mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / fs / proc / vmcore.c

/*
 *      fs/proc/vmcore.c Interface for accessing the crash
 *                               dump from the system's previous life.
 *      Heavily borrowed from fs/proc/kcore.c
 *      Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *      Copyright (C) IBM Corporation, 2004. All rights reserved
 *
 */

#include <linux/mm.h>
#include <linux/kcore.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <linux/bootmem.h>
#include <linux/init.h>
#include <linux/crash_dump.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
#include <asm/io.h>
#include "internal.h"

/* List representing chunks of contiguous memory areas and their offsets in
 * vmcore file.
 */
static LIST_HEAD(vmcore_list);

/* Stores the pointer to the buffer containing kernel elf core headers. */
static char *elfcorebuf;
static size_t elfcorebuf_sz;
static size_t elfcorebuf_sz_orig;

static char *elfnotes_buf;
static size_t elfnotes_sz;

/* Total size of vmcore file. */
static u64 vmcore_size;

static struct proc_dir_entry *proc_vmcore;

/*
 * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
 * The called function has to take care of module refcounting.
 */
static int (*oldmem_pfn_is_ram)(unsigned long pfn);

int register_oldmem_pfn_is_ram(int (*fn)(unsigned long pfn))
{
        if (oldmem_pfn_is_ram)
                return -EBUSY;
        oldmem_pfn_is_ram = fn;
        return 0;
}
EXPORT_SYMBOL_GPL(register_oldmem_pfn_is_ram);

void unregister_oldmem_pfn_is_ram(void)
{
        oldmem_pfn_is_ram = NULL;
        wmb();
}
EXPORT_SYMBOL_GPL(unregister_oldmem_pfn_is_ram);

static int pfn_is_ram(unsigned long pfn)
{
        int (*fn)(unsigned long pfn);
        /* pfn is ram unless fn() checks pagetype */
        int ret = 1;

        /*
         * Ask hypervisor if the pfn is really ram.
         * A ballooned page contains no data and reading from such a page
         * will cause high load in the hypervisor.
         */
        fn = oldmem_pfn_is_ram;
        if (fn)
                ret = fn(pfn);

        return ret;
}

/* Reads a page from the oldmem device from given offset. */
static ssize_t read_from_oldmem(char *buf, size_t count,
                                u64 *ppos, int userbuf)
{
        unsigned long pfn, offset;
        size_t nr_bytes;
        ssize_t read = 0, tmp;

        if (!count)
                return 0;

        offset = (unsigned long)(*ppos % PAGE_SIZE);
        pfn = (unsigned long)(*ppos / PAGE_SIZE);

        do {
                if (count > (PAGE_SIZE - offset))
                        nr_bytes = PAGE_SIZE - offset;
                else
                        nr_bytes = count;

                /* If pfn is not ram, return zeros for sparse dump files */
                if (pfn_is_ram(pfn) == 0)
                        memset(buf, 0, nr_bytes);
                else {
                        tmp = copy_oldmem_page(pfn, buf, nr_bytes,
                                                offset, userbuf);
                        if (tmp < 0)
                                return tmp;
                }
                *ppos += nr_bytes;
                count -= nr_bytes;
                buf += nr_bytes;
                read += nr_bytes;
                ++pfn;
                offset = 0;
        } while (count);

        return read;
}

/*
 * Architectures may override this function to allocate ELF header in 2nd kernel
 */
int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
{
        return 0;
}

/*
 * Architectures may override this function to free header
 */
void __weak elfcorehdr_free(unsigned long long addr)
{}

/*
 * Architectures may override this function to read from ELF header
 */
ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
{
        return read_from_oldmem(buf, count, ppos, 0);
}

/*
 * Architectures may override this function to read from notes sections
 */
ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
{
        return read_from_oldmem(buf, count, ppos, 0);
}

/*
 * Architectures may override this function to map oldmem
 */
int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
                                  unsigned long from, unsigned long pfn,
                                  unsigned long size, pgprot_t prot)
{
        return remap_pfn_range(vma, from, pfn, size, prot);
}

/*
 * Architectures which support memory encryption override this.
 */
ssize_t __weak
copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
                           unsigned long offset, int userbuf)
{
        return copy_oldmem_page(pfn, buf, csize, offset, userbuf);
}

/*
 * Copy to either kernel or user space
 */
static int copy_to(void *target, void *src, size_t size, int userbuf)
{
        if (userbuf) {
                if (copy_to_user((char __user *) target, src, size))
                        return -EFAULT;
        } else {
                memcpy(target, src, size);
        }
        return 0;
}

/* Read from the ELF header and then the crash dump. On error, negative value is
 * returned otherwise number of bytes read are returned.
 */
static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
                             int userbuf)
{
        ssize_t acc = 0, tmp;
        size_t tsz;
        u64 start;
        struct vmcore *m = NULL;

        if (buflen == 0 || *fpos >= vmcore_size)
                return 0;

