include/link.h

/*
 * RRS section definitions.
 * Nomenclature and, more importantly, the layout of the various
 * data structures defined in this header file are borrowed from
 * Sun Microsystems' original <link.h>, so we can provide compatibility
 * with the SunOS 4.x shared library scheme.
 *
 *      $Id: link.h,v 1.2 1993/10/22 21:04:19 pk Exp $
 *              (derived from: @(#)link.h 1.6 88/08/19 SMI
 *              Copyright (c) 1987 by Sun Microsystems, Inc.)
 */

#ifndef _LINK_H_
#define _LINK_H_

/*
 * A `link_object' structure descibes a shared object that is needed
 * to complete the link edit process of the object containing it.
 * A list of such objects (chained through `lo_next') is pointed at
 * by `ld_need' in the link_dynamic_2 structure.
 */

struct link_object {
        long    lo_name;                /* name (relative to load address) */
        u_int   lo_library : 1,         /* searched for by library rules */
                lo_unused : 31;
        short   lo_major;               /* major version number */
        short   lo_minor;               /* minor version number */
        long    lo_next;                /* next one (often relative) */
};

/*
 * `link_maps' are used by the run-time link editor (ld.so) to keep
 * track of all shared objects loaded into a process' address space.
 * These structures are only used at run-time and do not occur within
 * the text or data segment of an executable or shared library.
 */
struct link_map {
        caddr_t lm_addr;                /* address at which object mapped */
        char    *lm_name;               /* full name of loaded object */
        struct  link_map *lm_next;      /* next object in map */
        struct  link_object *lm_lop;    /* link object that got us here */
        caddr_t lm_lob;                 /* base address for said link object */
        u_int   lm_rwt : 1;             /* text is read/write */
        struct  link_dynamic *lm_ld;    /* dynamic structure */
        caddr_t lm_lpd;                 /* loader private data */
};

/*
 * Symbol description with size. This is simply an `nlist' with
 * one field (nz_size) added.
 * Used to convey size information on items in the data segment
 * of shared objects. An array of these live in the shared object's
 * text segment and is address by the `ld_symbols' field.
 */
struct nzlist {
        struct nlist    nlist;
        u_long          nz_size;
#define nz_un           nlist.n_un
#define nz_strx         nlist.n_un.n_strx
#define nz_name         nlist.n_un.n_name
#define nz_type         nlist.n_type
#define nz_value        nlist.n_value
#define nz_desc         nlist.n_desc
#define nz_other        nlist.n_other
};

/*
 * The `link_dynamic_2' structure contains offsets to various data
 * structures needed to do run-time relocation.
 */
struct link_dynamic_2 {
        struct  link_map *ld_loaded;    /* list of loaded objects */
        long    ld_need;                /* list of needed objects */
        long    ld_rules;               /* search rules for library objects */
        long    ld_got;                 /* global offset table */
        long    ld_plt;                 /* procedure linkage table */
        long    ld_rel;                 /* relocation table */
        long    ld_hash;                /* symbol hash table */
        long    ld_symbols;             /* symbol table itself */
        long    (*ld_stab_hash)();      /* "pointer" to symbol hash function */
        long    ld_buckets;             /* number of hash buckets */
        long    ld_strings;             /* symbol strings */
        long    ld_str_sz;              /* size of symbol strings */
        long    ld_text_sz;             /* size of text area */
        long    ld_plt_sz;              /* size of procedure linkage table */
};

/*
 * RRS symbol hash table, addressed by `ld_hash' in link_dynamic_2
 * Used to quickly lookup symbols of the shared object by hashing
 * on the symbol's name. `rh_symbolnum' is the index of the symbol
 * in the shared object's symbol list (`ld_symbols'), `rh_next' is
 * the next symbol in the hash bucket (in case of collisions).
 */
struct rrs_hash {
        int     rh_symbolnum;           /* symbol number */
        int     rh_next;                /* next hash entry */
};

/*
 * `rt_symbols' is used to keep track of run-time allocated commons
 * and data items copied from shared objects.
 */
struct rt_symbol {
        struct nzlist           *rt_sp;         /* the symbol */
        struct rt_symbol        *rt_next;       /* next in linear list */
        struct rt_symbol        *rt_link;       /* next in bucket */
        caddr_t                 rt_srcaddr;     /* address of "master" copy */
};

/*
 * Debugger interface structure.
 */
struct  ld_debug {
        int     ldd_version;            /* version # of interface */
        int     ldd_in_debugger;        /* a debugger is running us */
        int     ldd_sym_loaded;         /* we loaded some symbols */
        char    *ldd_bp_addr;           /* place for ld-generated bpt */
        int     ldd_bp_inst;            /* instruction which was there */
        struct rt_symbol *ldd_cp;       /* commons we built */
};

