binfmt_loader.c

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#include <linux/init.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm_types.h>
#include <linux/binfmts.h>
#include <linux/a.out.h>

static int load_binary(struct linux_binprm *bprm, struct pt_regs *regs)
{
    struct exec *eh = (struct exec *)bprm->buf;
    unsigned long loader;
    struct file *file;
    int retval;

    if (eh->fh.f_magic != 0x183 || (eh->fh.f_flags & 0x3000) != 0x3000)
        return -ENOEXEC;

    if (bprm->loader)
        return -ENOEXEC;

    allow_write_access(bprm->file);
    fput(bprm->file);
    bprm->file = NULL;

    loader = bprm->vma->vm_end - sizeof(void *);

    file = open_exec("/sbin/loader");
    retval = PTR_ERR(file);
    if (IS_ERR(file))
        return retval;

    /* Remember if the application is TASO.  */
    bprm->taso = eh->ah.entry < 0x100000000UL;

    bprm->file = file;
    bprm->loader = loader;
    retval = prepare_binprm(bprm);
    if (retval < 0)
        return retval;
    return search_binary_handler(bprm,regs);
}

static struct linux_binfmt loader_format = {
    .load_binary    = load_binary,
};

static int __init init_loader_binfmt(void)
{
    insert_binfmt(&loader_format);
    return 0;
}
arch_initcall(init_loader_binfmt);