        /* trim buflen to not go beyond EOF */
        if (buflen > vmcore_size - *fpos)
                buflen = vmcore_size - *fpos;

        /* Read ELF core header */
        if (*fpos < elfcorebuf_sz) {
                tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
                if (copy_to(buffer, elfcorebuf + *fpos, tsz, userbuf))
                        return -EFAULT;
                buflen -= tsz;
                *fpos += tsz;
                buffer += tsz;
                acc += tsz;

                /* leave now if filled buffer already */
                if (buflen == 0)
                        return acc;
        }

        /* Read Elf note segment */
        if (*fpos < elfcorebuf_sz + elfnotes_sz) {
                void *kaddr;

                tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
                kaddr = elfnotes_buf + *fpos - elfcorebuf_sz;
                if (copy_to(buffer, kaddr, tsz, userbuf))
                        return -EFAULT;
                buflen -= tsz;
                *fpos += tsz;
                buffer += tsz;
                acc += tsz;

                /* leave now if filled buffer already */
                if (buflen == 0)
                        return acc;
        }

        list_for_each_entry(m, &vmcore_list, list) {
                if (*fpos < m->offset + m->size) {
                        tsz = (size_t)min_t(unsigned long long,
                                            m->offset + m->size - *fpos,
                                            buflen);
                        start = m->paddr + *fpos - m->offset;
                        tmp = read_from_oldmem(buffer, tsz, &start, userbuf);
                        if (tmp < 0)
                                return tmp;
                        buflen -= tsz;
                        *fpos += tsz;
                        buffer += tsz;
                        acc += tsz;

                        /* leave now if filled buffer already */
                        if (buflen == 0)
                                return acc;
                }
        }

        return acc;
}

static ssize_t read_vmcore(struct file *file, char __user *buffer,
                           size_t buflen, loff_t *fpos)
{
        return __read_vmcore((__force char *) buffer, buflen, fpos, 1);
}

/*
 * The vmcore fault handler uses the page cache and fills data using the
 * standard __vmcore_read() function.
 *
 * On s390 the fault handler is used for memory regions that can't be mapped
 * directly with remap_pfn_range().
 */
static int mmap_vmcore_fault(struct vm_fault *vmf)
{
#ifdef CONFIG_S390
        struct address_space *mapping = vmf->vma->vm_file->f_mapping;
        pgoff_t index = vmf->pgoff;
        struct page *page;
        loff_t offset;
        char *buf;
        int rc;

        page = find_or_create_page(mapping, index, GFP_KERNEL);
        if (!page)
                return VM_FAULT_OOM;
        if (!PageUptodate(page)) {
                offset = (loff_t) index << PAGE_SHIFT;
                buf = __va((page_to_pfn(page) << PAGE_SHIFT));
                rc = __read_vmcore(buf, PAGE_SIZE, &offset, 0);
                if (rc < 0) {
                        unlock_page(page);
                        put_page(page);
                        return (rc == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS;
                }
                SetPageUptodate(page);
        }
        unlock_page(page);
        vmf->page = page;
        return 0;
#else
        return VM_FAULT_SIGBUS;
#endif
}

static const struct vm_operations_struct vmcore_mmap_ops = {
        .fault = mmap_vmcore_fault,
};

/**
 * alloc_elfnotes_buf - allocate buffer for ELF note segment in
 *                      vmalloc memory
 *
 * @notes_sz: size of buffer
 *
 * If CONFIG_MMU is defined, use vmalloc_user() to allow users to mmap
 * the buffer to user-space by means of remap_vmalloc_range().
 *
 * If CONFIG_MMU is not defined, use vzalloc() since mmap_vmcore() is
 * disabled and there's no need to allow users to mmap the buffer.
 */
static inline char *alloc_elfnotes_buf(size_t notes_sz)
{
#ifdef CONFIG_MMU
        return vmalloc_user(notes_sz);
#else
        return vzalloc(notes_sz);
#endif
}

/*
 * Disable mmap_vmcore() if CONFIG_MMU is not defined. MMU is
 * essential for mmap_vmcore() in order to map physically
 * non-contiguous objects (ELF header, ELF note segment and memory
 * regions in the 1st kernel pointed to by PT_LOAD entries) into
 * virtually contiguous user-space in ELF layout.
 */
#ifdef CONFIG_MMU
/*
 * remap_oldmem_pfn_checked - do remap_oldmem_pfn_range replacing all pages
 * reported as not being ram with the zero page.
 *
 * @vma: vm_area_struct describing requested mapping
 * @from: start remapping from
 * @pfn: page frame number to start remapping to
 * @size: remapping size
 * @prot: protection bits
 *
 * Returns zero on success, -EAGAIN on failure.
 */
static int remap_oldmem_pfn_checked(struct vm_area_struct *vma,
                                    unsigned long from, unsigned long pfn,
                                    unsigned long size, pgprot_t prot)
{
        unsigned long map_size;
        unsigned long pos_start, pos_end, pos;
        unsigned long zeropage_pfn = my_zero_pfn(0);
        size_t len = 0;

