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H.J. Lu f753fa7dea x86: Support IBT and SHSTK in Intel CET [BZ #21598]
Intel Control-flow Enforcement Technology (CET) instructions:

https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-en
forcement-technology-preview.pdf

includes Indirect Branch Tracking (IBT) and Shadow Stack (SHSTK).

GNU_PROPERTY_X86_FEATURE_1_IBT is added to GNU program property to
indicate that all executable sections are compatible with IBT when
ENDBR instruction starts each valid target where an indirect branch
instruction can land.  Linker sets GNU_PROPERTY_X86_FEATURE_1_IBT on
output only if it is set on all relocatable inputs.

On an IBT capable processor, the following steps should be taken:

1. When loading an executable without an interpreter, enable IBT and
lock IBT if GNU_PROPERTY_X86_FEATURE_1_IBT is set on the executable.
2. When loading an executable with an interpreter, enable IBT if
GNU_PROPERTY_X86_FEATURE_1_IBT is set on the interpreter.
  a. If GNU_PROPERTY_X86_FEATURE_1_IBT isn't set on the executable,
     disable IBT.
  b. Lock IBT.
3. If IBT is enabled, when loading a shared object without
GNU_PROPERTY_X86_FEATURE_1_IBT:
  a. If legacy interwork is allowed, then mark all pages in executable
     PT_LOAD segments in legacy code page bitmap.  Failure of legacy code
     page bitmap allocation causes an error.
  b. If legacy interwork isn't allowed, it causes an error.

GNU_PROPERTY_X86_FEATURE_1_SHSTK is added to GNU program property to
indicate that all executable sections are compatible with SHSTK where
return address popped from shadow stack always matches return address
popped from normal stack.  Linker sets GNU_PROPERTY_X86_FEATURE_1_SHSTK
on output only if it is set on all relocatable inputs.

On a SHSTK capable processor, the following steps should be taken:

1. When loading an executable without an interpreter, enable SHSTK if
GNU_PROPERTY_X86_FEATURE_1_SHSTK is set on the executable.
2. When loading an executable with an interpreter, enable SHSTK if
GNU_PROPERTY_X86_FEATURE_1_SHSTK is set on interpreter.
  a. If GNU_PROPERTY_X86_FEATURE_1_SHSTK isn't set on the executable
     or any shared objects loaded via the DT_NEEDED tag, disable SHSTK.
  b. Otherwise lock SHSTK.
3. After SHSTK is enabled, it is an error to load a shared object
without GNU_PROPERTY_X86_FEATURE_1_SHSTK.

To enable CET support in glibc, --enable-cet is required to configure
glibc.  When CET is enabled, both compiler and assembler must support
CET.  Otherwise, it is a configure-time error.

To support CET run-time control,

1. _dl_x86_feature_1 is added to the writable ld.so namespace to indicate
if IBT or SHSTK are enabled at run-time.  It should be initialized by
init_cpu_features.
2. For dynamic executables:
   a. A l_cet field is added to struct link_map to indicate if IBT or
      SHSTK is enabled in an ELF module.  _dl_process_pt_note or
      _rtld_process_pt_note is called to process PT_NOTE segment for
      GNU program property and set l_cet.
   b. _dl_open_check is added to check IBT and SHSTK compatibilty when
      dlopening a shared object.
3. Replace i386 _dl_runtime_resolve and _dl_runtime_profile with
_dl_runtime_resolve_shstk and _dl_runtime_profile_shstk, respectively if
SHSTK is enabled.

CET run-time control can be changed via GLIBC_TUNABLES with

$ export GLIBC_TUNABLES=glibc.tune.x86_shstk=[permissive|on|off]
$ export GLIBC_TUNABLES=glibc.tune.x86_ibt=[permissive|on|off]

1. permissive: SHSTK is disabled when dlopening a legacy ELF module.
2. on: IBT or SHSTK are always enabled, regardless if there are IBT or
SHSTK bits in GNU program property.
3. off: IBT or SHSTK are always disabled, regardless if there are IBT or
SHSTK bits in GNU program property.

