// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Firmware Assisted dump: A robust mechanism to get reliable kernel crash
 * dump with assistance from firmware. This approach does not use kexec,
 * instead firmware assists in booting the kdump kernel while preserving
 * memory contents. The most of the code implementation has been adapted
 * from phyp assisted dump implementation written by Linas Vepstas and
 * Manish Ahuja
 *
 * Copyright 2011 IBM Corporation
 * Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
 */

#undef DEBUG
#define pr_fmt(fmt) "fadump: " fmt

#include <linux/string.h>
#include <linux/memblock.h>
#include <linux/delay.h>
#include <linux/seq_file.h>
#include <linux/crash_dump.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <linux/slab.h>
#include <linux/cma.h>
#include <linux/hugetlb.h>

#include <asm/debugfs.h>
#include <asm/page.h>
#include <asm/prom.h>
#include <asm/fadump.h>
#include <asm/fadump-internal.h>
#include <asm/setup.h>

static struct fw_dump fw_dump;

static void __init fadump_reserve_crash_area(u64 base);

#ifndef CONFIG_PRESERVE_FA_DUMP
static DEFINE_MUTEX(fadump_mutex);
struct fadump_mrange_info crash_mrange_info = { "crash", NULL, 0, 0, 0 };
struct fadump_mrange_info reserved_mrange_info = { "reserved", NULL, 0, 0, 0 };

#ifdef CONFIG_CMA
static struct cma *fadump_cma;

/*
 * fadump_cma_init() - Initialize CMA area from a fadump reserved memory
 *
 * This function initializes CMA area from fadump reserved memory.
 * The total size of fadump reserved memory covers for boot memory size
 * + cpu data size + hpte size and metadata.
 * Initialize only the area equivalent to boot memory size for CMA use.
 * The reamining portion of fadump reserved memory will be not given
 * to CMA and pages for thoes will stay reserved. boot memory size is
 * aligned per CMA requirement to satisy cma_init_reserved_mem() call.
 * But for some reason even if it fails we still have the memory reservation
 * with us and we can still continue doing fadump.
 */
int __init fadump_cma_init(void)
{
        unsigned long long base, size;
        int rc;

        if (!fw_dump.fadump_enabled)
                return 0;

        /*
         * Do not use CMA if user has provided fadump=nocma kernel parameter.
         * Return 1 to continue with fadump old behaviour.
         */
        if (fw_dump.nocma)
                return 1;

        base = fw_dump.reserve_dump_area_start;
        size = fw_dump.boot_memory_size;

        if (!size)
                return 0;

        rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
        if (rc) {
                pr_err("Failed to init cma area for firmware-assisted dump,%d\n", rc);
                /*
                 * Though the CMA init has failed we still have memory
                 * reservation with us. The reserved memory will be
                 * blocked from production system usage.  Hence return 1,
                 * so that we can continue with fadump.
                 */
                return 1;
        }

        /*
         * So we now have successfully initialized cma area for fadump.
         */
        pr_info("Initialized 0x%lx bytes cma area at %ldMB from 0x%lx "
                "bytes of memory reserved for firmware-assisted dump\n",
                cma_get_size(fadump_cma),
                (unsigned long)cma_get_base(fadump_cma) >> 20,
                fw_dump.reserve_dump_area_size);
        return 1;
}
#else
static int __init fadump_cma_init(void) { return 1; }
#endif /* CONFIG_CMA */

/* Scan the Firmware Assisted dump configuration details. */
int __init early_init_dt_scan_fw_dump(unsigned long node, const char *uname,
                                      int depth, void *data)
{
        if (depth != 1)
                return 0;

        if (strcmp(uname, "rtas") == 0) {
                rtas_fadump_dt_scan(&fw_dump, node);
                return 1;
        }

        if (strcmp(uname, "ibm,opal") == 0) {
                opal_fadump_dt_scan(&fw_dump, node);
                return 1;
        }

        return 0;
}

/*
 * If fadump is registered, check if the memory provided
 * falls within boot memory area and reserved memory area.
 */
int is_fadump_memory_area(u64 addr, unsigned long size)
{
        u64 d_start, d_end;

        if (!fw_dump.dump_registered)
                return 0;

        if (!size)
                return 0;

        d_start = fw_dump.reserve_dump_area_start;
        d_end = d_start + fw_dump.reserve_dump_area_size;
        if (((addr + size) > d_start) && (addr <= d_end))
                return 1;

        return (addr <= fw_dump.boot_mem_top);
}

int should_fadump_crash(void)
{
        if (!fw_dump.dump_registered || !fw_dump.fadumphdr_addr)
                return 0;
        return 1;
}

int is_fadump_active(void)
{
        return fw_dump.dump_active;
}

/*
 * Returns true, if there are no holes in memory area between d_start to d_end,
 * false otherwise.
 */
static bool is_fadump_mem_area_contiguous(u64 d_start, u64 d_end)
{
        struct memblock_region *reg;
        bool ret = false;
        u64 start, end;

        for_each_memblock(memory, reg) {
                start = max_t(u64, d_start, reg->base);
                end = min_t(u64, d_end, (reg->base + reg->size));
                if (d_start < end) {
                        /* Memory hole from d_start to start */
                        if (start > d_start)
                                break;

                        if (end == d_end) {
                                ret = true;
                                break;
                        }

                        d_start = end + 1;
                }
        }

        return ret;
}

/*
 * Returns true, if there are no holes in boot memory area,
 * false otherwise.
 */
bool is_fadump_boot_mem_contiguous(void)
{
        unsigned long d_start, d_end;
        bool ret = false;
        int i;

        for (i = 0; i < fw_dump.boot_mem_regs_cnt; i++) {
                d_start = fw_dump.boot_mem_addr[i];
                d_end   = d_start + fw_dump.boot_mem_sz[i];

                ret = is_fadump_mem_area_contiguous(d_start, d_end);
                if (!ret)
                        break;
        }

        return ret;
}

/*
 * Returns true, if there are no holes in reserved memory area,
 * false otherwise.
 */
bool is_fadump_reserved_mem_contiguous(void)
{
        u64 d_start, d_end;

        d_start = fw_dump.reserve_dump_area_start;
        d_end   = d_start + fw_dump.reserve_dump_area_size;
        return is_fadump_mem_area_contiguous(d_start, d_end);
}