        pos_start = pfn;
        pos_end = pfn + (size >> PAGE_SHIFT);

        for (pos = pos_start; pos < pos_end; ++pos) {
                if (!pfn_is_ram(pos)) {
                        /*
                         * We hit a page which is not ram. Remap the continuous
                         * region between pos_start and pos-1 and replace
                         * the non-ram page at pos with the zero page.
                         */
                        if (pos > pos_start) {
                                /* Remap continuous region */
                                map_size = (pos - pos_start) << PAGE_SHIFT;
                                if (remap_oldmem_pfn_range(vma, from + len,
                                                           pos_start, map_size,
                                                           prot))
                                        goto fail;
                                len += map_size;
                        }
                        /* Remap the zero page */
                        if (remap_oldmem_pfn_range(vma, from + len,
                                                   zeropage_pfn,
                                                   PAGE_SIZE, prot))
                                goto fail;
                        len += PAGE_SIZE;
                        pos_start = pos + 1;
                }
        }
        if (pos > pos_start) {
                /* Remap the rest */
                map_size = (pos - pos_start) << PAGE_SHIFT;
                if (remap_oldmem_pfn_range(vma, from + len, pos_start,
                                           map_size, prot))
                        goto fail;
        }
        return 0;
fail:
        do_munmap(vma->vm_mm, from, len, NULL);
        return -EAGAIN;
}

static int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
                            unsigned long from, unsigned long pfn,
                            unsigned long size, pgprot_t prot)
{
        /*
         * Check if oldmem_pfn_is_ram was registered to avoid
         * looping over all pages without a reason.
         */
        if (oldmem_pfn_is_ram)
                return remap_oldmem_pfn_checked(vma, from, pfn, size, prot);
        else
                return remap_oldmem_pfn_range(vma, from, pfn, size, prot);
}

static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
{
        size_t size = vma->vm_end - vma->vm_start;
        u64 start, end, len, tsz;
        struct vmcore *m;

        start = (u64)vma->vm_pgoff << PAGE_SHIFT;
        end = start + size;

        if (size > vmcore_size || end > vmcore_size)
                return -EINVAL;

        if (vma->vm_flags & (VM_WRITE | VM_EXEC))
                return -EPERM;

        vma->vm_flags &= ~(VM_MAYWRITE | VM_MAYEXEC);
        vma->vm_flags |= VM_MIXEDMAP;
        vma->vm_ops = &vmcore_mmap_ops;

        len = 0;

        if (start < elfcorebuf_sz) {
                u64 pfn;

                tsz = min(elfcorebuf_sz - (size_t)start, size);
                pfn = __pa(elfcorebuf + start) >> PAGE_SHIFT;
                if (remap_pfn_range(vma, vma->vm_start, pfn, tsz,
                                    vma->vm_page_prot))
                        return -EAGAIN;
                size -= tsz;
                start += tsz;
                len += tsz;

                if (size == 0)
                        return 0;
        }

        if (start < elfcorebuf_sz + elfnotes_sz) {
                void *kaddr;

                tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)start, size);
                kaddr = elfnotes_buf + start - elfcorebuf_sz;
                if (remap_vmalloc_range_partial(vma, vma->vm_start + len,
                                                kaddr, 0, tsz))
                        goto fail;
                size -= tsz;
                start += tsz;
                len += tsz;

                if (size == 0)
                        return 0;
        }

        list_for_each_entry(m, &vmcore_list, list) {
                if (start < m->offset + m->size) {
                        u64 paddr = 0;

                        tsz = (size_t)min_t(unsigned long long,
                                            m->offset + m->size - start, size);
                        paddr = m->paddr + start - m->offset;
                        if (vmcore_remap_oldmem_pfn(vma, vma->vm_start + len,
                                                    paddr >> PAGE_SHIFT, tsz,
                                                    vma->vm_page_prot))
                                goto fail;
                        size -= tsz;
                        start += tsz;
                        len += tsz;

                        if (size == 0)
                                return 0;
                }
        }

        return 0;
fail:
        do_munmap(vma->vm_mm, vma->vm_start, len, NULL);
        return -EAGAIN;
}
#else
static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
{
        return -ENOSYS;
}
#endif

static const struct file_operations proc_vmcore_operations = {
        .read           = read_vmcore,
        .llseek         = default_llseek,
        .mmap           = mmap_vmcore,
};

static struct vmcore* __init get_new_element(void)
{
        return kzalloc(sizeof(struct vmcore), GFP_KERNEL);
}

static u64 __init get_vmcore_size(size_t elfsz, size_t elfnotesegsz,
                                  struct list_head *vc_list)
{
        u64 size;
        struct vmcore *m;

        size = elfsz + elfnotesegsz;
        list_for_each_entry(m, vc_list, list) {
                size += m->size;
        }
        return size;
}

