dlopen_pa.3c (2010 09)

ManualsBrandsHP ManualsSoftwareHP-UX Manpages

dlopen_pa(3C)

PA-RISC Systems Only

dlopen_pa(3C)

NAME

dlopen_pa: dlopen(), dlopene() - open an HP 9000 shared library; open an HP 9000 64-bit shared library

with explicit load address

SYNOPSIS

Command:

cc [ﬂag]... cﬁle...

-ldl [library ]...

#include <dlfcn.h>

void *dlopen(const char *file, int mode);

void *dlopene(const char *file, int mode, struct dlopen_opts *opts);

Remarks

This manpage describes dlopen() on HP 9000 systems. For

dlopen() on Integrity systems, see

dlopen_ia (3C).

Multithread Usage

These routines are thread-safe.

Note: The dynamic loader

dld.sl serializes the loading and unloading of shared libraries in

multithreaded applications using a recursive pthread mutex lock. See the HP-UX Linker and

Libraries Online User Guide for more information.

DESCRIPTION

dlopen() and dlopene() are members of a family of routines that give the user direct access to the

dynamic linking facilities (using the -ldl option on the compiler or ld command line).

dlopen() makes a shared object speciﬁed by a ﬁle available to a running process. A shared object may

specify other objects that it "needs" in order to execute properly. These dependencies are speciﬁed by

DT_NEEDED entries in the .dynamic section of the original object. Each needed object may, in turn,

specify other needed objects. All such objects are loaded along with the original object as a result of the

call to dlopen().

dlopene() is an extension to dlopen() which allows the caller to specify explicitly the placement of a

shared library’s text and data segment when the library is dynamically loaded.

A successful

dlopen() or dlopene() call returns to the process a handle which the process may use

on subsequent calls to dlsym() and dlclose(). This value should not be interpreted in any way by

the process.

ﬁle is used to construct a path name to the object ﬁle. If ﬁle contains a slash character, the ﬁle argument

itself is used as the path name. Otherwise

dlopen() searches a series of directories, in the following

order, for ﬁle :

• Any directories speciﬁed by the dynamic path set by calling

dlsetlibpath()

• Any directories speciﬁed by the environment variable

LD_LIBRARY_PATH.

• Any directories speciﬁed by

SHLIB_PATH.

• For ELF applications, any directories speciﬁed by a

DT_RPATH entry in the .dynamic section of

the original program object.

• The directories

/usr/lib and usr/ccs/lib in 32-bit mode and /usr/lib/pa20_64 and

/usr/ccs/lib/pa20_64 in 64-bit mode.

• The current working directory.

The use of

SHLIB_PATH is static. This means that when the program starts, the dynamic loader dld

uses the value in environment variable SHLIB_PATH. Any change to SHLIB_PATH during the program

execution has no effect. The dld_getenv() function removes this constraint. With dld_getenv()

you can change the SHLIB_PATH value (using putenv) and call dld_getenv() to cause dld to read

current SHLIB_PATH value. You can use this new SHLIB_PATH value for subsequent library searching.

You can use

dld_getenv() while loading shared libraries using shl_load() or dlopen().As

described earlier, you should enable SHLIB_PATH searching using the chatr +s enable option. In

case of shl_load(), you should use the DYNAMIC_PATH ﬂag.

The following example demonstrates the

dld_getenv() function:

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
dlopen_pa(3C) dlopen_pa(3C) PA-RISC Systems Only NAME dlopen_pa: dlopen(), dlopene() - open an HP 9000 shared library; open an HP 9000 64-bit shared library with explicit load address SYNOPSIS Command: cc [flag]... cfile ... -ldl [library ]... #include void *dlopen(const char *file, int mode); void *dlopene(const char *file, int mode, struct dlopen_opts *opts); Remarks This manpage describes dlopen() on HP 9000 systems. For dlopen() on Integrity systems, see dlopen_ia (3C).
PAGE 2
dlopen_pa(3C) A PA-RISC Systems Only dlopen_pa(3C) #include #include main(int argc, char **argv) { char * str; shl_t shl; void (*fptr)(void); char *strpath[267]; sprintf(strpath, %s%s", SHLIB_PATH= ,argv[1]); putenv(strpath); dld_getenv(); shl = shl_load( a.sl", BIND_IMMEDIATE | DYNAMIC_PATH, 0); if(!shl) { printf("shl_load failed\n"); exit(-1); } } dA If the value of file is 0, dlopen() provides a handle on a "global symbol object".
PAGE 3
dlopen_pa(3C) dlopen_pa(3C) PA-RISC Systems Only To determine the scope of symbols that are made available for relocation processing of objects loaded in a dlopen() invocation, the mode parameter can be bitwise or’ed with one of the following values: RTLD_GROUP Under this mode, the specified object, and its dependencies, behave as if they were built with -B group (see ld(1)). Only symbols from objects loaded in the same dlopen() invocation are made available for relocation.
PAGE 4
dlopen_pa(3C) dlopen_pa(3C) PA-RISC Systems Only externally visible symbols are typically exported: specifically those referenced by the shared objects with which the a.out is linked. The exact set of exported symbols for any shared object or the a.out can be controlled using the linker (see ld(1)).
PAGE 5
dlopen_pa(3C) dlopen_pa(3C) PA-RISC Systems Only [RTLD_ERR_BAD_DLL_SEGMENT_COUNT] Library needs a shared fixed address but has multiple data segments. [RTLD_ERR_BAD_ELF_VER] Unknown elf version in library. [RTLD_ERR_BAD_RELOC] Unknown relocation type. [RTLD_ERR_CANT_APPLY_RELOC] Cannot apply relocation in library. [RTLD_ERR_CODE_UNSAT] Unsatisfied code symbol in library. [RTLD_ERR_DATA_UNSAT] Unsatisfied data symbol in library.
PAGE 6
dlopen_pa(3C) dlopen_pa(3C) PA-RISC Systems Only memset(&info, 0, sizeof(info)); memset(&opts, 0, sizeof(opts)); /* Get file info */ status = dlgetfileinfo("libfoo.so", sizeof(info), &info); opts.flags = RTLD_EXT_DATA_ADDR; /* allocate memory for the data segment */ opts.data_addr = (char*) mmap(0, info.data_size, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0); A /* call dlopene */ handle = dlopene("libfoo.