kcore.c

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/*
 *  fs/proc/kcore.c kernel ELF core dumper
 *
 *  Modelled on fs/exec.c:aout_core_dump()
 *  Jeremy Fitzhardinge <[email protected]>
 *  ELF version written by David Howells <[email protected]>
 *  Modified and incorporated into 2.3.x by Tigran Aivazian <[email protected]>
 *  Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <[email protected]>
 *  Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <[email protected]>
 */

#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/user.h>
#include <linux/capability.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/vmalloc.h>
#include <linux/highmem.h>
#include <linux/bootmem.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/memory.h>
#include <asm/sections.h>

#define CORE_STR "CORE"

#ifndef ELF_CORE_EFLAGS
#define ELF_CORE_EFLAGS 0
#endif

static struct proc_dir_entry *proc_root_kcore;


#ifndef kc_vaddr_to_offset
#define kc_vaddr_to_offset(v) ((v) - PAGE_OFFSET)
#endif
#ifndef kc_offset_to_vaddr
#define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET)
#endif

/* An ELF note in memory */
struct memelfnote
{
    const char *name;
    int type;
    unsigned int datasz;
    void *data;
};

static LIST_HEAD(kclist_head);
static DEFINE_RWLOCK(kclist_lock);
static int kcore_need_update = 1;

void
kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
{
    new->addr = (unsigned long)addr;
    new->size = size;
    new->type = type;

    write_lock(&kclist_lock);
    list_add_tail(&new->list, &kclist_head);
    write_unlock(&kclist_lock);
}

static size_t get_kcore_size(int *nphdr, size_t *elf_buflen)
{
    size_t try, size;
    struct kcore_list *m;

    *nphdr = 1; /* PT_NOTE */
    size = 0;

    list_for_each_entry(m, &kclist_head, list) {
        try = kc_vaddr_to_offset((size_t)m->addr + m->size);
        if (try > size)
            size = try;
        *nphdr = *nphdr + 1;
    }
    *elf_buflen =   sizeof(struct elfhdr) + 
            (*nphdr + 2)*sizeof(struct elf_phdr) + 
            3 * ((sizeof(struct elf_note)) +
                 roundup(sizeof(CORE_STR), 4)) +
            roundup(sizeof(struct elf_prstatus), 4) +
            roundup(sizeof(struct elf_prpsinfo), 4) +
            roundup(sizeof(struct task_struct), 4);
    *elf_buflen = PAGE_ALIGN(*elf_buflen);
    return size + *elf_buflen;
}

static void free_kclist_ents(struct list_head *head)
{
    struct kcore_list *tmp, *pos;

    list_for_each_entry_safe(pos, tmp, head, list) {
        list_del(&pos->list);
        kfree(pos);
    }
}
/*
 * Replace all KCORE_RAM/KCORE_VMEMMAP information with passed list.
 */
static void __kcore_update_ram(struct list_head *list)
{
    int nphdr;
    size_t size;
    struct kcore_list *tmp, *pos;
    LIST_HEAD(garbage);

    write_lock(&kclist_lock);
    if (kcore_need_update) {
        list_for_each_entry_safe(pos, tmp, &kclist_head, list) {
            if (pos->type == KCORE_RAM
                || pos->type == KCORE_VMEMMAP)
                list_move(&pos->list, &garbage);
        }
        list_splice_tail(list, &kclist_head);
    } else
        list_splice(list, &garbage);
    kcore_need_update = 0;
    proc_root_kcore->size = get_kcore_size(&nphdr, &size);
    write_unlock(&kclist_lock);

    free_kclist_ents(&garbage);
}


#ifdef CONFIG_HIGHMEM
/*
 * If no highmem, we can assume [0...max_low_pfn) continuous range of memory
 * because memory hole is not as big as !HIGHMEM case.
 * (HIGHMEM is special because part of memory is _invisible_ from the kernel.)
 */
static int kcore_update_ram(void)
{
    LIST_HEAD(head);
    struct kcore_list *ent;
    int ret = 0;

    ent = kmalloc(sizeof(*ent), GFP_KERNEL);
    if (!ent)
        return -ENOMEM;
    ent->addr = (unsigned long)__va(0);
    ent->size = max_low_pfn << PAGE_SHIFT;
    ent->type = KCORE_RAM;
    list_add(&ent->list, &head);
    __kcore_update_ram(&head);
    return ret;
}