/**
 * update_note_header_size_elf64 - update p_memsz member of each PT_NOTE entry
 *
 * @ehdr_ptr: ELF header
 *
 * This function updates p_memsz member of each PT_NOTE entry in the
 * program header table pointed to by @ehdr_ptr to real size of ELF
 * note segment.
 */
static int __init update_note_header_size_elf64(const Elf64_Ehdr *ehdr_ptr)
{
        int i, rc=0;
        Elf64_Phdr *phdr_ptr;
        Elf64_Nhdr *nhdr_ptr;

        phdr_ptr = (Elf64_Phdr *)(ehdr_ptr + 1);
        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                void *notes_section;
                u64 offset, max_sz, sz, real_sz = 0;
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                max_sz = phdr_ptr->p_memsz;
                offset = phdr_ptr->p_offset;
                notes_section = kmalloc(max_sz, GFP_KERNEL);
                if (!notes_section)
                        return -ENOMEM;
                rc = elfcorehdr_read_notes(notes_section, max_sz, &offset);
                if (rc < 0) {
                        kfree(notes_section);
                        return rc;
                }
                nhdr_ptr = notes_section;
                while (nhdr_ptr->n_namesz != 0) {
                        sz = sizeof(Elf64_Nhdr) +
                                (((u64)nhdr_ptr->n_namesz + 3) & ~3) +
                                (((u64)nhdr_ptr->n_descsz + 3) & ~3);
                        if ((real_sz + sz) > max_sz) {
                                pr_warn("Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x%x, n_descsz=0x%x\n",
                                        nhdr_ptr->n_namesz, nhdr_ptr->n_descsz);
                                break;
                        }
                        real_sz += sz;
                        nhdr_ptr = (Elf64_Nhdr*)((char*)nhdr_ptr + sz);
                }
                kfree(notes_section);
                phdr_ptr->p_memsz = real_sz;
                if (real_sz == 0) {
                        pr_warn("Warning: Zero PT_NOTE entries found\n");
                }
        }

        return 0;
}

/**
 * get_note_number_and_size_elf64 - get the number of PT_NOTE program
 * headers and sum of real size of their ELF note segment headers and
 * data.
 *
 * @ehdr_ptr: ELF header
 * @nr_ptnote: buffer for the number of PT_NOTE program headers
 * @sz_ptnote: buffer for size of unique PT_NOTE program header
 *
 * This function is used to merge multiple PT_NOTE program headers
 * into a unique single one. The resulting unique entry will have
 * @sz_ptnote in its phdr->p_mem.
 *
 * It is assumed that program headers with PT_NOTE type pointed to by
 * @ehdr_ptr has already been updated by update_note_header_size_elf64
 * and each of PT_NOTE program headers has actual ELF note segment
 * size in its p_memsz member.
 */
static int __init get_note_number_and_size_elf64(const Elf64_Ehdr *ehdr_ptr,
                                                 int *nr_ptnote, u64 *sz_ptnote)
{
        int i;
        Elf64_Phdr *phdr_ptr;

        *nr_ptnote = *sz_ptnote = 0;

        phdr_ptr = (Elf64_Phdr *)(ehdr_ptr + 1);
        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                *nr_ptnote += 1;
                *sz_ptnote += phdr_ptr->p_memsz;
        }

        return 0;
}

/**
 * copy_notes_elf64 - copy ELF note segments in a given buffer
 *
 * @ehdr_ptr: ELF header
 * @notes_buf: buffer into which ELF note segments are copied
 *
 * This function is used to copy ELF note segment in the 1st kernel
 * into the buffer @notes_buf in the 2nd kernel. It is assumed that
 * size of the buffer @notes_buf is equal to or larger than sum of the
 * real ELF note segment headers and data.
 *
 * It is assumed that program headers with PT_NOTE type pointed to by
 * @ehdr_ptr has already been updated by update_note_header_size_elf64
 * and each of PT_NOTE program headers has actual ELF note segment
 * size in its p_memsz member.
 */
static int __init copy_notes_elf64(const Elf64_Ehdr *ehdr_ptr, char *notes_buf)
{
        int i, rc=0;
        Elf64_Phdr *phdr_ptr;

        phdr_ptr = (Elf64_Phdr*)(ehdr_ptr + 1);

        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                u64 offset;
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                offset = phdr_ptr->p_offset;
                rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz,
                                           &offset);
                if (rc < 0)
                        return rc;
                notes_buf += phdr_ptr->p_memsz;
        }

        return 0;
}

/* Merges all the PT_NOTE headers into one. */
static int __init merge_note_headers_elf64(char *elfptr, size_t *elfsz,
                                           char **notes_buf, size_t *notes_sz)
{
        int i, nr_ptnote=0, rc=0;
        char *tmp;
        Elf64_Ehdr *ehdr_ptr;
        Elf64_Phdr phdr;
        u64 phdr_sz = 0, note_off;

        ehdr_ptr = (Elf64_Ehdr *)elfptr;

        rc = update_note_header_size_elf64(ehdr_ptr);
        if (rc < 0)
                return rc;

        rc = get_note_number_and_size_elf64(ehdr_ptr, &nr_ptnote, &phdr_sz);
        if (rc < 0)
                return rc;

