path: root/linux-user/elfload.c

/* This is the Linux kernel elf-loading code, ported into user space */

#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <string.h>

#include "qemu.h"
#include "disas.h"

#ifdef TARGET_I386

#define ELF_START_MMAP 0x80000000

typedef uint32_t  elf_greg_t;

#define ELF_NGREG (sizeof (struct target_pt_regs) / sizeof(elf_greg_t))
typedef elf_greg_t elf_gregset_t[ELF_NGREG];

typedef struct user_i387_struct elf_fpregset_t;

/*
 * This is used to ensure we don't load something for the wrong architecture.
 */
#define elf_check_arch(x) ( ((x) == EM_386) || ((x) == EM_486) )

/*
 * These are used to set parameters in the core dumps.
 */
#define ELF_CLASS	ELFCLASS32
#define ELF_DATA	ELFDATA2LSB
#define ELF_ARCH	EM_386

	/* SVR4/i386 ABI (pages 3-31, 3-32) says that when the program
	   starts %edx contains a pointer to a function which might be
	   registered using `atexit'.  This provides a mean for the
	   dynamic linker to call DT_FINI functions for shared libraries
	   that have been loaded before the code runs.

	   A value of 0 tells we have no such handler.  */
#define ELF_PLAT_INIT(_r)	_r->edx = 0

#define USE_ELF_CORE_DUMP
#define ELF_EXEC_PAGESIZE	4096

#endif

#include "elf.h"

/*
 * MAX_ARG_PAGES defines the number of pages allocated for arguments
 * and envelope for the new program. 32 should suffice, this gives
 * a maximum env+arg of 128kB w/4KB pages!
 */
#define MAX_ARG_PAGES 32

/*
 * This structure is used to hold the arguments that are 
 * used when loading binaries.
 */
struct linux_binprm {
        char buf[128];
        unsigned long page[MAX_ARG_PAGES];
        unsigned long p;
        int sh_bang;
	int fd;
        int e_uid, e_gid;
        int argc, envc;
        char * filename;        /* Name of binary */
        unsigned long loader, exec;
        int dont_iput;          /* binfmt handler has put inode */
};

struct exec
{
  unsigned int a_info;   /* Use macros N_MAGIC, etc for access */
  unsigned int a_text;   /* length of text, in bytes */
  unsigned int a_data;   /* length of data, in bytes */
  unsigned int a_bss;    /* length of uninitialized data area, in bytes */
  unsigned int a_syms;   /* length of symbol table data in file, in bytes */
  unsigned int a_entry;  /* start address */
  unsigned int a_trsize; /* length of relocation info for text, in bytes */
  unsigned int a_drsize; /* length of relocation info for data, in bytes */
};


#define N_MAGIC(exec) ((exec).a_info & 0xffff)
#define OMAGIC 0407
#define NMAGIC 0410
#define ZMAGIC 0413
#define QMAGIC 0314

/* max code+data+bss space allocated to elf interpreter */
#define INTERP_MAP_SIZE (32 * 1024 * 1024)

/* max code+data+bss+brk space allocated to ET_DYN executables */
#define ET_DYN_MAP_SIZE (128 * 1024 * 1024)

/* from personality.h */

/* Flags for bug emulation. These occupy the top three bytes. */
#define STICKY_TIMEOUTS		0x4000000
#define WHOLE_SECONDS		0x2000000

/* Personality types. These go in the low byte. Avoid using the top bit,
 * it will conflict with error returns.
 */
#define PER_MASK		(0x00ff)
#define PER_LINUX		(0x0000)
#define PER_SVR4		(0x0001 | STICKY_TIMEOUTS)
#define PER_SVR3		(0x0002 | STICKY_TIMEOUTS)
#define PER_SCOSVR3		(0x0003 | STICKY_TIMEOUTS | WHOLE_SECONDS)
#define PER_WYSEV386		(0x0004 | STICKY_TIMEOUTS)
#define PER_ISCR4		(0x0005 | STICKY_TIMEOUTS)
#define PER_BSD			(0x0006)
#define PER_XENIX		(0x0007 | STICKY_TIMEOUTS)

/* Necessary parameters */
#define NGROUPS 32

#define TARGET_ELF_EXEC_PAGESIZE TARGET_PAGE_SIZE
#define TARGET_ELF_PAGESTART(_v) ((_v) & ~(unsigned long)(TARGET_ELF_EXEC_PAGESIZE-1))
#define TARGET_ELF_PAGEOFFSET(_v) ((_v) & (TARGET_ELF_EXEC_PAGESIZE-1))

#define INTERPRETER_NONE 0
#define INTERPRETER_AOUT 1
#define INTERPRETER_ELF 2

#define DLINFO_ITEMS 12

#define put_user(x,ptr) (void)(*(ptr) = (typeof(*ptr))(x))
#define get_user(ptr) (typeof(*ptr))(*(ptr))

static inline void memcpy_fromfs(void * to, const void * from, unsigned long n)
{
	memcpy(to, from, n);
}

static inline void memcpy_tofs(void * to, const void * from, unsigned long n)
{
	memcpy(to, from, n);
}

extern unsigned long x86_stack_size;

static int load_aout_interp(void * exptr, int interp_fd);

