diff options
Diffstat (limited to 'lib/csu/i386')
-rw-r--r-- | lib/csu/i386/Makefile | 64 | ||||
-rw-r--r-- | lib/csu/i386/c++rt0.c | 86 | ||||
-rw-r--r-- | lib/csu/i386/crt0.c | 433 | ||||
-rw-r--r-- | lib/csu/i386/dlfcn.h | 53 | ||||
-rw-r--r-- | lib/csu/i386/dlopen.3 | 213 |
5 files changed, 849 insertions, 0 deletions
diff --git a/lib/csu/i386/Makefile b/lib/csu/i386/Makefile new file mode 100644 index 0000000..1b3e61f --- /dev/null +++ b/lib/csu/i386/Makefile @@ -0,0 +1,64 @@ +# from: @(#)Makefile 5.6 (Berkeley) 5/22/91 +# $Id$ + +CFLAGS+= -DLIBC_SCCS -fno-omit-frame-pointer +OBJS= crt0.o c++rt0.o gcrt0.o scrt0.o sgcrt0.o +CLEANFILES+= a.out +MAN3+= dlopen.3 +MLINKS+= dlopen.3 dlsym.3 \ + dlopen.3 dlerror.3 \ + dlopen.3 dlclose.3 + +all: ${OBJS} + +crt0.o: crt0.c + ${CC} ${CFLAGS} -c -DCRT0 -DDYNAMIC ${.CURDIR}/crt0.c -o ${.TARGET} + ${LD} -x -r ${.TARGET} + mv -f a.out ${.TARGET} + +c++rt0.o: c++rt0.c + ${CC} ${CFLAGS} -fpic -c ${.CURDIR}/c++rt0.c + @${LD} -x -r ${.TARGET} + @mv -f a.out ${.TARGET} + +# +# gcrt0.o doesn't really depend on crt0.o, but this is the easiest way +# to get the dependencies mostly correct. +# +gcrt0.o: crt0.o + ${CC} ${CFLAGS} -c -DMCRT0 -DDYNAMIC ${.CURDIR}/crt0.c -o ${.TARGET} + ${LD} -x -r ${.TARGET} + mv -f a.out ${.TARGET} + +# dependencies fudged as for gcrt0.o +scrt0.o: crt0.o + ${CC} ${CFLAGS} -c -DCRT0 ${.CURDIR}/crt0.c -o ${.TARGET} + ${LD} -x -r ${.TARGET} + mv -f a.out ${.TARGET} + +# dependencies fudged as for gcrt0.o +sgcrt0.o: scrt0.o + ${CC} ${CFLAGS} -c -DMCRT0 ${.CURDIR}/crt0.c -o ${.TARGET} + ${LD} -x -r ${.TARGET} + mv -f a.out ${.TARGET} + +beforeinstall: + ${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 ${.CURDIR}/dlfcn.h \ + ${DESTDIR}/usr/include + +realinstall: +.for i in ${OBJS} + ${INSTALL} ${COPY} -o ${BINOWN} -g ${BINGRP} -m 444 $i \ + ${DESTDIR}/usr/lib +.endfor + +depend: .depend + +.depend: crt0.c c++rt0.c + rm -f .depend + mkdep ${CFLAGS} -DCRT0 -DDYNAMIC ${.CURDIR}/crt0.c + mkdep -a ${CFLAGS} ${.CURDIR}/c++rt0.c + +lint tags: + +.include <bsd.prog.mk> diff --git a/lib/csu/i386/c++rt0.c b/lib/csu/i386/c++rt0.c new file mode 100644 index 0000000..94fa5c5 --- /dev/null +++ b/lib/csu/i386/c++rt0.c @@ -0,0 +1,86 @@ +/* + * Copyright (c) 1993 Paul Kranenburg + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by Paul Kranenburg. + * 4. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * $Id$ + */ + +/* + * Run-time module for GNU C++ compiled shared libraries. + * + * The linker constructs the following arrays of pointers to global + * constructors and destructors. The first element contains the + * number of pointers in each. + * The tables are also null-terminated. + */ +void (*__CTOR_LIST__[2])(void); +void (*__DTOR_LIST__[2])(void); + +static void +__dtors(void) +{ + unsigned long i = (unsigned long) __DTOR_LIST__[0]; + void (**p)(void) = __DTOR_LIST__ + i; + + while (i--) + (**p--)(); +} + +static void +__ctors(void) +{ + void (**p)(void) = __CTOR_LIST__ + 1; + + while (*p) + (**p++)(); +} + +extern void __init() asm(".init"); +extern void __fini() asm(".fini"); + +void +__init(void) +{ + static int initialized = 0; + + /* + * Call global constructors. + * Arrange