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x86, setup: compile with -DDISABLE_BRANCH_PROFILING
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Impact: code size reduction (possibly critical)

The x86 boot and decompression code has no use of the branch profiling
constructs, so disable them.  This would bloat the setup code by as
much as 14K, eating up a fairly large chunk of the 32K area we are
guaranteed to have.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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H. Peter Anvin authored and Ingo Molnar committed Apr 3, 2009
1 parent a7f8c50 commit 95a38f3
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Showing 2 changed files with 3 additions and 1 deletion.
3 changes: 2 additions & 1 deletion arch/x86/boot/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,7 @@ $(obj)/cpustr.h: $(obj)/mkcpustr FORCE
# How to compile the 16-bit code. Note we always compile for -march=i386,
# that way we can complain to the user if the CPU is insufficient.
KBUILD_CFLAGS := $(LINUXINCLUDE) -g -Os -D_SETUP -D__KERNEL__ \
-DDISABLE_BRANCH_PROFILING \
-Wall -Wstrict-prototypes \
-march=i386 -mregparm=3 \
-include $(srctree)/$(src)/code16gcc.h \
Expand All @@ -66,7 +67,7 @@ KBUILD_CFLAGS := $(LINUXINCLUDE) -g -Os -D_SETUP -D__KERNEL__ \
$(call cc-option, -fno-unit-at-a-time)) \
$(call cc-option, -fno-stack-protector) \
$(call cc-option, -mpreferred-stack-boundary=2)
KBUILD_CFLAGS += $(call cc-option,-m32)
KBUILD_CFLAGS += $(call cc-option, -m32)
KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__

$(obj)/bzImage: asflags-y := $(SVGA_MODE)
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1 change: 1 addition & 0 deletions arch/x86/boot/compressed/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma h

KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2
KBUILD_CFLAGS += -fno-strict-aliasing -fPIC
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
cflags-$(CONFIG_X86_64) := -mcmodel=small
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
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