kernel: add another missing KASAN symbol

Enabling KERNEL_KASAN exposes yet another missing symbol. This did not
appear on bcm27xx but is appearing now on x86/64. Add a new kernel build
option for KASAN_VMALLOC to fix build on x86/64 with KERNEL_KASAN
enabled.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 902e211ea1ed435d1544de30bb276840b6f2db2b..f5b42b71ee43c6c90bc6b3a540cd0037a7aecc79 100644 (file)
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -170,6 +170,22 @@ config KERNEL_KASAN_EXTRA
          compile time.
          https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 has more
 
+CONFIG KERNEL_KASAN_VMALLOC
+       bool "Back mappings in vmalloc space with real shadow memory"
+       depends on KERNEL_KASAN
+         By default, the shadow region for vmalloc space is the read-only
+         zero page. This means that KASAN cannot detect errors involving
+         vmalloc space.
+
+         Enabling this option will hook in to vmap/vmalloc and back those
+         mappings with real shadow memory allocated on demand. This allows
+         for KASAN to detect more sorts of errors (and to support vmapped
+         stacks), but at the cost of higher memory usage.
+
+         This option depends on HAVE_ARCH_KASAN_VMALLOC, but we can't
+         depend on that in here, so it is possible that enabling this
+         will have no effect.
+
 if KERNEL_KASAN
        config KERNEL_KASAN_GENERIC
        def_bool y