#else /* !CONFIG_HIGHMEM */

#ifdef CONFIG_SPARSEMEM_VMEMMAP
/* calculate vmemmap's address from given system ram pfn and register it */
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
    unsigned long pfn = __pa(ent->addr) >> PAGE_SHIFT;
    unsigned long nr_pages = ent->size >> PAGE_SHIFT;
    unsigned long start, end;
    struct kcore_list *vmm, *tmp;


    start = ((unsigned long)pfn_to_page(pfn)) & PAGE_MASK;
    end = ((unsigned long)pfn_to_page(pfn + nr_pages)) - 1;
    end = ALIGN(end, PAGE_SIZE);
    /* overlap check (because we have to align page */
    list_for_each_entry(tmp, head, list) {
        if (tmp->type != KCORE_VMEMMAP)
            continue;
        if (start < tmp->addr + tmp->size)
            if (end > tmp->addr)
                end = tmp->addr;
    }
    if (start < end) {
        vmm = kmalloc(sizeof(*vmm), GFP_KERNEL);
        if (!vmm)
            return 0;
        vmm->addr = start;
        vmm->size = end - start;
        vmm->type = KCORE_VMEMMAP;
        list_add_tail(&vmm->list, head);
    }
    return 1;

}
#else
static int
get_sparsemem_vmemmap_info(struct kcore_list *ent, struct list_head *head)
{
    return 1;
}

#endif

static int
kclist_add_private(unsigned long pfn, unsigned long nr_pages, void *arg)
{
    struct list_head *head = (struct list_head *)arg;
    struct kcore_list *ent;

    ent = kmalloc(sizeof(*ent), GFP_KERNEL);
    if (!ent)
        return -ENOMEM;
    ent->addr = (unsigned long)__va((pfn << PAGE_SHIFT));
    ent->size = nr_pages << PAGE_SHIFT;

    /* Sanity check: Can happen in 32bit arch...maybe */
    if (ent->addr < (unsigned long) __va(0))
        goto free_out;

    /* cut not-mapped area. ....from ppc-32 code. */
    if (ULONG_MAX - ent->addr < ent->size)
        ent->size = ULONG_MAX - ent->addr;

    /* cut when vmalloc() area is higher than direct-map area */
    if (VMALLOC_START > (unsigned long)__va(0)) {
        if (ent->addr > VMALLOC_START)
            goto free_out;
        if (VMALLOC_START - ent->addr < ent->size)
            ent->size = VMALLOC_START - ent->addr;
    }

    ent->type = KCORE_RAM;
    list_add_tail(&ent->list, head);

    if (!get_sparsemem_vmemmap_info(ent, head)) {
        list_del(&ent->list);
        goto free_out;
    }

    return 0;
free_out:
    kfree(ent);
    return 1;
}

static int kcore_update_ram(void)
{
    int nid, ret;
    unsigned long end_pfn;
    LIST_HEAD(head);

    /* Not inialized....update now */
    /* find out "max pfn" */
    end_pfn = 0;
    for_each_node_state(nid, N_HIGH_MEMORY) {
        unsigned long node_end;
        node_end  = NODE_DATA(nid)->node_start_pfn +
            NODE_DATA(nid)->node_spanned_pages;
        if (end_pfn < node_end)
            end_pfn = node_end;
    }
    /* scan 0 to max_pfn */
    ret = walk_system_ram_range(0, end_pfn, &head, kclist_add_private);
    if (ret) {
        free_kclist_ents(&head);
        return -ENOMEM;
    }
    __kcore_update_ram(&head);
    return ret;
}
#endif /* CONFIG_HIGHMEM */

/*****************************************************************************/
/*
 * determine size of ELF note
 */
static int notesize(struct memelfnote *en)
{
    int sz;

    sz = sizeof(struct elf_note);
    sz += roundup((strlen(en->name) + 1), 4);
    sz += roundup(en->datasz, 4);

    return sz;
} /* end notesize() */

/*****************************************************************************/
/*
 * store a note in the header buffer
 */
static char *storenote(struct memelfnote *men, char *bufp)
{
    struct elf_note en;

#define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0)

    en.n_namesz = strlen(men->name) + 1;
    en.n_descsz = men->datasz;
    en.n_type = men->type;

    DUMP_WRITE(&en, sizeof(en));
    DUMP_WRITE(men->name, en.n_namesz);

    /* XXX - cast from long long to long to avoid need for libgcc.a */
    bufp = (char*) roundup((unsigned long)bufp,4);
    DUMP_WRITE(men->data, men->datasz);
    bufp = (char*) roundup((unsigned long)bufp,4);

#undef DUMP_WRITE

    return bufp;
} /* end storenote() */

/*
 * store an ELF coredump header in the supplied buffer
 * nphdr is the number of elf_phdr to insert
 */
static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
{
    struct elf_prstatus prstatus;   /* NT_PRSTATUS */
    struct elf_prpsinfo prpsinfo;   /* NT_PRPSINFO */
    struct elf_phdr *nhdr, *phdr;
    struct elfhdr *elf;
    struct memelfnote notes[3];
    off_t offset = 0;
    struct kcore_list *m;

