X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=Makefile;h=a897c50db515d7adf8dec34f7c3298c9988be953;hb=d27c0d90184a13e9e9f28c38e84f889a259f6b5f;hp=d0901b46b4bfd15aedfd3a0ccfa2d3c3255ff8fc;hpb=0c6287ec12fa8f7e295a6ebc5fd331647c5a5469;p=deliverable%2Flinux.git

diff --git a/Makefile b/Makefile
index d0901b46b4bf..a897c50db515 100644
--- a/Makefile
+++ b/Makefile
@@ -621,6 +621,9 @@ else
 KBUILD_CFLAGS	+= -O2
 endif
 
+# Tell gcc to never replace conditional load with a non-conditional one
+KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
+
 ifdef CONFIG_READABLE_ASM
 # Disable optimizations that make assembler listings hard to read.
 # reorder blocks reorders the control in the function
@@ -636,6 +639,22 @@ 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)),)