/* Print firmware assisted dump configurations for debugging purpose. */
static void fadump_show_config(void)
{
        int i;

        pr_debug("Support for firmware-assisted dump (fadump): %s\n",
                        (fw_dump.fadump_supported ? "present" : "no support"));

        if (!fw_dump.fadump_supported)
                return;

        pr_debug("Fadump enabled    : %s\n",
                                (fw_dump.fadump_enabled ? "yes" : "no"));
        pr_debug("Dump Active       : %s\n",
                                (fw_dump.dump_active ? "yes" : "no"));
        pr_debug("Dump section sizes:\n");
        pr_debug("    CPU state data size: %lx\n", fw_dump.cpu_state_data_size);
        pr_debug("    HPTE region size   : %lx\n", fw_dump.hpte_region_size);
        pr_debug("    Boot memory size   : %lx\n", fw_dump.boot_memory_size);
        pr_debug("    Boot memory top    : %llx\n", fw_dump.boot_mem_top);
        pr_debug("Boot memory regions cnt: %llx\n", fw_dump.boot_mem_regs_cnt);
        for (i = 0; i < fw_dump.boot_mem_regs_cnt; i++) {
                pr_debug("[%03d] base = %llx, size = %llx\n", i,
                         fw_dump.boot_mem_addr[i], fw_dump.boot_mem_sz[i]);
        }
}

/**
 * fadump_calculate_reserve_size(): reserve variable boot area 5% of System RAM
 *
 * Function to find the largest memory size we need to reserve during early
 * boot process. This will be the size of the memory that is required for a
 * kernel to boot successfully.
 *
 * This function has been taken from phyp-assisted dump feature implementation.
 *
 * returns larger of 256MB or 5% rounded down to multiples of 256MB.
 *
 * TODO: Come up with better approach to find out more accurate memory size
 * that is required for a kernel to boot successfully.
 *
 */
static inline u64 fadump_calculate_reserve_size(void)
{
        u64 base, size, bootmem_min;
        int ret;

        if (fw_dump.reserve_bootvar)
                pr_warn("'fadump_reserve_mem=' parameter is deprecated in favor of 'crashkernel=' parameter.\n");

        /*
         * Check if the size is specified through crashkernel= cmdline
         * option. If yes, then use that but ignore base as fadump reserves
         * memory at a predefined offset.
         */
        ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
                                &size, &base);
        if (ret == 0 && size > 0) {
                unsigned long max_size;

                if (fw_dump.reserve_bootvar)
                        pr_info("Using 'crashkernel=' parameter for memory reservation.\n");

                fw_dump.reserve_bootvar = (unsigned long)size;

                /*
                 * Adjust if the boot memory size specified is above
                 * the upper limit.
                 */
                max_size = memblock_phys_mem_size() / MAX_BOOT_MEM_RATIO;
                if (fw_dump.reserve_bootvar > max_size) {
                        fw_dump.reserve_bootvar = max_size;
                        pr_info("Adjusted boot memory size to %luMB\n",
                                (fw_dump.reserve_bootvar >> 20));
                }

                return fw_dump.reserve_bootvar;
        } else if (fw_dump.reserve_bootvar) {
                /*
                 * 'fadump_reserve_mem=' is being used to reserve memory
                 * for firmware-assisted dump.
                 */
                return fw_dump.reserve_bootvar;
        }

        /* divide by 20 to get 5% of value */
        size = memblock_phys_mem_size() / 20;

        /* round it down in multiples of 256 */
        size = size & ~0x0FFFFFFFUL;

        /* Truncate to memory_limit. We don't want to over reserve the memory.*/
        if (memory_limit && size > memory_limit)
                size = memory_limit;

        bootmem_min = fw_dump.ops->fadump_get_bootmem_min();
        return (size > bootmem_min ? size : bootmem_min);
}

/*
 * Calculate the total memory size required to be reserved for
 * firmware-assisted dump registration.
 */
static unsigned long get_fadump_area_size(void)
{
        unsigned long size = 0;

        size += fw_dump.cpu_state_data_size;
        size += fw_dump.hpte_region_size;
        size += fw_dump.boot_memory_size;
        size += sizeof(struct fadump_crash_info_header);
        size += sizeof(struct elfhdr); /* ELF core header.*/
        size += sizeof(struct elf_phdr); /* place holder for cpu notes */
        /* Program headers for crash memory regions. */
        size += sizeof(struct elf_phdr) * (memblock_num_regions(memory) + 2);

        size = PAGE_ALIGN(size);

        /* This is to hold kernel metadata on platforms that support it */
        size += (fw_dump.ops->fadump_get_metadata_size ?
                 fw_dump.ops->fadump_get_metadata_size() : 0);
        return size;
}

static int __init add_boot_mem_region(unsigned long rstart,
                                      unsigned long rsize)
{
        int i = fw_dump.boot_mem_regs_cnt++;

        if (fw_dump.boot_mem_regs_cnt > FADUMP_MAX_MEM_REGS) {
                fw_dump.boot_mem_regs_cnt = FADUMP_MAX_MEM_REGS;
                return 0;
        }

        pr_debug("Added boot memory range[%d] [%#016lx-%#016lx)\n",
                 i, rstart, (rstart + rsize));
        fw_dump.boot_mem_addr[i] = rstart;
        fw_dump.boot_mem_sz[i] = rsize;
        return 1;
}

