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H.J. Lu 9d7a3741c9 Add --enable-static-pie configure option to build static PIE [BZ #19574]
Static PIE extends address space layout randomization to static
executables.  It provides additional security hardening benefits at
the cost of some memory and performance.

Dynamic linker, ld.so, is a standalone program which can be loaded at
any address.  This patch adds a configure option, --enable-static-pie,
to embed the part of ld.so in static executable to create static position
independent executable (static PIE).  A static PIE is similar to static
executable, but can be loaded at any address without help from a dynamic
linker.  When --enable-static-pie is used to configure glibc, libc.a is
built as PIE and all static executables, including tests, are built as
static PIE.  The resulting libc.a can be used together with GCC 8 or
above to build static PIE with the compiler option, -static-pie.  But
GCC 8 isn't required to build glibc with --enable-static-pie.  Only GCC
with PIE support is needed.  When an older GCC is used to build glibc
with --enable-static-pie, proper input files are passed to linker to
create static executables as static PIE, together with "-z text" to
prevent dynamic relocations in read-only segments, which are not allowed
in static PIE.

The following changes are made for static PIE:

1. Add a new function, _dl_relocate_static_pie, to:
   a. Get the run-time load address.
   b. Read the dynamic section.
   c. Perform dynamic relocations.
Dynamic linker also performs these steps.  But static PIE doesn't load
any shared objects.
2. Call _dl_relocate_static_pie at entrance of LIBC_START_MAIN in
libc.a.  crt1.o, which is used to create dynamic and non-PIE static
executables, is updated to include a dummy _dl_relocate_static_pie.
rcrt1.o is added to create static PIE, which will link in the real
_dl_relocate_static_pie.  grcrt1.o is also added to create static PIE
with -pg.  GCC 8 has been updated to support rcrt1.o and grcrt1.o for
static PIE.

Static PIE can work on all architectures which support PIE, provided:

1. Target must support accessing of local functions without dynamic
relocations, which is needed in start.S to call __libc_start_main with
function addresses of __libc_csu_init, __libc_csu_fini and main.  All
functions in static PIE are local functions.  If PIE start.S can't reach
main () defined in a shared object, the code sequence:

	pass address of local_main to __libc_start_main
	...

local_main:
	tail call to main via PLT

can be used.
2. start.S is updated to check PIC instead SHARED for PIC code path and
avoid dynamic relocation, when PIC is defined and SHARED isn't defined,
to support static PIE.
3. All assembly codes are updated check PIC instead SHARED for PIC code
path to avoid dynamic relocations in read-only sections.
4. All assembly codes are updated check SHARED instead PIC for static
symbol name.
5. elf_machine_load_address in dl-machine.h are updated to support static
PIE.
6. __brk works without TLS nor dynamic relocations in read-only section
so that it can be used by __libc_setup_tls to initializes TLS in static
PIE.

NB: When glibc is built with GCC defaulted to PIE, libc.a is compiled
with -fPIE, regardless if --enable-static-pie is used to configure glibc.
When glibc is configured with --enable-static-pie, libc.a is compiled
with -fPIE, regardless whether GCC defaults to PIE or not.  The same
libc.a can be used to build both static executable and static PIE.
There is no need for separate PIE copy of libc.a.

On x86-64, the normal static sln:

   text	   data	    bss	    dec	    hex	filename
 625425	   8284	   5456	 639165	  9c0bd	elf/sln

the static PIE sln:

   text	   data	    bss	    dec	    hex	filename
 657626	  20636	   5392	 683654	  a6e86	elf/sln

The code size is increased by 5% and the binary size is increased by 7%.

Linker requirements to build glibc with --enable-static-pie:

1. Linker supports --no-dynamic-linker to remove PT_INTERP segment from
static PIE.
2. Linker can create working static PIE.  The x86-64 linker needs the
fix for

https://sourceware.org/bugzilla/show_bug.cgi?id=21782

The i386 linker needs to be able to convert "movl main@GOT(%ebx), %eax"
to "leal main@GOTOFF(%ebx), %eax" if main is defined locally.

