Jacob Garber has uploaded this change for review.
xcompile: Disable dangerous optimizations
According to the C standard, GCC is allowed to perform optimizations
based on undefined behaviour. However, much of this undefined behaviour
is difficult to detect and sometimes is even intentional (eg. accessing
memory at address 0), so these optimizations can silently break code.
This patch disables the following optimizations in the coreboot tree,
which is already done in several other projects (eg. Linux kernel,
Chromium EC):
-fno-delete-null-pointer-checks
-fno-strict-aliasing
-fno-strict-overflow
Disabling these optimizations is particularly important when using link
time optimization, since LTO allows the compiler to perform deeper code
inspection and potentially uncover issues that weren't previously
apparent. For example, coreinfo compiled with LTO libpayload crashes
without -fno-delete-null-pointer-checks, presumably because the compiler
is optimizing something out that it shouldn't.
Change-Id: I4492277f02418ade3fe7a75304e8e0611f49ef36
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
---
M Makefile.inc
M src/vendorcode/amd/agesa/Makefile.inc
M src/vendorcode/amd/pi/00670F00/Makefile.inc
M src/vendorcode/amd/pi/Makefile.inc
M util/xcompile/xcompile
5 files changed, 4 insertions(+), 4 deletions(-)
git pull ssh://review.coreboot.org:29418/coreboot refs/changes/89/38289/1
diff --git a/Makefile.inc b/Makefile.inc
index 002d3e7..caf82f4 100644
--- a/Makefile.inc
+++ b/Makefile.inc
@@ -414,7 +414,6 @@
CFLAGS_common += -fno-common -ffreestanding -fno-builtin -fomit-frame-pointer
CFLAGS_common += -ffunction-sections -fdata-sections -fno-pie
ifeq ($(CONFIG_COMPILER_GCC),y)
-CFLAGS_common += -fno-delete-null-pointer-checks
# Don't add these GCC specific flags when running scan-build
ifeq ($(CCC_ANALYZER_OUTPUT_FORMAT),)
CFLAGS_common += -Wno-packed-not-aligned
diff --git a/src/vendorcode/amd/agesa/Makefile.inc b/src/vendorcode/amd/agesa/Makefile.inc
index b96af84..6381324 100644
--- a/src/vendorcode/amd/agesa/Makefile.inc
+++ b/src/vendorcode/amd/agesa/Makefile.inc
@@ -12,7 +12,7 @@
libagesa-generic-ccopts += -fno-zero-initialized-in-bss
libagesa-generic-ccopts += $(AGESA_INC) $(AGESA_AUTOINCLUDES)
-AGESA_CFLAGS := -march=k8-sse3 -mtune=k8-sse3 -fno-strict-aliasing
+AGESA_CFLAGS := -march=k8-sse3 -mtune=k8-sse3
CFLAGS_x86_32 += $(AGESA_CFLAGS)
CFLAGS_x86_64 += $(AGESA_CFLAGS)
diff --git a/src/vendorcode/amd/pi/00670F00/Makefile.inc b/src/vendorcode/amd/pi/00670F00/Makefile.inc
index f6cd8eb..cee4672 100644
--- a/src/vendorcode/amd/pi/00670F00/Makefile.inc
+++ b/src/vendorcode/amd/pi/00670F00/Makefile.inc
@@ -55,7 +55,7 @@
AGESA_INC += -I$(src)/commonlib/include
AGESA_INC += -I$(VBOOT_SOURCE)/firmware/include
-AGESA_CFLAGS += -march=amdfam10 -fno-strict-aliasing -D__LIBAGESA__
+AGESA_CFLAGS += -march=amdfam10 -D__LIBAGESA__
CC_bootblock := $(CC_bootblock) $(BINARY_PI_INC)
CC_romstage := $(CC_romstage) $(BINARY_PI_INC)
diff --git a/src/vendorcode/amd/pi/Makefile.inc b/src/vendorcode/amd/pi/Makefile.inc
index 9b3a0e6..d55de29 100644
--- a/src/vendorcode/amd/pi/Makefile.inc
+++ b/src/vendorcode/amd/pi/Makefile.inc
@@ -69,7 +69,7 @@
AGESA_INC += -I$(VBOOT_SOURCE)/firmware/include
AGESA_CFLAGS += -march=amdfam10 -mno-3dnow
-AGESA_CFLAGS += -fno-strict-aliasing -D__LIBAGESA__
+AGESA_CFLAGS += -D__LIBAGESA__
CFLAGS_x86_32 += $(AGESA_CFLAGS)
CFLAGS_x86_64 += $(AGESA_CFLAGS)
diff --git a/util/xcompile/xcompile b/util/xcompile/xcompile
index 8335c34..cc4641e 100755
--- a/util/xcompile/xcompile
+++ b/util/xcompile/xcompile
@@ -222,6 +222,7 @@
GCC_CFLAGS_${TARCH}:=${CFLAGS_GCC}
# Generally available for GCC's cc1:
GCC_CFLAGS_${TARCH}+=-Wlogical-op
+GCC_CFLAGS_${TARCH}+=-fno-delete-null-pointer-checks -fno-strict-aliasing -fno-strict-overflow
GCC_ADAFLAGS_${TARCH}:=${CFLAGS_GCC}
GCC_COMPILER_RT_${TARCH}:=${CC_RT_GCC}
GCC_COMPILER_RT_FLAGS_${TARCH}:=${CC_RT_EXTRA_GCC}
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