/*
 * Firmware usually has a hard limit on the data it can copy per region.
 * Honour that by splitting a memory range into multiple regions.
 */
static int __init add_boot_mem_regions(unsigned long mstart,
                                       unsigned long msize)
{
        unsigned long rstart, rsize, max_size;
        int ret = 1;

        rstart = mstart;
        max_size = fw_dump.max_copy_size ? fw_dump.max_copy_size : msize;
        while (msize) {
                if (msize > max_size)
                        rsize = max_size;
                else
                        rsize = msize;

                ret = add_boot_mem_region(rstart, rsize);
                if (!ret)
                        break;

                msize -= rsize;
                rstart += rsize;
        }

        return ret;
}

static int __init fadump_get_boot_mem_regions(void)
{
        unsigned long base, size, cur_size, hole_size, last_end;
        unsigned long mem_size = fw_dump.boot_memory_size;
        struct memblock_region *reg;
        int ret = 1;

        fw_dump.boot_mem_regs_cnt = 0;

        last_end = 0;
        hole_size = 0;
        cur_size = 0;
        for_each_memblock(memory, reg) {
                base = reg->base;
                size = reg->size;
                hole_size += (base - last_end);

                if ((cur_size + size) >= mem_size) {
                        size = (mem_size - cur_size);
                        ret = add_boot_mem_regions(base, size);
                        break;
                }

                mem_size -= size;
                cur_size += size;
                ret = add_boot_mem_regions(base, size);
                if (!ret)
                        break;

                last_end = base + size;
        }
        fw_dump.boot_mem_top = PAGE_ALIGN(fw_dump.boot_memory_size + hole_size);

        return ret;
}

int __init fadump_reserve_mem(void)
{
        u64 base, size, mem_boundary, bootmem_min, align = PAGE_SIZE;
        bool is_memblock_bottom_up = memblock_bottom_up();
        int ret = 1;

        if (!fw_dump.fadump_enabled)
                return 0;

        if (!fw_dump.fadump_supported) {
                pr_info("Firmware-Assisted Dump is not supported on this hardware\n");
                goto error_out;
        }

        /*
         * Initialize boot memory size
         * If dump is active then we have already calculated the size during
         * first kernel.
         */
        if (!fw_dump.dump_active) {
                fw_dump.boot_memory_size =
                        PAGE_ALIGN(fadump_calculate_reserve_size());
#ifdef CONFIG_CMA
                if (!fw_dump.nocma) {
                        align = FADUMP_CMA_ALIGNMENT;
                        fw_dump.boot_memory_size =
                                ALIGN(fw_dump.boot_memory_size, align);
                }
#endif

                bootmem_min = fw_dump.ops->fadump_get_bootmem_min();
                if (fw_dump.boot_memory_size < bootmem_min) {
                        pr_err("Can't enable fadump with boot memory size (0x%lx) less than 0x%llx\n",
                               fw_dump.boot_memory_size, bootmem_min);
                        goto error_out;
                }

                if (!fadump_get_boot_mem_regions()) {
                        pr_err("Too many holes in boot memory area to enable fadump\n");
                        goto error_out;
                }
        }

        /*
         * Calculate the memory boundary.
         * If memory_limit is less than actual memory boundary then reserve
         * the memory for fadump beyond the memory_limit and adjust the
         * memory_limit accordingly, so that the running kernel can run with
         * specified memory_limit.
         */
        if (memory_limit && memory_limit < memblock_end_of_DRAM()) {
                size = get_fadump_area_size();
                if ((memory_limit + size) < memblock_end_of_DRAM())
                        memory_limit += size;
                else
                        memory_limit = memblock_end_of_DRAM();
                printk(KERN_INFO "Adjusted memory_limit for firmware-assisted"
                                " dump, now %#016llx\n", memory_limit);
        }
        if (memory_limit)
                mem_boundary = memory_limit;
        else
                mem_boundary = memblock_end_of_DRAM();

        base = fw_dump.boot_mem_top;
        size = get_fadump_area_size();
        fw_dump.reserve_dump_area_size = size;
        if (fw_dump.dump_active) {
                pr_info("Firmware-assisted dump is active.\n");

#ifdef CONFIG_HUGETLB_PAGE
                /*
                 * FADump capture kernel doesn't care much about hugepages.
                 * In fact, handling hugepages in capture kernel is asking for
                 * trouble. So, disable HugeTLB support when fadump is active.
                 */
                hugetlb_disabled = true;
#endif
                /*
                 * If last boot has crashed then reserve all the memory
                 * above boot memory size so that we don't touch it until
                 * dump is written to disk by userspace tool. This memory
                 * can be released for general use by invalidating fadump.
                 */
                fadump_reserve_crash_area(base);

                pr_debug("fadumphdr_addr = %#016lx\n", fw_dump.fadumphdr_addr);
                pr_debug("Reserve dump area start address: 0x%lx\n",
                         fw_dump.reserve_dump_area_start);
        } else {
                /*
                 * Reserve memory at an offset closer to bottom of the RAM to
                 * minimize the impact of memory hot-remove operation.
                 */
                memblock_set_bottom_up(true);
                base = memblock_find_in_range(base, mem_boundary, size, align);

                /* Restore the previous allocation mode */
                memblock_set_bottom_up(is_memblock_bottom_up);

                if (!base) {
                        pr_err("Failed to find memory chunk for reservation!\n");
                        goto error_out;
                }
                fw_dump.reserve_dump_area_start = base;

                /*
                 * Calculate the kernel metadata address and register it with
                 * f/w if the platform supports.
                 */
                if (fw_dump.ops->fadump_setup_metadata &&
                    (fw_dump.ops->fadump_setup_metadata(&fw_dump) < 0))
                        goto error_out;

                if (memblock_reserve(base, size)) {
                        pr_err("Failed to reserve memory!\n");
                        goto error_out;
                }

                pr_info("Reserved %lldMB of memory at %#016llx (System RAM: %lldMB)\n",
                        (size >> 20), base, (memblock_phys_mem_size() >> 20));

                ret = fadump_cma_init();
        }

        return ret;
error_out:
        fw_dump.fadump_enabled = 0;
        return 0;
}

/* Look for fadump= cmdline option. */
static int __init early_fadump_param(char *p)
{
        if (!p)
                return 1;

        if (strncmp(p, "on", 2) == 0)
                fw_dump.fadump_enabled = 1;
        else if (strncmp(p, "off", 3) == 0)
                fw_dump.fadump_enabled = 0;
        else if (strncmp(p, "nocma", 5) == 0) {
                fw_dump.fadump_enabled = 1;
                fw_dump.nocma = 1;
        }

        return 0;
}
early_param("fadump", early_fadump_param);

