openwrt-xburst/target/linux/generic-2.6/patches-2.6.25/024-mips_disable_fpu.patch

MIPS: allow disabling the kernel FPU emulator

This patch allows turning off the in-kernel Algorithmics
FPU emulator support, which allows one to save a couple of
precious blocks on an embedded system.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
--
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -831,6 +831,17 @@ config I8259
 config MIPS_BONITO64
 	bool
 
+config MIPS_FPU_EMU
+	bool "Enable FPU emulation"
+	default y
+	help
+	   This option allows building a kernel with or without the Algorithmics
+	   FPU emulator enabled. Turning off this option results in a kernel which
+	   does not catch floating operations exceptions. Make sure that your toolchain
+	   is configured to enable software floating point emulation in that case.
+		
+	   If unsure say Y here.
+
 config MIPS_MSC
 	bool
 
--- a/arch/mips/math-emu/Makefile
+++ b/arch/mips/math-emu/Makefile
@@ -2,12 +2,14 @@
 # Makefile for the Linux/MIPS kernel FPU emulation.
 #
 
-obj-y	:= cp1emu.o ieee754m.o ieee754d.o ieee754dp.o ieee754sp.o ieee754.o \
+obj-y	:=	kernel_linkage.o dsemul.o cp1emu.o
+
+obj-$(CONFIG_MIPS_FPU_EMU)	+= ieee754m.o ieee754d.o ieee754dp.o ieee754sp.o ieee754.o \
 	   ieee754xcpt.o dp_frexp.o dp_modf.o dp_div.o dp_mul.o dp_sub.o \
 	   dp_add.o dp_fsp.o dp_cmp.o dp_logb.o dp_scalb.o dp_simple.o \
 	   dp_tint.o dp_fint.o dp_tlong.o dp_flong.o sp_frexp.o sp_modf.o \
 	   sp_div.o sp_mul.o sp_sub.o sp_add.o sp_fdp.o sp_cmp.o sp_logb.o \
 	   sp_scalb.o sp_simple.o sp_tint.o sp_fint.o sp_tlong.o sp_flong.o \
-	   dp_sqrt.o sp_sqrt.o kernel_linkage.o dsemul.o
+	   dp_sqrt.o sp_sqrt.o
 
 EXTRA_CFLAGS += -Werror
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -57,6 +57,12 @@
 #endif
 #define __mips 4
 
+/* Further private data for which no space exists in mips_fpu_struct */
+
+struct mips_fpu_emulator_stats fpuemustats;
+
+#ifdef CONFIG_MIPS_FPU_EMU
+
 /* Function which emulates a floating point instruction. */
 
 static int fpu_emu(struct pt_regs *, struct mips_fpu_struct *,
@@ -67,10 +73,6 @@ static int fpux_emu(struct pt_regs *,
 	struct mips_fpu_struct *, mips_instruction);
 #endif
 
-/* Further private data for which no space exists in mips_fpu_struct */
-
-struct mips_fpu_emulator_stats fpuemustats;
-
 /* Control registers */
 
 #define FPCREG_RID	0	/* $0  = revision id */
@@ -1277,6 +1279,13 @@ int fpu_emulator_cop1Handler(struct pt_r
 
 	return sig;
 }
+#else
+int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
+        int has_fpu)
+{
+	return 0;
+}
+#endif /* CONFIG_MIPS_FPU_EMU */
 
 #ifdef CONFIG_DEBUG_FS
 extern struct dentry *mips_debugfs_dir;
--- a/arch/mips/math-emu/dsemul.c
+++ b/arch/mips/math-emu/dsemul.c
@@ -110,6 +110,7 @@ int mips_dsemul(struct pt_regs *regs, mi
 	return SIGILL;		/* force out of emulation loop */
 }
 
+#ifdef CONFIG_MIPS_FPU_EMU
 int do_dsemulret(struct pt_regs *xcp)
 {
 	struct emuframe __user *fr;
@@ -166,3 +167,9 @@ int do_dsemulret(struct pt_regs *xcp)
 
 	return 1;
 }
+#else
+int do_dsemulret(struct pt_regs *xcp)
+{
+	return 0;
+}
+#endif /* CONFIG_MIPS_FPU_EMU */
--- a/arch/mips/math-emu/kernel_linkage.c
+++ b/arch/mips/math-emu/kernel_linkage.c
@@ -28,6 +28,7 @@
 
 #define SIGNALLING_NAN 0x7ff800007ff80000LL
 
+#ifdef CONFIG_MIPS_FPU_EMU
 void fpu_emulator_init_fpu(void)
 {
 	static int first = 1;
@@ -111,4 +112,36 @@ int fpu_emulator_restore_context32(struc
 
 	return err;
 }
-#endif
+#endif	/* CONFIG_64BIT */
+#else
+
+void fpu_emulator_init_fpu(void)
+{
+	printk(KERN_INFO "FPU emulator disabled, make sure your toolchain"
+		"was compiled with software floating point support (soft-float)\n");
+	return;
+}
+
+int fpu_emulator_save_context(struct sigcontext __user *sc)
+{
+	return 0;
+}
+
+int fpu_emulator_restore_context(struct sigcontext __user *sc)
+{
+	return 0;
+}
+
+#ifdef CONFIG_64BIT
+int fpu_emulator_save_context32(struct sigcontext32 __user *sc)
+{
+	return 0;
+}
+
+int fpu_emulator_restore_context32(struct sigcontext32 __user *sc)
+{
+	return 0;
+}
+
+#endif	/* CONFIG_64BIT */
+#endif /* CONFIG_MIPS_FPU_EMU */