MIPS: Add IEEE Std 754 conformance mode selection (503943e0) · Commits · 戴 / test

Documentation/kernel-parameters.txt

+35 −0

Original line number	Diff line number	Diff line
		@@ -1436,6 +1436,41 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
		In such case C2/C3 won't be used again.
		idle=nomwait: Disable mwait for CPU C-states

		ieee754= [MIPS] Select IEEE Std 754 conformance mode
		Format: { strict \| legacy \| 2008 \| relaxed }
		Default: strict

		Choose which programs will be accepted for execution
		based on the IEEE 754 NaN encoding(s) supported by
		the FPU and the NaN encoding requested with the value
		of an ELF file header flag individually set by each
		binary. Hardware implementations are permitted to
		support either or both of the legacy and the 2008 NaN
		encoding mode.

		Available settings are as follows:
		strict accept binaries that request a NaN encoding
		supported by the FPU
		legacy only accept legacy-NaN binaries, if supported
		by the FPU
		2008 only accept 2008-NaN binaries, if supported
		by the FPU
		relaxed accept any binaries regardless of whether
		supported by the FPU

		The FPU emulator is always able to support both NaN
		encodings, so if no FPU hardware is present or it has
		been disabled with 'nofpu', then the settings of
		'legacy' and '2008' strap the emulator accordingly,
		'relaxed' straps the emulator for both legacy-NaN and
		2008-NaN, whereas 'strict' enables legacy-NaN only on
		legacy processors and both NaN encodings on MIPS32 or
		MIPS64 CPUs.

		The setting for ABS.fmt/NEG.fmt instruction execution
		mode generally follows that for the NaN encoding,
		except where unsupported by hardware.

		ignore_loglevel [KNL]
		Ignore loglevel setting - this will print /all/
		kernel messages to the console. Useful for debugging.

arch/mips/include/asm/elf.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -447,6 +447,10 @@ struct arch_elf_state {
		.overall_fp_mode = -1, \
		}

		/* Whether to accept legacy-NaN and 2008-NaN user binaries. */
		extern bool mips_use_nan_legacy;
		extern bool mips_use_nan_2008;

		extern int arch_elf_pt_proc(void ehdr, void phdr, struct file *elf,
		bool is_interp, struct arch_elf_state *state);

arch/mips/kernel/cpu-probe.c

+95 −10

Original line number	Diff line number	Diff line
		@@ -151,24 +151,107 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
		}

		/*
		* Set the IEEE 754 NaN encodings and ABS.fmt/NEG.fmt execution modes
		* for the FPU emulator. Clear the flags where required in case called
		* from `fpu_disable', to override details obtained from FPU hardware.
		* IEEE 754 conformance mode to use. Affects the NaN encoding and the
		* ABS.fmt/NEG.fmt execution mode.
		*/
		static enum { STRICT, LEGACY, STD2008, RELAXED } ieee754 = STRICT;

		/*
		* Set the IEEE 754 NaN encodings and the ABS.fmt/NEG.fmt execution modes
		* to support by the FPU emulator according to the IEEE 754 conformance
		* mode selected. Note that "relaxed" straps the emulator so that it
		* allows 2008-NaN binaries even for legacy processors.
		*/
		static void cpu_set_nofpu_2008(struct cpuinfo_mips *c)
		{
		c->options &= ~(MIPS_CPU_NAN_2008 \| MIPS_CPU_NAN_LEGACY);
		c->fpu_csr31 &= ~(FPU_CSR_ABS2008 \| FPU_CSR_NAN2008);
		c->fpu_msk31 &= ~(FPU_CSR_ABS2008 \| FPU_CSR_NAN2008);

