2008-07-08 15:35:40 +00:00
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.\" Copyright (c) 2008, Linux Foundation, written by by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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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.\" manual page may be incorrect or out-of-date.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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.\" 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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.\"
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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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.TH END 3 2008-07-17 "GNU" "Linux Programmer's Manual"
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.SH NAME
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etext, edata, end \- end of program segments
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.SH SYNOPSIS
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.nf
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.BI extern " etext" ;
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.BI extern " edata" ;
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.BI extern " end" ;
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.fi
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.SH DESCRIPTION
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The addresses of these symbols indicate the end of various program
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segments:
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.TP
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.I etext
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This is the first address past the end of the text segment
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(the program code).
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.TP
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2008-07-17 14:03:52 +00:00
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.I edata
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2008-07-08 15:35:40 +00:00
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This is the first address past the end of the
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initialized data segment.
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.TP
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.I end
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This is the first address past the end of the
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uninitialized data segment (also known as the BSS segment).
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.SH CONFORMING TO
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intro.1, time.1, accept.2, bind.2, connect.2, execve.2, flock.2, getdents.2, getpriority.2, getuid.2, intro.2, ioctl.2, mincore.2, mknod.2, personality.2, ptrace.2, read.2, recv.2, select_tut.2, send.2, sendfile.2, shmctl.2, sigaction.2, signal.2, stat.2, times.2, truncate.2, umask.2, wait.2, MB_CUR_MAX.3, MB_LEN_MAX.3, argz_add.3, btowc.3, clearenv.3, clock.3, cmsg.3, end.3, endian.3, errno.3, exit.3, fgetwc.3, fgetws.3, fopen.3, fputwc.3, fputws.3, fseek.3, fwide.3, getfsent.3, getgrnam.3, gethostid.3, getipnodebyname.3, getmntent.3, getpwnam.3, getwchar.3, grantpt.3, iconv.3, iconv_close.3, iconv_open.3, insque.3, intro.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, malloc.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, mkstemp.3, mktemp.3, nl_langinfo.3, openpty.3, posix_openpt.3, printf.3, ptsname.3, putwchar.3, qecvt.3, rcmd.3, readdir.3, rexec.3, rpc.3, setnetgrent.3, shm_open.3, sigpause.3, stdin.3, stpcpy.3, strftime.3, strptime.3, syslog.3, towctrans.3, towlower.3, towupper.3, ttyslot.3, ungetwc.3, unlocked_stdio.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wprintf.3, console_ioctl.4, pts.4, elf.5, filesystems.5, hosts.5, proc.5, ttytype.5, boot.7, capabilities.7, credentials.7, epoll.7, glob.7, koi8-r.7, path_resolution.7, pty.7, signal.7, suffixes.7, time.7, unicode.7, unix.7, uri.7, utf-8.7: global fix: s/Unix/UNIX/
The man pages were rather inconsistent in the use of "Unix"
versus "UNIX". Let's go with the trademark usage.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2010-10-12 04:45:38 +00:00
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Although these symbols have long been provided on most UNIX systems,
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2008-07-17 14:03:52 +00:00
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they are not standardized; use with caution.
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2008-07-08 15:35:40 +00:00
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.SH NOTES
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The program must explicitly declare these symbols;
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they are not defined in any header file.
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On some systems the names of these symbols are preceded by underscores,
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thus:
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.IR _etext ,
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.IR _edata ,
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and
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.IR _end .
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These symbols are also defined for programs compiled on Linux.
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At the start of program execution,
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the program break will be somewhere near
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2008-07-09 13:55:24 +00:00
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.IR &end
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2008-07-08 15:35:40 +00:00
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(perhaps at the start of the following page).
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However, the break will change as memory is allocated via
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.BR brk (2)
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or
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.BR malloc (3).
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Use
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.BR sbrk (2)
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with an argument of zero to find the current value of the program break.
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.SH EXAMPLE
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When run, the program below produces output such as the following:
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.in +4n
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.nf
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eventfd.2, execve.2, getdents.2, ioprio_set.2, mprotect.2, signalfd.2, timerfd_create.2, wait.2, backtrace.3, clock_getcpuclockid.3, end.3, fmemopen.3, fopencookie.3, frexp.3, getdate.3, getgrouplist.3, getprotoent_r.3, getservent_r.3, gnu_get_libc_version.3, inet.3, inet_pton.3, makecontext.3, malloc.3, matherr.3, offsetof.3, pthread_attr_init.3, pthread_create.3, pthread_getattr_np.3, sem_wait.3, strftime.3, strtok.3, strtol.3, core.5, proc.5, cpuset.7, mq_overview.7: Global fix: Format user input in shell sessions in boldface
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2008-10-28 15:37:22 +00:00
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.RB "$" " ./a.out"
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2008-07-08 15:35:40 +00:00
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First address past:
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program text (etext) 0x8048568
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initialized data (edata) 0x804a01c
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uninitialized data (end) 0x804a024
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.fi
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.in
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eventfd.2, getdents.2, mprotect.2, signalfd.2, timerfd_create.2, wait.2, backtrace.3, clock_getcpuclockid.3, end.3, fmemopen.3, fopencookie.3, getdate.3, getgrouplist.3, getprotoent_r.3, getservent_r.3, gnu_get_libc_version.3, inet.3, inet_pton.3, makecontext.3, matherr.3, offsetof.3, pthread_attr_init.3, pthread_create.3, pthread_getattr_np.3, sem_wait.3, strtol.3, core.5: global fix: Add ".SS Program source" to EXAMPLE
Add ".SS Program source" to clearly distinguish shell session and
descriptive text from actual program code.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2008-10-28 15:51:05 +00:00
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.SS Program source
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eventfd.2, getdents.2, mprotect.2, signalfd.2, timerfd_create.2, wait.2, backtrace.3, clock_getcpuclockid.3, end.3, fmemopen.3, fopencookie.3, frexp.3, getaddrinfo.3, getdate.3, getgrouplist.3, getprotoent_r.3, getservent_r.3, gnu_get_libc_version.3, inet.3, inet_pton.3, makecontext.3, matherr.3, offsetof.3, pthread_attr_init.3, pthread_create.3, pthread_getattr_np.3, sem_wait.3, strftime.3, strtok.3, strtol.3, core.5: srcfix
s/\.R " "/\\\&/ as a way of getting a blank line after a .SS heading.
(Suggested by Sam Varshavchik <mrsam@courier-mta.com>)
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2008-11-05 01:42:45 +00:00
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\&
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2008-07-08 15:35:40 +00:00
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.nf
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#include <stdio.h>
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#include <stdlib.h>
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extern char etext, edata, end; /* The symbols must have some type,
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or "gcc -Wall" complains */
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int
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main(int argc, char *argv[])
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{
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printf("First address past:\\n");
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printf(" program text (etext) %10p\\n", &etext);
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printf(" initialized data (edata) %10p\\n", &edata);
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printf(" uninitialized data (end) %10p\\n", &end);
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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 objdump (1),
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.BR readelf (1),
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2008-07-17 14:03:52 +00:00
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.BR sbrk (2),
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.BR elf (5)
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