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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.
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* All files with FSF copyright notices: Update copyright dates
using scripts/update-copyrights.
* locale/programs/charmap-kw.h: Regenerated.
* locale/programs/locfile-kw.h: Likewise.
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We need to save/restore bound registers and add a BND prefix before
branches in _dl_runtime_profile so that bound registers for pointer
pass and return are preserved when LD_AUDIT is used.
[BZ #18134]
* sysdeps/i386/configure.ac: Set HAVE_MPX_SUPPORT.
* sysdeps/i386/configure: Regenerated.
* sysdeps/i386/dl-trampoline.S (PRESERVE_BND_REGS_PREFIX): New.
(_dl_runtime_profile): Save and restore Intel MPX return bound
registers when calling _dl_call_pltexit. Add
PRESERVE_BND_REGS_PREFIX before return.
* sysdeps/i386/link-defines.sym (LRV_BND0_OFFSET): New.
(LRV_BND1_OFFSET): Likewise.
* sysdeps/x86/bits/link.h (La_i86_retval): Add lrv_bnd0 and
lrv_bnd1.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_profile): Fix
typo in bndmov encoding.
* sysdeps/x86_64/dl-trampoline.h: Properly save and restore
Intel MPX bound registers. Add PRESERVE_BND_REGS_PREFIX before
branch instructions to preserve bounds.
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Define macros for fields in La_i86_regs and La_i86_retval and use them
in dl-trampoline.S, instead of hardcoded values.
* sysdeps/i386/Makefile (gen-as-const-headers)[elf]: Add
link-defines.sym.
* sysdeps/i386/dl-trampoline.S: Include <link-defines.h>.
(_dl_runtime_profile): Use LONG_DOUBLE_SIZE, LRV_SIZE,
LRV_EAX_OFFSET, LRV_EDX_OFFSET, LRV_ST0_OFFSET, LRV_ST1_OFFSET
and LR_SIZE.
* sysdeps/i386/link-defines.sym: New file.
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_dl_runtime_profile function has wrong cfi directive when
rewinding stack back for the pltexit path.
Only 8 bytes - 2 'pop edx' instructions from the pltentry-only
code should be rewinded back.
With attached patch, I'm able to rewind stack correctly
throught the rtld code from audit library callback.
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* sysdeps/i386/dl-trampoline.S (_dl_runtime_profile): Fix a few
more little bugs in creating the stack frame when pltexit has to
be called.
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* sysdeps/i386/dl-trampoline.S (_dl_runtime_profile): Correctly
align for function call in case pltexit has to be called later.
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implicit atomic operation when storing function pointer.
(_dl_runtime_profile): Likewise.
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names not numbers in cfi_*.
ADDR_LIMIT_3GB, PER_LINUX_32BIT, PER_LINUX32_3GB): Add.
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consider_profiling always to zero. Don't count of compiler to
remove unreached if block.
* sysdeps/x86_64/dl-trampoline.S [PROF] (_dl_runtime_profile):
Don't compile.
* sysdeps/i386/dl-trampoline.S [PROF] (_dl_runtime_profile): Likewise.
* sysdeps/ia64/dl-trampoline.S [PROF] (_dl_runtime_profile): Likewise.
* sysdeps/s390/s390-64/dl-trampoline.S [PROF] (_dl_runtime_profile):
Likewise.
* sysdeps/s390/s390-32/dl-trampoline.S [PROF] (_dl_runtime_profile):
Likewise.
* sysdeps/powerpc/powerpc64/dl-trampoline.S [PROF]
(_dl_profile_resolve): Likewise.
* sysdeps/powerpc/powerpc32/dl-trampoline.S [PROF]
(_dl_profile_resolve): Likewise.
* gmon/Makefile: Add rules to build and run tst-profile-static.
* gmon/tst-profile-static.c: New file.
* Makeconfig (+link-static): Allow passing program-specific flags.
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* sysdeps/generic/libc-start.c: Don't register program destructor here.
* dlfcn/Makefile: Add rules to build dlfcn.c.
(LDFLAGS-dl.so): Removed.
* dlfcn/dlclose.c: _dl_close is now in ld.so, use function pointer
table.
* dlfcn/dlmopen.c: Likewise for _dl_open.
* dlfcn/dlopen.c: Likewise.
* dlfcn/dlopenold.c: Likewise.
* elf/dl-libc.c: Likewise for _dl_open and _dl_close.
* elf/Makefile (routines): Remove dl-open and dl-close.
(dl-routines): Add dl-open, dl-close, and dl-trampoline.
Add rules to build and run tst-audit1.