Binutils 2.29 or above are OK for i686 and x86-64.  But linker status for
other targets need to be verified.

3. Linker should resolve undefined weak symbols to 0 in static PIE:

https://sourceware.org/bugzilla/show_bug.cgi?id=22269

4. Many ELF backend linkers incorrectly check bfd_link_pic for TLS
relocations, which should check bfd_link_executable instead:

https://sourceware.org/bugzilla/show_bug.cgi?id=22263

Tested on aarch64, i686 and x86-64.

Using GCC 7 and binutils master branch, build-many-glibcs.py with
--enable-static-pie with all patches for static PIE applied have the
following build successes:

PASS: glibcs-aarch64_be-linux-gnu build
PASS: glibcs-aarch64-linux-gnu build
PASS: glibcs-armeb-linux-gnueabi-be8 build
PASS: glibcs-armeb-linux-gnueabi build
PASS: glibcs-armeb-linux-gnueabihf-be8 build
PASS: glibcs-armeb-linux-gnueabihf build
PASS: glibcs-arm-linux-gnueabi build
PASS: glibcs-arm-linux-gnueabihf build
PASS: glibcs-arm-linux-gnueabihf-v7a build
PASS: glibcs-arm-linux-gnueabihf-v7a-disable-multi-arch build
PASS: glibcs-m68k-linux-gnu build
PASS: glibcs-microblazeel-linux-gnu build
PASS: glibcs-microblaze-linux-gnu build
PASS: glibcs-mips64el-linux-gnu-n32 build
PASS: glibcs-mips64el-linux-gnu-n32-nan2008 build
PASS: glibcs-mips64el-linux-gnu-n32-nan2008-soft build
PASS: glibcs-mips64el-linux-gnu-n32-soft build
PASS: glibcs-mips64el-linux-gnu-n64 build
PASS: glibcs-mips64el-linux-gnu-n64-nan2008 build
PASS: glibcs-mips64el-linux-gnu-n64-nan2008-soft build
PASS: glibcs-mips64el-linux-gnu-n64-soft build
PASS: glibcs-mips64-linux-gnu-n32 build
PASS: glibcs-mips64-linux-gnu-n32-nan2008 build
PASS: glibcs-mips64-linux-gnu-n32-nan2008-soft build
PASS: glibcs-mips64-linux-gnu-n32-soft build
PASS: glibcs-mips64-linux-gnu-n64 build
PASS: glibcs-mips64-linux-gnu-n64-nan2008 build
PASS: glibcs-mips64-linux-gnu-n64-nan2008-soft build
PASS: glibcs-mips64-linux-gnu-n64-soft build
PASS: glibcs-mipsel-linux-gnu build
PASS: glibcs-mipsel-linux-gnu-nan2008 build
PASS: glibcs-mipsel-linux-gnu-nan2008-soft build
PASS: glibcs-mipsel-linux-gnu-soft build
PASS: glibcs-mips-linux-gnu build
PASS: glibcs-mips-linux-gnu-nan2008 build
PASS: glibcs-mips-linux-gnu-nan2008-soft build
PASS: glibcs-mips-linux-gnu-soft build
PASS: glibcs-nios2-linux-gnu build
PASS: glibcs-powerpc64le-linux-gnu build
PASS: glibcs-powerpc64-linux-gnu build
PASS: glibcs-tilegxbe-linux-gnu-32 build
PASS: glibcs-tilegxbe-linux-gnu build
PASS: glibcs-tilegx-linux-gnu-32 build
PASS: glibcs-tilegx-linux-gnu build
PASS: glibcs-tilepro-linux-gnu build

and the following build failures:

FAIL: glibcs-alpha-linux-gnu build

elf/sln is failed to link due to:

assertion fail bfd/elf64-alpha.c:4125

This is caused by linker bug and/or non-PIC code in PIE libc.a.

