target/linux/generic/patches-3.10/304-mips_disable_fpu.patch

   1 MIPS: allow disabling the kernel FPU emulator
   2
   3 This patch allows turning off the in-kernel Algorithmics
   4 FPU emulator support, which allows one to save a couple of
   5 precious blocks on an embedded system.
   6
   7 Signed-off-by: Florian Fainelli <florian@openwrt.org>
   8 --
   9 --- a/arch/mips/Kconfig
  10 +++ b/arch/mips/Kconfig
  11 @@ -976,6 +976,17 @@ config I8259
  12  config MIPS_BONITO64
  13         bool
  14
  15 +config MIPS_FPU_EMU
  16 +       bool "Enable FPU emulation"
  17 +       default y
  18 +       help
  19 +          This option allows building a kernel with or without the Algorithmics
  20 +          FPU emulator enabled. Turning off this option results in a kernel which
  21 +          does not catch floating operations exceptions. Make sure that your toolchain
  22 +          is configured to enable software floating point emulation in that case.
  23 +
  24 +          If unsure say Y here.
  25 +
  26  config MIPS_MSC
  27         bool
  28
  29 --- a/arch/mips/math-emu/Makefile
  30 +++ b/arch/mips/math-emu/Makefile
  31 @@ -2,10 +2,11 @@
  32  # Makefile for the Linux/MIPS kernel FPU emulation.
  33  #
  34
  35 -obj-y  := cp1emu.o ieee754m.o ieee754d.o ieee754dp.o ieee754sp.o ieee754.o \
  36 +obj-y  := kernel_linkage.o dsemul.o cp1emu.o
  37 +obj-$(CONFIG_MIPS_FPU_EMU)     += ieee754m.o ieee754d.o ieee754dp.o ieee754sp.o ieee754.o \
  38            ieee754xcpt.o dp_frexp.o dp_modf.o dp_div.o dp_mul.o dp_sub.o \
  39            dp_add.o dp_fsp.o dp_cmp.o dp_logb.o dp_scalb.o dp_simple.o \
  40            dp_tint.o dp_fint.o dp_tlong.o dp_flong.o sp_frexp.o sp_modf.o \
  41            sp_div.o sp_mul.o sp_sub.o sp_add.o sp_fdp.o sp_cmp.o sp_logb.o \
  42            sp_scalb.o sp_simple.o sp_tint.o sp_fint.o sp_tlong.o sp_flong.o \
  43 -          dp_sqrt.o sp_sqrt.o kernel_linkage.o dsemul.o
  44 +          dp_sqrt.o sp_sqrt.o
  45 --- a/arch/mips/math-emu/cp1emu.c
  46 +++ b/arch/mips/math-emu/cp1emu.c
  47 @@ -59,7 +59,11 @@
  48  #define __mips 4
  49
  50  /* Function which emulates a floating point instruction. */
  51 +#ifdef CONFIG_DEBUG_FS
  52 +DEFINE_PER_CPU(struct mips_fpu_emulator_stats, fpuemustats);
  53 +#endif
  54
  55 +#ifdef CONFIG_MIPS_FPU_EMU
  56  static int fpu_emu(struct pt_regs *, struct mips_fpu_struct *,
  57         mips_instruction);
  58
  59 @@ -70,10 +74,6 @@ static int fpux_emu(struct pt_regs *,
  60
  61  /* Further private data for which no space exists in mips_fpu_struct */
  62
  63 -#ifdef CONFIG_DEBUG_FS
  64 -DEFINE_PER_CPU(struct mips_fpu_emulator_stats, fpuemustats);
  65 -#endif
  66 -
  67  /* Control registers */
  68
  69  #define FPCREG_RID     0       /* $0  = revision id */
  70 @@ -82,11 +82,15 @@ DEFINE_PER_CPU(struct mips_fpu_emulator_
  71  /* Determine rounding mode from the RM bits of the FCSR */
  72  #define modeindex(v) ((v) & FPU_CSR_RM)
  73
  74 +#endif /* CONFIG_MIPS_FPU_EMU */
  75 +
  76  /* microMIPS bitfields */
  77  #define MM_POOL32A_MINOR_MASK  0x3f
  78  #define MM_POOL32A_MINOR_SHIFT 0x6
  79  #define MM_MIPS32_COND_FC      0x30
  80
  81 +#ifdef CONFIG_MIPS_FPU_EMU
  82 +
  83  /* Convert Mips rounding mode (0..3) to IEEE library modes. */
  84  static const unsigned char ieee_rm[4] = {
  85         [FPU_CSR_RN] = IEEE754_RN,
  86 @@ -116,9 +120,13 @@ static const unsigned int fpucondbit[8]
  87  };
  88  #endif
  89
