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@xxxxxxxx> --- arch/mips/Kconfig | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 2b3891c45461..ffcf72aa9955 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -2255,7 +2255,19 @@ 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 -- 2.19.1