FAIL: glibcs-hppa-linux-gnu build

elf/sln is failed to link due to:

collect2: fatal error: ld terminated with signal 11 [Segmentation fault]

https://sourceware.org/bugzilla/show_bug.cgi?id=22537

FAIL: glibcs-ia64-linux-gnu build

elf/sln is failed to link due to:

collect2: fatal error: ld terminated with signal 11 [Segmentation fault]

FAIL: glibcs-powerpc-linux-gnu build
FAIL: glibcs-powerpc-linux-gnu-soft build
FAIL: glibcs-powerpc-linux-gnuspe build
FAIL: glibcs-powerpc-linux-gnuspe-e500v1 build

elf/sln is failed to link due to:

ld: read-only segment has dynamic relocations.

This is caused by linker bug and/or non-PIC code in PIE libc.a.  See:

https://sourceware.org/bugzilla/show_bug.cgi?id=22264

FAIL: glibcs-powerpc-linux-gnu-power4 build

elf/sln is failed to link due to:

findlocale.c:96:(.text+0x22c): @local call to ifunc memchr

This is caused by linker bug and/or non-PIC code in PIE libc.a.

FAIL: glibcs-s390-linux-gnu build

elf/sln is failed to link due to:

collect2: fatal error: ld terminated with signal 11 [Segmentation fault], core dumped

assertion fail bfd/elflink.c:14299

This is caused by linker bug and/or non-PIC code in PIE libc.a.

FAIL: glibcs-sh3eb-linux-gnu build
FAIL: glibcs-sh3-linux-gnu build
FAIL: glibcs-sh4eb-linux-gnu build
FAIL: glibcs-sh4eb-linux-gnu-soft build
FAIL: glibcs-sh4-linux-gnu build
FAIL: glibcs-sh4-linux-gnu-soft build

elf/sln is failed to link due to:

ld: read-only segment has dynamic relocations.

This is caused by linker bug and/or non-PIC code in PIE libc.a.  See:

https://sourceware.org/bugzilla/show_bug.cgi?id=22263

Also TLS code sequence in SH assembly syscalls in glibc doesn't match TLS
code sequence expected by ld:

https://sourceware.org/bugzilla/show_bug.cgi?id=22270

FAIL: glibcs-sparc64-linux-gnu build
FAIL: glibcs-sparcv9-linux-gnu build
FAIL: glibcs-tilegxbe-linux-gnu build
FAIL: glibcs-tilegxbe-linux-gnu-32 build
FAIL: glibcs-tilegx-linux-gnu build
FAIL: glibcs-tilegx-linux-gnu-32 build
FAIL: glibcs-tilepro-linux-gnu build

elf/sln is failed to link due to:

ld: read-only segment has dynamic relocations.

This is caused by linker bug and/or non-PIC code in PIE libc.a.  See:

https://sourceware.org/bugzilla/show_bug.cgi?id=22263

	[BZ #19574]
	* INSTALL: Regenerated.
	* Makeconfig (real-static-start-installed-name): New.
	(pic-default): Updated for --enable-static-pie.
	(pie-default): New for --enable-static-pie.
	(default-pie-ldflag): Likewise.
	(+link-static-before-libc): Replace $(DEFAULT-LDFLAGS-$(@F))
	with $(if $($(@F)-no-pie),$(no-pie-ldflag),$(default-pie-ldflag)).
	Replace $(static-start-installed-name) with
	$(real-static-start-installed-name).
	(+prectorT): Updated for --enable-static-pie.
	(+postctorT): Likewise.
	(CFLAGS-.o): Add $(pie-default).
	(CFLAGS-.op): Likewise.
	* NEWS: Mention --enable-static-pie.
	* config.h.in (ENABLE_STATIC_PIE): New.
	* configure.ac (--enable-static-pie): New configure option.
	(have-no-dynamic-linker): New LIBC_CONFIG_VAR.
	(have-static-pie): Likewise.
	Enable static PIE if linker supports --no-dynamic-linker.
	(ENABLE_STATIC_PIE): New AC_DEFINE.
	(enable-static-pie): New LIBC_CONFIG_VAR.
	* configure: Regenerated.
	* csu/Makefile (omit-deps): Add r$(start-installed-name) and
	gr$(start-installed-name) for --enable-static-pie.
	(extra-objs): Likewise.
	(install-lib): Likewise.
	(extra-objs): Add static-reloc.o and static-reloc.os
	($(objpfx)$(start-installed-name)): Also depend on
	$(objpfx)static-reloc.o.
	($(objpfx)r$(start-installed-name)): New.
	($(objpfx)g$(start-installed-name)): Also depend on
	$(objpfx)static-reloc.os.
	($(objpfx)gr$(start-installed-name)): New.
	* csu/libc-start.c (LIBC_START_MAIN): Call _dl_relocate_static_pie
	in libc.a.
	* csu/libc-tls.c (__libc_setup_tls): Add main_map->l_addr to
	initimage.
	* csu/static-reloc.c: New file.
	* elf/Makefile (routines): Add dl-reloc-static-pie.
	(elide-routines.os): Likewise.
	(DEFAULT-LDFLAGS-tst-tls1-static-non-pie): Removed.
	(tst-tls1-static-non-pie-no-pie): New.
	* elf/dl-reloc-static-pie.c: New file.
	* elf/dl-support.c (_dl_get_dl_main_map): New function.
	* elf/dynamic-link.h (ELF_DURING_STARTUP): Also check
	STATIC_PIE_BOOTSTRAP.
	* elf/get-dynamic-info.h (elf_get_dynamic_info): Likewise.
	* gmon/Makefile (tests): Add tst-gmon-static-pie.
	(tests-static): Likewise.
	(DEFAULT-LDFLAGS-tst-gmon-static): Removed.
	(tst-gmon-static-no-pie): New.
	(CFLAGS-tst-gmon-static-pie.c): Likewise.
	(CRT-tst-gmon-static-pie): Likewise.
	(tst-gmon-static-pie-ENV): Likewise.
	(tests-special): Likewise.
	($(objpfx)tst-gmon-static-pie.out): Likewise.
	(clean-tst-gmon-static-pie-data): Likewise.
	($(objpfx)tst-gmon-static-pie-gprof.out): Likewise.
	* gmon/tst-gmon-static-pie.c: New file.
	* manual/install.texi: Document --enable-static-pie.
	* sysdeps/generic/ldsodefs.h (_dl_relocate_static_pie): New.
	(_dl_get_dl_main_map): Likewise.
	* sysdeps/i386/configure.ac: Check if linker supports static PIE.
	* sysdeps/x86_64/configure.ac: Likewise.
	* sysdeps/i386/configure: Regenerated.
	* sysdeps/x86_64/configure: Likewise.
	* sysdeps/mips/Makefile (ASFLAGS-.o): Add $(pie-default).
	(ASFLAGS-.op): Likewise.
2017-12-15 17:12:14 -08:00
argp Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
assert Fix position of tests-unsupported definition in assert/Makefile. 2017-08-22 00:30:51 +00:00
benchtests Convert strcmp benchmark output to json format 2017-12-15 02:31:41 +05:30
bits Add _Float32 function aliases. 2017-12-07 00:48:31 +00:00
catgets Don't compile non-lib modules as lib modules [BZ #21864] 2017-08-21 05:34:54 -07:00
ChangeLog.old Add missing reference to bug 21654 2017-10-07 13:14:36 +02:00
conform Fix mcontext_t sigcontext namespace (bug 21457). 2017-08-30 22:02:04 +00:00
crypt Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
csu Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
ctype Use locale_t, not __locale_t, throughout glibc 2017-06-20 20:30:06 -04:00
debug Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
dev Rename xlocale.h to bits/types/__locale_t.h. 2017-06-20 20:28:11 -04:00
dirent Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
dlfcn Prefer https for Sourceware links 2017-11-16 11:49:26 +05:30
elf Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
gmon Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
gnulib Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
grp Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
gshadow Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
hesiod Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
hurd hurd: fix gethostname(NULL, 0) 2017-09-07 00:51:17 +02:00
iconv Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
iconvdata Add new codepage charmaps/IBM858 [BZ #21084] 2017-09-14 15:50:57 +02:00
include Properly compute offsets of note descriptor and next note [BZ #22370] 2017-11-28 09:57:00 -08:00
inet Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
intl Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
io Fix testing with read-only source directory. 2017-12-15 22:37:17 +00:00
libidn Remove add-ons mechanism. 2017-10-05 15:58:13 +00:00
libio libio: Free backup area when it not required (BZ#22415) 2017-12-12 17:29:54 -02:00