to call global destructors at exit. + */ + if (!initialized) { + initialized = 1; + __ctors(); + } + +} + +void +__fini(void) +{ + __dtors(); +} diff --git a/lib/csu/i386/crt0.c b/lib/csu/i386/crt0.c new file mode 100644 index 0000000..5f7e4ab --- /dev/null +++ b/lib/csu/i386/crt0.c @@ -0,0 +1,433 @@ +/* + * Copyright (c) 1993 Paul Kranenburg + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by Paul Kranenburg. + * 4. The name of the author may not be used to endorse or promote products + * derived from this software without specific prior written permission + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * $Id$ + */ + +#include <sys/param.h> + +#include <stdlib.h> +#include <dlfcn.h> + +#ifdef DYNAMIC +#include <sys/types.h> +#include <sys/syscall.h> +#include <a.out.h> +#include <string.h> +#include <sys/mman.h> +#include <link.h> + +/* !!! + * This is gross, ld.so is a ZMAGIC a.out, but has `sizeof(hdr)' for + * an entry point and not at PAGSIZ as the N_*ADDR macros assume. + */ +#undef N_DATADDR +#define N_DATADDR(x) ((x).a_text) + +#undef N_BSSADDR +#define N_BSSADDR(x) ((x).a_text + (x).a_data) + +#ifndef N_GETMAGIC +#define N_GETMAGIC(x) ((x).a_magic) +#endif /* N_GETMAGIC */ + +#ifndef MAP_PRIVATE +#define MAP_PRIVATE MAP_COPY +#endif /* MAP_PRIVATE */ + +#ifndef MAP_FILE +#define MAP_FILE 0 +#endif /* MAP_FILE */ + +#ifndef MAP_ANON +#define MAP_ANON 0 +#endif /* MAP_ANON */ + +#ifdef DEBUG +/* + * We need these two because we are going to call them before the ld.so is + * finished (as a matter of fact before we know if it exists !) so we must + * provide these versions for them + */ +static char *_getenv(); +static int _strncmp(); +#endif /* DEBUG */ + +#ifndef LDSO +#define LDSO "/usr/libexec/ld.so" +#endif /* LDSO */ + +extern struct _dynamic _DYNAMIC; +static struct ld_entry *ld_entry; +static void __do_dynamic_link (); +#endif /* DYNAMIC */ + +int _callmain(); +int errno; +static char empty[1]; +char *__progname = empty; +char **environ; + +extern unsigned char etext; +extern unsigned char eprol asm ("eprol"); +extern start() asm("start"); +extern mcount() asm ("mcount"); +extern int main(int argc, char **argv, char **envp); +int __syscall(int syscall,...); +#ifdef MCRT0 +void monstartup(void *low, void *high); +#endif /* MCRT0 */ + + +/* + * We need these system calls, but can't use library stubs because the are + * not accessible until we have done the ld.so stunt. + */ + +#define _exit(v) \ + __syscall(SYS_exit, (int)(v)) +#define _open(name, f, m) \ + __syscall(SYS_open, (char *)(name), (int)(f), (int)(m)) +#define _read(fd, s, n) \ + __syscall(SYS_read, (int)(fd), (void *)(s), (size_t)(n)) +#define _write(fd, s, n) \ + __syscall(SYS_write, (int)(fd), (void *)(s), (size_t)(n)) +#define _mmap(addr, len, prot, flags, fd, off) \ + (caddr_t) __syscall(SYS_mmap, (caddr_t)(addr), (size_t)(len), \ + (int)(prot), (int)(flags), (int)(fd), (long)0L, (off_t)(off)) + +#define _PUTNMSG(str, len) _write(2, (str), (len)) +#define _PUTMSG(str) _PUTNMSG((str), sizeof (str) - 1) +#define _FATAL(str) ( _PUTMSG(str), _exit(1) ) + + +int +start() +{ + struct kframe { + int kargc; + char *kargv[1]; /* size