/*
 * Look for fadump_reserve_mem= cmdline option
 * TODO: Remove references to 'fadump_reserve_mem=' parameter,
 *       the sooner 'crashkernel=' parameter is accustomed to.
 */
static int __init early_fadump_reserve_mem(char *p)
{
        if (p)
                fw_dump.reserve_bootvar = memparse(p, &p);
        return 0;
}
early_param("fadump_reserve_mem", early_fadump_reserve_mem);

void crash_fadump(struct pt_regs *regs, const char *str)
{
        struct fadump_crash_info_header *fdh = NULL;
        int old_cpu, this_cpu;

        if (!should_fadump_crash())
                return;

        /*
         * old_cpu == -1 means this is the first CPU which has come here,
         * go ahead and trigger fadump.
         *
         * old_cpu != -1 means some other CPU has already on it's way
         * to trigger fadump, just keep looping here.
         */
        this_cpu = smp_processor_id();
        old_cpu = cmpxchg(&crashing_cpu, -1, this_cpu);

        if (old_cpu != -1) {
                /*
                 * We can't loop here indefinitely. Wait as long as fadump
                 * is in force. If we race with fadump un-registration this
                 * loop will break and then we go down to normal panic path
                 * and reboot. If fadump is in force the first crashing
                 * cpu will definitely trigger fadump.
                 */
                while (fw_dump.dump_registered)
                        cpu_relax();
                return;
        }

        fdh = __va(fw_dump.fadumphdr_addr);
        fdh->crashing_cpu = crashing_cpu;
        crash_save_vmcoreinfo();

        if (regs)
                fdh->regs = *regs;
        else
                ppc_save_regs(&fdh->regs);

        fdh->online_mask = *cpu_online_mask;

        fw_dump.ops->fadump_trigger(fdh, str);
}

u32 *fadump_regs_to_elf_notes(u32 *buf, struct pt_regs *regs)
{
        struct elf_prstatus prstatus;

        memset(&prstatus, 0, sizeof(prstatus));
        /*
         * FIXME: How do i get PID? Do I really need it?
         * prstatus.pr_pid = ????
         */
        elf_core_copy_kernel_regs(&prstatus.pr_reg, regs);
        buf = append_elf_note(buf, CRASH_CORE_NOTE_NAME, NT_PRSTATUS,
                              &prstatus, sizeof(prstatus));
        return buf;
}

void fadump_update_elfcore_header(char *bufp)
{
        struct elfhdr *elf;
        struct elf_phdr *phdr;

        elf = (struct elfhdr *)bufp;
        bufp += sizeof(struct elfhdr);

        /* First note is a place holder for cpu notes info. */
        phdr = (struct elf_phdr *)bufp;

        if (phdr->p_type == PT_NOTE) {
                phdr->p_paddr   = __pa(fw_dump.cpu_notes_buf_vaddr);
                phdr->p_offset  = phdr->p_paddr;
                phdr->p_filesz  = fw_dump.cpu_notes_buf_size;
                phdr->p_memsz = fw_dump.cpu_notes_buf_size;
        }
        return;
}

static void *fadump_alloc_buffer(unsigned long size)
{
        unsigned long count, i;
        struct page *page;
        void *vaddr;

        vaddr = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO);
        if (!vaddr)
                return NULL;

        count = PAGE_ALIGN(size) / PAGE_SIZE;
        page = virt_to_page(vaddr);
        for (i = 0; i < count; i++)
                mark_page_reserved(page + i);
        return vaddr;
}

static void fadump_free_buffer(unsigned long vaddr, unsigned long size)
{
        free_reserved_area((void *)vaddr, (void *)(vaddr + size), -1, NULL);
}

s32 fadump_setup_cpu_notes_buf(u32 num_cpus)
{
        /* Allocate buffer to hold cpu crash notes. */
        fw_dump.cpu_notes_buf_size = num_cpus * sizeof(note_buf_t);
        fw_dump.cpu_notes_buf_size = PAGE_ALIGN(fw_dump.cpu_notes_buf_size);
        fw_dump.cpu_notes_buf_vaddr =
                (unsigned long)fadump_alloc_buffer(fw_dump.cpu_notes_buf_size);
        if (!fw_dump.cpu_notes_buf_vaddr) {
                pr_err("Failed to allocate %ld bytes for CPU notes buffer\n",
                       fw_dump.cpu_notes_buf_size);
                return -ENOMEM;
        }

        pr_debug("Allocated buffer for cpu notes of size %ld at 0x%lx\n",
                 fw_dump.cpu_notes_buf_size,
                 fw_dump.cpu_notes_buf_vaddr);
        return 0;
}

void fadump_free_cpu_notes_buf(void)
{
        if (!fw_dump.cpu_notes_buf_vaddr)
                return;

        fadump_free_buffer(fw_dump.cpu_notes_buf_vaddr,
                           fw_dump.cpu_notes_buf_size);
        fw_dump.cpu_notes_buf_vaddr = 0;
        fw_dump.cpu_notes_buf_size = 0;
}

static void fadump_free_mem_ranges(struct fadump_mrange_info *mrange_info)
{
        kfree(mrange_info->mem_ranges);
        mrange_info->mem_ranges = NULL;
        mrange_info->mem_ranges_sz = 0;
        mrange_info->max_mem_ranges = 0;
}

/*
 * Allocate or reallocate mem_ranges array in incremental units
 * of PAGE_SIZE.
 */
static int fadump_alloc_mem_ranges(struct fadump_mrange_info *mrange_info)
{
        struct fadump_memory_range *new_array;
        u64 new_size;

        new_size = mrange_info->mem_ranges_sz + PAGE_SIZE;
        pr_debug("Allocating %llu bytes of memory for %s memory ranges\n",
                 new_size, mrange_info->name);

        new_array = krealloc(mrange_info->mem_ranges, new_size, GFP_KERNEL);
        if (new_array == NULL) {
                pr_err("Insufficient memory for setting up %s memory ranges\n",
                       mrange_info->name);
                fadump_free_mem_ranges(mrange_info);
                return -ENOMEM;
        }

        mrange_info->mem_ranges = new_array;
        mrange_info->mem_ranges_sz = new_size;
        mrange_info->max_mem_ranges = (new_size /
                                       sizeof(struct fadump_memory_range));
        return 0;
}

static inline int fadump_add_mem_range(struct fadump_mrange_info *mrange_info,
                                       u64 base, u64 end)
{
        struct fadump_memory_range *mem_ranges = mrange_info->mem_ranges;
        bool is_adjacent = false;
        u64 start, size;

        if (base == end)
                return 0;