#ifdef BSWAP_NEEDED
static void bswap_ehdr(Elf32_Ehdr *ehdr)
{
    bswap16s(&ehdr->e_type);			/* Object file type */
    bswap16s(&ehdr->e_machine);		/* Architecture */
    bswap32s(&ehdr->e_version);		/* Object file version */
    bswap32s(&ehdr->e_entry);		/* Entry point virtual address */
    bswap32s(&ehdr->e_phoff);		/* Program header table file offset */
    bswap32s(&ehdr->e_shoff);		/* Section header table file offset */
    bswap32s(&ehdr->e_flags);		/* Processor-specific flags */
    bswap16s(&ehdr->e_ehsize);		/* ELF header size in bytes */
    bswap16s(&ehdr->e_phentsize);		/* Program header table entry size */
    bswap16s(&ehdr->e_phnum);		/* Program header table entry count */
    bswap16s(&ehdr->e_shentsize);		/* Section header table entry size */
    bswap16s(&ehdr->e_shnum);		/* Section header table entry count */
    bswap16s(&ehdr->e_shstrndx);		/* Section header string table index */
}

static void bswap_phdr(Elf32_Phdr *phdr)
{
    bswap32s(&phdr->p_type);			/* Segment type */
    bswap32s(&phdr->p_offset);		/* Segment file offset */
    bswap32s(&phdr->p_vaddr);		/* Segment virtual address */
    bswap32s(&phdr->p_paddr);		/* Segment physical address */
    bswap32s(&phdr->p_filesz);		/* Segment size in file */
    bswap32s(&phdr->p_memsz);		/* Segment size in memory */
    bswap32s(&phdr->p_flags);		/* Segment flags */
    bswap32s(&phdr->p_align);		/* Segment alignment */
}

static void bswap_shdr(Elf32_Shdr *shdr)
{
    bswap32s(&shdr->sh_name);
    bswap32s(&shdr->sh_type);
    bswap32s(&shdr->sh_flags);
    bswap32s(&shdr->sh_addr);
    bswap32s(&shdr->sh_offset);
    bswap32s(&shdr->sh_size);
    bswap32s(&shdr->sh_link);
    bswap32s(&shdr->sh_info);
    bswap32s(&shdr->sh_addralign);
    bswap32s(&shdr->sh_entsize);
}

static void bswap_sym(Elf32_Sym *sym)
{
    bswap32s(&sym->st_name);
    bswap32s(&sym->st_value);
    bswap32s(&sym->st_size);
    bswap16s(&sym->st_shndx);
}
#endif

static void * get_free_page(void)
{
    void *	retval;

    /* User-space version of kernel get_free_page.  Returns a page-aligned
     * page-sized chunk of memory.
     */
    retval = (void *)target_mmap(0, host_page_size, PROT_READ|PROT_WRITE, 
                                 MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);

    if((long)retval == -1) {
	perror("get_free_page");
	exit(-1);
    }
    else {
	return(retval);
    }
}

static void free_page(void * pageaddr)
{
    target_munmap((unsigned long)pageaddr, host_page_size);
}

/*
 * 'copy_string()' copies argument/envelope strings from user
 * memory to free pages in kernel mem. These are in a format ready
 * to be put directly into the top of new user memory.
 *
 */
static unsigned long copy_strings(int argc,char ** argv,unsigned long *page,
                unsigned long p)
{
    char *tmp, *tmp1, *pag = NULL;
    int len, offset = 0;

    if (!p) {
	return 0;       /* bullet-proofing */
    }
    while (argc-- > 0) {
	if (!(tmp1 = tmp = get_user(argv+argc))) {
	    fprintf(stderr, "VFS: argc is wrong");
	    exit(-1);
	}
	while (get_user(tmp++));
	len = tmp - tmp1;
	if (p < len) {  /* this shouldn't happen - 128kB */
		return 0;
	}
	while (len) {
	    --p; --tmp; --len;
	    if (--offset < 0) {
		offset = p % TARGET_PAGE_SIZE;
		if (!(pag = (char *) page[p/TARGET_PAGE_SIZE]) &&
		    !(pag = (char *) page[p/TARGET_PAGE_SIZE] =
		      (unsigned long *) get_free_page())) {
			return 0;
		}
	    }
	    if (len == 0 || offset == 0) {
	        *(pag + offset) = get_user(tmp);
	    }
	    else {
	      int bytes_to_copy = (len > offset) ? offset : len;
	      tmp -= bytes_to_copy;
	      p -= bytes_to_copy;
	      offset -= bytes_to_copy;
	      len -= bytes_to_copy;
	      memcpy_fromfs(pag + offset, tmp, bytes_to_copy + 1);
	    }
	}
    }
    return p;
}

