root/fs/proc/kcore.c

DEFINITIONS

1. open_kcore
2. kclist_add
3. get_kcore_size
4. notesize
5. storenote
6. elf_kcore_store_hdr
7. read_kcore

/*
 *      fs/proc/kcore.c kernel ELF core dumper
 *
 *      Modelled on fs/exec.c:aout_core_dump()
 *      Jeremy Fitzhardinge <jeremy@sw.oz.au>
 *      ELF version written by David Howells <David.Howells@nexor.co.uk>
 *      Modified and incorporated into 2.3.x by Tigran Aivazian <tigran@veritas.com>
 *      Support to dump vmalloc'd areas (ELF only), Tigran Aivazian <tigran@veritas.com>
 *      Safe accesses to vmalloc/direct-mapped discontiguous areas, Kanoj Sarcar <kanoj@sgi.com>
 */

#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/init.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define CORE_STR "CORE"

#ifndef ELF_CORE_EFLAGS
#define ELF_CORE_EFLAGS 0
#endif

static int open_kcore(struct inode * inode, struct file * filp)
{
        return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

static ssize_t read_kcore(struct file *, char __user *, size_t, loff_t *);

const struct file_operations proc_kcore_operations = {
        .read           = read_kcore,
        .open           = open_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 struct kcore_list *kclist;
static DEFINE_RWLOCK(kclist_lock);

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

        write_lock(&kclist_lock);
        new->next = kclist;
        kclist = new;
        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;

        for (m=kclist; m; m=m->next) {
                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;
}


/*****************************************************************************/
/*
 * 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 */
        for (m=kclist; m; m=m->next) {
                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);
        proc_root_kcore->size = 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);
                for (m=kclist; m; m=m->next) {
                        if (start >= m->addr && start < (m->addr+m->size))
                                break;
                }
                read_unlock(&kclist_lock);

                if (m == NULL) {
                        if (clear_user(buffer, tsz))
                                return -EFAULT;
                } else if (is_vmalloc_addr((void *)start)) {
                        char * elf_buf;
                        struct vm_struct *m;
                        unsigned long curstart = start;
                        unsigned long cursize = tsz;

                        elf_buf = kzalloc(tsz, GFP_KERNEL);
                        if (!elf_buf)
                                return -ENOMEM;

                        read_lock(&vmlist_lock);
                        for (m=vmlist; m && cursize; m=m->next) {
                                unsigned long vmstart;
                                unsigned long vmsize;
                                unsigned long msize = m->size - PAGE_SIZE;

                                if (((unsigned long)m->addr + msize) < 
                                                                curstart)
                                        continue;
                                if ((unsigned long)m->addr > (curstart + 
                                                                cursize))
                                        break;
                                vmstart = (curstart < (unsigned long)m->addr ? 
                                        (unsigned long)m->addr : curstart);
                                if (((unsigned long)m->addr + msize) > 
                                                        (curstart + cursize))
                                        vmsize = curstart + cursize - vmstart;
                                else
                                        vmsize = (unsigned long)m->addr + 
                                                        msize - vmstart;
                                curstart = vmstart + vmsize;
                                cursize -= vmsize;
                                /* don't dump ioremap'd stuff! (TA) */
                                if (m->flags & VM_IOREMAP)
                                        continue;
                                memcpy(elf_buf + (vmstart - start),
                                        (char *)vmstart, vmsize);
                        }
                        read_unlock(&vmlist_lock);
                        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 distingush 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;
}