depends on kargc */ + char kargstr[1]; /* size varies */ + char kenvstr[1]; /* size varies */ + }; + /* + * ALL REGISTER VARIABLES!!! + */ + register struct kframe *kfp; + register char **targv; + register char **argv; + extern void _mcleanup(); +#ifdef DYNAMIC + volatile caddr_t x; +#endif + +#ifdef lint + kfp = 0; +#else /* not lint */ + /* just above the saved frame pointer */ + asm ("lea 4(%%ebp), %0" : "=r" (kfp) ); +#endif /* not lint */ + for (argv = targv = &kfp->kargv[0]; *targv++; /* void */) + /* void */ ; + if (targv >= (char **)(*argv)) + --targv; + environ = targv; + + if (argv[0]) { + register char *s; + __progname = argv[0]; + for (s=__progname; *s != '\0'; s++) + if (*s == '/') + __progname = s+1; + } + +#ifdef DYNAMIC + /* ld(1) convention: if DYNAMIC = 0 then statically linked */ + /* sometimes GCC is too smart/stupid for its own good */ + x = (caddr_t)&_DYNAMIC; + if (x) + __do_dynamic_link(); +#endif /* DYNAMIC */ + +asm("eprol:"); + +#ifdef MCRT0 + atexit(_mcleanup); + monstartup(&eprol, &etext); +#endif /* MCRT0 */ + +asm ("__callmain:"); /* Defined for the benefit of debuggers */ + exit(main(kfp->kargc, argv, environ)); +} + +#ifdef DYNAMIC +static void +__do_dynamic_link () +{ + struct crt_ldso crt; + struct exec hdr; + char *ldso; + int (*entry)(); + int ret; + +#ifdef DEBUG + /* Provision for alternate ld.so - security risk! */ + if (!(ldso = _getenv("LDSO"))) +#endif + ldso = LDSO; + + crt.crt_ldfd = _open(ldso, 0, 0); + if (crt.crt_ldfd == -1) { + _PUTMSG("Couldn't open "); + _PUTMSG(LDSO); + _FATAL(".\n"); + } + + /* Read LDSO exec header */ + if (_read(crt.crt_ldfd, &hdr, sizeof hdr) < sizeof hdr) { + _FATAL("Failure reading ld.so\n"); + } + if ((N_GETMAGIC_NET(hdr) != ZMAGIC) && (N_GETMAGIC(hdr) != QMAGIC)) { + _FATAL("Bad magic: ld.so\n"); + } + + /* We use MAP_ANON */ + crt.crt_dzfd = -1; + + /* Map in ld.so */ + crt.crt_ba = (int)_mmap(0, hdr.a_text, + PROT_READ|PROT_EXEC, + MAP_FILE|MAP_PRIVATE, + crt.crt_ldfd, N_TXTOFF(hdr)); + if (crt.crt_ba == -1) { + _FATAL("Cannot map ld.so (text)\n"); + } + + /* Map in data segment of ld.so writable */ + if ((int)_mmap((caddr_t)(crt.crt_ba+N_DATADDR(hdr)), hdr.a_data, + PROT_READ|PROT_WRITE, + MAP_FIXED|MAP_FILE|MAP_PRIVATE, + crt.crt_ldfd, N_DATOFF(hdr)) == -1) { + _FATAL("Cannot map ld.so (data)\n"); + } + + /* Map bss segment of ld.so zero */ + if (hdr.a_bss && (int)_mmap((caddr_t)(crt.crt_ba+N_BSSADDR(hdr)), + hdr.a_bss, + PROT_READ|PROT_WRITE, + MAP_FIXED|MAP_ANON|MAP_PRIVATE, + crt.crt_dzfd, 0) == -1) { + _FATAL("Cannot map ld.so (bss)\n"); + } + + crt.crt_dp = &_DYNAMIC; + crt.crt_ep = environ; + crt.crt_bp = (caddr_t)_callmain; + crt.crt_prog = __progname; + crt.crt_ldso = ldso; + crt.crt_ldentry = NULL; + + entry = (int (*)())(crt.crt_ba + sizeof hdr); + ret = (*entry)(CRT_VERSION_BSD_4, &crt); + ld_entry = crt.crt_ldentry; + if (ret == -1 && ld_entry == NULL) { + /* if version 4 not recognised, try version 3 */ + ret = (*entry)(CRT_VERSION_BSD_3, &crt); + ld_entry = _DYNAMIC.d_entry; + } + if (ret == -1) { + _PUTMSG("ld.so failed"); + if (ld_entry != NULL) { + char *msg = (ld_entry->dlerror)(); + if(msg != NULL) { + char *endp; + _PUTMSG(": "); + for(endp = msg; *endp != '\0'; ++endp) + ; /* Find the end */ + _PUTNMSG(msg, endp - msg); + } + } + _FATAL("\n"); + } + + + if (ret >= LDSO_VERSION_HAS_DLEXIT) + atexit(ld_entry->dlexit); + + return; +} + +/* + * DL stubs + */ + +void * +dlopen(name, mode) +char *name; +int mode; +{ + if (ld_entry == NULL) + return NULL; + + return (ld_entry->dlopen)(name, mode); +} + +int +dlclose(fd) +void *fd; +{ + if (ld_entry == NULL) + return -1; + + return (ld_entry->dlclose)(fd); +} + +void * +dlsym(fd, name) +void *fd; +char *name; +{ + if (ld_entry == NULL) + return NULL; + + return (ld_entry->dlsym)(fd, name); +} + + +char * +dlerror() +{ + if (ld_entry == NULL) + return "Service unavailable"; + + return (ld_entry->dlerror)(); +} + + +/* + * Support routines + */ + +#ifdef DEBUG +static int +_strncmp(s1, s2, n) + register char *s1, *s2; + register n; +{ + + if (n == 0) + return (0); + do { + if (*s1 != *s2++) + return (*(unsigned char *)s1 - *(unsigned char *)--s2); + if (*s1++ == 0) + break; + } while (--n != 0); + return (0); +} + +static char * +_getenv(name) + register char *name; +{ + extern char **environ; + register int len; + register char **P, *C; + + for (C = name, len = 0; *C && *C != '='; ++C, ++len); + for (P = environ; *P; ++P) + if (!_strncmp(*P, name, len)) + if (*(C = *P + len) == '=') { + return(++C); + } + return (char *)0; +} + +#endif /* DEBUG */ + + asm(" ___syscall:"); + asm(" popl %ecx"); + asm(" popl %eax"); + asm(" pushl %ecx"); + asm(" .byte 0x9a"); + asm(" .long 0"); + asm(" .word 7"); + asm(" pushl %ecx"); + asm(" jc 1f"); + asm(" ret"); + asm(" 1:"); + asm(" movl $-1,%eax"); + asm(" ret"); + +#else /* DYNAMIC */ + +/* + * DL stubs for static linking case (just return error) + */ + +void * +dlopen(name, mode) +char *name; +int mode; +{ + return NULL; +} + +int +dlclose(fd) +void *fd; +{ + return -1; +} + +void * +dlsym(fd, name) +void *fd; +char *name; +{ + return NULL; +} + + +char * +dlerror() +{ + return "Service unavailable"; +} +#endif /* DYNAMIC */ + + +/* + * Support routines + */ + +#ifdef MCRT0 +asm (" .text"); +asm ("_eprol:"); +#endif diff --git a/lib/csu/i386/dlfcn.h b/lib/csu/i386/dlfcn.h new file mode 100644 index 0000000..feadf90 --- /dev/null +++ b/lib/csu/i386/dlfcn.h @@ -0,0 +1,53 @@ +/* + * Copyright (c) 1994 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)err.h 8.1 (Berkeley) 6/2/93 + */ + +#ifndef _DLFCN_H_ +#define _DLFCN_H_ +#include <sys/cdefs.h> + +/* + * Modes for dlopen(). + */ +#define RTLD_LAZY 1 /* Bind function calls lazily */ +#define RTLD_NOW 2 /* Bind function calls immediately */ + +__BEGIN_DECLS +void *dlopen __P((char *, int)); +void *dlsym __P((void *, char *)); +char *dlerror __P((void)); +int dlclose __P((void *)); +__END_DECLS + +#endif /* !_DLFCN_H_ */ diff --git a/lib/csu/i386/dlopen.3 b/lib/csu/i386/dlopen.3 new file mode 100644 index 0000000..82651c6 --- /dev/null +++ b/lib/csu/i386/dlopen.3 @@ -0,0 +1,213 @@ +.\" This source code is a product of Sun Microsystems, Inc. and is provided +.\" for unrestricted use provided that this legend is included on all tape +.\" media and as a part of the software program in whole or part. Users +.