static int in_group_p(gid_t g)
{
    /* return TRUE if we're in the specified group, FALSE otherwise */
    int		ngroup;
    int		i;
    gid_t	grouplist[NGROUPS];

    ngroup = getgroups(NGROUPS, grouplist);
    for(i = 0; i < ngroup; i++) {
	if(grouplist[i] == g) {
	    return 1;
	}
    }
    return 0;
}

static int count(char ** vec)
{
    int		i;

    for(i = 0; *vec; i++) {
        vec++;
    }

    return(i);
}

static int prepare_binprm(struct linux_binprm *bprm)
{
    struct stat		st;
    int mode;
    int retval, id_change;

    if(fstat(bprm->fd, &st) < 0) {
	return(-errno);
    }

    mode = st.st_mode;
    if(!S_ISREG(mode)) {	/* Must be regular file */
	return(-EACCES);
    }
    if(!(mode & 0111)) {	/* Must have at least one execute bit set */
	return(-EACCES);
    }

    bprm->e_uid = geteuid();
    bprm->e_gid = getegid();
    id_change = 0;

    /* Set-uid? */
    if(mode & S_ISUID) {
    	bprm->e_uid = st.st_uid;
	if(bprm->e_uid != geteuid()) {
	    id_change = 1;
	}
    }

    /* Set-gid? */
    /*
     * If setgid is set but no group execute bit then this
     * is a candidate for mandatory locking, not a setgid
     * executable.
     */
    if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
	bprm->e_gid = st.st_gid;
	if (!in_group_p(bprm->e_gid)) {
		id_change = 1;
	}
    }

    memset(bprm->buf, 0, sizeof(bprm->buf));
    retval = lseek(bprm->fd, 0L, SEEK_SET);
    if(retval >= 0) {
        retval = read(bprm->fd, bprm->buf, 128);
    }
    if(retval < 0) {
	perror("prepare_binprm");
	exit(-1);
	/* return(-errno); */
    }
    else {
	return(retval);
    }
}

unsigned long setup_arg_pages(unsigned long p, struct linux_binprm * bprm,
						struct image_info * info)
{
    unsigned long stack_base, size, error;
    int i;

    /* Create enough stack to hold everything.  If we don't use
     * it for args, we'll use it for something else...
     */
    size = x86_stack_size;
    if (size < MAX_ARG_PAGES*TARGET_PAGE_SIZE)
        size = MAX_ARG_PAGES*TARGET_PAGE_SIZE;
    error = target_mmap(0, 
                        size + host_page_size,
                        PROT_READ | PROT_WRITE,
                        MAP_PRIVATE | MAP_ANONYMOUS,
                        -1, 0);
    if (error == -1) {
        perror("stk mmap");
        exit(-1);
    }
    /* we reserve one extra page at the top of the stack as guard */
    target_mprotect(error + size, host_page_size, PROT_NONE);

    stack_base = error + size - MAX_ARG_PAGES*TARGET_PAGE_SIZE;
    p += stack_base;

    if (bprm->loader) {
	bprm->loader += stack_base;
    }
    bprm->exec += stack_base;

    for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
	if (bprm->page[i]) {
	    info->rss++;

	    memcpy((void *)stack_base, (void *)bprm->page[i], TARGET_PAGE_SIZE);
	    free_page((void *)bprm->page[i]);
	}
	stack_base += TARGET_PAGE_SIZE;
    }
    return p;
}

static void set_brk(unsigned long start, unsigned long end)
{
	/* page-align the start and end addresses... */
        start = HOST_PAGE_ALIGN(start);
        end = HOST_PAGE_ALIGN(end);
        if (end <= start)
                return;
        if(target_mmap(start, end - start,
                       PROT_READ | PROT_WRITE | PROT_EXEC,
                       MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0) == -1) {
	    perror("cannot mmap brk");
	    exit(-1);
	}
}


/* We need to explicitly zero any fractional pages
   after the data section (i.e. bss).  This would
   contain the junk from the file that should not
   be in memory */


static void padzero(unsigned long elf_bss)
{
        unsigned long nbyte;
        char * fpnt;

        nbyte = elf_bss & (host_page_size-1);	/* was TARGET_PAGE_SIZE - JRP */
        if (nbyte) {
	    nbyte = host_page_size - nbyte;
	    fpnt = (char *) elf_bss;
	    do {
		*fpnt++ = 0;
	    } while (--nbyte);
        }
}

static unsigned int * create_elf_tables(char *p, int argc, int envc,
                                        struct elfhdr * exec,
                                        unsigned long load_addr,
                                        unsigned long load_bias,
                                        unsigned long interp_load_addr, int ibcs,
                                        struct image_info *info)
{
        target_ulong *argv, *envp, *dlinfo;
        target_ulong *sp;

        /*
         * Force 16 byte alignment here for generality.
         */
        sp = (unsigned int *) (~15UL & (unsigned long) p);
        sp -= exec ? DLINFO_ITEMS*2 : 2;
        dlinfo = sp;
        sp -= envc+1;
        envp = sp;
        sp -= argc+1;
        argv = sp;
        if (!ibcs) {
                put_user(tswapl((target_ulong)envp),--sp);
                put_user(tswapl((target_ulong)argv),--sp);
        }