locale Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
localedata lt_LT locale: Base collation on copy "iso14651_t1" [BZ #22524] 2017-12-07 15:38:11 +01:00
login Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
mach hurd: Remove duplicate symbol version 2017-08-28 14:19:55 +02:00
malloc Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
manual Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
math [BZ #22593] Fix nextafter and nexttoward declaration 2017-12-12 13:59:18 +00:00
mathvec Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
misc Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
nis nss: Export nscd hash function as __nss_hash [BZ #22459] 2017-11-23 14:08:11 +01:00
nptl Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
nptl_db Move all old ChangeLogs to a top-level ChangeLog.old directory. 2017-09-01 09:31:43 -04:00
nscd Increase buffer size due to warning from ToT GCC 2017-12-15 09:08:23 -08:00
nss nss: Export nscd hash function as __nss_hash [BZ #22459] 2017-11-23 14:08:11 +01:00
po Do not build .mo files in source directory (bug 14121). 2017-12-15 14:27:20 +00:00
posix Fix testing with read-only source directory. 2017-12-15 22:37:17 +00:00
pwd Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
resolv Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
resource Hide internal __setrlimit function [BZ #18822] 2017-10-01 17:46:54 -07:00
rt Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
scripts Correct build-many-glibcs.py arm-linux-gnueabihf configurations. 2017-12-15 16:57:29 +00:00
setjmp x86: Make a space in jmpbuf for shadow stack pointer 2017-11-30 04:58:01 -08:00
shadow Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
signal Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
socket __opensock: Remove internal_function attribute 2017-08-17 10:18:15 +02:00
soft-fp Add sysdeps/ieee754/soft-fp. 2017-12-12 23:35:21 +00:00
stdio-common Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
stdlib Fix testing with read-only source directory. 2017-12-15 22:37:17 +00:00
streams Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
string string: Replace = with += in CFLAGS-xxx.c 2017-12-11 08:39:24 -08:00
sunrpc Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
support support: Simplify compiling most of support/ outside of glibc 2017-12-14 13:48:56 +01:00
sysdeps Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
sysvipc Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
termios Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
time Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
timezone Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
wcsmbs Replace = with += in CFLAGS-xxx.c/CPPFLAGS-xxx.c 2017-12-11 13:11:33 -08:00
wctype Use locale_t, not __locale_t, throughout glibc 2017-06-20 20:30:06 -04:00
.gitattributes Assume __NR_openat is always defined 2016-03-23 23:35:08 +01:00
.gitignore Add *.pyc to .gitignore 2015-05-18 15:26:26 +05:30
abi-tags Remove the bulk of the NaCl port. 2017-05-20 08:09:10 -04:00
aclocal.m4 gmon: Add test for basic mcount/gprof functionality 2017-08-15 15:49:45 +02:00
ChangeLog Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
config.h.in Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
config.make.in Remove --with-fp / --without-fp. 2017-12-12 13:56:47 +00:00
configure Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
configure.ac Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
COPYING Update to latest versions of GPL-2.0 and LGPL-2.1 2013-09-09 12:52:48 +10:00
COPYING.LIB Update to latest versions of GPL-2.0 and LGPL-2.1 2013-09-09 12:52:48 +10:00
extra-lib.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
gen-locales.mk Split locale generation snippet into a separate file 2015-05-13 13:05:28 +05:30
INSTALL Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
libc-abis A few more archs have IFUNC support. 2010-03-17 02:43:12 -07:00
libof-iterator.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
LICENSES Expand LICENSES file. 2012-12-05 21:56:15 +00:00
MAINTAINERS Add MAINTAINERS 2017-05-11 13:38:30 -04:00
Makeconfig Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
Makefile Remove add-ons mechanism. 2017-10-05 15:58:13 +00:00
Makefile.in New make target to only build benchmark binaries 2016-04-20 10:23:28 +05:30
Makerules Use newly built crt*.o files to build shared objects [BZ #22362] 2017-11-06 08:29:57 -08:00
NEWS Add --enable-static-pie configure option to build static PIE [BZ #19574] 2017-12-15 17:12:14 -08:00
o-iterator.mk Fri Mar 17 12:58:37 1995 Roland McGrath <roland@churchy.gnu.ai.mit.edu> 1995-03-17 18:42:51 +00:00
README Require Linux kernel 3.2 or later on x86 / x86_64. 2017-05-08 10:45:20 +00:00
Rules Suppress internal declarations for most of the testsuite. 2017-05-11 19:27:59 -04:00
shlib-versions Extend NSS test suite 2017-07-17 15:52:44 -04:00
test-skeleton.c Update copyright dates with scripts/update-copyrights. 2017-01-01 00:14:16 +00:00
version.h version.h: Switch to ".9000" as the suffix for the development version 2017-10-16 21:39:18 +02:00

