Unverified Commit 183b40f9 authored Nov 07, 2018 by Paul Burton

MIPS: Allow FP support to be disabled



Allow the user to configure the kernel to omit support for floating
point, by setting CONFIG_MIPS_FP_SUPPORT=n. In an attempt to avoid
problems for users who don't understand the impact of this, only expose
the option when CONFIG_EXPERT=y.

When CONFIG_MIPS_FP_SUPPORT=n all support for FPU hardware, FPU
emulation & FP context will be removed from the kernel. If a userland
program attempts to execute a floating point instruction it will receive
a SIGILL.

Setting CONFIG_MIPS_FP_SUPPORT=n shaves around 112KB from a
64r6el_defconfig build using GCC 8.1.0.

This also helps prepare us for supporting the nanoMIPS ISA, for which
floating point support has not been finalized.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21014/
Cc: linux-mips@linux-mips.org

parent 2725f377

arch/mips/Kconfig

+13 −1

Original line number	Diff line number	Diff line
		@@ -2256,7 +2256,19 @@ config CPU_GENERIC_DUMP_TLB
		default y if !(CPU_R3000 \|\| CPU_R8000 \|\| CPU_TX39XX)

		config MIPS_FP_SUPPORT
		def_bool y
		bool "Floating Point support" if EXPERT
		default y
		help
		Select y to include support for floating point in the kernel
		including initialization of FPU hardware, FP context save & restore
		and emulation of an FPU where necessary. Without this support any
		userland program attempting to use floating point instructions will
		receive a SIGILL.

		If you know that your userland will not attempt to use floating point
		instructions then you can say n here to shrink the kernel a little.

		If unsure, say y.

		config CPU_R2300_FPU
		bool

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