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Add -fno-builtin to CFLAGS 

Disable the automatic substitution of functions with builtins. The
existing -ffreestanding option should already do this but explicitly
adding -fno-builtin reduces the risk of compiler variation. With this
option, GCC is not supposed to be able to make assumptions on what the
function does, which could otherwise lead to security-sensitive code
removal.

This can lead to potentially less efficient code but improves
predictability of what code is actually compiled into the binary.

Change-Id: I06ad151c61318bd1b00d84976f051d2d94314acc
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
This commit is contained in:
Douglas Raillard 2017-01-16 11:32:28 +00:00
parent d7aa7b44d6
commit e507f8e7fe
1 changed files with 1 additions and 1 deletions
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Makefile
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@ -149,7 +149,7 @@ ASFLAGS += $(CPPFLAGS) $(ASFLAGS_$(ARCH)) \
-D__ASSEMBLY__ -ffreestanding \
-Wa,--fatal-warnings
TF_CFLAGS += $(CPPFLAGS) $(TF_CFLAGS_$(ARCH)) \
-ffreestanding -Wall -std=c99 -Os \
-ffreestanding -fno-builtin -Wall -std=c99 -Os \
-ffunction-sections -fdata-sections
LDFLAGS += --fatal-warnings -O1