        *notes_sz = roundup(phdr_sz, PAGE_SIZE);
        *notes_buf = alloc_elfnotes_buf(*notes_sz);
        if (!*notes_buf)
                return -ENOMEM;

        rc = copy_notes_elf64(ehdr_ptr, *notes_buf);
        if (rc < 0)
                return rc;

        /* Prepare merged PT_NOTE program header. */
        phdr.p_type    = PT_NOTE;
        phdr.p_flags   = 0;
        note_off = sizeof(Elf64_Ehdr) +
                        (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf64_Phdr);
        phdr.p_offset  = roundup(note_off, PAGE_SIZE);
        phdr.p_vaddr   = phdr.p_paddr = 0;
        phdr.p_filesz  = phdr.p_memsz = phdr_sz;
        phdr.p_align   = 0;

        /* Add merged PT_NOTE program header*/
        tmp = elfptr + sizeof(Elf64_Ehdr);
        memcpy(tmp, &phdr, sizeof(phdr));
        tmp += sizeof(phdr);

        /* Remove unwanted PT_NOTE program headers. */
        i = (nr_ptnote - 1) * sizeof(Elf64_Phdr);
        *elfsz = *elfsz - i;
        memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf64_Ehdr)-sizeof(Elf64_Phdr)));
        memset(elfptr + *elfsz, 0, i);
        *elfsz = roundup(*elfsz, PAGE_SIZE);

        /* Modify e_phnum to reflect merged headers. */
        ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;

        return 0;
}

/**
 * update_note_header_size_elf32 - update p_memsz member of each PT_NOTE entry
 *
 * @ehdr_ptr: ELF header
 *
 * This function updates p_memsz member of each PT_NOTE entry in the
 * program header table pointed to by @ehdr_ptr to real size of ELF
 * note segment.
 */
static int __init update_note_header_size_elf32(const Elf32_Ehdr *ehdr_ptr)
{
        int i, rc=0;
        Elf32_Phdr *phdr_ptr;
        Elf32_Nhdr *nhdr_ptr;

        phdr_ptr = (Elf32_Phdr *)(ehdr_ptr + 1);
        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                void *notes_section;
                u64 offset, max_sz, sz, real_sz = 0;
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                max_sz = phdr_ptr->p_memsz;
                offset = phdr_ptr->p_offset;
                notes_section = kmalloc(max_sz, GFP_KERNEL);
                if (!notes_section)
                        return -ENOMEM;
                rc = elfcorehdr_read_notes(notes_section, max_sz, &offset);
                if (rc < 0) {
                        kfree(notes_section);
                        return rc;
                }
                nhdr_ptr = notes_section;
                while (nhdr_ptr->n_namesz != 0) {
                        sz = sizeof(Elf32_Nhdr) +
                                (((u64)nhdr_ptr->n_namesz + 3) & ~3) +
                                (((u64)nhdr_ptr->n_descsz + 3) & ~3);
                        if ((real_sz + sz) > max_sz) {
                                pr_warn("Warning: Exceeded p_memsz, dropping PT_NOTE entry n_namesz=0x%x, n_descsz=0x%x\n",
                                        nhdr_ptr->n_namesz, nhdr_ptr->n_descsz);
                                break;
                        }
                        real_sz += sz;
                        nhdr_ptr = (Elf32_Nhdr*)((char*)nhdr_ptr + sz);
                }
                kfree(notes_section);
                phdr_ptr->p_memsz = real_sz;
                if (real_sz == 0) {
                        pr_warn("Warning: Zero PT_NOTE entries found\n");
                }
        }

        return 0;
}

/**
 * get_note_number_and_size_elf32 - get the number of PT_NOTE program
 * headers and sum of real size of their ELF note segment headers and
 * data.
 *
 * @ehdr_ptr: ELF header
 * @nr_ptnote: buffer for the number of PT_NOTE program headers
 * @sz_ptnote: buffer for size of unique PT_NOTE program header
 *
 * This function is used to merge multiple PT_NOTE program headers
 * into a unique single one. The resulting unique entry will have
 * @sz_ptnote in its phdr->p_mem.
 *
 * It is assumed that program headers with PT_NOTE type pointed to by
 * @ehdr_ptr has already been updated by update_note_header_size_elf32
 * and each of PT_NOTE program headers has actual ELF note segment
 * size in its p_memsz member.
 */
static int __init get_note_number_and_size_elf32(const Elf32_Ehdr *ehdr_ptr,
                                                 int *nr_ptnote, u64 *sz_ptnote)
{
        int i;
        Elf32_Phdr *phdr_ptr;