<cet.h> from CET-enabled GCC is automatically included by assembly codes
to add GNU_PROPERTY_X86_FEATURE_1_IBT and GNU_PROPERTY_X86_FEATURE_1_SHSTK
to GNU program property.  _CET_ENDBR is added at the entrance of all
assembly functions whose address may be taken.  _CET_NOTRACK is used to
insert NOTRACK prefix with indirect jump table to support IBT.  It is
defined as notrack when _CET_NOTRACK is defined in <cet.h>.

	 [BZ #21598]
	* configure.ac: Add --enable-cet.
	* configure: Regenerated.
	* elf/Makefille (all-built-dso): Add a comment.
	* elf/dl-load.c (filebuf): Moved before "dynamic-link.h".
	Include <dl-prop.h>.
	(_dl_map_object_from_fd): Call _dl_process_pt_note on PT_NOTE
	segment.
	* elf/dl-open.c: Include <dl-prop.h>.
	(dl_open_worker): Call _dl_open_check.
	* elf/rtld.c: Include <dl-prop.h>.
	(dl_main): Call _rtld_process_pt_note on PT_NOTE segment.  Call
	_rtld_main_check.
	* sysdeps/generic/dl-prop.h: New file.
	* sysdeps/i386/dl-cet.c: Likewise.
	* sysdeps/unix/sysv/linux/x86/cpu-features.c: Likewise.
	* sysdeps/unix/sysv/linux/x86/dl-cet.h: Likewise.
	* sysdeps/x86/cet-tunables.h: Likewise.
	* sysdeps/x86/check-cet.awk: Likewise.
	* sysdeps/x86/configure: Likewise.
	* sysdeps/x86/configure.ac: Likewise.
	* sysdeps/x86/dl-cet.c: Likewise.
	* sysdeps/x86/dl-procruntime.c: Likewise.
	* sysdeps/x86/dl-prop.h: Likewise.
	* sysdeps/x86/libc-start.h: Likewise.
	* sysdeps/x86/link_map.h: Likewise.
	* sysdeps/i386/dl-trampoline.S (_dl_runtime_resolve): Add
	_CET_ENDBR.
	(_dl_runtime_profile): Likewise.
	(_dl_runtime_resolve_shstk): New.
	(_dl_runtime_profile_shstk): Likewise.
	* sysdeps/linux/x86/Makefile (sysdep-dl-routines): Add dl-cet
	if CET is enabled.
	(CFLAGS-.o): Add -fcf-protection if CET is enabled.
	(CFLAGS-.os): Likewise.
	(CFLAGS-.op): Likewise.
	(CFLAGS-.oS): Likewise.
	(asm-CPPFLAGS): Add -fcf-protection -include cet.h if CET
	is enabled.
	(tests-special): Add $(objpfx)check-cet.out.
	(cet-built-dso): New.
	(+$(cet-built-dso:=.note)): Likewise.
	(common-generated): Add $(cet-built-dso:$(common-objpfx)%=%.note).
	($(objpfx)check-cet.out): New.
	(generated): Add check-cet.out.
	* sysdeps/x86/cpu-features.c: Include <dl-cet.h> and
	<cet-tunables.h>.
	(TUNABLE_CALLBACK (set_x86_ibt)): New prototype.
	(TUNABLE_CALLBACK (set_x86_shstk)): Likewise.
	(init_cpu_features): Call get_cet_status to check CET status
	and update dl_x86_feature_1 with CET status.  Call
	TUNABLE_CALLBACK (set_x86_ibt) and TUNABLE_CALLBACK
	(set_x86_shstk).  Disable and lock CET in libc.a.
	* sysdeps/x86/cpu-tunables.c: Include <cet-tunables.h>.
	(TUNABLE_CALLBACK (set_x86_ibt)): New function.
	(TUNABLE_CALLBACK (set_x86_shstk)): Likewise.
	* sysdeps/x86/sysdep.h (_CET_NOTRACK): New.
	(_CET_ENDBR): Define if not defined.
	(ENTRY): Add _CET_ENDBR.
	* sysdeps/x86/dl-tunables.list (glibc.tune): Add x86_ibt and
	x86_shstk.
	* sysdeps/x86_64/dl-trampoline.h (_dl_runtime_resolve): Add
	_CET_ENDBR.
	(_dl_runtime_profile): Likewise.
2018-07-16 14:08:27 -07:00
argp Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
assert Fix uninitialized variable in assert_perror (bug 22761) 2018-02-05 11:06:15 +01:00
benchtests Improve strstr performance 2018-07-16 17:51:52 +01:00
bits hurd: Fix shmid_ds's shm_segsz field type 2018-06-02 21:52:43 +02:00
catgets intl/tst-gettext: fix failure with newest msgfmt 2018-02-18 18:16:05 +01:00
ChangeLog.old Add missing reference to bug 21654 2017-10-07 13:14:36 +02:00