\" may copy or modify this source code without charge, but are not authorized +.\" to license or distribute it to anyone else except as part of a product or +.\" program developed by the user. +.\" +.\" THIS PROGRAM CONTAINS SOURCE CODE COPYRIGHTED BY SUN MICROSYSTEMS, INC. +.\" SUN MICROSYSTEMS, INC., MAKES NO REPRESENTATIONS ABOUT THE SUITABLITY +.\" OF SUCH SOURCE CODE FOR ANY PURPOSE. IT IS PROVIDED "AS IS" WITHOUT +.\" EXPRESS OR IMPLIED WARRANTY OF ANY KIND. SUN MICROSYSTEMS, INC. DISCLAIMS +.\" ALL WARRANTIES WITH REGARD TO SUCH SOURCE CODE, INCLUDING ALL IMPLIED +.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN +.\" NO EVENT SHALL SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY SPECIAL, INDIRECT, +.\" INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING +.\" FROM USE OF SUCH SOURCE CODE, REGARDLESS OF THE THEORY OF LIABILITY. +.\" +.\" This source code is provided with no support and without any obligation on +.\" the part of Sun Microsystems, Inc. to assist in its use, correction, +.\" modification or enhancement. +.\" +.\" SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE +.\" INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS +.\" SOURCE CODE OR ANY PART THEREOF. +.\" +.\" Sun Microsystems, Inc. +.\" 2550 Garcia Avenue +.\" Mountain View, California 94043 +.\" +.\" Copyright (c) 1991 Sun Microsystems, Inc. +.\" +.\" @(#) dlopen.3 1.6 90/01/31 SMI +.Dd September 24, 1989 +.Os FreeBSD +.Dt DLOPEN 3 +.Sh NAME +.Nm dlopen, dlsym, dlerror, dlclose +.Nd programmatic interface to the dynamic linker +.Sh SYNOPSIS +.Fd #include <dlfcn.h> +.Ft void * +.Fn dlopen "char *path" "int mode" +.Ft void * +.Fn dlsym "void *handle" "char *symbol" +.Ft char * +.Fn dlerror "void" +.Ft int +.Fn dlclose "void *handle" +.Sh DESCRIPTION +These functions provide a simple programmatic interface to the services of the +dynamic linker. +Operations are provided to add new shared objects to a +program's address space, to obtain the address bindings of symbols +defined by such +objects, and to remove such objects when their use is no longer required. +.Pp +.Fn dlopen +provides access to the shared object in +.Fa path , +returning a descriptor that can be used for later +references to the object in calls to +.Fn dlsym +and +.Fn dlclose . +If +.Fa path +was not in the address space prior to the call to +.Fn dlopen , +it is placed in the address space. +When an object is first loaded into the address space in this way, its +function +.Fn _init , +if any, is called by the dynamic linker. +(Note that +.Ql _init +is the name as expressed in the C language. +From assembly language, the name would appear as +.Ql __init +instead.) +If +.Fa path +has already been placed in the address space in a previous call to +.Fn dlopen , +it is not added a second time, although a reference count of +.Fn dlopen +operations on +.Fa path +is maintained. +A null pointer supplied for +.Fa path +is interpreted as a reference to the main +executable of the process. +.Fa mode +controls the way in which external function references from the +loaded object are bound to their referents. +It must contains one of the following values: +.Bl -tag -width RTLD_LAZYX +.It Dv