#define NEW_AUX_ENT(id, val) \
          put_user (tswapl(id), dlinfo++); \
          put_user (tswapl(val), dlinfo++)

        if (exec) { /* Put this here for an ELF program interpreter */
          NEW_AUX_ENT (AT_PHDR, (target_ulong)(load_addr + exec->e_phoff));
          NEW_AUX_ENT (AT_PHENT, (target_ulong)(sizeof (struct elf_phdr)));
          NEW_AUX_ENT (AT_PHNUM, (target_ulong)(exec->e_phnum));
          NEW_AUX_ENT (AT_PAGESZ, (target_ulong)(TARGET_PAGE_SIZE));
          NEW_AUX_ENT (AT_BASE, (target_ulong)(interp_load_addr));
          NEW_AUX_ENT (AT_FLAGS, (target_ulong)0);
          NEW_AUX_ENT (AT_ENTRY, load_bias + exec->e_entry);
          NEW_AUX_ENT (AT_UID, (target_ulong) getuid());
          NEW_AUX_ENT (AT_EUID, (target_ulong) geteuid());
          NEW_AUX_ENT (AT_GID, (target_ulong) getgid());
          NEW_AUX_ENT (AT_EGID, (target_ulong) getegid());
        }
        NEW_AUX_ENT (AT_NULL, 0);
#undef NEW_AUX_ENT
        put_user(tswapl(argc),--sp);
        info->arg_start = (unsigned int)((unsigned long)p & 0xffffffff);
        while (argc-->0) {
                put_user(tswapl((target_ulong)p),argv++);
                while (get_user(p++)) /* nothing */ ;
        }
        put_user(0,argv);
        info->arg_end = info->env_start = (unsigned int)((unsigned long)p & 0xffffffff);
        while (envc-->0) {
                put_user(tswapl((target_ulong)p),envp++);
                while (get_user(p++)) /* nothing */ ;
        }
        put_user(0,envp);
        info->env_end = (unsigned int)((unsigned long)p & 0xffffffff);
        return sp;
}



static unsigned long load_elf_interp(struct elfhdr * interp_elf_ex,
				     int interpreter_fd,
				     unsigned long *interp_load_addr)
{
	struct elf_phdr *elf_phdata  =  NULL;
	struct elf_phdr *eppnt;
	unsigned long load_addr = 0;
	int load_addr_set = 0;
	int retval;
	unsigned long last_bss, elf_bss;
	unsigned long error;
	int i;
	
	elf_bss = 0;
	last_bss = 0;
	error = 0;

#ifdef BSWAP_NEEDED
        bswap_ehdr(interp_elf_ex);
#endif
	/* First of all, some simple consistency checks */
	if ((interp_elf_ex->e_type != ET_EXEC && 
             interp_elf_ex->e_type != ET_DYN) || 
	   !elf_check_arch(interp_elf_ex->e_machine)) {
		return ~0UL;
	}
	

	/* Now read in all of the header information */
	
	if (sizeof(struct elf_phdr) * interp_elf_ex->e_phnum > TARGET_PAGE_SIZE)
	    return ~0UL;
	
	elf_phdata =  (struct elf_phdr *) 
		malloc(sizeof(struct elf_phdr) * interp_elf_ex->e_phnum);

	if (!elf_phdata)
	  return ~0UL;
	
	/*
	 * If the size of this structure has changed, then punt, since
	 * we will be doing the wrong thing.
	 */
	if (interp_elf_ex->e_phentsize != sizeof(struct elf_phdr)) {
	    free(elf_phdata);
	    return ~0UL;
        }

	retval = lseek(interpreter_fd, interp_elf_ex->e_phoff, SEEK_SET);
	if(retval >= 0) {
	    retval = read(interpreter_fd,
			   (char *) elf_phdata,
			   sizeof(struct elf_phdr) * interp_elf_ex->e_phnum);
	}
	if (retval < 0) {
		perror("load_elf_interp");
		exit(-1);
		free (elf_phdata);
		return retval;
 	}
#ifdef BSWAP_NEEDED
	eppnt = elf_phdata;
	for (i=0; i<interp_elf_ex->e_phnum; i++, eppnt++) {
            bswap_phdr(eppnt);
        }
#endif

        if (interp_elf_ex->e_type == ET_DYN) {
            /* in order to avoid harcoding the interpreter load
               address in qemu, we allocate a big enough memory zone */
            error = target_mmap(0, INTERP_MAP_SIZE,
                                PROT_NONE, MAP_PRIVATE | MAP_ANON, 
                                -1, 0);
            if (error == -1) {
                perror("mmap");
                exit(-1);
            }
            load_addr = error;
            load_addr_set = 1;
        }

	eppnt = elf_phdata;
	for(i=0; i<interp_elf_ex->e_phnum; i++, eppnt++)
	  if (eppnt->p_type == PT_LOAD) {
	    int elf_type = MAP_PRIVATE | MAP_DENYWRITE;
	    int elf_prot = 0;
	    unsigned long vaddr = 0;
	    unsigned long k;