        /*
         * Fold adjacent memory ranges to bring down the memory ranges/
         * PT_LOAD segments count.
         */
        if (mrange_info->mem_range_cnt) {
                start = mem_ranges[mrange_info->mem_range_cnt - 1].base;
                size  = mem_ranges[mrange_info->mem_range_cnt - 1].size;

                if ((start + size) == base)
                        is_adjacent = true;
        }
        if (!is_adjacent) {
                /* resize the array on reaching the limit */
                if (mrange_info->mem_range_cnt == mrange_info->max_mem_ranges) {
                        int ret;

                        ret = fadump_alloc_mem_ranges(mrange_info);
                        if (ret)
                                return ret;

                        /* Update to the new resized array */
                        mem_ranges = mrange_info->mem_ranges;
                }

                start = base;
                mem_ranges[mrange_info->mem_range_cnt].base = start;
                mrange_info->mem_range_cnt++;
        }

        mem_ranges[mrange_info->mem_range_cnt - 1].size = (end - start);
        pr_debug("%s_memory_range[%d] [%#016llx-%#016llx], %#llx bytes\n",
                 mrange_info->name, (mrange_info->mem_range_cnt - 1),
                 start, end - 1, (end - start));
        return 0;
}

static int fadump_exclude_reserved_area(u64 start, u64 end)
{
        u64 ra_start, ra_end;
        int ret = 0;

        ra_start = fw_dump.reserve_dump_area_start;
        ra_end = ra_start + fw_dump.reserve_dump_area_size;

        if ((ra_start < end) && (ra_end > start)) {
                if ((start < ra_start) && (end > ra_end)) {
                        ret = fadump_add_mem_range(&crash_mrange_info,
                                                   start, ra_start);
                        if (ret)
                                return ret;

                        ret = fadump_add_mem_range(&crash_mrange_info,
                                                   ra_end, end);
                } else if (start < ra_start) {
                        ret = fadump_add_mem_range(&crash_mrange_info,
                                                   start, ra_start);
                } else if (ra_end < end) {
                        ret = fadump_add_mem_range(&crash_mrange_info,
                                                   ra_end, end);
                }
        } else
                ret = fadump_add_mem_range(&crash_mrange_info, start, end);

        return ret;
}

static int fadump_init_elfcore_header(char *bufp)
{
        struct elfhdr *elf;

        elf = (struct elfhdr *) bufp;
        bufp += sizeof(struct elfhdr);
        memcpy(elf->e_ident, ELFMAG, SELFMAG);
        elf->e_ident[EI_CLASS] = ELF_CLASS;
        elf->e_ident[EI_DATA] = ELF_DATA;
        elf->e_ident[EI_VERSION] = EV_CURRENT;
        elf->e_ident[EI_OSABI] = ELF_OSABI;
        memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD);
        elf->e_type = ET_CORE;
        elf->e_machine = ELF_ARCH;
        elf->e_version = EV_CURRENT;
        elf->e_entry = 0;
        elf->e_phoff = sizeof(struct elfhdr);
        elf->e_shoff = 0;
#if defined(_CALL_ELF)
        elf->e_flags = _CALL_ELF;
#else
        elf->e_flags = 0;
#endif
        elf->e_ehsize = sizeof(struct elfhdr);
        elf->e_phentsize = sizeof(struct elf_phdr);
        elf->e_phnum = 0;
        elf->e_shentsize = 0;
        elf->e_shnum = 0;
        elf->e_shstrndx = 0;

        return 0;
}

/*
 * Traverse through memblock structure and setup crash memory ranges. These
 * ranges will be used create PT_LOAD program headers in elfcore header.
 */
static int fadump_setup_crash_memory_ranges(void)
{
        struct memblock_region *reg;
        u64 start, end;
        int i, ret;

        pr_debug("Setup crash memory ranges.\n");
        crash_mrange_info.mem_range_cnt = 0;

        /*
         * Boot memory region(s) registered with firmware are moved to
         * different location at the time of crash. Create separate program
         * header(s) for this memory chunk(s) with the correct offset.
         */
        for (i = 0; i < fw_dump.boot_mem_regs_cnt; i++) {
                start = fw_dump.boot_mem_addr[i];
                end = start + fw_dump.boot_mem_sz[i];
                ret = fadump_add_mem_range(&crash_mrange_info, start, end);
                if (ret)
                        return ret;
        }

        for_each_memblock(memory, reg) {
                start = (u64)reg->base;
                end = start + (u64)reg->size;

                /*
                 * skip the memory chunk that is already added
                 * (0 through boot_memory_top).
                 */
                if (start < fw_dump.boot_mem_top) {
                        if (end > fw_dump.boot_mem_top)
                                start = fw_dump.boot_mem_top;
                        else
                                continue;
                }

                /* add this range excluding the reserved dump area. */
                ret = fadump_exclude_reserved_area(start, end);
                if (ret)
                        return ret;
        }

        return 0;
}

/*
 * If the given physical address falls within the boot memory region then
 * return the relocated address that points to the dump region reserved
 * for saving initial boot memory contents.
 */
static inline unsigned long fadump_relocate(unsigned long paddr)
{
        unsigned long raddr, rstart, rend, rlast, hole_size;
        int i;

        hole_size = 0;
        rlast = 0;
        raddr = paddr;
        for (i = 0; i < fw_dump.boot_mem_regs_cnt; i++) {
                rstart = fw_dump.boot_mem_addr[i];
                rend = rstart + fw_dump.boot_mem_sz[i];
                hole_size += (rstart - rlast);

                if (paddr >= rstart && paddr < rend) {
                        raddr += fw_dump.boot_mem_dest_addr - hole_size;
                        break;
                }

                rlast = rend;
        }

        pr_debug("vmcoreinfo: paddr = 0x%lx, raddr = 0x%lx\n", paddr, raddr);
        return raddr;
}

static int fadump_create_elfcore_headers(char *bufp)
{
        unsigned long long raddr, offset;
        struct elf_phdr *phdr;
        struct elfhdr *elf;
        int i, j;

        fadump_init_elfcore_header(bufp);
        elf = (struct elfhdr *)bufp;
        bufp += sizeof(struct elfhdr);

