[tip: x86/entry] kasan: Bump required compiler version

["tip-bot2 for Marco Elver" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     7b861a53e46b6b42ab8560b105af308cb72d7285
Gitweb:        https://git.kernel.org/tip/7b861a53e46b6b42ab8560b105af308cb72d7285
Author:        Marco Elver <elver@google.com>
AuthorDate:    Thu, 04 Jun 2020 07:58:10 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 15 Jun 2020 14:10:09 +02:00

kasan: Bump required compiler version

Adds config variable CC_HAS_WORKING_NOSANITIZE_ADDRESS, which will be
true if we have a compiler that does not fail builds due to
no_sanitize_address functions. This does not yet mean they work as
intended, but for automated build-tests, this is the minimum
requirement.

For example, we require that __always_inline functions used from
no_sanitize_address functions do not generate instrumentation. On GCC <=
7 this fails to build entirely, therefore we make the minimum version
GCC 8.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lkml.kernel.org/r/20200602175859.GC2604@hirez.programming.kicks-ass.net
---
 lib/Kconfig.kasan | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
index 81f5464..af0dd09 100644
--- a/lib/Kconfig.kasan
+++ b/lib/Kconfig.kasan
@@ -15,11 +15,15 @@ config CC_HAS_KASAN_GENERIC
 config CC_HAS_KASAN_SW_TAGS
 	def_bool $(cc-option, -fsanitize=kernel-hwaddress)
 
+config CC_HAS_WORKING_NOSANITIZE_ADDRESS
+	def_bool !CC_IS_GCC || GCC_VERSION >= 80000
+
 config KASAN
 	bool "KASAN: runtime memory debugger"
 	depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
 		   (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)
 	depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
+	depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
 	help
 	  Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
 	  designed to find out-of-bounds accesses and use-after-free bugs.