		switch (ieee754) {
		case STRICT:
		if (c->isa_level & (MIPS_CPU_ISA_M32R1 \| MIPS_CPU_ISA_M64R1 \|
		MIPS_CPU_ISA_M32R2 \| MIPS_CPU_ISA_M64R2 \|
		MIPS_CPU_ISA_M32R6 \| MIPS_CPU_ISA_M64R6)) {
		c->options \|= MIPS_CPU_NAN_2008 \| MIPS_CPU_NAN_LEGACY;
		c->fpu_msk31 &= ~(FPU_CSR_ABS2008 \| FPU_CSR_NAN2008);
		} else {
		c->options &= ~MIPS_CPU_NAN_2008;
		c->options \|= MIPS_CPU_NAN_LEGACY;
		c->fpu_msk31 \|= FPU_CSR_ABS2008 \| FPU_CSR_NAN2008;
		}
		break;
		case LEGACY:
		c->options \|= MIPS_CPU_NAN_LEGACY;
		c->fpu_msk31 \|= FPU_CSR_ABS2008 \| FPU_CSR_NAN2008;
		break;
		case STD2008:
		c->options \|= MIPS_CPU_NAN_2008;
		c->fpu_csr31 \|= FPU_CSR_ABS2008 \| FPU_CSR_NAN2008;
		c->fpu_msk31 \|= FPU_CSR_ABS2008 \| FPU_CSR_NAN2008;
		break;
		case RELAXED:
		c->options \|= MIPS_CPU_NAN_2008 \| MIPS_CPU_NAN_LEGACY;
		break;
		}
		}

		/*
		* Override the IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode
		* according to the "ieee754=" parameter.
		*/
		static void cpu_set_nan_2008(struct cpuinfo_mips *c)
		{
		switch (ieee754) {
		case STRICT:
		mips_use_nan_legacy = !!cpu_has_nan_legacy;
		mips_use_nan_2008 = !!cpu_has_nan_2008;
		break;
		case LEGACY:
		mips_use_nan_legacy = !!cpu_has_nan_legacy;
		mips_use_nan_2008 = !cpu_has_nan_legacy;
		break;
		case STD2008:
		mips_use_nan_legacy = !cpu_has_nan_2008;
		mips_use_nan_2008 = !!cpu_has_nan_2008;
		break;
		case RELAXED:
		mips_use_nan_legacy = true;
		mips_use_nan_2008 = true;
		break;
		}
		}

		/*
		* IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode override
		* settings:
		*
		* strict: accept binaries that request a NaN encoding supported by the FPU
		* legacy: only accept legacy-NaN binaries
		* 2008: only accept 2008-NaN binaries
		* relaxed: accept any binaries regardless of whether supported by the FPU
		*/
		static int __init ieee754_setup(char *s)
		{
		if (!s)
		return -1;
		else if (!strcmp(s, "strict"))
		ieee754 = STRICT;
		else if (!strcmp(s, "legacy"))
		ieee754 = LEGACY;
		else if (!strcmp(s, "2008"))
		ieee754 = STD2008;
		else if (!strcmp(s, "relaxed"))
		ieee754 = RELAXED;
		else
		return -1;

		if (!(boot_cpu_data.options & MIPS_CPU_FPU))
		cpu_set_nofpu_2008(&boot_cpu_data);
		cpu_set_nan_2008(&boot_cpu_data);

		return 0;
		}

		early_param("ieee754", ieee754_setup);

		/*
		* Set the FIR feature flags for the FPU emulator.
		@@ -212,6 +295,7 @@ static void cpu_set_fpu_opts(struct cpuinfo_mips *c)

		cpu_set_fpu_fcsr_mask(c);
		cpu_set_fpu_2008(c);
		cpu_set_nan_2008(c);
		}

		/*
		@@ -223,6 +307,7 @@ static void cpu_set_nofpu_opts(struct cpuinfo_mips *c)
		c->fpu_msk31 = mips_nofpu_msk31;

		cpu_set_nofpu_2008(c);
		cpu_set_nan_2008(c);
		cpu_set_nofpu_id(c);
		}

arch/mips/kernel/elf.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -13,6 +13,10 @@

		#include <asm/cpu-info.h>

		/* Whether to accept legacy-NaN and 2008-NaN user binaries. */
		bool mips_use_nan_legacy;
		bool mips_use_nan_2008;

		/* FPU modes */
		enum {
		FP_FRE,
		@@ -150,16 +154,16 @@ int arch_check_elf(void _ehdr, bool has_interpreter, void _interp_ehdr,
		flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;

		/*
		* Determine the NaN personality, reject the binary if no hardware
		* support. Also ensure that any interpreter matches the executable.
		* Determine the NaN personality, reject the binary if not allowed.
		* Also ensure that any interpreter matches the executable.
		*/
		if (flags & EF_MIPS_NAN2008) {
		if (cpu_has_nan_2008)
		if (mips_use_nan_2008)
		state->nan_2008 = 1;
		else
		return -ENOEXEC;
		} else {
		if (cpu_has_nan_legacy)
		if (mips_use_nan_legacy)
		state->nan_2008 = 0;
		else
		return -ENOEXEC;

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