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Subject[PATCH] x86: Add "make tinyconfig" to configure the tiniest possible kernel
Since commit 5d2acfc7b974bbd3858b4dd3f2cdc6362dd8843a ("kconfig: make
allnoconfig disable options behind EMBEDDED and EXPERT") in 3.15-rc1,
"make allnoconfig" disables every possible config option.

However, a few configuration options (CC_OPTIMIZE_FOR_SIZE,
OPTIMIZE_INLINING) produce a smaller kernel when turned on, and a few
choices exist (compression, highmem, allocator) for which a non-default
option produces a smaller kernel.

Add a "tinyconfig" target, which starts from allnoconfig and then sets
these options to configure the tiniest possible kernel. This provides a
better baseline for embedded systems or efforts to reduce kernel size.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
---
arch/x86/Makefile | 6 ++++++
arch/x86/configs/tiny.config | 5 +++++
2 files changed, 11 insertions(+)
create mode 100644 arch/x86/configs/tiny.config

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index c65fd96..f20abcd 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -253,6 +253,11 @@ kvmconfig:
$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m -O $(objtree) $(objtree)/.config $(srctree)/arch/x86/configs/kvm_guest.config
$(Q)yes "" | $(MAKE) -f $(srctree)/Makefile oldconfig

+PHONY += tinyconfig
+tinyconfig: allnoconfig
+ $(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m -O $(objtree) $(objtree)/.config $(srctree)/arch/x86/configs/tiny.config
+ $(Q)yes "" | $(MAKE) -f $(srctree)/Makefile oldconfig
+
define archhelp
echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)'
echo ' install - Install kernel using'
@@ -267,4 +272,5 @@ define archhelp
echo ' FDARGS="..." arguments for the booted kernel'
echo ' FDINITRD=file initrd for the booted kernel'
echo ' kvmconfig - Enable additional options for guest kernel support'
+ echo ' tinyconfig - Configure the tiniest possible kernel'
endef
diff --git a/arch/x86/configs/tiny.config b/arch/x86/configs/tiny.config
new file mode 100644
index 0000000..8f0e54c
--- /dev/null
+++ b/arch/x86/configs/tiny.config
@@ -0,0 +1,5 @@
+CONFIG_CC_OPTIMIZE_FOR_SIZE=y
+CONFIG_KERNEL_XZ=y
+CONFIG_NOHIGHMEM=y
+CONFIG_OPTIMIZE_INLINING=y
+CONFIG_SLOB=y
--
2.0.1


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