[PATCH v3 0/6] arm64: module: improve module VA range selection

[Mark Rutland]

This series (based on v6.4-rc3) aims to make arm64's module allocation
code more robust. To that end:

* Redundant code for KASAN && !KASAN_VMALLOC is removed, as this
  combination is no longer possible.

* Module PLT support is mandated, always allowing for the use of a 2G
  module region. Practically speaking, this is already the case for almost
  all users as module PLT support is mandated by both KASLR (which most
  distros including Android, enable this), and by the workaround for ARM
  erratum 843419 (required by Cortex-A53).

* The module VA region selection is moved to module.c, making it
  self-contained and easier to follow.

* The default module VA region is expanded to 2G. This ensures that
  there is sufficient space for the full region using PLTs even when
  KASLR is disabled or no seed provided.

* The module VA range init code is updated to log when the kernel is too
  large to support the use of a 128M or 2G module region, to enable
  debugging of these cases. Contemporary kernels built with debug
  options can be bigger than 128M, and a kernel bigger than 2G is
  unlikely but theoretically possible. Adding this logging should help
  to debug or filter away reports for such cases.

This should allow for loading of very large modules, as Shanker reported
was an issue:

  https://lore.kernel.org/linux-arm-kernel/20230326170756.3021936-1-sdonthineni@nvidia.com/
  https://lore.kernel.org/linux-arm-kernel/20230330140437.984211-1-sdonthineni@nvidia.com/

... and as Ard had an alternative series for:

  https://lore.kernel.org/linux-arm-kernel/20230404135437.2744866-1-ardb@kernel.org/

Since v1 [1]:
* Log the number of pages in range
* Remove unused kasan_mod_shadow_end
* Only randomize when kaslr_enabled()
* Simplify control-flow

Since v2 [2]:
* Apply Ard's Reviewed-by tags
* Fix typos
* Rebave to v6.4-rc3 (trivial)

[1] https://lore.kernel.org/linux-arm-kernel/20230509111451.4184972-1-mark.rutland@arm.com/
[2] https://lore.kernel.org/linux-arm-kernel/20230512152210.3072475-1-mark.rutland@arm.com/

Thanks,
Mark.

Mark Rutland (6):
  arm64: module: remove old !KASAN_VMALLOC logic
  arm64: kasan: remove !KASAN_VMALLOC remnants
  arm64: kaslr: split kaslr/module initialization
  arm64: module: move module randomization to module.c
  arm64: module: mandate MODULE_PLTS
  arm64: module: rework module VA range selection

 Documentation/arm64/memory.rst      |   8 +-
 arch/arm64/Kconfig                  |  28 +----
 arch/arm64/include/asm/memory.h     |  16 +--
 arch/arm64/include/asm/module.h     |   8 --
 arch/arm64/include/asm/module.lds.h |   2 -
 arch/arm64/kernel/Makefile          |   3 +-
 arch/arm64/kernel/ftrace.c          |   8 +-
 arch/arm64/kernel/kaslr.c           |  83 +++------------
 arch/arm64/kernel/module.c          | 159 +++++++++++++++++++++-------
 arch/arm64/kernel/setup.c           |   2 +
 arch/arm64/mm/kasan_init.c          |  17 +--
 11 files changed, 159 insertions(+), 175 deletions(-)

-- 
2.30.2