RTLD_LAZY +Each external function reference is resolved when the function is first +called. +.It Dv RTLD_NOW +All external function references are bound immediately by +.Fn dlopen . +.El +.Pp +.Dv RTLD_LAZY +is normally preferred, for reasons of efficiency. +However, +.Dv RTLD_NOW +is useful to ensure that any undefined symbols are discovered during the +call to +.Fn dlopen . +If +.Fn dlopen +fails, it returns a null pointer, and sets an error condition which may +be interrogated with +.Fn dlerror . +.Pp +.Fn dlsym +returns the address binding of the symbol described in the null-terminated +character string +.Fa symbol , +as it occurs in the shared object identified by +.Fa handle . +Note that +.Fa symbol +is the assembly language representation of the symbol name. +The assembly language representation of a C language symbol contains an +extra underscore at the beginning. +For example, the symbol +.Ql foo +in C would appear as +.Ql _foo +in assembly language, and in the +.Fa symbol +argument to +.Fn dlsym . +The symbols exported by objects added to the address space by +.Fn dlopen +can be accessed only through calls to +.Fn dlsym . +Such symbols do not supersede any definition of those symbols already present +in the address space when the object is loaded, nor are they available to +satisfy normal dynamic linking references. +A null pointer supplied as the value of +.Fa handle +is interpreted as a reference to the executable from which the call to +.Fn dlsym +is being made. Thus a shared object can reference its own symbols. +.Fn dlsym +returns a null pointer if the symbol cannot be found, and sets an error +condition which may be queried with +.Fn dlerror . +.Pp +.Fn dlerror +returns a null-terminated character string describing the last error that +occurred during a call to +.Fn dlopen , +.Fn dlsym , +or +.Fn dlclose . +If no such error has occurred, +.Fn dlerror +returns a null pointer. +At each call to +.Fn dlerror , +the error indication is reset. Thus in the case of two calls +to +.Fn dlerror , +where the second call follows the first immediately, the second call +will always return a null pointer. +.Pp +.Fn dlclose +deletes a reference to the shared object referenced by +.Fa handle . +If the reference count drops to 0, the object is removed from the +address space, and +.Fa handle +is rendered invalid. +Just before removing a shared object in this way, the dynamic linker +calls the object's +.Fn _fini +function, if such a function is defined by the object. +As with +.Ql _init , +.Ql _fini +is the C language name of the function. +If +.Fn dlclose +is successful, it returns a value of 0. +Otherwise it returns -1, and sets an error condition that can be +interrogated with +.Fn dlerror . +.Pp +The object-intrinsic functions +.Fn _init +and +.Fn _fini +are called with no arguments, and are not expected to return values. +.Sh ERRORS +.Fn dlopen +and +.Fn dlsym +return the null pointer in the event of errors. +.Fn dlclose +returns 0 on success, or -1 if an error occurred. +Whenever an error has been detected, a message detailing it can be +retrieved via a call to +.Fn dlerror . +.Sh SEE ALSO +.Xr ld 1 , +.Xr link 5 , +.Xr rtld 1 |