conform conform/conformtest.pl: Escape literal braces in regular expressions 2018-07-06 16:31:55 +02:00
crypt New configure option --disable-crypt. 2018-06-29 16:53:47 +02:00
csu Build csu/elf-init.c and csu/static-reloc.c with stack protector 2018-07-05 22:57:45 +02:00
ctype Use libc_hidden_* for tolower, toupper (bug 15105). 2018-02-23 13:54:53 +00:00
debug Compile debug/stack_chk_fail_local.c with stack protector 2018-07-05 19:28:35 +02:00
dirent Consolidate alphasort{64} and versionsort{64} implementation 2018-04-23 17:35:16 -03:00
dlfcn libc: Extend __libc_freeres framework (Bug 23329). 2018-06-29 22:39:06 -04:00
elf x86: Support IBT and SHSTK in Intel CET [BZ #21598] 2018-07-16 14:08:27 -07:00
gmon Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
gnulib Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
grp Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
gshadow Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
hesiod Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
htl hurd: Fix missing __pthread_get_cleanup_stack symbol 2018-06-16 10:52:04 +02:00
hurd hurd: Silence warning 2018-04-04 02:06:16 +02:00
iconv Fix s390 -Os iconv build. 2018-03-05 21:46:55 +00:00
iconvdata localedata: Make IBM273 compatible with ISO-8859-1 [BZ #23290] 2018-06-14 22:34:10 +02:00
include Add the statx function 2018-07-10 16:14:45 +02:00
inet manual: Revise crypt.texi. 2018-06-29 16:53:37 +02:00
intl intl/tst-gettext: fix failure with newest msgfmt 2018-02-18 18:16:05 +01:00
io Install <bits/statx.h> header 2018-07-11 08:59:51 +02:00
libio Fix copyright years in recent commits 2018-07-10 11:03:08 +02:00
locale Fix two more -Os strcoll / wcscoll build failures. 2018-02-27 16:55:42 +00:00
localedata dsb_DE locale: Fix syntax error and add tests (bug 23208). 2018-07-13 23:06:32 +02:00
login Fix Linux fcntl OFD locks for non-LFS architectures (BZ#20251) 2018-06-26 13:22:53 -03:00
mach hurd: Avoid PLT references to syscalls 2018-06-16 02:50:36 +02:00
malloc libc: Extend __libc_freeres framework (Bug 23329). 2018-06-29 22:39:06 -04:00
manual Add the statx function 2018-07-10 16:14:45 +02:00
math Add a generic significand implementation 2018-06-20 18:15:06 -03:00
mathvec Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
misc Implement allocate_once for atomic initialization with allocation 2018-05-23 15:27:01 +02:00
nis nisplus: Correct pwent parsing issue and resulting build error [BZ #23266] 2018-06-27 21:12:16 +01:00
nptl x86: Rename __glibc_reserved1 to feature_1 in tcbhead_t [BZ #22563] 2018-07-14 05:56:46 -07:00
nptl_db nptl_db: Remove stale match_pid' parameter from iterate_thread_list' 2018-03-01 16:10:05 +00:00
nscd manual: Revise crypt.texi. 2018-06-29 16:53:37 +02:00
nss Fix copyright years in recent commits 2018-07-10 11:03:08 +02:00
po Update translations from the Translation Project 2018-03-12 13:24:46 +00:00
posix regexec: Fix off-by-one bug in weight comparison [BZ #23036] 2018-07-10 11:18:26 +02:00
pwd manual: Revise crypt.texi. 2018-06-29 16:53:37 +02:00
resolv libc: Extend __libc_freeres framework (Bug 23329). 2018-06-29 22:39:06 -04:00
resource resource/tst-getrlimit.c: Add copyright header 2018-01-05 20:34:10 +01:00
rt hurd: Add hurd thread library 2018-04-02 01:44:14 +02:00
scripts Fix hardcoded /tmp paths in testing (bug 13888). 2018-06-26 21:48:48 +00:00
setjmp x86: Use pad in pthread_unwind_buf to preserve shadow stack register 2018-05-02 06:17:41 -07:00
