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
@@ -976,6 +976,17 @@ 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
@@ -2,10 +2,11 @@
# 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
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -59,7 +59,11 @@
#define __mips 4
/* Function which emulates a floating point instruction. */
+#ifdef CONFIG_DEBUG_FS
+DEFINE_PER_CPU(struct mips_fpu_emulator_stats, fpuemustats);
+#endif
+#ifdef CONFIG_MIPS_FPU_EMU
static int fpu_emu(struct pt_regs *, struct mips_fpu_struct *,
mips_instruction);
@@ -70,10 +74,6 @@ static int fpux_emu(struct pt_regs *,
/* Further private data for which no space exists in mips_fpu_struct */
-#ifdef CONFIG_DEBUG_FS
-DEFINE_PER_CPU(struct mips_fpu_emulator_stats, fpuemustats);
-#endif
-
/* Control registers */
#define FPCREG_RID 0 /* $0 = revision id */
@@ -82,11 +82,15 @@ DEFINE_PER_CPU(struct mips_fpu_emulator_
/* Determine rounding mode from the RM bits of the FCSR */
#define modeindex(v) ((v) & FPU_CSR_RM)
+#endif /* CONFIG_MIPS_FPU_EMU */
+
/* microMIPS bitfields */
#define MM_POOL32A_MINOR_MASK 0x3f
#define MM_POOL32A_MINOR_SHIFT 0x6
#define MM_MIPS32_COND_FC 0x30
+#ifdef CONFIG_MIPS_FPU_EMU
+
/* Convert Mips rounding mode (0..3) to IEEE library modes. */
static const unsigned char ieee_rm[4] = {
[FPU_CSR_RN] = IEEE754_RN,
@@ -116,9 +120,13 @@ static const unsigned int fpucondbit[8]
};
#endif
+#endif /* CONFIG_MIPS_FPU_EMU */
+
/* (microMIPS) Convert 16-bit register encoding to 32-bit register encoding. */
static const unsigned int reg16to32map[8] = {16, 17, 2, 3, 4, 5, 6, 7};
+#ifdef CONFIG_MIPS_FPU_EMU
+
/* (microMIPS) Convert certain microMIPS instructions to MIPS32 format. */
static const int sd_format[] = {16, 17, 0, 0, 0, 0, 0, 0};
static const int sdps_format[] = {16, 17, 22, 0, 0, 0, 0, 0};
@@ -463,6 +471,8 @@ static int microMIPS32_to_MIPS32(union m
return 0;
}
+#endif /* CONFIG_MIPS_FPU_EMU */
+
int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
unsigned long *contpc)
{
@@ -667,6 +677,8 @@ int mm_isBranchInstr(struct pt_regs *reg
return 0;
}
+#ifdef CONFIG_MIPS_FPU_EMU
+
/*
* Redundant with logic already in kernel/branch.c,
* embedded in compute_return_epc. At some point,
@@ -2102,7 +2114,6 @@ int fpu_emulator_cop1Handler(struct pt_r
return sig;
}
-
#ifdef CONFIG_DEBUG_FS
static int fpuemu_stat_get(void *data, u64 *val)
@@ -2151,4 +2162,11 @@ static int __init debugfs_fpuemu(void)
return 0;
}
__initcall(debugfs_fpuemu);
-#endif
+#endif /* CONFIG_DEBUGFS */
+#else
+int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
+ int has_fpu, void *__user *fault_addr)
+{
+ return 0;
+}
+#endif /* CONFIG_MIPS_FPU_EMU */
--- a/arch/mips/math-emu/dsemul.c
+++ b/arch/mips/math-emu/dsemul.c
@@ -119,6 +119,7 @@ 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;
@@ -182,3 +183,9 @@ 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
@@ -29,6 +29,7 @@
#define SIGNALLING_NAN 0x7ff800007ff80000LL
+#ifdef CONFIG_MIPS_FPU_EMU
void fpu_emulator_init_fpu(void)
{
static int first = 1;
@@ -112,4 +113,36 @@ 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;
+}
+
+int fpu_emulator_save_context32(struct sigcontext32 __user *sc)
+{
+ return 0;
+}
+
+int fpu_emulator_restore_context32(struct sigcontext32 __user *sc)
+{
+ return 0;
+}
+
+#ifdef CONFIG_64BIT
+#endif /* CONFIG_64BIT */
+#endif /* CONFIG_MIPS_FPU_EMU */