objtool: Add CONFIG_OBJTOOL

Now that stack validation is an optional feature of objtool, add
CONFIG_OBJTOOL and replace most usages of CONFIG_STACK_VALIDATION with
it.

CONFIG_STACK_VALIDATION can now be considered to be frame-pointer
specific.  CONFIG_UNWINDER_ORC is already inherently valid for live
patching, so no need to "validate" it.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/939bf3d85604b2a126412bf11af6e3bd3b872bcb.1650300597.git.jpoimboe@redhat.com

3 files changed, 14 insertions, 11 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 075cd25363ac..c0e4e47f3ce3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -485,24 +485,25 @@ config FRAME_POINTER
 	  larger and slower, but it gives very useful debugging information
 	  in case of kernel bugs. (precise oopses/stacktraces/warnings)
 
+config OBJTOOL
+	bool
+
 config STACK_VALIDATION
 	bool "Compile-time stack metadata validation"
-	depends on HAVE_STACK_VALIDATION
+	depends on HAVE_STACK_VALIDATION && UNWINDER_FRAME_POINTER
+	select OBJTOOL
 	default n
 	help
-	  Add compile-time checks to validate stack metadata, including frame
-	  pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
-	  that runtime stack traces are more reliable.
-
-	  This is also a prerequisite for generation of ORC unwind data, which
-	  is needed for CONFIG_UNWINDER_ORC.
+	  Validate frame pointer rules at compile-time.  This helps ensure that
+	  runtime stack traces are more reliable.
 
 	  For more information, see
 	  tools/objtool/Documentation/stack-validation.txt.
 
 config VMLINUX_VALIDATION
 	bool
-	depends on STACK_VALIDATION && DEBUG_ENTRY
+	depends on HAVE_OBJTOOL && DEBUG_ENTRY
+	select OBJTOOL
 	default y
 
 config VMLINUX_MAP
@@ -2035,10 +2036,11 @@ config KCOV
 	bool "Code coverage for fuzzing"
 	depends on ARCH_HAS_KCOV
 	depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
-	depends on !ARCH_WANTS_NO_INSTR || STACK_VALIDATION || \
+	depends on !ARCH_WANTS_NO_INSTR || HAVE_OBJTOOL || \
 		   GCC_VERSION >= 120000 || CLANG_VERSION >= 130000
 	select DEBUG_FS
 	select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
+	select OBJTOOL if HAVE_OBJTOOL
 	help
 	  KCOV exposes kernel code coverage information in a form suitable
 	  for coverage-guided fuzzing (randomized testing).
diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index de022445fbba..901c3b509aca 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -187,7 +187,8 @@ config KCSAN_WEAK_MEMORY
 	# We can either let objtool nop __tsan_func_{entry,exit}() and builtin
 	# atomics instrumentation in .noinstr.text, or use a compiler that can
 	# implement __no_kcsan to really remove all instrumentation.
-	depends on STACK_VALIDATION || CC_IS_GCC || CLANG_VERSION >= 140000
+	depends on HAVE_OBJTOOL || CC_IS_GCC || CLANG_VERSION >= 140000
+	select OBJTOOL if HAVE_OBJTOOL
 	help
 	  Enable support for modeling a subset of weak memory, which allows
 	  detecting a subset of data races due to missing memory barriers.
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index f3c57ed51838..c4fe15d38b60 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -94,7 +94,7 @@ config UBSAN_UNREACHABLE
 	bool "Perform checking for unreachable code"
 	# objtool already handles unreachable checking and gets angry about
 	# seeing UBSan instrumentation located in unreachable places.
-	depends on !STACK_VALIDATION
+	depends on !(OBJTOOL && (STACK_VALIDATION || UNWINDER_ORC || X86_SMAP))
 	depends on $(cc-option,-fsanitize=unreachable)
 	help
 	  This option enables -fsanitize=unreachable which checks for control