Go to file
Fangrui Song e895cff59a elf: Support DT_RELR relative relocation format [BZ #27924]
PIE and shared objects usually have many relative relocations. In
2017/2018, SHT_RELR/DT_RELR was proposed on
https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR
usually takes 3% or smaller space than R_*_RELATIVE relocations. The
virtual memory size of a mostly statically linked PIE is typically 5~10%
smaller.

---

Notes I will not include in the submitted commit:

Available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr

"pre-standard": even Solaris folks are happy with the refined generic-abi
proposal. Cary Coutant will apply the change
https://sourceware.org/pipermail/libc-alpha/2021-October/131781.html

This patch is simpler than Chrome OS's glibc patch and makes ELF_DYNAMIC_DO_RELR
available to all ports. I don't think the current glibc implementation
supports ia64 in an ELFCLASS32 container. That said, the style I used is
works with an ELFCLASS32 container for 64-bit machine if ElfW(Addr) is
64-bit.

* Chrome OS folks have carried a local patch since 2018 (latest version:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
  I.e. this feature has been battle tested.
* Android bionic supports 2018 and switched to DT_RELR==36 in 2020.
* The Linux kernel has supported CONFIG_RELR since 2019-08
  (https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
* A musl patch (by me) exists but is not applied:
  https://www.openwall.com/lists/musl/2019/03/06/3
* rtld-elf from FreeBSD 14 will support DT_RELR.

I believe upstream glibc should support DT_RELR to benefit all Linux
distributions. I filed some feature requests to get their attention:

* Gentoo: https://bugs.gentoo.org/818376
* Arch Linux: https://bugs.archlinux.org/task/72433
* Debian https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996598
* Fedora https://bugzilla.redhat.com/show_bug.cgi?id=2014699

As of linker support (to the best of my knowledge):

* LLD support DT_RELR.
* https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
  has a gold patch.
* GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923

Changes from the original patch:

