objtool: Add CONFIG_OBJTOOL_WERROR

Objtool warnings can be indicative of crashes, broken live patching, or
even boot failures.  Ignoring them is not recommended.

Add CONFIG_OBJTOOL_WERROR to upgrade objtool warnings to errors by
enabling the objtool --Werror option.  Also set --backtrace to print the
branches leading up to the warning, which can help considerably when
debugging certain warnings.

To avoid breaking bots too badly for now, make it the default for real
world builds only (!COMPILE_TEST).

Co-developed-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/3e7c109313ff15da6c80788965cc7450115b0196.1741975349.git.jpoimboe@kernel.org

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 35796c290ca351b9906dc37651197aefb9100990..a9709a6db30f3f65e5576336e200ce8c5eb19cca 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -545,6 +545,17 @@ config FRAME_POINTER
 config OBJTOOL
        bool
 
+config OBJTOOL_WERROR
+       bool "Upgrade objtool warnings to errors"
+       depends on OBJTOOL && !COMPILE_TEST
+       help
+         Fail the build on objtool warnings.
+
+         Objtool warnings can indicate kernel instability, including boot
+         failures.  This option is highly recommended.
+
+         If unsure, say Y.
+
 config STACK_VALIDATION
        bool "Compile-time stack metadata validation"
        depends on HAVE_STACK_VALIDATION && UNWINDER_FRAME_POINTER

diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index cad20f0e66ee9cf5942b51f37cdd8e52802493e4..99e281966ba31c6399ad50532a0ee0fa94d1ad8d 100644 (file)
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -277,6 +277,7 @@ objtool-args-$(CONFIG_HAVE_STATIC_CALL_INLINE)              += --static-call
 objtool-args-$(CONFIG_HAVE_UACCESS_VALIDATION)         += --uaccess
 objtool-args-$(CONFIG_GCOV_KERNEL)                     += --no-unreachable
 objtool-args-$(CONFIG_PREFIX_SYMBOLS)                  += --prefix=$(CONFIG_FUNCTION_PADDING_BYTES)
+objtool-args-$(CONFIG_OBJTOOL_WERROR)                  += --Werror --backtrace
 
 objtool-args = $(objtool-args-y)                                       \
        $(if $(delay-objtool), --link)                                  \