MIPS: Kconfig option to better exercise/debug hybrid FPRs (f4af6fb2) · Commits · 戴 / test

The hybrid FPR scheme exists to allow for compatibility between existing FP32 code and newly compiled FP64A code. Such code should hopefully be rare in the real world, and for the moment is difficult to come across. All code except that built for the FP64 ABI can correctly execute using the hybrid FPR scheme, so debugging the hybrid FPR implementation can be eased by forcing all such code to use it. This is undesirable in general due to the trap & emulate overhead of the hybrid FPR implementation, but is a very useful option to have for debugging. Signed-off-by:

Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/7680/ Signed-off-by:

Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig.debug

+13 −0

Original line number	Diff line number	Diff line
		@@ -122,4 +122,17 @@ config SPINLOCK_TEST
		help
		Add several files to the debugfs to test spinlock speed.

		config FP32XX_HYBRID_FPRS
		bool "Run FP32 & FPXX code with hybrid FPRs"
		depends on MIPS_O32_FP64_SUPPORT
		help
		The hybrid FPR scheme is normally used only when a program needs to
		execute a mix of FP32 & FP64A code, since the trapping & emulation
		that it entails is expensive. When enabled, this option will lead
		to the kernel running programs which use the FP32 & FPXX FP ABIs
		using the hybrid FPR scheme, which can be useful for debugging
		purposes.

		If unsure, say N.

		endmenu

arch/mips/kernel/elf.c

+18 −0

Original line number	Diff line number	Diff line
		@@ -134,6 +134,24 @@ int arch_check_elf(void *_ehdr, bool has_interpreter,

		void mips_set_personality_fp(struct arch_elf_state *state)
		{
		if (config_enabled(CONFIG_FP32XX_HYBRID_FPRS)) {
		/*
		* Use hybrid FPRs for all code which can correctly execute
		* with that mode.
		*/
		switch (state->overall_abi) {
		case MIPS_ABI_FP_DOUBLE:
		case MIPS_ABI_FP_SINGLE:
		case MIPS_ABI_FP_SOFT:
		case MIPS_ABI_FP_XX:
		case MIPS_ABI_FP_ANY:
		/* FR=1, FRE=1 */
		clear_thread_flag(TIF_32BIT_FPREGS);
		set_thread_flag(TIF_HYBRID_FPREGS);
		return;
		}
		}

		switch (state->overall_abi) {
		case MIPS_ABI_FP_DOUBLE:
		case MIPS_ABI_FP_SINGLE:

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