    /* setup ELF header */
    elf = (struct elfhdr *) bufp;
    bufp += sizeof(struct elfhdr);
    offset += 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;
    elf->e_flags    = ELF_CORE_EFLAGS;
    elf->e_ehsize   = sizeof(struct elfhdr);
    elf->e_phentsize= sizeof(struct elf_phdr);
    elf->e_phnum    = nphdr;
    elf->e_shentsize= 0;
    elf->e_shnum    = 0;
    elf->e_shstrndx = 0;

    /* setup ELF PT_NOTE program header */
    nhdr = (struct elf_phdr *) bufp;
    bufp += sizeof(struct elf_phdr);
    offset += sizeof(struct elf_phdr);
    nhdr->p_type    = PT_NOTE;
    nhdr->p_offset  = 0;
    nhdr->p_vaddr   = 0;
    nhdr->p_paddr   = 0;
    nhdr->p_filesz  = 0;
    nhdr->p_memsz   = 0;
    nhdr->p_flags   = 0;
    nhdr->p_align   = 0;

    /* setup ELF PT_LOAD program header for every area */
    list_for_each_entry(m, &kclist_head, list) {
        phdr = (struct elf_phdr *) bufp;
        bufp += sizeof(struct elf_phdr);
        offset += sizeof(struct elf_phdr);

        phdr->p_type    = PT_LOAD;
        phdr->p_flags   = PF_R|PF_W|PF_X;
        phdr->p_offset  = kc_vaddr_to_offset(m->addr) + dataoff;
        phdr->p_vaddr   = (size_t)m->addr;
        phdr->p_paddr   = 0;
        phdr->p_filesz  = phdr->p_memsz = m->size;
        phdr->p_align   = PAGE_SIZE;
    }

    /*
     * Set up the notes in similar form to SVR4 core dumps made
     * with info from their /proc.
     */
    nhdr->p_offset  = offset;

    /* set up the process status */
    notes[0].name = CORE_STR;
    notes[0].type = NT_PRSTATUS;
    notes[0].datasz = sizeof(struct elf_prstatus);
    notes[0].data = &prstatus;

    memset(&prstatus, 0, sizeof(struct elf_prstatus));

    nhdr->p_filesz  = notesize(&notes[0]);
    bufp = storenote(&notes[0], bufp);

    /* set up the process info */
    notes[1].name   = CORE_STR;
    notes[1].type   = NT_PRPSINFO;
    notes[1].datasz = sizeof(struct elf_prpsinfo);
    notes[1].data   = &prpsinfo;

    memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo));
    prpsinfo.pr_state   = 0;
    prpsinfo.pr_sname   = 'R';
    prpsinfo.pr_zomb    = 0;

    strcpy(prpsinfo.pr_fname, "vmlinux");
    strncpy(prpsinfo.pr_psargs, saved_command_line, ELF_PRARGSZ);

    nhdr->p_filesz  += notesize(&notes[1]);
    bufp = storenote(&notes[1], bufp);

    /* set up the task structure */
    notes[2].name   = CORE_STR;
    notes[2].type   = NT_TASKSTRUCT;
    notes[2].datasz = sizeof(struct task_struct);
    notes[2].data   = current;

    nhdr->p_filesz  += notesize(&notes[2]);
    bufp = storenote(&notes[2], bufp);

} /* end elf_kcore_store_hdr() */

/*****************************************************************************/
/*
 * read from the ELF header and then kernel memory
 */
static ssize_t
read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
{
    ssize_t acc = 0;
    size_t size, tsz;
    size_t elf_buflen;
    int nphdr;
    unsigned long start;

    read_lock(&kclist_lock);
    size = get_kcore_size(&nphdr, &elf_buflen);

    if (buflen == 0 || *fpos >= size) {
        read_unlock(&kclist_lock);
        return 0;
    }

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

    /* construct an ELF core header if we'll need some of it */
    if (*fpos < elf_buflen) {
        char * elf_buf;

        tsz = elf_buflen - *fpos;
        if (buflen < tsz)
            tsz = buflen;
        elf_buf = kzalloc(elf_buflen, GFP_ATOMIC);
        if (!elf_buf) {
            read_unlock(&kclist_lock);
            return -ENOMEM;
        }
        elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen);
        read_unlock(&kclist_lock);
        if (copy_to_user(buffer, elf_buf + *fpos, tsz)) {
            kfree(elf_buf);
            return -EFAULT;
        }
        kfree(elf_buf);
        buflen -= tsz;
        *fpos += tsz;
        buffer += tsz;
        acc += tsz;