  90 +#endif /* CONFIG_MIPS_FPU_EMU */
  91 +
  92  /* (microMIPS) Convert 16-bit register encoding to 32-bit register encoding. */
  93  static const unsigned int reg16to32map[8] = {16, 17, 2, 3, 4, 5, 6, 7};
  94
  95 +#ifdef CONFIG_MIPS_FPU_EMU
  96 +
  97  /* (microMIPS) Convert certain microMIPS instructions to MIPS32 format. */
  98  static const int sd_format[] = {16, 17, 0, 0, 0, 0, 0, 0};
  99  static const int sdps_format[] = {16, 17, 22, 0, 0, 0, 0, 0};
 100 @@ -463,6 +471,8 @@ static int microMIPS32_to_MIPS32(union m
 101         return 0;
 102  }
 103
 104 +#endif /* CONFIG_MIPS_FPU_EMU */
 105 +
 106  int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 107                      unsigned long *contpc)
 108  {
 109 @@ -667,6 +677,8 @@ int mm_isBranchInstr(struct pt_regs *reg
 110         return 0;
 111  }
 112
 113 +#ifdef CONFIG_MIPS_FPU_EMU
 114 +
 115  /*
 116   * Redundant with logic already in kernel/branch.c,
 117   * embedded in compute_return_epc.  At some point,
 118 @@ -2102,7 +2114,6 @@ int fpu_emulator_cop1Handler(struct pt_r
 119
 120         return sig;
 121  }
 122 -
 123  #ifdef CONFIG_DEBUG_FS
 124
 125  static int fpuemu_stat_get(void *data, u64 *val)
 126 @@ -2151,4 +2162,11 @@ static int __init debugfs_fpuemu(void)
 127         return 0;
 128  }
 129  __initcall(debugfs_fpuemu);
 130 -#endif
 131 +#endif /* CONFIG_DEBUGFS */
 132 +#else
 133 +int fpu_emulator_cop1Handler(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
 134 +        int has_fpu, void *__user *fault_addr)
 135 +{
 136 +       return 0;
 137 +}
 138 +#endif /* CONFIG_MIPS_FPU_EMU */
 139 --- a/arch/mips/math-emu/dsemul.c
 140 +++ b/arch/mips/math-emu/dsemul.c
 141 @@ -119,6 +119,7 @@ int mips_dsemul(struct pt_regs *regs, mi
 142         return SIGILL;          /* force out of emulation loop */
 143  }
 144
 145 +#ifdef CONFIG_MIPS_FPU_EMU
 146  int do_dsemulret(struct pt_regs *xcp)
 147  {
 148         struct emuframe __user *fr;
 149 @@ -182,3 +183,9 @@ int do_dsemulret(struct pt_regs *xcp)
 150
 151         return 1;
 152  }
 153 +#else
 154 +int do_dsemulret(struct pt_regs *xcp)
 155 +{
 156 +       return 0;
 157 +}
 158 +#endif /* CONFIG_MIPS_FPU_EMU */
 159 --- a/arch/mips/math-emu/kernel_linkage.c
 160 +++ b/arch/mips/math-emu/kernel_linkage.c
 161 @@ -29,6 +29,7 @@
 162
 163  #define SIGNALLING_NAN 0x7ff800007ff80000LL
 164
 165 +#ifdef CONFIG_MIPS_FPU_EMU
 166  void fpu_emulator_init_fpu(void)
 167  {
 168         static int first = 1;
 169 @@ -112,4 +113,36 @@ int fpu_emulator_restore_context32(struc
 170
 171         return err;
 172  }
 173 -#endif
 174 +#endif /* CONFIG_64BIT */
 175 +#else
 176 +
 177 +void fpu_emulator_init_fpu(void)
 178 +{
 179 +       printk(KERN_INFO "FPU emulator disabled, make sure your toolchain"
 180 +               "was compiled with software floating point support (soft-float)\n");
 181 +       return;
 182 +}
 183 +
 184 +int fpu_emulator_save_context(struct sigcontext __user *sc)
 185 +{
 186 +       return 0;
 187 +}
 188 +
 189 +int fpu_emulator_restore_context(struct sigcontext __user *sc)
 190 +{
 191 +       return 0;
 192 +}
 193 +
 194 +int fpu_emulator_save_context32(struct sigcontext32 __user *sc)
 195 +{
 196 +       return 0;
 197 +}
 198 +
 199 +int fpu_emulator_restore_context32(struct sigcontext32 __user *sc)
 200 +{
 201 +       return 0;
 202 +}
 203 +
 204 +#ifdef CONFIG_64BIT
 205 +#endif /* CONFIG_64BIT */
 206 +#endif /* CONFIG_MIPS_FPU_EMU */