        /*
         * setup ELF PT_NOTE, place holder for cpu notes info. The notes info
         * will be populated during second kernel boot after crash. Hence
         * this PT_NOTE will always be the first elf note.
         *
         * NOTE: Any new ELF note addition should be placed after this note.
         */
        phdr = (struct elf_phdr *)bufp;
        bufp += sizeof(struct elf_phdr);
        phdr->p_type = PT_NOTE;
        phdr->p_flags = 0;
        phdr->p_vaddr = 0;
        phdr->p_align = 0;

        phdr->p_offset = 0;
        phdr->p_paddr = 0;
        phdr->p_filesz = 0;
        phdr->p_memsz = 0;

        (elf->e_phnum)++;

        /* setup ELF PT_NOTE for vmcoreinfo */
        phdr = (struct elf_phdr *)bufp;
        bufp += sizeof(struct elf_phdr);
        phdr->p_type    = PT_NOTE;
        phdr->p_flags   = 0;
        phdr->p_vaddr   = 0;
        phdr->p_align   = 0;

        phdr->p_paddr   = fadump_relocate(paddr_vmcoreinfo_note());
        phdr->p_offset  = phdr->p_paddr;
        phdr->p_memsz   = phdr->p_filesz = VMCOREINFO_NOTE_SIZE;

        /* Increment number of program headers. */
        (elf->e_phnum)++;

        /* setup PT_LOAD sections. */
        j = 0;

        offset = 0;
        raddr = fw_dump.boot_mem_addr[0];
        for (i = 0; i < crash_mrange_info.mem_range_cnt; i++) {
                u64 mbase, msize;

                mbase = crash_mrange_info.mem_ranges[i].base;
                msize = crash_mrange_info.mem_ranges[i].size;
                if (!msize)
                        continue;

                phdr = (struct elf_phdr *)bufp;
                bufp += sizeof(struct elf_phdr);
                phdr->p_type    = PT_LOAD;
                phdr->p_flags   = PF_R|PF_W|PF_X;
                phdr->p_offset  = mbase;

                if (mbase == raddr) {
                        /*
                         * The entire real memory region will be moved by
                         * firmware to the specified destination_address.
                         * Hence set the correct offset.
                         */
                        phdr->p_offset = fw_dump.boot_mem_dest_addr + offset;
                        if (j < (fw_dump.boot_mem_regs_cnt - 1)) {
                                offset += fw_dump.boot_mem_sz[j];
                                raddr = fw_dump.boot_mem_addr[++j];
                        }
                }

                phdr->p_paddr = mbase;
                phdr->p_vaddr = (unsigned long)__va(mbase);
                phdr->p_filesz = msize;
                phdr->p_memsz = msize;
                phdr->p_align = 0;

                /* Increment number of program headers. */
                (elf->e_phnum)++;
        }
        return 0;
}

static unsigned long init_fadump_header(unsigned long addr)
{
        struct fadump_crash_info_header *fdh;

        if (!addr)
                return 0;

        fdh = __va(addr);
        addr += sizeof(struct fadump_crash_info_header);

        memset(fdh, 0, sizeof(struct fadump_crash_info_header));
        fdh->magic_number = FADUMP_CRASH_INFO_MAGIC;
        fdh->elfcorehdr_addr = addr;
        /* We will set the crashing cpu id in crash_fadump() during crash. */
        fdh->crashing_cpu = FADUMP_CPU_UNKNOWN;

        return addr;
}

static int register_fadump(void)
{
        unsigned long addr;
        void *vaddr;
        int ret;

        /*
         * If no memory is reserved then we can not register for firmware-
         * assisted dump.
         */
        if (!fw_dump.reserve_dump_area_size)
                return -ENODEV;

        ret = fadump_setup_crash_memory_ranges();
        if (ret)
                return ret;

        addr = fw_dump.fadumphdr_addr;

        /* Initialize fadump crash info header. */
        addr = init_fadump_header(addr);
        vaddr = __va(addr);

        pr_debug("Creating ELF core headers at %#016lx\n", addr);
        fadump_create_elfcore_headers(vaddr);

        /* register the future kernel dump with firmware. */
        pr_debug("Registering for firmware-assisted kernel dump...\n");
        return fw_dump.ops->fadump_register(&fw_dump);
}

void fadump_cleanup(void)
{
        if (!fw_dump.fadump_supported)
                return;

        /* Invalidate the registration only if dump is active. */
        if (fw_dump.dump_active) {
                pr_debug("Invalidating firmware-assisted dump registration\n");
                fw_dump.ops->fadump_invalidate(&fw_dump);
        } else if (fw_dump.dump_registered) {
                /* Un-register Firmware-assisted dump if it was registered. */
                fw_dump.ops->fadump_unregister(&fw_dump);
                fadump_free_mem_ranges(&crash_mrange_info);
        }

        if (fw_dump.ops->fadump_cleanup)
                fw_dump.ops->fadump_cleanup(&fw_dump);
}

static void fadump_free_reserved_memory(unsigned long start_pfn,
                                        unsigned long end_pfn)
{
        unsigned long pfn;
        unsigned long time_limit = jiffies + HZ;

        pr_info("freeing reserved memory (0x%llx - 0x%llx)\n",
                PFN_PHYS(start_pfn), PFN_PHYS(end_pfn));

        for (pfn = start_pfn; pfn < end_pfn; pfn++) {
                free_reserved_page(pfn_to_page(pfn));

                if (time_after(jiffies, time_limit)) {
                        cond_resched();
                        time_limit = jiffies + HZ;
                }
        }
}

