X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=Makefile;h=af2f2fcfe01c17d387970d10c5062777d9377b55;hb=2502722ddedc4f0a110646134d7937287c904c68;hp=d0901b46b4bfd15aedfd3a0ccfa2d3c3255ff8fc;hpb=98a96f202203fecad65b44449077c695686ad4db;p=firefly-linux-kernel-4.4.55.git

diff --git a/Makefile b/Makefile
index d0901b46b4bf..af2f2fcfe01c 100644
--- a/Makefile
+++ b/Makefile
@@ -636,6 +636,22 @@ KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
 endif
 
 # Handle stack protector mode.
+#
+# Since kbuild can potentially perform two passes (first with the old
+# .config values and then with updated .config values), we cannot error out
+# if a desired compiler option is unsupported. If we were to error, kbuild
+# could never get to the second pass and actually notice that we changed
+# the option to something that was supported.
+#
+# Additionally, we don't want to fallback and/or silently change which compiler
+# flags will be used, since that leads to producing kernels with different
+# security feature characteristics depending on the compiler used. ("But I
+# selected CC_STACKPROTECTOR_STRONG! Why did it build with _REGULAR?!")
+#
+# The middle ground is to warn here so that the failed option is obvious, but
+# to let the build fail with bad compiler flags so that we can't produce a
+# kernel when there is a CONFIG and compiler mismatch.
+#
 ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
   stackp-flag := -fstack-protector
   ifeq ($(call cc-option, $(stackp-flag)),)