	    if (eppnt->p_flags & PF_R) elf_prot =  PROT_READ;
	    if (eppnt->p_flags & PF_W) elf_prot |= PROT_WRITE;
	    if (eppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;
	    if (interp_elf_ex->e_type == ET_EXEC || load_addr_set) {
	    	elf_type |= MAP_FIXED;
	    	vaddr = eppnt->p_vaddr;
	    }
	    error = target_mmap(load_addr+TARGET_ELF_PAGESTART(vaddr),
		 eppnt->p_filesz + TARGET_ELF_PAGEOFFSET(eppnt->p_vaddr),
		 elf_prot,
		 elf_type,
		 interpreter_fd,
		 eppnt->p_offset - TARGET_ELF_PAGEOFFSET(eppnt->p_vaddr));
	    
	    if (error > -1024UL) {
	      /* Real error */
	      close(interpreter_fd);
	      free(elf_phdata);
	      return ~0UL;
	    }

	    if (!load_addr_set && interp_elf_ex->e_type == ET_DYN) {
	      load_addr = error;
	      load_addr_set = 1;
	    }

	    /*
	     * Find the end of the file  mapping for this phdr, and keep
	     * track of the largest address we see for this.
	     */
	    k = load_addr + eppnt->p_vaddr + eppnt->p_filesz;
	    if (k > elf_bss) elf_bss = k;

	    /*
	     * Do the same thing for the memory mapping - between
	     * elf_bss and last_bss is the bss section.
	     */
	    k = load_addr + eppnt->p_memsz + eppnt->p_vaddr;
	    if (k > last_bss) last_bss = k;
	  }
	
	/* Now use mmap to map the library into memory. */

	close(interpreter_fd);

	/*
	 * Now fill out the bss section.  First pad the last page up
	 * to the page boundary, and then perform a mmap to make sure
	 * that there are zeromapped pages up to and including the last
	 * bss page.
	 */
	padzero(elf_bss);
	elf_bss = TARGET_ELF_PAGESTART(elf_bss + host_page_size - 1); /* What we have mapped so far */

	/* Map the last of the bss segment */
	if (last_bss > elf_bss) {
            target_mmap(elf_bss, last_bss-elf_bss,
                        PROT_READ|PROT_WRITE|PROT_EXEC,
                        MAP_FIXED|MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
	}
	free(elf_phdata);

	*interp_load_addr = load_addr;
	return ((unsigned long) interp_elf_ex->e_entry) + load_addr;
}

/* Best attempt to load symbols from this ELF object. */
static void load_symbols(struct elfhdr *hdr, int fd)
{
    unsigned int i;
    struct elf_shdr sechdr, symtab, strtab;
    char *strings;

    lseek(fd, hdr->e_shoff, SEEK_SET);
    for (i = 0; i < hdr->e_shnum; i++) {
	if (read(fd, &sechdr, sizeof(sechdr)) != sizeof(sechdr))
	    return;
#ifdef BSWAP_NEEDED
	bswap_shdr(&sechdr);
#endif
	if (sechdr.sh_type == SHT_SYMTAB) {
	    symtab = sechdr;
	    lseek(fd, hdr->e_shoff
		  + sizeof(sechdr) * sechdr.sh_link, SEEK_SET);
	    if (read(fd, &strtab, sizeof(strtab))
		!= sizeof(strtab))
		return;
#ifdef BSWAP_NEEDED
	    bswap_shdr(&strtab);
#endif
	    goto found;
	}
    }
    return; /* Shouldn't happen... */

 found:
    /* Now know where the strtab and symtab are.  Snarf them. */
    disas_symtab = malloc(symtab.sh_size);
    disas_strtab = strings = malloc(strtab.sh_size);
    if (!disas_symtab || !disas_strtab)
	return;
	
    lseek(fd, symtab.sh_offset, SEEK_SET);
    if (read(fd, disas_symtab, symtab.sh_size) != symtab.sh_size)
	return;

#ifdef BSWAP_NEEDED
    for (i = 0; i < symtab.sh_size / sizeof(struct elf_sym); i++)
	bswap_sym(disas_symtab + sizeof(struct elf_sym)*i);
#endif

    lseek(fd, strtab.sh_offset, SEEK_SET);
    if (read(fd, strings, strtab.sh_size) != strtab.sh_size)
	return;
    disas_num_syms = symtab.sh_size / sizeof(struct elf_sym);
}

static int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
                           struct image_info * info)
{
    struct elfhdr elf_ex;
    struct elfhdr interp_elf_ex;
    struct exec interp_ex;
    int interpreter_fd = -1; /* avoid warning */
    unsigned long load_addr, load_bias;
    int load_addr_set = 0;
    unsigned int interpreter_type = INTERPRETER_NONE;
    unsigned char ibcs2_interpreter;
    int i;
    unsigned long mapped_addr;
    struct elf_phdr * elf_ppnt;
    struct elf_phdr *elf_phdata;
    unsigned long elf_bss, k, elf_brk;
    int retval;
    char * elf_interpreter;
    unsigned long elf_entry, interp_load_addr = 0;
    int status;
    unsigned long start_code, end_code, end_data;
    unsigned long elf_stack;
    char passed_fileno[6];

