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authorJason A. Donenfeld <Jason@zx2c4.com>2022-10-19 18:26:48 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-11-19 00:56:15 +0100
commit3bc753c06dd02a3517c9b498e3846ebfc94ac3ee (patch)
treebc56dfe86a9f735c0bc099513988a56d0a0ffbff /Makefile
parentmedia: atomisp: make hive_int8 explictly signed (diff)
downloadlinux-3bc753c06dd02a3517c9b498e3846ebfc94ac3ee.tar.xz
linux-3bc753c06dd02a3517c9b498e3846ebfc94ac3ee.zip
kbuild: treat char as always unsigned
Recently, some compile-time checking I added to the clamp_t family of functions triggered a build error when a poorly written driver was compiled on ARM, because the driver assumed that the naked `char` type is signed, but ARM treats it as unsigned, and the C standard says it's architecture-dependent. I doubt this particular driver is the only instance in which unsuspecting authors make assumptions about `char` with no `signed` or `unsigned` specifier. We were lucky enough this time that that driver used `clamp_t(char, negative_value, positive_value)`, so the new checking code found it, and I've sent a patch to fix it, but there are likely other places lurking that won't be so easily unearthed. So let's just eliminate this particular variety of heisensign bugs entirely. Set `-funsigned-char` globally, so that gcc makes the type unsigned on all architectures. This will break things in some places and fix things in others, so this will likely cause a bit of churn while reconciling the type misuse. Cc: Masahiro Yamada <masahiroy@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/lkml/202210190108.ESC3pc3D-lkp@intel.com/ Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'Makefile')
-rw-r--r--Makefile2
1 files changed, 1 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index 58cd4f5e1c3a..c329c910c8b0 100644
--- a/Makefile
+++ b/Makefile
@@ -562,7 +562,7 @@ KBUILD_AFLAGS := -D__ASSEMBLY__ -fno-PIE
KBUILD_CFLAGS := -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE \
-Werror=implicit-function-declaration -Werror=implicit-int \
- -Werror=return-type -Wno-format-security \
+ -Werror=return-type -Wno-format-security -funsigned-char \
-std=gnu11
KBUILD_CPPFLAGS := -D__KERNEL__
KBUILD_RUSTFLAGS := $(rust_common_flags) \