// SPDX-License-Identifier: GPL-2.0-only
/*
 * Architecture specific (PPC64) functions for kexec based crash dumps.
 *
 * Copyright (C) 2005, IBM Corp.
 *
 * Created by: Haren Myneni
 */

#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/export.h>
#include <linux/crash_dump.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/types.h>
#include <linux/libfdt.h>
#include <linux/memory.h>

#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/kexec.h>
#include <asm/smp.h>
#include <asm/setjmp.h>
#include <asm/debug.h>
#include <asm/interrupt.h>
#include <asm/kexec_ranges.h>

/*
 * The primary CPU waits a while for all secondary CPUs to enter. This is to
 * avoid sending an IPI if the secondary CPUs are entering
 * crash_kexec_secondary on their own (eg via a system reset).
 *
 * The secondary timeout has to be longer than the primary. Both timeouts are
 * in milliseconds.
 */
#define PRIMARY_TIMEOUT         500
#define SECONDARY_TIMEOUT       1000

#define IPI_TIMEOUT             10000
#define REAL_MODE_TIMEOUT       10000

static int time_to_dump;

/*
 * In case of system reset, secondary CPUs enter crash_kexec_secondary with out
 * having to send an IPI explicitly. So, indicate if the crash is via
 * system reset to avoid sending another IPI.
 */
static int is_via_system_reset;

/*
 * crash_wake_offline should be set to 1 by platforms that intend to wake
 * up offline cpus prior to jumping to a kdump kernel. Currently powernv
 * sets it to 1, since we want to avoid things from happening when an
 * offline CPU wakes up due to something like an HMI (malfunction error),
 * which propagates to all threads.
 */
int crash_wake_offline;

#define CRASH_HANDLER_MAX 3
/* List of shutdown handles */
static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
static DEFINE_SPINLOCK(crash_handlers_lock);

static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
static int crash_shutdown_cpu = -1;

static int handle_fault(struct pt_regs *regs)
{
        if (crash_shutdown_cpu == smp_processor_id())
                longjmp(crash_shutdown_buf, 1);
        return 0;
}

#ifdef CONFIG_SMP

static atomic_t cpus_in_crash;
void crash_ipi_callback(struct pt_regs *regs)
{
        static cpumask_t cpus_state_saved = CPU_MASK_NONE;

        int cpu = smp_processor_id();

        hard_irq_disable();
        if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
                crash_save_cpu(regs, cpu);
                cpumask_set_cpu(cpu, &cpus_state_saved);
        }

        atomic_inc(&cpus_in_crash);
        smp_mb__after_atomic();

        /*
         * Starting the kdump boot.
         * This barrier is needed to make sure that all CPUs are stopped.
         */
        while (!time_to_dump)
                cpu_relax();

        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(1, 1);

#ifdef CONFIG_PPC64
        kexec_smp_wait();
#else
        for (;;);       /* FIXME */
#endif

        /* NOTREACHED */
}

static void crash_kexec_prepare_cpus(void)
{
        unsigned int msecs;
        volatile unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
        volatile int tries = 0;
        int (*old_handler)(struct pt_regs *regs);

        printk(KERN_EMERG "Sending IPI to other CPUs\n");

        if (crash_wake_offline)
                ncpus = num_present_cpus() - 1;

        /*
         * If we came in via system reset, secondaries enter via crash_kexec_secondary().
         * So, wait a while for the secondary CPUs to enter for that case.
         * Else, send IPI to all other CPUs.
         */
        if (is_via_system_reset)
                mdelay(PRIMARY_TIMEOUT);
        else
                crash_send_ipi(crash_ipi_callback);
        smp_wmb();

again:
        /*
         * FIXME: Until we will have the way to stop other CPUs reliably,
         * the crash CPU will send an IPI and wait for other CPUs to
         * respond.
         */
        msecs = IPI_TIMEOUT;
        while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
                mdelay(1);

        /* Would it be better to replace the trap vector here? */

        if (atomic_read(&cpus_in_crash) >= ncpus) {
                printk(KERN_EMERG "IPI complete\n");
                return;
        }

        printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
                ncpus - atomic_read(&cpus_in_crash));