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

    /*
     * Check to see if our file offset matches with any of
     * the addresses in the elf_phdr on our list.
     */
    start = kc_offset_to_vaddr(*fpos - elf_buflen);
    if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen)
        tsz = buflen;
        
    while (buflen) {
        struct kcore_list *m;

        read_lock(&kclist_lock);
        list_for_each_entry(m, &kclist_head, list) {
            if (start >= m->addr && start < (m->addr+m->size))
                break;
        }
        read_unlock(&kclist_lock);

        if (&m->list == &kclist_head) {
            if (clear_user(buffer, tsz))
                return -EFAULT;
        } else if (is_vmalloc_or_module_addr((void *)start)) {
            char * elf_buf;

            elf_buf = kzalloc(tsz, GFP_KERNEL);
            if (!elf_buf)
                return -ENOMEM;
            vread(elf_buf, (char *)start, tsz);
            /* we have to zero-fill user buffer even if no read */
            if (copy_to_user(buffer, elf_buf, tsz)) {
                kfree(elf_buf);
                return -EFAULT;
            }
            kfree(elf_buf);
        } else {
            if (kern_addr_valid(start)) {
                unsigned long n;

                n = copy_to_user(buffer, (char *)start, tsz);
                /*
                 * We cannot distinguish between fault on source
                 * and fault on destination. When this happens
                 * we clear too and hope it will trigger the
                 * EFAULT again.
                 */
                if (n) { 
                    if (clear_user(buffer + tsz - n,
                                n))
                        return -EFAULT;
                }
            } else {
                if (clear_user(buffer, tsz))
                    return -EFAULT;
            }
        }
        buflen -= tsz;
        *fpos += tsz;
        buffer += tsz;
        acc += tsz;
        start += tsz;
        tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
    }

    return acc;
}


static int open_kcore(struct inode *inode, struct file *filp)
{
    if (!capable(CAP_SYS_RAWIO))
        return -EPERM;
    if (kcore_need_update)
        kcore_update_ram();
    if (i_size_read(inode) != proc_root_kcore->size) {
        mutex_lock(&inode->i_mutex);
        i_size_write(inode, proc_root_kcore->size);
        mutex_unlock(&inode->i_mutex);
    }
    return 0;
}


static const struct file_operations proc_kcore_operations = {
    .read       = read_kcore,
    .open       = open_kcore,
    .llseek     = default_llseek,
};

#ifdef CONFIG_MEMORY_HOTPLUG
/* just remember that we have to update kcore */
static int __meminit kcore_callback(struct notifier_block *self,
                    unsigned long action, void *arg)
{
    switch (action) {
    case MEM_ONLINE:
    case MEM_OFFLINE:
        write_lock(&kclist_lock);
        kcore_need_update = 1;
        write_unlock(&kclist_lock);
    }
    return NOTIFY_OK;
}
#endif


static struct kcore_list kcore_vmalloc;

#ifdef CONFIG_ARCH_PROC_KCORE_TEXT
static struct kcore_list kcore_text;
/*
 * If defined, special segment is used for mapping kernel text instead of
 * direct-map area. We need to create special TEXT section.
 */
static void __init proc_kcore_text_init(void)
{
    kclist_add(&kcore_text, _text, _end - _text, KCORE_TEXT);
}
#else
static void __init proc_kcore_text_init(void)
{
}
#endif

#if defined(CONFIG_MODULES) && defined(MODULES_VADDR)
/*
 * MODULES_VADDR has no intersection with VMALLOC_ADDR.
 */
struct kcore_list kcore_modules;
static void __init add_modules_range(void)
{
    kclist_add(&kcore_modules, (void *)MODULES_VADDR,
            MODULES_END - MODULES_VADDR, KCORE_VMALLOC);
}
#else
static void __init add_modules_range(void)
{
}
#endif

static int __init proc_kcore_init(void)
{
    proc_root_kcore = proc_create("kcore", S_IRUSR, NULL,
                      &proc_kcore_operations);
    if (!proc_root_kcore) {
        printk(KERN_ERR "couldn't create /proc/kcore\n");
        return 0; /* Always returns 0. */
    }
    /* Store text area if it's special */
    proc_kcore_text_init();
    /* Store vmalloc area */
    kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
        VMALLOC_END - VMALLOC_START, KCORE_VMALLOC);
    add_modules_range();
    /* Store direct-map area from physical memory map */
    kcore_update_ram();
    hotplug_memory_notifier(kcore_callback, 0);

    return 0;
}
module_init(proc_kcore_init);