[PATCH v5 00/23] aarch64: Add support for Guarded Control Stack extension

[Yury Khrustalev]

This patch series adds support for the Guarded Control Stack extension [1] that
allows to use shadow stacks on AArch64 systems with enabled GCS.

This patch series includes:
 - Definition of jmp_buf offset for GCS
 - GCS support in longjmp, vfork, setcontext, makecontext
 - GCS support in static startup code and dynamic linker
 - Handling of GCS marking in dynamic binaries and DSOs
 - Handling of GCS marking in static binaries
 - Mark swapcontext with indirect_return
 - Reserved tunable names glibc.cpu.aarch64_gcs and glibc.cpu.aarch64_gcs_policy

GCS marking for binaries is specified in [2].
Regression tested on AArch64 and no regressions have been found.
Applies to f43eb2cf30 in master.
Any feedback is welcome and appreciated.

Sources and branches:
 - binutils-gdb: sourceware.org/git/binutils-gdb.git master
 - gcc: gcc.gnu.org/git/gcc.git master
 - glibc: this patch series
 - kernel: git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/gcs

Cross-building the toolchain for target aarch64-none-linux-gnu:
 - build and install binutils-gdb
 - build and install GCC stage 1
 - install kernel headers
 - install glibc headers
 - build and install GCC stage 2 configuring with --enable-standard-branch-protection
 - build and install glibc
 - build and install GCC stage 3 along with target libraries configuring with --enable-standard-branch-protection

FVP model provided by the Shrinkwrap tool [3] can be used for testing.

To enable GCS, run tests with environment variable:

  GLIBC_TUNABLES=glibc.cpu.aarch64_gcs=1:glibc.cpu.aarch64_gcs_policy=2

[1] https://developer.arm.com/documentation/ddi0487/ka/ (chapter D11)
[2] https://github.com/ARM-software/abi-aa/blob/main/sysvabi64/sysvabi64.rst
[3] https://git.gitlab.arm.com/tooling/shrinkwrap.git

---

Changes in v5:
 - Reworked patch series to exclude exporting new public header constants.
 - Fixed minor style issues.
 - Added reserved names for new Glibc tunables to the manual.
 - GCS tunables are now using internally defined HWCAP_GCS unless it is
   already defined.
 - vfork() does not clear x30 before "returning" to child any more as this
   would be unnecessary in most cases but might create some undocumented
   "de facto" ABI.

Link to v4:
https://inbox.sourceware.org/libc-alpha/20241129163721.2385847-1-yury.khrustalev@arm.com/

Changes in v4:
 - Merged patches 17 and 18 from v3 series.
 - Amended tests that would fail if executed on a system with GCS.

Link to v3:
https://inbox.sourceware.org/libc-alpha/20241023083920.466015-1-yury.khrustalev@arm.com/

---

Szabolcs Nagy (20):
  aarch64: Add asm helpers for GCS
  elf.h: Define GNU_PROPERTY_AARCH64_FEATURE_1_GCS
  aarch64: Define jmp_buf offset for GCS
  aarch64: Add GCS support to longjmp
  aarch64: Add GCS support to vfork
  aarch64: Add GCS support for setcontext
  aarch64: Mark swapcontext with indirect_return
  aarch64: Add GCS support for makecontext
  aarch64: Try to free the GCS of makecontext
  aarch64: Add glibc.cpu.aarch64_gcs tunable
  aarch64: Enable GCS in static linked exe
  aarch64: Enable GCS in dynamic linked exe
  aarch64: Mark objects with GCS property note
  aarch64: Add glibc.cpu.aarch64_gcs_policy tunable
  aarch64: Use l_searchlist.r_list for bti
  aarch64: Handle GCS marking
  aarch64: Ignore GCS property of ld.so
  aarch64: Process gnu properties in static exe
  aarch64: Add GCS user-space allocation logic
  aarch64: Use __alloc_gcs in makecontext

Yury Khrustalev (3):
  manual: Add glibc.cpu.aarch64_gcs tunable
  manual: Add glibc.cpu.aarch64_gcs_policy tunable
  aarch64: Fix tests not compatible with targets supporting GCS

 elf/elf.h                                     |  1 +
 elf/tst-asm-helper.h                          | 49 ++++++++++
 elf/tst-big-note-lib.S                        |  2 +
 elf/tst-ro-dynamic-mod.map                    |  7 +-
 include/set-freeres.h                         |  4 +
 malloc/thread-freeres.c                       |  3 +
 manual/tunables.texi                          | 12 +++
 sysdeps/aarch64/Makefile                      | 11 ++-
 sysdeps/aarch64/__alloc_gcs.c                 | 66 +++++++++++++
 sysdeps/aarch64/__longjmp.S                   | 30 ++++++
 sysdeps/aarch64/aarch64-gcs.h                 | 28 ++++++
 sysdeps/aarch64/bits/indirect-return.h        | 36 +++++++
 sysdeps/aarch64/dl-bti.c                      |  5 +-
 sysdeps/aarch64/dl-gcs.c                      | 64 ++++++++++++
 sysdeps/aarch64/dl-prop.h                     | 15 ++-
 sysdeps/aarch64/dl-start.S                    | 23 ++++-
 sysdeps/aarch64/dl-tunables.list              | 10 ++
 sysdeps/aarch64/jmpbuf-offsets.h              | 62 ++++++++++++
 sysdeps/aarch64/linkmap.h                     |  1 +
 sysdeps/aarch64/rtld-global-offsets.sym       |  5 +
 sysdeps/aarch64/setjmp.S                      | 10 ++
 sysdeps/aarch64/sysdep.h                      | 12 ++-
 sysdeps/aarch64/tst-vpcs-mod.S                |  4 +-
 .../unix/sysv/linux/aarch64/cpu-features.c    | 13 +++
 sysdeps/unix/sysv/linux/aarch64/dl-procinfo.c | 13 +++
 .../unix/sysv/linux/aarch64/dl-procruntime.c  | 37 +++++++
 sysdeps/unix/sysv/linux/aarch64/getcontext.S  | 17 +++-
 sysdeps/unix/sysv/linux/aarch64/libc-start.h  | 56 +++++++++++
 sysdeps/unix/sysv/linux/aarch64/makecontext.c | 97 ++++++++++++++++++-
 sysdeps/unix/sysv/linux/aarch64/setcontext.S  | 57 ++++++++++-
 sysdeps/unix/sysv/linux/aarch64/swapcontext.S | 32 ++++--
 sysdeps/unix/sysv/linux/aarch64/sysdep.h      |  6 +-
 .../sysv/linux/aarch64/ucontext-internal.h    |  5 +
 sysdeps/unix/sysv/linux/aarch64/vfork.S       |  5 +-
 34 files changed, 764 insertions(+), 34 deletions(-)
 create mode 100644 elf/tst-asm-helper.h
 create mode 100644 sysdeps/aarch64/__alloc_gcs.c
 create mode 100644 sysdeps/aarch64/aarch64-gcs.h
 create mode 100644 sysdeps/aarch64/bits/indirect-return.h
 create mode 100644 sysdeps/aarch64/dl-gcs.c
 create mode 100644 sysdeps/unix/sysv/linux/aarch64/dl-procruntime.c
 create mode 100644 sysdeps/unix/sysv/linux/aarch64/libc-start.h

-- 
2.39.5