latent_entropy: raise CONFIG_FRAME_WARN by default

When building with the latent_entropy plugin, set the default
CONFIG_FRAME_WARN to 2048, since some __init functions have many basic
blocks that, when instrumented by the latent_entropy plugin, grow beyond
1024 byte stack size on 32-bit builds.

Link: http://lkml.kernel.org/r/20161018211216.GA39687@beast
Signed-off-by: Kees Cook <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Cc: Emese Revfy <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Nikolay Aleksandrov <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

lib/Kconfig.debug

@@ -198,6 +198,7 @@ config FRAME_WARN
 	int "Warn for stack frames larger than (needs gcc 4.4)"
 	range 0 8192
 	default 0 if KASAN
+	default 2048 if GCC_PLUGIN_LATENT_ENTROPY
 	default 1024 if !64BIT
 	default 2048 if 64BIT
 	help