        /*
         * If we have a panic timeout set then we can't wait indefinitely
         * for someone to activate system reset. We also give up on the
         * second time through if system reset fail to work.
         */
        if ((panic_timeout > 0) || (tries > 0))
                return;

        /*
         * A system reset will cause all CPUs to take an 0x100 exception.
         * The primary CPU returns here via setjmp, and the secondary
         * CPUs reexecute the crash_kexec_secondary path.
         */
        old_handler = __debugger;
        __debugger = handle_fault;
        crash_shutdown_cpu = smp_processor_id();

        if (setjmp(crash_shutdown_buf) == 0) {
                printk(KERN_EMERG "Activate system reset (dumprestart) "
                                  "to stop other cpu(s)\n");

                /*
                 * A system reset will force all CPUs to execute the
                 * crash code again. We need to reset cpus_in_crash so we
                 * wait for everyone to do this.
                 */
                atomic_set(&cpus_in_crash, 0);
                smp_mb();

                while (atomic_read(&cpus_in_crash) < ncpus)
                        cpu_relax();
        }

        crash_shutdown_cpu = -1;
        __debugger = old_handler;

        tries++;
        goto again;
}

/*
 * This function will be called by secondary cpus.
 */
void crash_kexec_secondary(struct pt_regs *regs)
{
        unsigned long flags;
        int msecs = SECONDARY_TIMEOUT;

        local_irq_save(flags);

        /* Wait for the primary crash CPU to signal its progress */
        while (crashing_cpu < 0) {
                if (--msecs < 0) {
                        /* No response, kdump image may not have been loaded */
                        local_irq_restore(flags);
                        return;
                }

                mdelay(1);
        }

        crash_ipi_callback(regs);
}

#else   /* ! CONFIG_SMP */

static void crash_kexec_prepare_cpus(void)
{
        /*
         * move the secondaries to us so that we can copy
         * the new kernel 0-0x100 safely
         *
         * do this if kexec in setup.c ?
         */
#ifdef CONFIG_PPC64
        smp_release_cpus();
#else
        /* FIXME */
#endif
}

void crash_kexec_secondary(struct pt_regs *regs)
{
}
#endif  /* CONFIG_SMP */

/* wait for all the CPUs to hit real mode but timeout if they don't come in */
#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
noinstr static void __maybe_unused crash_kexec_wait_realmode(int cpu)
{
        unsigned int msecs;
        int i;

        msecs = REAL_MODE_TIMEOUT;
        for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
                if (i == cpu)
                        continue;

                while (paca_ptrs[i]->kexec_state < KEXEC_STATE_REAL_MODE) {
                        barrier();
                        if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
                                break;
                        msecs--;
                        mdelay(1);
                }
        }
        mb();
}
#else
static inline void crash_kexec_wait_realmode(int cpu) {}
#endif  /* CONFIG_SMP && CONFIG_PPC64 */

void crash_kexec_prepare(void)
{
        /* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
        printk_deferred_enter();

        /*
         * This function is only called after the system
         * has panicked or is otherwise in a critical state.
         * The minimum amount of code to allow a kexec'd kernel
         * to run successfully needs to happen here.
         *
         * In practice this means stopping other cpus in
         * an SMP system.
         * The kernel is broken so disable interrupts.
         */
        hard_irq_disable();

        /*
         * Make a note of crashing cpu. Will be used in machine_kexec
         * such that another IPI will not be sent.
         */
        crashing_cpu = smp_processor_id();

        crash_kexec_prepare_cpus();
}

/*
 * Register a function to be called on shutdown.  Only use this if you
 * can't reset your device in the second kernel.
 */
int crash_shutdown_register(crash_shutdown_t handler)
{
        unsigned int i, rc;

        spin_lock(&crash_handlers_lock);
        for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
                if (!crash_shutdown_handles[i]) {
                        /* Insert handle at first empty entry */
                        crash_shutdown_handles[i] = handler;
                        rc = 0;
                        break;
                }

        if (i == CRASH_HANDLER_MAX) {
                printk(KERN_ERR "Crash shutdown handles full, "
                       "not registered.\n");
                rc = 1;
        }

