2007-09-20 06:52:22 +00:00
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.\" Copyright (c) 2003 by Michael Kerrisk <mtk.manpages@gmail.com>
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2004-11-03 13:51:07 +00:00
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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2008-03-18 14:47:54 +00:00
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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2004-11-03 13:51:07 +00:00
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" License.
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.\"
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2007-05-30 05:36:26 +00:00
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.TH DL_ITERATE_PHDR 3 2007-05-18 "GNU" "Linux Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.SH NAME
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dl_iterate_phdr \- walk through list of shared objects
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.SH SYNOPSIS
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.nf
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2007-07-08 11:17:59 +00:00
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.B #define _GNU_SOURCE
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.B #include <link.h>
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\fBint dl_iterate_phdr(\fP
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\fBint (*\fPcallback\fB) \
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(struct dl_phdr_info *\fPinfo\fB,\fP
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\fBsize_t\fP size\fB, void *\fPdata\fB),\fP
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\fBvoid *\fPdata\fB);\fP
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.fi
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.SH DESCRIPTION
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The
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.BR dl_iterate_phdr ()
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function allows an application to inquire at run time to find
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out which shared objects it has loaded.
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The
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.BR dl_iterate_phdr ()
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function walks through the list of an
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application's shared objects and calls the function
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.I callback
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once for each object,
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until either all shared objects have been processed or
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.I callback
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intro.1, time.1, adjtimex.2, capget.2, eventfd.2, fcntl.2, getrlimit.2, getsockopt.2, gettimeofday.2, intro.2, ioctl_list.2, ioperm.2, mlock.2, pivot_root.2, poll.2, prctl.2, ptrace.2, sched_setscheduler.2, select_tut.2, semget.2, sigaltstack.2, signalfd.2, sysctl.2, timer_settime.2, timerfd_create.2, wait.2, CPU_SET.3, argz_add.3, assert_perror.3, atexit.3, backtrace.3, bcmp.3, clearenv.3, ctime.3, dl_iterate_phdr.3, dlopen.3, ecvt.3, errno.3, error.3, ether_aton.3, exit.3, fenv.3, ferror.3, finite.3, flockfile.3, fnmatch.3, fpathconf.3, fpclassify.3, ftime.3, ftok.3, ftw.3, fwide.3, getaddrinfo.3, gethostbyname.3, getlogin.3, getnameinfo.3, getnetent.3, getopt.3, getprotoent.3, getrpcent.3, getservent.3, glob.3, hsearch.3, inet.3, isalpha.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, longjmp.3, lsearch.3, malloc.3, matherr.3, mblen.3, mbsinit.3, mbtowc.3, on_exit.3, printf.3, pthread_attr_init.3, pthread_attr_setaffinity_np.3, pthread_attr_setdetachstate.3, pthread_attr_setguardsize.3, pthread_attr_setinheritsched.3, pthread_attr_setschedparam.3, pthread_attr_setschedpolicy.3, pthread_attr_setscope.3, pthread_attr_setstack.3, pthread_attr_setstackaddr.3, pthread_attr_setstacksize.3, pthread_cancel.3, pthread_cleanup_push.3, pthread_equal.3, pthread_getattr_np.3, pthread_getcpuclockid.3, pthread_setaffinity_np.3, pthread_setcancelstate.3, pthread_setconcurrency.3, pthread_setschedparam.3, pthread_setschedprio.3, ptsname.3, putenv.3, putgrent.3, raise.3, rcmd.3, regex.3, rexec.3, rpc.3, rpmatch.3, rtnetlink.3, scandir.3, sem_init.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, signbit.3, stdio_ext.3, strtod.3, strtol.3, strtoul.3, system.3, termios.3, timeradd.3, tzset.3, ualarm.3, wctomb.3, xdr.3, st.4, tty_ioctl.4, core.5, elf.5, proc.5, bootparam.7, capabilities.7, icmp.7, ip.7, ipv6.7, math_error.7, mdoc.samples.7, mq_overview.7, pthreads.7, raw.7, regex.7, socket.7, tcp.7, tzselect.8: Global fix: s/non-zero/nonzero/
The tendency in English, as prescribed in style guides like
Chicago MoS, is towards removing hyphens after prefixes
like "non-" etc.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-01-16 16:40:55 +00:00
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returns a nonzero value.
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Each call to
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.I callback
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receives three arguments:
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.IR info ,
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which is a pointer to a structure containing information
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about the shared object;
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.IR size ,
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which is the size of the structure pointed to by
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.IR info ;
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and
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.IR data ,
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which is a copy of whatever value was passed by the calling
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program as the second argument (also named
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.IR data )
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in the call to
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.BR dl_iterate_phdr ().
