objtool: Add CONFIG_OBJTOOL_WERROR

JIRA: https://issues.redhat.com/browse/RHEL-85302

commit 3679906
Author: Josh Poimboeuf <jpoimboe@kernel.org>
Date:   Fri Mar 14 12:29:11 2025 -0700

    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

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

Author: joe-lawrence

lib/Kconfig.debug

@@ -467,6 +467,17 @@ 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

scripts/Makefile.lib

@@ -258,6 +258,7 @@ 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)					\