        *nr_ptnote = *sz_ptnote = 0;

        phdr_ptr = (Elf32_Phdr *)(ehdr_ptr + 1);
        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                *nr_ptnote += 1;
                *sz_ptnote += phdr_ptr->p_memsz;
        }

        return 0;
}

/**
 * copy_notes_elf32 - copy ELF note segments in a given buffer
 *
 * @ehdr_ptr: ELF header
 * @notes_buf: buffer into which ELF note segments are copied
 *
 * This function is used to copy ELF note segment in the 1st kernel
 * into the buffer @notes_buf in the 2nd kernel. It is assumed that
 * size of the buffer @notes_buf is equal to or larger than sum of the
 * real ELF note segment headers and data.
 *
 * It is assumed that program headers with PT_NOTE type pointed to by
 * @ehdr_ptr has already been updated by update_note_header_size_elf32
 * and each of PT_NOTE program headers has actual ELF note segment
 * size in its p_memsz member.
 */
static int __init copy_notes_elf32(const Elf32_Ehdr *ehdr_ptr, char *notes_buf)
{
        int i, rc=0;
        Elf32_Phdr *phdr_ptr;

        phdr_ptr = (Elf32_Phdr*)(ehdr_ptr + 1);

        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                u64 offset;
                if (phdr_ptr->p_type != PT_NOTE)
                        continue;
                offset = phdr_ptr->p_offset;
                rc = elfcorehdr_read_notes(notes_buf, phdr_ptr->p_memsz,
                                           &offset);
                if (rc < 0)
                        return rc;
                notes_buf += phdr_ptr->p_memsz;
        }

        return 0;
}

/* Merges all the PT_NOTE headers into one. */
static int __init merge_note_headers_elf32(char *elfptr, size_t *elfsz,
                                           char **notes_buf, size_t *notes_sz)
{
        int i, nr_ptnote=0, rc=0;
        char *tmp;
        Elf32_Ehdr *ehdr_ptr;
        Elf32_Phdr phdr;
        u64 phdr_sz = 0, note_off;

        ehdr_ptr = (Elf32_Ehdr *)elfptr;

        rc = update_note_header_size_elf32(ehdr_ptr);
        if (rc < 0)
                return rc;

        rc = get_note_number_and_size_elf32(ehdr_ptr, &nr_ptnote, &phdr_sz);
        if (rc < 0)
                return rc;

        *notes_sz = roundup(phdr_sz, PAGE_SIZE);
        *notes_buf = alloc_elfnotes_buf(*notes_sz);
        if (!*notes_buf)
                return -ENOMEM;

        rc = copy_notes_elf32(ehdr_ptr, *notes_buf);
        if (rc < 0)
                return rc;

        /* Prepare merged PT_NOTE program header. */
        phdr.p_type    = PT_NOTE;
        phdr.p_flags   = 0;
        note_off = sizeof(Elf32_Ehdr) +
                        (ehdr_ptr->e_phnum - nr_ptnote +1) * sizeof(Elf32_Phdr);
        phdr.p_offset  = roundup(note_off, PAGE_SIZE);
        phdr.p_vaddr   = phdr.p_paddr = 0;
        phdr.p_filesz  = phdr.p_memsz = phdr_sz;
        phdr.p_align   = 0;

        /* Add merged PT_NOTE program header*/
        tmp = elfptr + sizeof(Elf32_Ehdr);
        memcpy(tmp, &phdr, sizeof(phdr));
        tmp += sizeof(phdr);

        /* Remove unwanted PT_NOTE program headers. */
        i = (nr_ptnote - 1) * sizeof(Elf32_Phdr);
        *elfsz = *elfsz - i;
        memmove(tmp, tmp+i, ((*elfsz)-sizeof(Elf32_Ehdr)-sizeof(Elf32_Phdr)));
        memset(elfptr + *elfsz, 0, i);
        *elfsz = roundup(*elfsz, PAGE_SIZE);

        /* Modify e_phnum to reflect merged headers. */
        ehdr_ptr->e_phnum = ehdr_ptr->e_phnum - nr_ptnote + 1;

        return 0;
}

/* Add memory chunks represented by program headers to vmcore list. Also update
 * the new offset fields of exported program headers. */
static int __init process_ptload_program_headers_elf64(char *elfptr,
                                                size_t elfsz,
                                                size_t elfnotes_sz,
                                                struct list_head *vc_list)
{
        int i;
        Elf64_Ehdr *ehdr_ptr;
        Elf64_Phdr *phdr_ptr;
        loff_t vmcore_off;
        struct vmcore *new;

        ehdr_ptr = (Elf64_Ehdr *)elfptr;
        phdr_ptr = (Elf64_Phdr*)(elfptr + sizeof(Elf64_Ehdr)); /* PT_NOTE hdr */