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The
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.I info
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argument is a structure of the following type:
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2007-12-19 06:57:44 +00:00
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.in +4n
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.nf
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2007-11-21 18:20:54 +00:00
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struct dl_phdr_info {
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ElfW(Addr) dlpi_addr; /* Base address of object */
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const char *dlpi_name; /* (Null-terminated) name of
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object */
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const ElfW(Phdr) *dlpi_phdr; /* Pointer to array of
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ELF program headers
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for this object */
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ElfW(Half) dlpi_phnum; /* # of items in \fIdlpi_phdr\fP */
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};
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.fi
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2007-11-21 18:20:54 +00:00
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.in
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(The
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2005-10-19 07:07:02 +00:00
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.IR ElfW ()
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macro definition turns its argument into the name of an ELF data
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type suitable for the hardware architecture.
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For example, on a 32-bit platform,
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ElfW(Addr) yields the data type name Elf32_Addr.
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Further information on these types can be found in the
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.IR <elf.h> " and " <link.h>
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header files.)
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The
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.I dlpi_addr
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field indicates the base address of the shared object
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(i.e., the difference between the virtual memory address of
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the shared object and the offset of that object in the file
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from which it was loaded).
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The
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.I dlpi_name
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field is a null-terminated string giving the pathname
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from which the shared object was loaded.
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To understand the meaning of the
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.I dlpi_phdr
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and
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.I dlpi_phnum
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fields, we need to be aware that an ELF shared object consists
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of a number of segments, each of which has a corresponding
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program header describing the segment.
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The
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.I dlpi_phdr
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field is a pointer to an array of the program headers for this
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shared object.
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The
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.I dlpi_phnum
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field indicates the size of this array.
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These program headers are structures of the following form:
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.in +4n
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.nf
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2007-11-21 18:20:54 +00:00
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typedef struct {
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Elf32_Word p_type; /* Segment type */
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Elf32_Off p_offset; /* Segment file offset */
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Elf32_Addr p_vaddr; /* Segment virtual address */
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Elf32_Addr p_paddr; /* Segment physical address */
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Elf32_Word p_filesz; /* Segment size in file */
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Elf32_Word p_memsz; /* Segment size in memory */
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Elf32_Word p_flags; /* Segment flags */
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Elf32_Word p_align; /* Segment alignment */
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} Elf32_Phdr;
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.fi
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.in
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Note that we can calculate the location of a particular program header,
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.IR x ,
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in virtual memory using the formula:
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.nf
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addr == info\->dlpi_addr + info\->dlpi_phdr[x].p_vaddr;
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.fi
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2007-05-19 04:30:20 +00:00
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.SH RETURN VALUE
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The
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.BR dl_iterate_phdr ()
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function returns whatever value was returned by the last call to
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.IR callback .
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2007-06-05 05:57:03 +00:00
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.SH VERSIONS
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.BR dl_iterate_phdr ()
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has been supported in glibc since version 2.2.4.
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2007-05-19 04:30:20 +00:00
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.SH "CONFORMING TO"
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The
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.BR dl_iterate_phdr ()
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2007-12-25 21:28:09 +00:00
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function is Linux-specific and should be avoided in portable applications.
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2006-05-22 19:44:47 +00:00
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.SH EXAMPLE
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2007-04-12 22:42:49 +00:00
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The following program displays a list of pathnames of the
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shared objects it has loaded.
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2007-04-12 22:42:49 +00:00
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For each shared object, the program lists the virtual addresses
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at which the object's ELF segments are loaded.
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.nf
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#define _GNU_SOURCE
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#include <link.h>
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#include <stdlib.h>
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#include <stdio.h>
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static int
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callback(struct dl_phdr_info *info, size_t size, void *data)
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{
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int j;
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2007-06-20 21:39:45 +00:00
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printf("name=%s (%d segments)\\n", info\->dlpi_name,
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info\->dlpi_phnum);
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2007-06-20 21:39:45 +00:00
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for (j = 0; j < info\->dlpi_phnum; j++)
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printf("\\t\\t header %2d: address=%10p\\n", j,
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(void *) (info\->dlpi_addr + info\->dlpi_phdr[j].p_vaddr));
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return 0;
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}
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int
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main(int argc, char *argv[])
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{
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dl_iterate_phdr(callback, NULL);
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exit(EXIT_SUCCESS);
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}
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.fi
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.SH "SEE ALSO"
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.BR ldd (1),
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.BR objdump (1),
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.BR readelf (1),
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.BR dlopen (3),
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2008-07-07 14:08:33 +00:00
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.BR elf (5),
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2007-01-28 20:00:24 +00:00
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.BR feature_test_macros (7),
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.BR ld.so (8),
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and the
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.I "Executable and Linking Format Specification"
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available at various locations online.
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