[v8,0/3] Add/enable stack protector

Message

Volodymyr Babchuk April 7, 2025, 10:40 p.m. UTC

Both GCC and Clang support -fstack-protector feature, which add stack
canaries to functions where stack corruption is possible. This series
makes possible to use this feature in Xen. I tested this on ARM64 and
it is working as intended. Tested both with GCC and Clang. Also tested
with "-fstack-protector-all" compilation option to ensure that
initialization code works as expected.

It is hard to enable this feature on x86, as GCC stores stack canary
in %fs:40 by default, but Xen can't use %fs for various reasons. It is
possibly to change stack canary location new newer GCC versions, but
attempt to do this uncovered a whole host problems with GNU ld.
So, this series focus mostly on ARM.

Changes in v8:
 - Added MISRA deviation for __stack_chk_fail()

Changes in v7:
 - Patch "common: remove -fno-stack-protector from EMBEDDED_EXTRA_CFLAGS"
   is taken into mainline
 - Updated CHANGELOG for v4.21
 - Updated stack-protector.h as per Jan's comments

Changes in v6:

 - Moved stack guard initialization code to the header file
 - Expanded commit message for "[PATCH v6 3/4] xen: arm:
   enable stack protector feature"
 - Dropped couple of R-b tags
 - Added comment to "PATCH v6 4/4] CHANGELOG.md: Mention
   stack-protector feature", mentioning that it should be reworked
   if (almost certainly) it will not get into 4.20.
 - Tested with "-fstack-protector-all"


Changes in v5:

 - ARM code calls boot_stack_chk_guard_setup() from early C code
 - Bringed back stack-protector.h because C code needs to call
   boot_stack_chk_guard_setup()
 - Fixed formatting
 - Added Andrew's R-b tag

Changes in v4:

 - Added patch to CHANGELOG.md
 - Removed stack-protector.h because we dropped support for
   Xen's built-in RNG code and rely only on own implementation
 - Changes in individual patches are covered in their respect commit
 messages

Changes in v3:

 - Removed patch for riscv
 - Changes in individual patches are covered in their respect commit
 messages

Changes in v2:

 - Patch "xen: common: add ability to enable stack protector" was
   divided into two patches.
 - Rebase onto Andrew's patch that removes -fno-stack-protector-all
 - Tested on RISC-V thanks to Oleksii Kurochko
 - Changes in individual patches covered in their respect commit
 messages


Volodymyr Babchuk (3):
  xen: common: add ability to enable stack protector
  xen: arm: enable stack protector feature
  CHANGELOG.md: Mention stack-protector feature

 CHANGELOG.md                      |  3 +++
 docs/misra/safe.json              |  8 +++++++
 xen/Makefile                      |  4 ++++
 xen/arch/arm/Kconfig              |  1 +
 xen/arch/arm/setup.c              |  3 +++
 xen/common/Kconfig                | 15 ++++++++++++
 xen/common/Makefile               |  1 +
 xen/common/stack-protector.c      | 22 +++++++++++++++++
 xen/include/xen/stack-protector.h | 39 +++++++++++++++++++++++++++++++
 9 files changed, 96 insertions(+)
 create mode 100644 xen/common/stack-protector.c
 create mode 100644 xen/include/xen/stack-protector.h