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| author | Kees Cook <keescook@chromium.org> | 2021-09-14 12:49:03 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2021-09-25 08:22:59 -0700 |
| commit | f02003c860d921171be4a27e2893766eb3bc6871 (patch) | |
| tree | 3743423cb2beaf8ff6638895827ffadd913723a8 /Makefile | |
| parent | e4e737bb5c170df6135a127739a9e6148ee3da82 (diff) | |
| download | lwn-f02003c860d921171be4a27e2893766eb3bc6871.tar.gz lwn-f02003c860d921171be4a27e2893766eb3bc6871.zip | |
hardening: Avoid harmless Clang option under CONFIG_INIT_STACK_ALL_ZERO
Currently under Clang, CC_HAS_AUTO_VAR_INIT_ZERO requires an extra
-enable flag compared to CC_HAS_AUTO_VAR_INIT_PATTERN. GCC 12[1] will
not, and will happily ignore the Clang-specific flag. However, its
presence on the command-line is both cumbersome and confusing. Due to
GCC's tolerant behavior, though, we can continue to use a single Kconfig
cc-option test for the feature on both compilers, but then drop the
Clang-specific option in the Makefile.
In other words, this patch does not change anything other than making the
compiler command line shorter once GCC supports -ftrivial-auto-var-init=zero.
[1] https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=a25e0b5e6ac8a77a71c229e0a7b744603365b0e9
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: llvm@lists.linux.dev
Fixes: dcb7c0b9461c ("hardening: Clarify Kconfig text for auto-var-init")
Suggested-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/lkml/20210914102837.6172-1-will@kernel.org/
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 6 |
1 files changed, 3 insertions, 3 deletions
@@ -831,12 +831,12 @@ endif # Initialize all stack variables with a zero value. ifdef CONFIG_INIT_STACK_ALL_ZERO -# Future support for zero initialization is still being debated, see -# https://bugs.llvm.org/show_bug.cgi?id=45497. These flags are subject to being -# renamed or dropped. KBUILD_CFLAGS += -ftrivial-auto-var-init=zero +ifdef CONFIG_CC_IS_CLANG +# https://bugs.llvm.org/show_bug.cgi?id=45497 KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang endif +endif # While VLAs have been removed, GCC produces unreachable stack probes # for the randomize_kstack_offset feature. Disable it for all compilers. |