This directory contains the sources of the GNU C Library.
See the file "version.h" for what release version you have.

The GNU C Library is the standard system C library for all GNU systems,
and is an important part of what makes up a GNU system.  It provides the
system API for all programs written in C and C-compatible languages such
as C++ and Objective C; the runtime facilities of other programming
languages use the C library to access the underlying operating system.

In GNU/Linux systems, the C library works with the Linux kernel to
implement the operating system behavior seen by user applications.
In GNU/Hurd systems, it works with a microkernel and Hurd servers.

The GNU C Library implements much of the POSIX.1 functionality in the
GNU/Hurd system, using configurations i[4567]86-*-gnu.  The current
GNU/Hurd support requires out-of-tree patches that will eventually be
incorporated into an official GNU C Library release.

When working with Linux kernels, this version of the GNU C Library
requires Linux kernel version 3.2 or later.

Also note that the shared version of the libgcc_s library must be
installed for the pthread library to work correctly.

The GNU C Library supports these configurations for using Linux kernels:

	aarch64*-*-linux-gnu
	alpha*-*-linux-gnu
	arm-*-linux-gnueabi
	hppa-*-linux-gnu	Not currently functional without patches.
	i[4567]86-*-linux-gnu
	x86_64-*-linux-gnu	Can build either x86_64 or x32
	ia64-*-linux-gnu
	m68k-*-linux-gnu
	microblaze*-*-linux-gnu
	mips-*-linux-gnu
	mips64-*-linux-gnu
	powerpc-*-linux-gnu	Hardware or software floating point, BE only.
	powerpc64*-*-linux-gnu	Big-endian and little-endian.
	s390-*-linux-gnu
	s390x-*-linux-gnu
	sh[34]-*-linux-gnu
	sparc*-*-linux-gnu
	sparc64*-*-linux-gnu
	tilegx-*-linux-gnu
	tilepro-*-linux-gnu

If you are interested in doing a port, please contact the glibc
maintainers; see http://www.gnu.org/software/libc/ for more
information.

See the file INSTALL to find out how to configure, build, and install
the GNU C Library.  You might also consider reading the WWW pages for
the C library at http://www.gnu.org/software/libc/.

The GNU C Library is (almost) completely documented by the Texinfo manual
found in the `manual/' subdirectory.  The manual is still being updated
and contains some known errors and omissions; we regret that we do not
have the resources to work on the manual as much as we would like.  For
corrections to the manual, please file a bug in the `manual' component,
following the bug-reporting instructions below.  Please be sure to check
the manual in the current development sources to see if your problem has
already been corrected.

Please see http://www.gnu.org/software/libc/bugs.html for bug reporting
information.  We are now using the Bugzilla system to track all bug reports.
This web page gives detailed information on how to report bugs properly.

The GNU C Library is free software.  See the file COPYING.LIB for copying
conditions, and LICENSES for notices about a few contributions that require
these additional notices to be distributed.  License copyright years may be
listed using range notation, e.g., 1996-2015, indicating that every year in
the range, inclusive, is a copyrightable year that would otherwise be listed
individually.