* elf/tst-audit1.c: New file.
* elf/tst-auditmod1.c: New file.
* elf/Versions [libc]: Remove _dl_open and _dl_close.
* elf/dl-close.c: Change for use inside ld.so instead of libc.so.
* elf/dl-open.c: Likewise.
* elf/dl-debug.c (_dl_debug_initialize): Allow reinitialization,
signaled by nonzero parameter.
* elf/dl-init.c: Fix use of r_state.
* elf/dl-load.c: Likewise.
* elf/dl-close.c: Add auditing checkpoints.
* elf/dl-open.c: Likewise.
* elf/dl-fini.c: Likewise.
* elf/dl-load.c: Likewise.
* elf/dl-sym.c: Likewise.
* sysdeps/generic/libc-start.c: Likewise.
* elf/dl-object.c: Allocate memory for auditing information.
* elf/dl-reloc.c: Remove RESOLV. We now always need the map.
Correctly initialize slotinfo.
* elf/dynamic-link.h: Adjust after removal of RESOLV.
* sysdeps/hppa/dl-lookupcfg.h: Likewise.
* sysdeps/ia64/dl-lookupcfg.h: Likewise.
* sysdeps/powerpc/powerpc64/dl-lookupcfg.h: Removed.
* elf/dl-runtime.c (_dl_fixup): Little cleanup.
(_dl_profile_fixup): New parameters to point to register struct and
variable for frame size.
Add auditing checkpoints.
(_dl_call_pltexit): New function.
Don't define trampoline code here.
* elf/rtld.c: Recognize LD_AUDIT. Load modules on startup.
Remove all the functions from _rtld_global_ro which only _dl_open
and _dl_close needed.
Add auditing checkpoints.
* elf/link.h: Define symbols for auditing interfaces.
* include/link.h: Likewise.
* include/dlfcn.h: Define __RTLD_AUDIT.
Remove prototypes for _dl_open and _dl_close.
Adjust access to argc and argv in libdl.
* dlfcn/dlfcn.c: New file.
* sysdeps/generic/dl-lookupcfg.h: Remove all content now that RESOLVE
is gone.
* sysdeps/generic/ldsodefs.h: Add definitions for auditing interfaces.
* sysdeps/generic/unsecvars.h: Add LD_AUDIT.
* sysdeps/i386/dl-machine.h: Remove trampoline code here.
Adjust for removal of RESOLVE.
* sysdeps/x86_64/dl-machine.h: Likewise.
* sysdeps/generic/dl-trampoline.c: New file.
* sysdeps/i386/dl-trampoline.c: New file.
* sysdeps/x86_64/dl-trampoline.c: New file.
* sysdeps/generic/dl-tls.c: Cleanups. Fixup for dtv_t change.
Fix updating of DTV.
* sysdeps/generic/libc-tls.c: Likewise.
* sysdeps/arm/bits/link.h: Renamed to ...
* sysdeps/arm/buts/linkmap.h: ...this.
* sysdeps/generic/bits/link.h: Renamed to...
* sysdeps/generic/bits/linkmap.h: ...this.
* sysdeps/hppa/bits/link.h: Renamed to...
* sysdeps/hppa/bits/linkmap.h: ...this.
* sysdeps/hppa/i386/link.h: Renamed to...
* sysdeps/hppa/i386/linkmap.h: ...this.
* sysdeps/hppa/ia64/link.h: Renamed to...
* sysdeps/hppa/ia64/linkmap.h: ...this.
* sysdeps/hppa/s390/link.h: Renamed to...
* sysdeps/hppa/s390/linkmap.h: ...this.
* sysdeps/hppa/sh/link.h: Renamed to...
* sysdeps/hppa/sh/linkmap.h: ...this.
* sysdeps/hppa/x86_64/link.h: Renamed to...
* sysdeps/hppa/x86_64/linkmap.h: ...this.
2005-01-06 Ulrich Drepper <drepper@redhat.com>
* allocatestack.c (init_one_static_tls): Adjust initialization of DTV
entry for static tls deallocation fix.
* sysdeps/alpha/tls.h (dtv_t): Change pointer type to be struct which
also contains information whether the memory pointed to is static
TLS or not.
* sysdeps/i386/tls.h: Likewise.
* sysdeps/ia64/tls.h: Likewise.
* sysdeps/powerpc/tls.h: Likewise.
* sysdeps/s390/tls.h: Likewise.
* sysdeps/sh/tls.h: Likewise.
* sysdeps/sparc/tls.h: Likewise.
* sysdeps/x86_64/tls.h: Likewise.
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