaddeadeeeeeeeUL;
        paca = (struct paca_struct *)RELOC_HIDE(&kexec_paca, 0) -
                kexec_paca.paca_index;
        setup_paca(&kexec_paca);

        /* XXX: If anyone does 'dynamic lppacas' this will also need to be
         * switched to a static version!
         */

        /* Some things are best done in assembly.  Finding globals with
         * a toc is easier in C, so pass in what we can.
         */
        kexec_sequence(&kexec_stack, image->start, image,
                        page_address(image->control_code_page),
                        ppc_md.hpte_clear_all);
        /* NOTREACHED */
}

/* Values we need to export to the second kernel via the device tree. */
static unsigned long htab_base;

static struct property htab_base_prop = {
        .name = "linux,htab-base",
        .length = sizeof(unsigned long),
        .value = &htab_base,
};

static struct property htab_size_prop = {
        .name = "linux,htab-size",
        .length = sizeof(unsigned long),
        .value = &htab_size_bytes,
};

static int __init export_htab_values(void)
{
        struct device_node *node;
        struct property *prop;

        /* On machines with no htab htab_address is NULL */
        if (!htab_address)
                return -ENODEV;

        node = of_find_node_by_path("/chosen");
        if (!node)
                return -ENODEV;

        /* remove any stale propertys so ours can be found */
        prop = of_find_property(node, htab_base_prop.name, NULL);
        if (prop)
                of_remove_property(node, prop);
        prop = of_find_property(node, htab_size_prop.name, NULL);
        if (prop)
                of_remove_property(node, prop);

        htab_base = __pa(htab_address);
        of_add_property(node, &htab_base_prop);
        of_add_property(node, &htab_size_prop);

        of_node_put(node);
        return 0;
}
late_initcall(export_htab_values);