/*
 * Skip memory holes and free memory that was actually reserved.
 */
static void fadump_release_reserved_area(u64 start, u64 end)
{
        u64 tstart, tend, spfn, epfn;
        struct memblock_region *reg;

        spfn = PHYS_PFN(start);
        epfn = PHYS_PFN(end);
        for_each_memblock(memory, reg) {
                tstart = max_t(u64, spfn, memblock_region_memory_base_pfn(reg));
                tend   = min_t(u64, epfn, memblock_region_memory_end_pfn(reg));
                if (tstart < tend) {
                        fadump_free_reserved_memory(tstart, tend);

                        if (tend == epfn)
                                break;

                        spfn = tend;
                }
        }
}

/*
 * Sort the mem ranges in-place and merge adjacent ranges
 * to minimize the memory ranges count.
 */
static void sort_and_merge_mem_ranges(struct fadump_mrange_info *mrange_info)
{
        struct fadump_memory_range *mem_ranges;
        struct fadump_memory_range tmp_range;
        u64 base, size;
        int i, j, idx;

        if (!reserved_mrange_info.mem_range_cnt)
                return;

        /* Sort the memory ranges */
        mem_ranges = mrange_info->mem_ranges;
        for (i = 0; i < mrange_info->mem_range_cnt; i++) {
                idx = i;
                for (j = (i + 1); j < mrange_info->mem_range_cnt; j++) {
                        if (mem_ranges[idx].base > mem_ranges[j].base)
                                idx = j;
                }
                if (idx != i) {
                        tmp_range = mem_ranges[idx];
                        mem_ranges[idx] = mem_ranges[i];
                        mem_ranges[i] = tmp_range;
                }
        }

        /* Merge adjacent reserved ranges */
        idx = 0;
        for (i = 1; i < mrange_info->mem_range_cnt; i++) {
                base = mem_ranges[i-1].base;
                size = mem_ranges[i-1].size;
                if (mem_ranges[i].base == (base + size))
                        mem_ranges[idx].size += mem_ranges[i].size;
                else {
                        idx++;
                        if (i == idx)
                                continue;

                        mem_ranges[idx] = mem_ranges[i];
                }
        }
        mrange_info->mem_range_cnt = idx + 1;
}

/*
 * Scan reserved-ranges to consider them while reserving/releasing
 * memory for FADump.
 */
static inline int fadump_scan_reserved_mem_ranges(void)
{
        struct device_node *root;
        const __be32 *prop;
        int len, ret = -1;
        unsigned long i;

        root = of_find_node_by_path("/");
        if (!root)
                return ret;

        prop = of_get_property(root, "reserved-ranges", &len);
        if (!prop)
                return ret;

        /*
         * Each reserved range is an (address,size) pair, 2 cells each,
         * totalling 4 cells per range.
         */
        for (i = 0; i < len / (sizeof(*prop) * 4); i++) {
                u64 base, size;

                base = of_read_number(prop + (i * 4) + 0, 2);
                size = of_read_number(prop + (i * 4) + 2, 2);

                if (size) {
                        ret = fadump_add_mem_range(&reserved_mrange_info,
                                                   base, base + size);
                        if (ret < 0) {
                                pr_warn("some reserved ranges are ignored!\n");
                                break;
                        }
                }
        }

        return ret;
}

/*
 * Release the memory that was reserved during early boot to preserve the
 * crash'ed kernel's memory contents except reserved dump area (permanent
 * reservation) and reserved ranges used by F/W. The released memory will
 * be available for general use.
 */
static void fadump_release_memory(u64 begin, u64 end)
{
        u64 ra_start, ra_end, tstart;
        int i, ret;

        fadump_scan_reserved_mem_ranges();

        ra_start = fw_dump.reserve_dump_area_start;
        ra_end = ra_start + fw_dump.reserve_dump_area_size;

        /*
         * Add reserved dump area to reserved ranges list
         * and exclude all these ranges while releasing memory.
         */
        ret = fadump_add_mem_range(&reserved_mrange_info, ra_start, ra_end);
        if (ret != 0) {
                /*
                 * Not enough memory to setup reserved ranges but the system is
                 * running shortage of memory. So, release all the memory except
                 * Reserved dump area (reused for next fadump registration).
                 */
                if (begin < ra_end && end > ra_start) {
                        if (begin < ra_start)
                                fadump_release_reserved_area(begin, ra_start);
                        if (end > ra_end)
                                fadump_release_reserved_area(ra_end, end);
                } else
                        fadump_release_reserved_area(begin, end);

                return;
        }

        /* Get the reserved ranges list in order first. */
        sort_and_merge_mem_ranges(&reserved_mrange_info);

        /* Exclude reserved ranges and release remaining memory */
        tstart = begin;
        for (i = 0; i < reserved_mrange_info.mem_range_cnt; i++) {
                ra_start = reserved_mrange_info.mem_ranges[i].base;
                ra_end = ra_start + reserved_mrange_info.mem_ranges[i].size;

                if (tstart >= ra_end)
                        continue;

                if (tstart < ra_start)
                        fadump_release_reserved_area(tstart, ra_start);
                tstart = ra_end;
        }

        if (tstart < end)
                fadump_release_reserved_area(tstart, end);
}

static void fadump_invalidate_release_mem(void)
{
        mutex_lock(&fadump_mutex);
        if (!fw_dump.dump_active) {
                mutex_unlock(&fadump_mutex);
                return;
        }

        fadump_cleanup();
        mutex_unlock(&fadump_mutex);

        fadump_release_memory(fw_dump.boot_mem_top, memblock_end_of_DRAM());
        fadump_free_cpu_notes_buf();

        /*
         * Setup kernel metadata and initialize the kernel dump
         * memory structure for FADump re-registration.
         */
        if (fw_dump.ops->fadump_setup_metadata &&
            (fw_dump.ops->fadump_setup_metadata(&fw_dump) < 0))
                pr_warn("Failed to setup kernel metadata!\n");
        fw_dump.ops->fadump_init_mem_struct(&fw_dump);
}

static ssize_t fadump_release_memory_store(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        const char *buf, size_t count)
{
        int input = -1;

        if (!fw_dump.dump_active)
                return -EPERM;

        if (kstrtoint(buf, 0, &input))
                return -EINVAL;

        if (input == 1) {
                /*
                 * Take away the '/proc/vmcore'. We are releasing the dump
                 * memory, hence it will not be valid anymore.
                 */
#ifdef CONFIG_PROC_VMCORE
                vmcore_cleanup();
#endif
                fadump_invalidate_release_mem();