/*
 * Entry points into ld.so - user interface to the run-time linker.
 * (see also libdl.a)
 */
struct ld_entry {
        int     (*dlopen)();
        int     (*dlclose)();
        int     (*dlsym)();
};

/*
 * This is the structure pointed at by the __DYNAMIC symbol if an
 * executable requires the attention of the run-time link editor.
 * __DYNAMIC is given the value zero if no run-time linking needs to
 * be done (it is always present in shared objects).
 * The union `ld_un' provides for different versions of the dynamic
 * linking mechanism (switched on by `ld_version'). The last version
 * used by Sun is 3. We leave some room here and go to version number
 * 8 for NetBSD, the main difference lying in the support for the
 * `nz_list' type of symbols.
 */

struct  link_dynamic {
        int     ld_version;             /* version # of this structure */
        struct  ld_debug *ldd;
        union {
                struct link_dynamic_2 *ld_2;
        } ld_un;
        struct  ld_entry *ld_entry;
};

#define LD_VERSION_SUN          (3)
#define LD_VERSION_BSD          (8)
#define LD_VERSION_NZLIST_P(v)  ((v) >= 8)

#define LD_GOT(x)       ((x)->ld_un.ld_2->ld_got)
#define LD_PLT(x)       ((x)->ld_un.ld_2->ld_plt)
#define LD_REL(x)       ((x)->ld_un.ld_2->ld_rel)
#define LD_SYMBOL(x)    ((x)->ld_un.ld_2->ld_symbols)
#define LD_HASH(x)      ((x)->ld_un.ld_2->ld_hash)
#define LD_STRINGS(x)   ((x)->ld_un.ld_2->ld_strings)
#define LD_NEED(x)      ((x)->ld_un.ld_2->ld_need)
#define LD_BUCKETS(x)   ((x)->ld_un.ld_2->ld_buckets)

#define LD_GOTSZ(x)     ((x)->ld_un.ld_2->ld_plt - (x)->ld_un.ld_2->ld_got)
#define LD_RELSZ(x)     ((x)->ld_un.ld_2->ld_hash - (x)->ld_un.ld_2->ld_rel)
#define LD_HASHSZ(x)    ((x)->ld_un.ld_2->ld_symbols - (x)->ld_un.ld_2->ld_hash)
#define LD_STABSZ(x)    ((x)->ld_un.ld_2->ld_strings - (x)->ld_un.ld_2->ld_symbols)
#define LD_PLTSZ(x)     ((x)->ld_un.ld_2->ld_plt_sz)
#define LD_STRSZ(x)     ((x)->ld_un.ld_2->ld_str_sz)
#define LD_TEXTSZ(x)    ((x)->ld_un.ld_2->ld_text_sz)

/*
 * Interface to ld.so (see link(5))
 */
struct crt_ldso {
        int             crt_ba;         /* Base address of ld.so */
        int             crt_dzfd;       /* "/dev/zero" file decriptor (SunOS) */
        int             crt_ldfd;       /* ld.so file descriptor */
        struct link_dynamic     *crt_dp;/* Main's __DYNAMIC */
        char            **crt_ep;       /* environment strings */
        caddr_t         crt_bp;         /* Breakpoint if run from debugger */
};

/*
 * Version passed from crt0 to ld.so (1st argument to _rtld()).
 */
#define CRT_VERSION_SUN         1
#define CRT_VERSION_BSD         2


/*
 * Maximum number of recognized shared object version numbers.
 */
#define MAXDEWEY        8

/*
 * Header of the hints file.
 */
struct hints_header {
        long            hh_magic;
#define HH_MAGIC        011421044151
        long            hh_version;     /* Interface version number */
#define LD_HINTS_VERSION_1      1
        long            hh_hashtab;     /* Location of hash table */
        long            hh_nbucket;     /* Number of buckets in hashtab */
        long            hh_strtab;      /* Location of strings */
        long            hh_strtab_sz;   /* Size of strings */
        long            hh_ehints;      /* End of hints (max offset in file) */
};

#define HH_BADMAG(hdr)  ((hdr).hh_magic != HH_MAGIC)

/*
 * Hash table element in hints file.
 */
struct hints_bucket {
        /* namex and pathx are indices into the string table */
        int             hi_namex;               /* Library name */
        int             hi_pathx;               /* Full path */
        int             hi_dewey[MAXDEWEY];     /* The versions */
        int             hi_ndewey;              /* Number of version numbers */
#define hi_major hi_dewey[0]
#define hi_minor hi_dewey[1]
        int             hi_next;                /* Next in this bucket */
};

#define _PATH_LD_HINTS          "/var/run/ld.so.hints"

#endif /* _LINK_H_ */