    ibcs2_interpreter = 0;
    status = 0;
    load_addr = 0;
    load_bias = 0;
    elf_ex = *((struct elfhdr *) bprm->buf);          /* exec-header */
#ifdef BSWAP_NEEDED
    bswap_ehdr(&elf_ex);
#endif

    if (elf_ex.e_ident[0] != 0x7f ||
	strncmp(&elf_ex.e_ident[1], "ELF",3) != 0) {
	    return  -ENOEXEC;
    }

    /* First of all, some simple consistency checks */
    if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
       				(! elf_check_arch(elf_ex.e_machine))) {
	    return -ENOEXEC;
    }

    /* Now read in all of the header information */

    elf_phdata = (struct elf_phdr *)malloc(elf_ex.e_phentsize*elf_ex.e_phnum);
    if (elf_phdata == NULL) {
	return -ENOMEM;
    }

    retval = lseek(bprm->fd, elf_ex.e_phoff, SEEK_SET);
    if(retval > 0) {
	retval = read(bprm->fd, (char *) elf_phdata, 
				elf_ex.e_phentsize * elf_ex.e_phnum);
    }

    if (retval < 0) {
	perror("load_elf_binary");
	exit(-1);
	free (elf_phdata);
	return -errno;
    }

#ifdef BSWAP_NEEDED
    elf_ppnt = elf_phdata;
    for (i=0; i<elf_ex.e_phnum; i++, elf_ppnt++) {
        bswap_phdr(elf_ppnt);
    }
#endif
    elf_ppnt = elf_phdata;

    elf_bss = 0;
    elf_brk = 0;


    elf_stack = ~0UL;
    elf_interpreter = NULL;
    start_code = ~0UL;
    end_code = 0;
    end_data = 0;

    for(i=0;i < elf_ex.e_phnum; i++) {
	if (elf_ppnt->p_type == PT_INTERP) {
	    if ( elf_interpreter != NULL )
	    {
		free (elf_phdata);
		free(elf_interpreter);
		close(bprm->fd);
		return -EINVAL;
	    }

	    /* This is the program interpreter used for
	     * shared libraries - for now assume that this
	     * is an a.out format binary
	     */

	    elf_interpreter = (char *)malloc(elf_ppnt->p_filesz);

	    if (elf_interpreter == NULL) {
		free (elf_phdata);
		close(bprm->fd);
		return -ENOMEM;
	    }

	    retval = lseek(bprm->fd, elf_ppnt->p_offset, SEEK_SET);
	    if(retval >= 0) {
		retval = read(bprm->fd, elf_interpreter, elf_ppnt->p_filesz);
	    }
	    if(retval < 0) {
	 	perror("load_elf_binary2");
		exit(-1);
	    }	

	    /* If the program interpreter is one of these two,
	       then assume an iBCS2 image. Otherwise assume
	       a native linux image. */

	    /* JRP - Need to add X86 lib dir stuff here... */

	    if (strcmp(elf_interpreter,"/usr/lib/libc.so.1") == 0 ||
		strcmp(elf_interpreter,"/usr/lib/ld.so.1") == 0) {
	      ibcs2_interpreter = 1;
	    }

#if 0
	    printf("Using ELF interpreter %s\n", elf_interpreter);
#endif
	    if (retval >= 0) {
		retval = open(path(elf_interpreter), O_RDONLY);
		if(retval >= 0) {
		    interpreter_fd = retval;
		}
		else {
		    perror(elf_interpreter);
		    exit(-1);
		    /* retval = -errno; */
		}
	    }

	    if (retval >= 0) {
		retval = lseek(interpreter_fd, 0, SEEK_SET);
		if(retval >= 0) {
		    retval = read(interpreter_fd,bprm->buf,128);
		}
	    }
	    if (retval >= 0) {
		interp_ex = *((struct exec *) bprm->buf); /* aout exec-header */
		interp_elf_ex=*((struct elfhdr *) bprm->buf); /* elf exec-header */
	    }
	    if (retval < 0) {
		perror("load_elf_binary3");
		exit(-1);
		free (elf_phdata);
		free(elf_interpreter);
		close(bprm->fd);
		return retval;
	    }
	}
	elf_ppnt++;
    }

    /* Some simple consistency checks for the interpreter */
    if (elf_interpreter){
	interpreter_type = INTERPRETER_ELF | INTERPRETER_AOUT;

