kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR

Until recent versions of GCC and Clang, it was not possible to disable
KCOV instrumentation via a function attribute.  The relevant function
attribute was introduced in 540540d06e9d9 ("kcov: add
__no_sanitize_coverage to fix noinstr for all architectures").

x86 was the first architecture to want a working noinstr, and at the
time no compiler support for the attribute existed yet.  Therefore,
commit 0f1441b44e823 ("objtool: Fix noinstr vs KCOV") introduced the
ability to NOP __sanitizer_cov_*() calls in .noinstr.text.

However, this doesn't work for other architectures like arm64 and s390
that want a working noinstr per ARCH_WANTS_NO_INSTR.

At the time of 0f1441b44e823, we didn't yet have ARCH_WANTS_NO_INSTR,
but now we can move the Kconfig dependency checks to the generic KCOV
option.  KCOV will be available if:

	- architecture does not care about noinstr, OR
	- we have objtool support (like on x86), OR
	- GCC is 12.0 or newer, OR
	- Clang is 13.0 or newer.

Link: https://lkml.kernel.org/r/20211201152604.3984495-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1275bab..f79a063 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -78,7 +78,7 @@ config X86
        select ARCH_HAS_FILTER_PGPROT
        select ARCH_HAS_FORTIFY_SOURCE
        select ARCH_HAS_GCOV_PROFILE_ALL
-       select ARCH_HAS_KCOV                    if X86_64 && STACK_VALIDATION
+       select ARCH_HAS_KCOV                    if X86_64
        select ARCH_HAS_MEM_ENCRYPT
        select ARCH_HAS_MEMBARRIER_SYNC_CORE
        select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 666e070..1a5d168 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1979,6 +1979,8 @@ 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 || \
+                  GCC_VERSION >= 120000 || CLANG_VERSION >= 130000
        select DEBUG_FS
        select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
        help