shadow manual: Revise crypt.texi. 2018-06-29 16:53:37 +02:00
signal Add tst-sigaction.c to test BZ #23069 2018-04-26 22:21:13 +02:00
socket Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
soft-fp Make powerpc-nofpu __sqrtsf2, __sqrtdf2 compat symbols (bug 18473). 2018-06-01 17:25:12 +00:00
stdio-common Add renameat2 function [BZ #17662] 2018-07-05 19:00:10 +02:00
stdlib Add long double input for strfmon test 2018-06-30 06:54:34 +05:30
streams Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
string Improve strstr performance 2018-07-16 17:51:52 +01:00
sunrpc libc: Extend __libc_freeres framework (Bug 23329). 2018-06-29 22:39:06 -04:00
support support: Add TEST_NO_SETVBUF 2018-06-26 12:30:50 +02:00
sysdeps x86: Support IBT and SHSTK in Intel CET [BZ #21598] 2018-07-16 14:08:27 -07:00
sysvipc Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
termios Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
time Use _STRUCT_TIMESPEC as guard in <bits/types/struct_timespec.h> [BZ #23349] 2018-06-28 13:12:16 +02:00
timezone Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
wcsmbs Add tests for sign of NaN returned by strtod (bug 23007). 2018-06-15 17:36:21 +00:00
wctype Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
.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 LIBC_SLIBDIR_RTLDDIR: substitute arguments in single quotes 2018-01-25 17:20:28 +01:00
ChangeLog x86: Support IBT and SHSTK in Intel CET [BZ #21598] 2018-07-16 14:08:27 -07:00
config.h.in Switch IDNA implementation to libidn2 [BZ #19728] [BZ #19729] [BZ #22247] 2018-05-23 15:27:24 +02:00
config.make.in New configure option --disable-crypt. 2018-06-29 16:53:47 +02:00
configure x86: Support IBT and SHSTK in Intel CET [BZ #21598] 2018-07-16 14:08:27 -07:00
configure.ac x86: Support IBT and SHSTK in Intel CET [BZ #21598] 2018-07-16 14:08:27 -07:00
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 Improve gen-locales.mk and gen-locale.sh to make test files with @ options work 2018-02-27 17:01:57 +01:00
INSTALL testrun.sh: Implement --tool=strace, --tool=valgrind 2018-07-04 15:30:45 +02:00
libc-abis libc-abis: Define ABSOLUTE ABI [BZ #19818][BZ #23307] 2018-07-05 18:06:43 +01:00
libof-iterator.mk Rename cppflags-iterator.mk to libof-iterator.mk, remove extra-modules.mk. 2017-05-09 07:06:29 -04:00
LICENSES stdio-common/tst-printf.c: Remove part under a non-free license [BZ #23363] 2018-07-03 18:29:16 +02:00
MAINTAINERS Add MAINTAINERS 2017-05-11 13:38:30 -04:00
Makeconfig New configure option --disable-crypt. 2018-06-29 16:53:47 +02:00
Makefile testrun.sh: Implement --tool=strace, --tool=valgrind 2018-07-04 15:30:45 +02:00
Makefile.in New make target to only build benchmark binaries 2016-04-20 10:23:28 +05:30
Makerules Run thread shutdown functions in an explicit order 2018-06-26 15:27:12 +02:00
NEWS Add the statx function 2018-07-10 16:14:45 +02:00
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 Remove tilegx port. 2018-04-27 19:11:24 +00:00
Rules Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
shlib-versions Extend NSS test suite 2017-07-17 15:52:44 -04:00
test-skeleton.c Update copyright dates with scripts/update-copyrights. 2018-01-01 00:32:25 +00:00
version.h Open master branch for glibc 2.28 development 2018-02-01 17:18:19 +00:00

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
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