1. Check the linker option, -z pack-relative-relocs, which add a
GLIBC_ABI_DT_RELR symbol version dependency on the shared C library if
it provides a GLIBC_2.XX symbol version.
2. Change make variale to have-dt-relr.
3. Rename tst-relr-no-pie to tst-relr-pie for --disable-default-pie.
4. Use TEST_VERIFY in tst-relr.c.
5. Add the check-tst-relr-pie.out test to check for linker generated
libc.so version dependency on GLIBC_ABI_DT_RELR.
6. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL.
2022-04-26 10:16:11 -07:00
argp Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
assert Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
benchtests benchtests: Improve bench-strrchr 2022-04-22 23:07:54 -05:00
bits elf: Issue la_symbind for bind-now (BZ #23734) 2022-02-01 14:49:46 -03:00
catgets Update copyright dates not handled by scripts/update-copyrights. 2022-01-01 11:42:26 -08:00
ChangeLog.old Create ChangeLog.old/ChangeLog.24. 2022-02-03 00:27:54 -05:00
conform hurd: drop SA_SIGINFO availability xfail 2022-01-15 17:43:07 +01:00
crypt crypt: Remove unused variable on cert test 2022-03-31 09:00:54 -03:00
csu elf: Remove __libc_init_secure 2022-04-19 15:52:27 -07:00
ctype Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
debug misc: Fix rare fortify crash on wchar funcs. [BZ 29030] 2022-04-25 17:32:30 +05:30
dirent associate a deallocation for opendir 2022-03-14 20:02:46 +05:30
dlfcn dlfcn: Do not use rtld_active () to determine ld.so state (bug 29078) 2022-04-26 14:24:36 +02:00
elf elf: Support DT_RELR relative relocation format [BZ #27924] 2022-04-26 10:16:11 -07:00
gmon Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
gnulib Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
grp Add access function attributes to grp and shadow headers 2022-03-14 20:02:30 +05:30
gshadow Add access function attributes to grp and shadow headers 2022-03-14 20:02:30 +05:30
hesiod Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
htl htl: Destroy thread-specific data before releasing joins 2022-02-14 19:29:02 +01:00
hurd Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
iconv Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
iconvdata Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
include Add GLIBC_ABI_DT_RELR for DT_RELR support 2022-04-26 10:16:11 -07:00
inet inet: Return EAI_MEMORY when nrl_domainname() fails to allocate memory 2022-03-08 12:51:29 -03:00
intl intl: Avoid -Wuse-after-free [BZ #26779] 2022-01-25 17:38:31 -07:00
io io: Add fsync call in tst-stat 2022-02-28 11:50:41 +01:00
libio libio: Flush-only _IO_str_overflow must not return EOF (bug 28949) 2022-03-18 21:40:02 +01:00
locale Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
localedata Add locale for syr_SY 2022-04-21 13:05:40 +02:00
login Update copyright dates not handled by scripts/update-copyrights. 2022-01-01 11:42:26 -08:00
mach mach: Fix LLL_SHARED value 2022-02-14 19:29:02 +01:00
malloc malloc: Fix duplicate inline for do_set_mxfast 2022-03-23 12:28:44 -03:00
manual INSTALL: Rephrase -with-default-link documentation 2022-04-26 14:22:23 +02:00
math math: Add more input to atanh accuracy tests 2022-02-24 09:20:43 -08:00
mathvec Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
misc misc: Fix rare fortify crash on wchar funcs. [BZ 29030] 2022-04-25 17:32:30 +05:30
nis Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
nptl nptl: Fix pthread_cancel cancelhandling atomic operations 2022-04-20 12:01:43 -03:00
nptl_db Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
nscd nscd: Remove unused variable 2022-03-23 15:33:17 -03:00
nss hurd: Fix arbitrary error code 2022-04-12 22:15:48 +02:00
po Update translations. 2022-02-02 23:30:15 -05:00
posix Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
pwd Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
resolv Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
resource Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
rt rt/tst-mqueue*: Return UNSUPPORTED when mq_open fails with ENOSYS 2022-01-17 19:17:41 +01:00
scripts Add GLIBC_ABI_DT_RELR for DT_RELR support 2022-04-26 10:16:11 -07:00
setjmp Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
shadow Add access function attributes to grp and shadow headers 2022-03-14 20:02:30 +05:30
signal Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
socket socket: Add the __sockaddr_un_set function 2022-01-17 10:21:53 +01:00
soft-fp Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
stdio-common stdio: Split __get_errname definition from errlist.c 2022-04-15 09:37:57 -03:00
stdlib stdlib: Reflow and sort most variable assignments 2022-04-13 16:52:39 -03:00
string Replace {u}int_fast{16|32} with {u}int32_t 2022-04-13 21:23:04 -05:00
sunrpc CVE-2022-23218: Buffer overflow in sunrpc svcunix_create (bug 28768) 2022-01-17 10:47:58 +01:00
support support: Add xmkfifo 2022-04-15 09:59:33 -03:00
sysdeps elf: Replace PI_STATIC_AND_HIDDEN with opposite HIDDEN_VAR_NEEDS_DYNAMIC_RELOC 2022-04-26 09:26:22 -07:00
sysvipc Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
termios posix: Add terminal control setting support for posix_spawn 2022-01-25 14:07:53 -03:00
time Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
timezone timezone: Fix tst-bz28707 Makefile rule 2022-01-12 10:30:10 -03:00
wcsmbs debug: Synchronize feature guards in fortified functions [BZ #28746] 2022-01-12 23:34:48 +05:30
wctype Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
.clang-format Add .clang-format style file 2022-04-11 10:51:03 -05:00
.gitattributes Assume __NR_openat is always defined 2016-03-23 23:35:08 +01:00
.gitignore
abi-tags Remove the bulk of the NaCl port. 2017-05-20 08:09:10 -04:00
aclocal.m4 Properly check linker option in LIBC_LINKER_FEATURE [BZ #28738] 2022-01-03 05:12:34 -08:00
config.h.in elf: Replace PI_STATIC_AND_HIDDEN with opposite HIDDEN_VAR_NEEDS_DYNAMIC_RELOC 2022-04-26 09:26:22 -07:00
config.make.in Remove -z combreloc and HAVE_Z_COMBRELOC 2022-04-04 17:19:07 -07:00
configure elf: Support DT_RELR relative relocation format [BZ #27924] 2022-04-26 10:16:11 -07:00
configure.ac elf: Support DT_RELR relative relocation format [BZ #27924] 2022-04-26 10:16:11 -07:00
CONTRIBUTED-BY Remove "Contributed by" lines 2021-09-03 22:06:44 +05:30
COPYING
COPYING.LIB
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 Improve gen-locales.mk and gen-locale.sh to make test files with @ options work 2018-02-27 17:01:57 +01:00
INSTALL INSTALL: Rephrase -with-default-link documentation 2022-04-26 14:22:23 +02:00
libc-abis riscv: support GNU indirect function 2021-01-10 21:25:13 -05:00
libof-iterator.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
LICENSES Prefer https to http for gnu.org and fsf.org URLs 2019-09-07 02:43:31 -07:00
MAINTAINERS Add MAINTAINERS 2017-05-11 13:38:30 -04:00
Makeconfig Remove -z combreloc and HAVE_Z_COMBRELOC 2022-04-04 17:19:07 -07:00
Makefile Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
Makefile.help Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
Makefile.in New make target to only build benchmark binaries 2016-04-20 10:23:28 +05:30
Makerules build: Properly generate .d dependency files [BZ #28922] 2022-02-25 10:35:45 -08:00
NEWS NEWS: Move PLT tracking slowdown to glibc 2.35. 2022-04-12 13:26:10 -04:00
o-iterator.mk
README Documentation for OpenRISC port 2022-01-05 06:40:06 +09:00
Rules Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
SHARED-FILES Mention today's regex merge in SHARED-FILES 2021-09-21 18:00:10 -07:00
shlib-versions nss: Do not mention NSS test modules in <gnu/lib-names.h> 2022-03-11 08:24:04 +01:00
test-skeleton.c Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
version.h Open master branch for glibc 2.36 development 2022-02-03 01:21:33 -05:00

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.

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
	arc*-*-linux-gnu
	arm-*-linux-gnueabi
	csky-*-linux-gnuabiv2
	hppa-*-linux-gnu
	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
	or1k-*-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
	riscv32-*-linux-gnu
	riscv64-*-linux-gnu
	sh[34]-*-linux-gnu
	sparc*-*-linux-gnu
	sparc64*-*-linux-gnu

If you are interested in doing a port, please contact the glibc
maintainers; see https://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 https://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 https://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.