[PATCH v2 0/5] Improvements of the stackleak gcc plugin

[Alexander Popov]

This is the v2 of the patch series with various improvements of the
stackleak gcc plugin.

The first three patches disable unneeded gcc plugin instrumentation for
some files.

The fourth patch is the main improvement. It eliminates an unwanted
side-effect of kernel code instrumentation performed by stackleak gcc
plugin. This patch is a deep reengineering of the idea described on
grsecurity blog:
  https://grsecurity.net/resolving_an_unfortunate_stackleak_interaction

The final patch adds 'verbose' stackleak parameter for printing additional
info about the kernel code instrumentation during kernel building.

I would like to thank Alexander Monakov <amonakov at ispras.ru> for his
advisory on gcc internals.

This patch series was tested for gcc version 4.8, 5, 6, 7, 8, 9, and 10
on x86_64, i386 and arm64.
That was done using the project 'kernel-build-containers':
  https://github.com/a13xp0p0v/kernel-build-containers

Changes from v1:
 - rebase onto 5.8.0-rc2;
 - don't exclude alloca() from the instrumentation logic, because it
   will be used in kernel stack offset randomization;
 - reorder patches in the series;
 - don't use gcc plugins for building vgettimeofday.c in arm and
   arm64 vDSO;
 - follow alphabetic order in include/linux/compiler_attributes.h.

Link to v1:
 https://lore.kernel.org/lkml/20200604134957.505389-1-alex.popov@linux.com/


Alexander Popov (5):
  gcc-plugins/stackleak: Don't instrument itself
  ARM: vdso: Don't use gcc plugins for building vgettimeofday.c
  arm64: vdso: Don't use gcc plugins for building vgettimeofday.c
  gcc-plugins/stackleak: Use asm instrumentation to avoid useless
    register saving
  gcc-plugins/stackleak: Add 'verbose' plugin parameter

 arch/arm/vdso/Makefile                 |   2 +-
 arch/arm64/kernel/vdso/Makefile        |   2 +-
 include/linux/compiler_attributes.h    |  13 ++
 kernel/Makefile                        |   1 +
 kernel/stackleak.c                     |  16 +-
 scripts/Makefile.gcc-plugins           |   2 +
 scripts/gcc-plugins/stackleak_plugin.c | 248 +++++++++++++++++++++----
 7 files changed, 239 insertions(+), 45 deletions(-)

-- 
2.25.4