	/* Now figure out which format our binary is */
	if ((N_MAGIC(interp_ex) != OMAGIC) && (N_MAGIC(interp_ex) != ZMAGIC) &&
	    	(N_MAGIC(interp_ex) != QMAGIC)) {
	  interpreter_type = INTERPRETER_ELF;
	}

	if (interp_elf_ex.e_ident[0] != 0x7f ||
	    	strncmp(&interp_elf_ex.e_ident[1], "ELF",3) != 0) {
	    interpreter_type &= ~INTERPRETER_ELF;
	}

	if (!interpreter_type) {
	    free(elf_interpreter);
	    free(elf_phdata);
	    close(bprm->fd);
	    return -ELIBBAD;
	}
    }

    /* OK, we are done with that, now set up the arg stuff,
       and then start this sucker up */

    if (!bprm->sh_bang) {
	char * passed_p;

	if (interpreter_type == INTERPRETER_AOUT) {
	    sprintf(passed_fileno, "%d", bprm->fd);
	    passed_p = passed_fileno;

	    if (elf_interpreter) {
		bprm->p = copy_strings(1,&passed_p,bprm->page,bprm->p);
		bprm->argc++;
	    }
	}
	if (!bprm->p) {
	    if (elf_interpreter) {
	        free(elf_interpreter);
	    }
	    free (elf_phdata);
	    close(bprm->fd);
	    return -E2BIG;
	}
    }

    /* OK, This is the point of no return */
    info->end_data = 0;
    info->end_code = 0;
    info->start_mmap = (unsigned long)ELF_START_MMAP;
    info->mmap = 0;
    elf_entry = (unsigned long) elf_ex.e_entry;

    /* Do this so that we can load the interpreter, if need be.  We will
       change some of these later */
    info->rss = 0;
    bprm->p = setup_arg_pages(bprm->p, bprm, info);
    info->start_stack = bprm->p;

    /* Now we do a little grungy work by mmaping the ELF image into
     * the correct location in memory.  At this point, we assume that
     * the image should be loaded at fixed address, not at a variable
     * address.
     */

    for(i = 0, elf_ppnt = elf_phdata; i < elf_ex.e_phnum; i++, elf_ppnt++) {
        int elf_prot = 0;
        int elf_flags = 0;
        unsigned long error;
        
	if (elf_ppnt->p_type != PT_LOAD)
            continue;
        
        if (elf_ppnt->p_flags & PF_R) elf_prot |= PROT_READ;
        if (elf_ppnt->p_flags & PF_W) elf_prot |= PROT_WRITE;
        if (elf_ppnt->p_flags & PF_X) elf_prot |= PROT_EXEC;
        elf_flags = MAP_PRIVATE | MAP_DENYWRITE;
        if (elf_ex.e_type == ET_EXEC || load_addr_set) {
            elf_flags |= MAP_FIXED;
        } else if (elf_ex.e_type == ET_DYN) {
            /* Try and get dynamic programs out of the way of the default mmap
               base, as well as whatever program they might try to exec.  This
               is because the brk will follow the loader, and is not movable.  */
            /* NOTE: for qemu, we do a big mmap to get enough space
               without harcoding any address */
            error = target_mmap(0, ET_DYN_MAP_SIZE,
                                PROT_NONE, MAP_PRIVATE | MAP_ANON, 
                                -1, 0);
            if (error == -1) {
                perror("mmap");
                exit(-1);
            }
            load_bias = TARGET_ELF_PAGESTART(error - elf_ppnt->p_vaddr);
        }
        
        error = target_mmap(TARGET_ELF_PAGESTART(load_bias + elf_ppnt->p_vaddr),
                            (elf_ppnt->p_filesz +
                             TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr)),
                            elf_prot,
                            (MAP_FIXED | MAP_PRIVATE | MAP_DENYWRITE),
                            bprm->fd,
                            (elf_ppnt->p_offset - 
                             TARGET_ELF_PAGEOFFSET(elf_ppnt->p_vaddr)));
        if (error == -1) {
            perror("mmap");
            exit(-1);
        }

#ifdef LOW_ELF_STACK
        if (TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr) < elf_stack)
            elf_stack = TARGET_ELF_PAGESTART(elf_ppnt->p_vaddr);
#endif
        
        if (!load_addr_set) {
            load_addr_set = 1;
            load_addr = elf_ppnt->p_vaddr - elf_ppnt->p_offset;
            if (elf_ex.e_type == ET_DYN) {
                load_bias += error -
                    TARGET_ELF_PAGESTART(load_bias + elf_ppnt->p_vaddr);
                load_addr += load_bias;
            }
        }
        k = elf_ppnt->p_vaddr;
        if (k < start_code) 
            start_code = k;
        k = elf_ppnt->p_vaddr + elf_ppnt->p_filesz;
        if (k > elf_bss) 
            elf_bss = k;
        if ((elf_ppnt->p_flags & PF_X) && end_code <  k)
            end_code = k;
        if (end_data < k) 
            end_data = k;
        k = elf_ppnt->p_vaddr + elf_ppnt->p_memsz;
        if (k > elf_brk) elf_brk = k;
    }

    elf_entry += load_bias;
    elf_bss += load_bias;
    elf_brk += load_bias;
    start_code += load_bias;
    end_code += load_bias;
    //    start_data += load_bias;
    end_data += load_bias;