        /* Skip Elf header, program headers and Elf note segment. */
        vmcore_off = elfsz + elfnotes_sz;

        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                u64 paddr, start, end, size;

                if (phdr_ptr->p_type != PT_LOAD)
                        continue;

                paddr = phdr_ptr->p_offset;
                start = rounddown(paddr, PAGE_SIZE);
                end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE);
                size = end - start;

                /* Add this contiguous chunk of memory to vmcore list.*/
                new = get_new_element();
                if (!new)
                        return -ENOMEM;
                new->paddr = start;
                new->size = size;
                list_add_tail(&new->list, vc_list);

                /* Update the program header offset. */
                phdr_ptr->p_offset = vmcore_off + (paddr - start);
                vmcore_off = vmcore_off + size;
        }
        return 0;
}

static int __init process_ptload_program_headers_elf32(char *elfptr,
                                                size_t elfsz,
                                                size_t elfnotes_sz,
                                                struct list_head *vc_list)
{
        int i;
        Elf32_Ehdr *ehdr_ptr;
        Elf32_Phdr *phdr_ptr;
        loff_t vmcore_off;
        struct vmcore *new;

        ehdr_ptr = (Elf32_Ehdr *)elfptr;
        phdr_ptr = (Elf32_Phdr*)(elfptr + sizeof(Elf32_Ehdr)); /* PT_NOTE hdr */

        /* Skip Elf header, program headers and Elf note segment. */
        vmcore_off = elfsz + elfnotes_sz;

        for (i = 0; i < ehdr_ptr->e_phnum; i++, phdr_ptr++) {
                u64 paddr, start, end, size;

                if (phdr_ptr->p_type != PT_LOAD)
                        continue;

                paddr = phdr_ptr->p_offset;
                start = rounddown(paddr, PAGE_SIZE);
                end = roundup(paddr + phdr_ptr->p_memsz, PAGE_SIZE);
                size = end - start;

                /* Add this contiguous chunk of memory to vmcore list.*/
                new = get_new_element();
                if (!new)
                        return -ENOMEM;
                new->paddr = start;
                new->size = size;
                list_add_tail(&new->list, vc_list);

                /* Update the program header offset */
                phdr_ptr->p_offset = vmcore_off + (paddr - start);
                vmcore_off = vmcore_off + size;
        }
        return 0;
}

/* Sets offset fields of vmcore elements. */
static void __init set_vmcore_list_offsets(size_t elfsz, size_t elfnotes_sz,
                                           struct list_head *vc_list)
{
        loff_t vmcore_off;
        struct vmcore *m;

        /* Skip Elf header, program headers and Elf note segment. */
        vmcore_off = elfsz + elfnotes_sz;

        list_for_each_entry(m, vc_list, list) {
                m->offset = vmcore_off;
                vmcore_off += m->size;
        }
}

static void free_elfcorebuf(void)
{
        free_pages((unsigned long)elfcorebuf, get_order(elfcorebuf_sz_orig));
        elfcorebuf = NULL;
        vfree(elfnotes_buf);
        elfnotes_buf = NULL;
}

static int __init parse_crash_elf64_headers(void)
{
        int rc=0;
        Elf64_Ehdr ehdr;
        u64 addr;

        addr = elfcorehdr_addr;

        /* Read Elf header */
        rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf64_Ehdr), &addr);
        if (rc < 0)
                return rc;

        /* Do some basic Verification. */
        if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
                (ehdr.e_type != ET_CORE) ||
                !vmcore_elf64_check_arch(&ehdr) ||
                ehdr.e_ident[EI_CLASS] != ELFCLASS64 ||
                ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
                ehdr.e_version != EV_CURRENT ||
                ehdr.e_ehsize != sizeof(Elf64_Ehdr) ||
                ehdr.e_phentsize != sizeof(Elf64_Phdr) ||
                ehdr.e_phnum == 0) {
                pr_warn("Warning: Core image elf header is not sane\n");
                return -EINVAL;
        }

        /* Read in all elf headers. */
        elfcorebuf_sz_orig = sizeof(Elf64_Ehdr) +
                                ehdr.e_phnum * sizeof(Elf64_Phdr);
        elfcorebuf_sz = elfcorebuf_sz_orig;
        elfcorebuf = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
                                              get_order(elfcorebuf_sz_orig));
        if (!elfcorebuf)
                return -ENOMEM;
        addr = elfcorehdr_addr;
        rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr);
        if (rc < 0)
                goto fail;