        spin_unlock(&crash_handlers_lock);
        return rc;
}
EXPORT_SYMBOL(crash_shutdown_register);

int crash_shutdown_unregister(crash_shutdown_t handler)
{
        unsigned int i, rc;

        spin_lock(&crash_handlers_lock);
        for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
                if (crash_shutdown_handles[i] == handler)
                        break;

        if (i == CRASH_HANDLER_MAX) {
                printk(KERN_ERR "Crash shutdown handle not found\n");
                rc = 1;
        } else {
                /* Shift handles down */
                for (; i < (CRASH_HANDLER_MAX - 1); i++)
                        crash_shutdown_handles[i] =
                                crash_shutdown_handles[i+1];
                /*
                 * Reset last entry to NULL now that it has been shifted down,
                 * this will allow new handles to be added here.
                 */
                crash_shutdown_handles[i] = NULL;
                rc = 0;
        }

        spin_unlock(&crash_handlers_lock);
        return rc;
}
EXPORT_SYMBOL(crash_shutdown_unregister);

void default_machine_crash_shutdown(struct pt_regs *regs)
{
        volatile unsigned int i;
        int (*old_handler)(struct pt_regs *regs);

        if (TRAP(regs) == INTERRUPT_SYSTEM_RESET)
                is_via_system_reset = 1;

        if (IS_ENABLED(CONFIG_SMP))
                crash_smp_send_stop();
        else
                crash_kexec_prepare();

        crash_save_cpu(regs, crashing_cpu);

        time_to_dump = 1;

        crash_kexec_wait_realmode(crashing_cpu);

        machine_kexec_mask_interrupts();

        /*
         * Call registered shutdown routines safely.  Swap out
         * __debugger_fault_handler, and replace on exit.
         */
        old_handler = __debugger_fault_handler;
        __debugger_fault_handler = handle_fault;
        crash_shutdown_cpu = smp_processor_id();
        for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
                if (setjmp(crash_shutdown_buf) == 0) {
                        /*
                         * Insert syncs and delay to ensure
                         * instructions in the dangerous region don't
                         * leak away from this protected region.
                         */
                        asm volatile("sync; isync");
                        /* dangerous region */
                        crash_shutdown_handles[i]();
                        asm volatile("sync; isync");
                }
        }
        crash_shutdown_cpu = -1;
        __debugger_fault_handler = old_handler;

        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(1, 0);
}

#ifdef CONFIG_CRASH_HOTPLUG
#undef pr_fmt
#define pr_fmt(fmt) "crash hp: " fmt

/*
 * Advertise preferred elfcorehdr size to userspace via
 * /sys/kernel/crash_elfcorehdr_size sysfs interface.
 */
unsigned int arch_crash_get_elfcorehdr_size(void)
{
        unsigned long phdr_cnt;

        /* A program header for possible CPUs + vmcoreinfo */
        phdr_cnt = num_possible_cpus() + 1;
        if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
                phdr_cnt += CONFIG_CRASH_MAX_MEMORY_RANGES;

        return sizeof(struct elfhdr) + (phdr_cnt * sizeof(Elf64_Phdr));
}

/**
 * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with old
 *                             elfcorehdr in the kexec segment array.
 * @image: the active struct kimage
 * @mn: struct memory_notify data handler
 */
static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *mn)
{
        int ret;
        struct crash_mem *cmem = NULL;
        struct kexec_segment *ksegment;
        void *ptr, *mem, *elfbuf = NULL;
        unsigned long elfsz, memsz, base_addr, size;

        ksegment = &image->segment[image->elfcorehdr_index];
        mem = (void *) ksegment->mem;
        memsz = ksegment->memsz;

        ret = get_crash_memory_ranges(&cmem);
        if (ret) {
                pr_err("Failed to get crash mem range\n");
                return;
        }