    if (elf_interpreter) {
	if (interpreter_type & 1) {
	    elf_entry = load_aout_interp(&interp_ex, interpreter_fd);
	}
	else if (interpreter_type & 2) {
	    elf_entry = load_elf_interp(&interp_elf_ex, interpreter_fd,
					    &interp_load_addr);
	}

	close(interpreter_fd);
	free(elf_interpreter);

	if (elf_entry == ~0UL) {
	    printf("Unable to load interpreter\n");
	    free(elf_phdata);
	    exit(-1);
	    return 0;
	}
    }

    free(elf_phdata);

    if (loglevel)
	load_symbols(&elf_ex, bprm->fd);

    if (interpreter_type != INTERPRETER_AOUT) close(bprm->fd);
    info->personality = (ibcs2_interpreter ? PER_SVR4 : PER_LINUX);

#ifdef LOW_ELF_STACK
    info->start_stack = bprm->p = elf_stack - 4;
#endif
    bprm->p = (unsigned long)
      create_elf_tables((char *)bprm->p,
		    bprm->argc,
		    bprm->envc,
		    (interpreter_type == INTERPRETER_ELF ? &elf_ex : NULL),
                    load_addr, load_bias,
		    interp_load_addr,
		    (interpreter_type == INTERPRETER_AOUT ? 0 : 1),
		    info);
    if (interpreter_type == INTERPRETER_AOUT)
      info->arg_start += strlen(passed_fileno) + 1;
    info->start_brk = info->brk = elf_brk;
    info->end_code = end_code;
    info->start_code = start_code;
    info->end_data = end_data;
    info->start_stack = bprm->p;

    /* Calling set_brk effectively mmaps the pages that we need for the bss and break
       sections */
    set_brk(elf_bss, elf_brk);

    padzero(elf_bss);

#if 0
    printf("(start_brk) %x\n" , info->start_brk);
    printf("(end_code) %x\n" , info->end_code);
    printf("(start_code) %x\n" , info->start_code);
    printf("(end_data) %x\n" , info->end_data);
    printf("(start_stack) %x\n" , info->start_stack);
    printf("(brk) %x\n" , info->brk);
#endif

    if ( info->personality == PER_SVR4 )
    {
	    /* Why this, you ask???  Well SVr4 maps page 0 as read-only,
	       and some applications "depend" upon this behavior.
	       Since we do not have the power to recompile these, we
	       emulate the SVr4 behavior.  Sigh.  */
	    mapped_addr = target_mmap(0, host_page_size, PROT_READ | PROT_EXEC,
                                      MAP_FIXED | MAP_PRIVATE, -1, 0);
    }

#ifdef ELF_PLAT_INIT
    /*
     * The ABI may specify that certain registers be set up in special
     * ways (on i386 %edx is the address of a DT_FINI function, for
     * example.  This macro performs whatever initialization to
     * the regs structure is required.
     */
    ELF_PLAT_INIT(regs);
#endif


    info->entry = elf_entry;

    return 0;
}



int elf_exec(const char * filename, char ** argv, char ** envp, 
             struct target_pt_regs * regs, struct image_info *infop)
{
        struct linux_binprm bprm;
        int retval;
        int i;

        bprm.p = TARGET_PAGE_SIZE*MAX_ARG_PAGES-sizeof(unsigned int);
        for (i=0 ; i<MAX_ARG_PAGES ; i++)       /* clear page-table */
                bprm.page[i] = 0;
        retval = open(filename, O_RDONLY);
        if (retval == -1) {
	    perror(filename);
	    exit(-1);
            /* return retval; */
	}
	else {
	    bprm.fd = retval;
	}
        bprm.filename = (char *)filename;
        bprm.sh_bang = 0;
        bprm.loader = 0;
        bprm.exec = 0;
        bprm.dont_iput = 0;
	bprm.argc = count(argv);
	bprm.envc = count(envp);

        retval = prepare_binprm(&bprm);

        if(retval>=0) {
	    bprm.p = copy_strings(1, &bprm.filename, bprm.page, bprm.p);
	    bprm.exec = bprm.p;
	    bprm.p = copy_strings(bprm.envc,envp,bprm.page,bprm.p);
	    bprm.p = copy_strings(bprm.argc,argv,bprm.page,bprm.p);
	    if (!bprm.p) {
		retval = -E2BIG;
	    }
        }

        if(retval>=0) {
	    retval = load_elf_binary(&bprm,regs,infop);
	}
        if(retval>=0) {
	    /* success.  Initialize important registers */
	    regs->esp = infop->start_stack;
	    regs->eip = infop->entry;
	    return retval;
	}

        /* Something went wrong, return the inode and free the argument pages*/
        for (i=0 ; i<MAX_ARG_PAGES ; i++) {
	    free_page((void *)bprm.page[i]);
	}
        return(retval);
}


static int load_aout_interp(void * exptr, int interp_fd)
{
    printf("a.out interpreter not yet supported\n");
    return(0);
}