        /* Merge all PT_NOTE headers into one. */
        rc = merge_note_headers_elf64(elfcorebuf, &elfcorebuf_sz,
                                      &elfnotes_buf, &elfnotes_sz);
        if (rc)
                goto fail;
        rc = process_ptload_program_headers_elf64(elfcorebuf, elfcorebuf_sz,
                                                  elfnotes_sz, &vmcore_list);
        if (rc)
                goto fail;
        set_vmcore_list_offsets(elfcorebuf_sz, elfnotes_sz, &vmcore_list);
        return 0;
fail:
        free_elfcorebuf();
        return rc;
}

static int __init parse_crash_elf32_headers(void)
{
        int rc=0;
        Elf32_Ehdr ehdr;
        u64 addr;

        addr = elfcorehdr_addr;

        /* Read Elf header */
        rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf32_Ehdr), &addr);
        if (rc < 0)
                return rc;

        /* Do some basic Verification. */
        if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0 ||
                (ehdr.e_type != ET_CORE) ||
                !vmcore_elf32_check_arch(&ehdr) ||
                ehdr.e_ident[EI_CLASS] != ELFCLASS32||
                ehdr.e_ident[EI_VERSION] != EV_CURRENT ||
                ehdr.e_version != EV_CURRENT ||
                ehdr.e_ehsize != sizeof(Elf32_Ehdr) ||
                ehdr.e_phentsize != sizeof(Elf32_Phdr) ||
                ehdr.e_phnum == 0) {
                pr_warn("Warning: Core image elf header is not sane\n");
                return -EINVAL;
        }

        /* Read in all elf headers. */
        elfcorebuf_sz_orig = sizeof(Elf32_Ehdr) + ehdr.e_phnum * sizeof(Elf32_Phdr);
        elfcorebuf_sz = elfcorebuf_sz_orig;
        elfcorebuf = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
                                              get_order(elfcorebuf_sz_orig));
        if (!elfcorebuf)
                return -ENOMEM;
        addr = elfcorehdr_addr;
        rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr);
        if (rc < 0)
                goto fail;

        /* Merge all PT_NOTE headers into one. */
        rc = merge_note_headers_elf32(elfcorebuf, &elfcorebuf_sz,
                                      &elfnotes_buf, &elfnotes_sz);
        if (rc)
                goto fail;
        rc = process_ptload_program_headers_elf32(elfcorebuf, elfcorebuf_sz,
                                                  elfnotes_sz, &vmcore_list);
        if (rc)
                goto fail;
        set_vmcore_list_offsets(elfcorebuf_sz, elfnotes_sz, &vmcore_list);
        return 0;
fail:
        free_elfcorebuf();
        return rc;
}

static int __init parse_crash_elf_headers(void)
{
        unsigned char e_ident[EI_NIDENT];
        u64 addr;
        int rc=0;

        addr = elfcorehdr_addr;
        rc = elfcorehdr_read(e_ident, EI_NIDENT, &addr);
        if (rc < 0)
                return rc;
        if (memcmp(e_ident, ELFMAG, SELFMAG) != 0) {
                pr_warn("Warning: Core image elf header not found\n");
                return -EINVAL;
        }

        if (e_ident[EI_CLASS] == ELFCLASS64) {
                rc = parse_crash_elf64_headers();
                if (rc)
                        return rc;
        } else if (e_ident[EI_CLASS] == ELFCLASS32) {
                rc = parse_crash_elf32_headers();
                if (rc)
                        return rc;
        } else {
                pr_warn("Warning: Core image elf header is not sane\n");
                return -EINVAL;
        }

        /* Determine vmcore size. */
        vmcore_size = get_vmcore_size(elfcorebuf_sz, elfnotes_sz,
                                      &vmcore_list);

        return 0;
}

/* Init function for vmcore module. */
static int __init vmcore_init(void)
{
        int rc = 0;

        /* Allow architectures to allocate ELF header in 2nd kernel */
        rc = elfcorehdr_alloc(&elfcorehdr_addr, &elfcorehdr_size);
        if (rc)
                return rc;
        /*
         * If elfcorehdr= has been passed in cmdline or created in 2nd kernel,
         * then capture the dump.
         */
        if (!(is_vmcore_usable()))
                return rc;
        rc = parse_crash_elf_headers();
        if (rc) {
                pr_warn("Kdump: vmcore not initialized\n");
                return rc;
        }
        elfcorehdr_free(elfcorehdr_addr);
        elfcorehdr_addr = ELFCORE_ADDR_ERR;

        proc_vmcore = proc_create("vmcore", S_IRUSR, NULL, &proc_vmcore_operations);
        if (proc_vmcore)
                proc_vmcore->size = vmcore_size;
        return 0;
}
fs_initcall(vmcore_init);

/* Cleanup function for vmcore module. */
void vmcore_cleanup(void)
{
        struct list_head *pos, *next;

        if (proc_vmcore) {
                proc_remove(proc_vmcore);
                proc_vmcore = NULL;
        }

        /* clear the vmcore list. */
        list_for_each_safe(pos, next, &vmcore_list) {
                struct vmcore *m;

                m = list_entry(pos, struct vmcore, list);
                list_del(&m->list);
                kfree(m);
        }
        free_elfcorebuf();
}