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[v4,0/6] x86/cet: Update CET kernel interface

Message ID 20231220145701.740912-1-hjl.tools@gmail.com
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Series x86/cet: Update CET kernel interface | expand

Message

H.J. Lu Dec. 20, 2023, 2:56 p.m. UTC 
Changes in v4.

1. Rebase.
2. Remove 3 patches which have been checked into master branch.

Changes in v3:

1. Remove 7 test patches which have been checked into master branch.

Changes in v2:

1. Add add extra 20 stack frames in shadow stack for signal handlers
when allocating shadow stack for ucontexts.
2. Remove the "x86: Check PT_GNU_PROPERTY early" patch which has been
checked into master branch.


Linux kernel 6.6 added SHSTK support for x86-64.  This patch set updates
CET kernel interface to Linux kernel 6.6.  The main difference from the
current glibc assumption is that SHSTK is enabled by glibc, instead of
kernel.  Glibc enables SHSTK after verifying that the application and
all dependency libraries are CET enabled.  SHSTK can only be enabled in a
function which will never return.  Otherwise, shadow stack will underflow
at the function return.

Not all CET enabled applications and libraries have been properly tested
in CET enabled environments.  Some CET enabled applications or libraries
will crash or misbehave when CET is enabled.  Don't set CET active by
default so that all applications and libraries will run normally regardless
of whether CET is active or not.  Shadow stack can be enabled by

$ export GLIBC_TUNABLES=glibc.cpu.hwcaps=SHSTK

at run-time if shadow stack can be enabled by kernel.

Since only x86-64 is supported, i386 shadow stack codes are unchanged
and CET shouldn't be enabled for i386.

NB: This change can be reverted if it is OK to enable CET by default for
all applications and libraries.

Tested on Intel Tiger Lake under Linux kernel 6.6.7.

H.J. Lu (6):
  x86/cet: Sync with Linux kernel 6.6 shadow stack interface
  elf: Always provide _dl_get_dl_main_map in libc.a
  x86/cet: Enable shadow stack during startup
  x86/cet: Check feature_1 in TCB for active IBT and SHSTK
  x86/cet: Don't set CET active by default
  x86/cet: Run some CET tests with shadow stack

 elf/dl-support.c                              |  2 -
 sysdeps/generic/ldsodefs.h                    |  8 +-
 sysdeps/unix/sysv/linux/x86/Makefile          |  1 +
 .../sysv/linux/x86/allocate-shadow-stack.c    | 62 +++++++++++++++
 ...cpu-features.c => allocate-shadow-stack.h} | 33 ++------
 sysdeps/unix/sysv/linux/x86/bits/mman.h       |  5 ++
 sysdeps/unix/sysv/linux/x86/dl-cet.h          | 39 +++++++++-
 .../unix/sysv/linux/x86/include/asm/prctl.h   | 37 ++++-----
 .../sysv/linux/x86/tst-cet-setcontext-1.c     | 17 ++--
 .../unix/sysv/linux/x86_64/__start_context.S  | 38 ++-------
 sysdeps/unix/sysv/linux/x86_64/dl-cet.h       | 47 +++++++++++
 sysdeps/unix/sysv/linux/x86_64/getcontext.S   | 30 ++------
 sysdeps/unix/sysv/linux/x86_64/makecontext.c  | 29 +++----
 sysdeps/unix/sysv/linux/x86_64/swapcontext.S  | 22 +-----
 sysdeps/x86/Makefile                          | 14 ++++
 sysdeps/x86/bits/platform/x86.h               |  8 ++
 sysdeps/x86/cpu-features-offsets.sym          |  1 +
 sysdeps/x86/cpu-features.c                    | 48 +-----------
 sysdeps/x86/cpu-tunables.c                    | 15 +++-
 sysdeps/x86/dl-cet.c                          | 77 +++++++++----------
 sysdeps/x86/get-cpuid-feature-leaf.c          | 13 +++-
 sysdeps/x86/include/cpu-features.h            |  3 +
 sysdeps/x86/libc-start.h                      | 54 ++++++++++++-
 sysdeps/x86/sys/platform/x86.h                | 17 ++++
 sysdeps/x86/tst-shstk-legacy-1e-static.sh     |  1 +
 sysdeps/x86/tst-shstk-legacy-1e.sh            |  1 +
 sysdeps/x86/tst-shstk-legacy-1g.sh            |  1 +
 sysdeps/x86_64/dl-machine.h                   | 12 ++-
 sysdeps/x86_64/nptl/tls.h                     |  2 +-
 29 files changed, 391 insertions(+), 246 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/x86/allocate-shadow-stack.c
 rename sysdeps/unix/sysv/linux/x86/{cpu-features.c => allocate-shadow-stack.h} (53%)
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/dl-cet.h