        } else
                return -EINVAL;
        return count;
}

static ssize_t fadump_enabled_show(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        char *buf)
{
        return sprintf(buf, "%d\n", fw_dump.fadump_enabled);
}

static ssize_t fadump_register_show(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        char *buf)
{
        return sprintf(buf, "%d\n", fw_dump.dump_registered);
}

static ssize_t fadump_register_store(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        const char *buf, size_t count)
{
        int ret = 0;
        int input = -1;

        if (!fw_dump.fadump_enabled || fw_dump.dump_active)
                return -EPERM;

        if (kstrtoint(buf, 0, &input))
                return -EINVAL;

        mutex_lock(&fadump_mutex);

        switch (input) {
        case 0:
                if (fw_dump.dump_registered == 0) {
                        goto unlock_out;
                }

                /* Un-register Firmware-assisted dump */
                pr_debug("Un-register firmware-assisted dump\n");
                fw_dump.ops->fadump_unregister(&fw_dump);
                break;
        case 1:
                if (fw_dump.dump_registered == 1) {
                        /* Un-register Firmware-assisted dump */
                        fw_dump.ops->fadump_unregister(&fw_dump);
                }
                /* Register Firmware-assisted dump */
                ret = register_fadump();
                break;
        default:
                ret = -EINVAL;
                break;
        }

unlock_out:
        mutex_unlock(&fadump_mutex);
        return ret < 0 ? ret : count;
}

static int fadump_region_show(struct seq_file *m, void *private)
{
        if (!fw_dump.fadump_enabled)
                return 0;

        mutex_lock(&fadump_mutex);
        fw_dump.ops->fadump_region_show(&fw_dump, m);
        mutex_unlock(&fadump_mutex);
        return 0;
}

static struct kobj_attribute fadump_release_attr = __ATTR(fadump_release_mem,
                                                0200, NULL,
                                                fadump_release_memory_store);
static struct kobj_attribute fadump_attr = __ATTR(fadump_enabled,
                                                0444, fadump_enabled_show,
                                                NULL);
static struct kobj_attribute fadump_register_attr = __ATTR(fadump_registered,
                                                0644, fadump_register_show,
                                                fadump_register_store);

DEFINE_SHOW_ATTRIBUTE(fadump_region);

static void fadump_init_files(void)
{
        struct dentry *debugfs_file;
        int rc = 0;

        rc = sysfs_create_file(kernel_kobj, &fadump_attr.attr);
        if (rc)
                printk(KERN_ERR "fadump: unable to create sysfs file"
                        " fadump_enabled (%d)\n", rc);

        rc = sysfs_create_file(kernel_kobj, &fadump_register_attr.attr);
        if (rc)
                printk(KERN_ERR "fadump: unable to create sysfs file"
                        " fadump_registered (%d)\n", rc);

        debugfs_file = debugfs_create_file("fadump_region", 0444,
                                        powerpc_debugfs_root, NULL,
                                        &fadump_region_fops);
        if (!debugfs_file)
                printk(KERN_ERR "fadump: unable to create debugfs file"
                                " fadump_region\n");

        if (fw_dump.dump_active) {
                rc = sysfs_create_file(kernel_kobj, &fadump_release_attr.attr);
                if (rc)
                        printk(KERN_ERR "fadump: unable to create sysfs file"
                                " fadump_release_mem (%d)\n", rc);
        }
        return;
}

/*
 * Prepare for firmware-assisted dump.
 */
int __init setup_fadump(void)
{
        if (!fw_dump.fadump_supported)
                return 0;

        fadump_init_files();
        fadump_show_config();

        if (!fw_dump.fadump_enabled)
                return 1;

        /*
         * If dump data is available then see if it is valid and prepare for
         * saving it to the disk.
         */
        if (fw_dump.dump_active) {
                /*
                 * if dump process fails then invalidate the registration
                 * and release memory before proceeding for re-registration.
                 */
                if (fw_dump.ops->fadump_process(&fw_dump) < 0)
                        fadump_invalidate_release_mem();
        }
        /* Initialize the kernel dump memory structure for FAD registration. */
        else if (fw_dump.reserve_dump_area_size)
                fw_dump.ops->fadump_init_mem_struct(&fw_dump);

        return 1;
}
subsys_initcall(setup_fadump);
#else /* !CONFIG_PRESERVE_FA_DUMP */

/* Scan the Firmware Assisted dump configuration details. */
int __init early_init_dt_scan_fw_dump(unsigned long node, const char *uname,
                                      int depth, void *data)
{
        if ((depth != 1) || (strcmp(uname, "ibm,opal") != 0))
                return 0;

        opal_fadump_dt_scan(&fw_dump, node);
        return 1;
}

/*
 * When dump is active but PRESERVE_FA_DUMP is enabled on the kernel,
 * preserve crash data. The subsequent memory preserving kernel boot
 * is likely to process this crash data.
 */
int __init fadump_reserve_mem(void)
{
        if (fw_dump.dump_active) {
                /*
                 * If last boot has crashed then reserve all the memory
                 * above boot memory to preserve crash data.
                 */
                pr_info("Preserving crash data for processing in next boot.\n");
                fadump_reserve_crash_area(fw_dump.boot_mem_top);
        } else
                pr_debug("FADump-aware kernel..\n");

        return 1;
}
#endif /* CONFIG_PRESERVE_FA_DUMP */

/* Preserve everything above the base address */
static void __init fadump_reserve_crash_area(u64 base)
{
        struct memblock_region *reg;
        u64 mstart, msize;

        for_each_memblock(memory, reg) {
                mstart = reg->base;
                msize  = reg->size;

                if ((mstart + msize) < base)
                        continue;

                if (mstart < base) {
                        msize -= (base - mstart);
                        mstart = base;
                }

                pr_info("Reserving %lluMB of memory at %#016llx for preserving crash data",
                        (msize >> 20), mstart);
                memblock_reserve(mstart, msize);
        }
}

unsigned long __init arch_reserved_kernel_pages(void)
{
        return memblock_reserved_size() / PAGE_SIZE;
}