Hi Kees,
Bill's PR to disable __counted_by for "whole struct" __bdos cases has now been merged into 19.1.3 [1], so here's the patch to disable __counted_by for clang versions < 19.1.3 in the kernel.
Hopefully in the near future __counted_by for whole struct __bdos can be enabled once again in coordination between the kernel, gcc, and clang. There has been recent progress on this in [2] thanks to Tavian.
Also see previous discussion on the mailing list [3]
Thanks to everyone for moving this issue along. In particular, Bill for his PR to clang/llvm, Kees and Thorsten for reproducers of the two issues, Nathan for Kconfig-ifying this patch, and Miguel for reviewing.
Info for the stable team:
This patch should be backported to kernels >= 6.6 to make sure that those build correctly with the effected clang versions. This patch cherry-picks cleanly onto linux-6.11.y. For linux-6.6.y three prerequiste commits are neded:
16c31dd7fdf6: Compiler Attributes: counted_by: bump min gcc version 2993eb7a8d34: Compiler Attributes: counted_by: fixup clang URL 231dc3f0c936: lkdtm/bugs: Improve warning message for compilers without counted_by support
There are still two merge conflicts even with those prerequistes. Here's the correct resolution:
1. include/linux/compiler_types.h: use the incoming change until before (but not including) the "Apply __counted_by() when the Endianness matches to increase test coverage." comment
2. lib/overflow_kunit.c: HEAD is correct
[1] https://github.com/llvm/llvm-project/pull/112786 [2] https://github.com/llvm/llvm-project/pull/112636 [3] https://lore.kernel.org/lkml/3E304FB2-799D-478F-889A-CDFC1A52DCD8@toblux.com...
Best Regards Jan
Jan Hendrik Farr (1): Compiler Attributes: disable __counted_by for clang < 19.1.3
drivers/misc/lkdtm/bugs.c | 2 +- include/linux/compiler_attributes.h | 13 ------------- include/linux/compiler_types.h | 19 +++++++++++++++++++ init/Kconfig | 9 +++++++++ lib/overflow_kunit.c | 2 +- 5 files changed, 30 insertions(+), 15 deletions(-)