8cdd23c23c
Commit 97fed779f2a6 ("arm64: bti: Provide Kconfig for kernel mode BTI")
disabled CONFIG_ARM64_BTI_KERNEL when CONFIG_GCOV_KERNEL was enabled and
compiling with clang because of warnings that were seen with
allmodconfig because LLVM was not emitting PAC/BTI instructions for
compiler generated functions:
| warning: some functions compiled with BTI and some compiled without BTI
| warning: not setting BTI in feature flags
This dependency was fine for avoiding the warnings with allmodconfig
until commit 51c2ee6d121c ("Kconfig: Introduce ARCH_WANTS_NO_INSTR and
CC_HAS_NO_PROFILE_FN_ATTR"), which prevents CONFIG_GCOV_KERNEL from
being enabled with clang 12.0.0 or older because those versions do not
support the no_profile_instrument_function attribute.
As a result, CONFIG_ARM64_BTI_KERNEL gets enabled with allmodconfig and
there are more warnings like the ones above due to CONFIG_KASAN, which
suffers from the same problem as CONFIG_GCOV_KERNEL. This was most
likely not noticed at the time because allmodconfig +
CONFIG_GCOV_KERNEL=n was not tested. defconfig + CONFIG_KASAN=y is
enough to reproduce the same warnings as above.
The root cause of the warnings was resolved in LLVM during the 12.0.0
release so rather than play whack-a-mole with the dependencies, just
update CONFIG_ARM64_BTI_KERNEL to require clang 12.0.0, which will have
all of the issues ironed out.
Link: https://github.com/ClangBuiltLinux/linux/issues/1428
Link: https://github.com/ClangBuiltLinux/continuous-integration2/runs/3010034706?check_suite_focus=true
Link: https://github.com/ClangBuiltLinux/continuous-integration2/runs/3010035725?check_suite_focus=true
Link: a88c722e68
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20210712214636.3134425-1-nathan@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.