        /*
         * The hot unplugged memory is part of crash memory ranges,
         * remove it here.
         */
        if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
                base_addr = PFN_PHYS(mn->start_pfn);
                size = mn->nr_pages * PAGE_SIZE;
                ret = remove_mem_range(&cmem, base_addr, size);
                if (ret) {
                        pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
                        goto out;
                }
        }

        ret = crash_prepare_elf64_headers(cmem, false, &elfbuf, &elfsz);
        if (ret) {
                pr_err("Failed to prepare elf header\n");
                goto out;
        }

        /*
         * It is unlikely that kernel hit this because elfcorehdr kexec
         * segment (memsz) is built with addition space to accommodate growing
         * number of crash memory ranges while loading the kdump kernel. It is
         * Just to avoid any unforeseen case.
         */
        if (elfsz > memsz) {
                pr_err("Updated crash elfcorehdr elfsz %lu > memsz %lu", elfsz, memsz);
                goto out;
        }

        ptr = __va(mem);
        if (ptr) {
                /* Temporarily invalidate the crash image while it is replaced */
                xchg(&kexec_crash_image, NULL);

                /* Replace the old elfcorehdr with newly prepared elfcorehdr */
                memcpy((void *)ptr, elfbuf, elfsz);

                /* The crash image is now valid once again */
                xchg(&kexec_crash_image, image);
        }
out:
        kvfree(cmem);
        kvfree(elfbuf);
}

/**
 * get_fdt_index - Loop through the kexec segment array and find
 *                 the index of the FDT segment.
 * @image: a pointer to kexec_crash_image
 *
 * Returns the index of FDT segment in the kexec segment array
 * if found; otherwise -1.
 */
static int get_fdt_index(struct kimage *image)
{
        void *ptr;
        unsigned long mem;
        int i, fdt_index = -1;

        /* Find the FDT segment index in kexec segment array. */
        for (i = 0; i < image->nr_segments; i++) {
                mem = image->segment[i].mem;
                ptr = __va(mem);

                if (ptr && fdt_magic(ptr) == FDT_MAGIC) {
                        fdt_index = i;
                        break;
                }
        }

        return fdt_index;
}

/**
 * update_crash_fdt - updates the cpus node of the crash FDT.
 *
 * @image: a pointer to kexec_crash_image
 */
static void update_crash_fdt(struct kimage *image)
{
        void *fdt;
        int fdt_index;

        fdt_index = get_fdt_index(image);
        if (fdt_index < 0) {
                pr_err("Unable to locate FDT segment.\n");
                return;
        }

        fdt = __va((void *)image->segment[fdt_index].mem);

        /* Temporarily invalidate the crash image while it is replaced */
        xchg(&kexec_crash_image, NULL);

        /* update FDT to reflect changes in CPU resources */
        if (update_cpus_node(fdt))
                pr_err("Failed to update crash FDT");

        /* The crash image is now valid once again */
        xchg(&kexec_crash_image, image);
}

int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)
{
#ifdef CONFIG_KEXEC_FILE
        if (image->file_mode)
                return 1;
#endif
        return kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT;
}

/**
 * arch_crash_handle_hotplug_event - Handle crash CPU/Memory hotplug events to update the
 *                                   necessary kexec segments based on the hotplug event.
 * @image: a pointer to kexec_crash_image
 * @arg: struct memory_notify handler for memory hotplug case and NULL for CPU hotplug case.
 *
 * Update the kdump image based on the type of hotplug event, represented by image->hp_action.
 * CPU add: Update the FDT segment to include the newly added CPU.
 * CPU remove: No action is needed, with the assumption that it's okay to have offline CPUs
 *             part of the FDT.
 * Memory add/remove: No action is taken as this is not yet supported.
 */
void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
{
        struct memory_notify *mn;

        switch (image->hp_action) {
        case KEXEC_CRASH_HP_REMOVE_CPU:
                return;

        case KEXEC_CRASH_HP_ADD_CPU:
                update_crash_fdt(image);
                break;

        case KEXEC_CRASH_HP_REMOVE_MEMORY:
        case KEXEC_CRASH_HP_ADD_MEMORY:
                mn = (struct memory_notify *)arg;
                update_crash_elfcorehdr(image, mn);
                return;
        default:
                pr_warn_once("Unknown hotplug action\n");
        }
}
#endif /* CONFIG_CRASH_HOTPLUG */