1 files changed, 95 insertions, 10 deletions

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index 0aa61a95eb4b..b725b713b9f8 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -151,26 +151,109 @@ 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);
-	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->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;
+		} else {
+			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.
  */
 static void cpu_set_nofpu_id(struct cpuinfo_mips *c)
@@ -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);
 }