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 @@ -981,6 +981,17 @@ 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 +2,12 @@
  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
  37 +
  38 +obj-$(CONFIG_MIPS_FPU_EMU)     += ieee754m.o ieee754d.o ieee754dp.o ieee754sp.o ieee754.o \
  39            ieee754xcpt.o dp_frexp.o dp_modf.o dp_div.o dp_mul.o dp_sub.o \
  40            dp_add.o dp_fsp.o dp_cmp.o dp_logb.o dp_scalb.o dp_simple.o \
  41            dp_tint.o dp_fint.o dp_tlong.o dp_flong.o sp_frexp.o sp_modf.o \
  42            sp_div.o sp_mul.o sp_sub.o sp_add.o sp_fdp.o sp_cmp.o sp_logb.o \
  43            sp_scalb.o sp_simple.o sp_tint.o sp_fint.o sp_tlong.o sp_flong.o \
  44 -          dp_sqrt.o sp_sqrt.o kernel_linkage.o dsemul.o
  45 +          dp_sqrt.o sp_sqrt.o dsemul.o cp1emu.o
  46 --- a/arch/mips/math-emu/kernel_linkage.c
  47 +++ b/arch/mips/math-emu/kernel_linkage.c
  48 @@ -29,6 +29,7 @@
  49
  50  #define SIGNALLING_NAN 0x7ff800007ff80000LL
  51
  52 +#ifdef CONFIG_MIPS_FPU_EMU
  53  void fpu_emulator_init_fpu(void)
  54  {
  55         static int first = 1;
  56 @@ -113,3 +114,36 @@ int fpu_emulator_restore_context32(struc
  57         return err;
  58  }
  59  #endif
  60 +
  61 +#else
  62 +
  63 +void fpu_emulator_init_fpu(void)
  64 +{
  65 +       printk(KERN_INFO "FPU emulator disabled, make sure your toolchain"
  66 +               "was compiled with software floating point support (soft-float)\n");
  67 +       return;
  68 +}
  69 +
  70 +int fpu_emulator_save_context(struct sigcontext __user *sc)
  71 +{
  72 +       return 0;
  73 +}
  74 +
  75 +int fpu_emulator_restore_context(struct sigcontext __user *sc)
  76 +{
  77 +       return 0;
  78 +}
  79 +
  80 +#ifdef CONFIG_64BIT
  81 +int fpu_emulator_save_context32(struct sigcontext32 __user *sc)
  82 +{
  83 +       return 0;
  84 +}
  85 +
  86 +int fpu_emulator_restore_context32(struct sigcontext32 __user *sc)
  87 +{
  88 +       return 0;
  89 +}
  90 +#endif /* CONFIG_64BIT */
  91 +
  92 +#endif /* CONFIG_MIPS_FPU_EMU */
  93 --- a/arch/mips/include/asm/fpu_emulator.h
  94 +++ b/arch/mips/include/asm/fpu_emulator.h
  95 @@ -27,6 +27,8 @@
  96  #include <asm/inst.h>
  97  #include <asm/local.h>
  98
  99 +#ifdef CONFIG_MIPS_FPU_EMU
 100 +
 101  #ifdef CONFIG_DEBUG_FS
 102
 103  struct mips_fpu_emulator_stats {
 104 @@ -60,6 +62,38 @@ extern int fpu_emulator_cop1Handler(stru
 105  int process_fpemu_return(int sig, void __user *fault_addr);
 106  int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
 107                      unsigned long *contpc);
 108 +#else
 109 +static inline int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
 110 +                             unsigned long cpc)
 111 +{
 112 +       return 0;
 113 +}
 114 +
 115 +static inline int do_dsemulret(struct pt_regs *xcp)
 116 +{
 117 +       return 0;
 118 +}
 119 +
 120 +static inline int fpu_emulator_cop1Handler(struct pt_regs *xcp,
 121 +                                          struct mips_fpu_struct *ctx,
 122 +                                          int has_fpu,
 123 +                                          void *__user *fault_addr)
 124 +{
 125 +       return 0;
 126 +}
 127 +
 128 +static inline int process_fpemu_return(int sig, void __user *fault_addr)
 129 +{
 130 +       return -EINVAL;
 131 +}
 132 +
 133 +static inline int mm_isBranchInstr(struct pt_regs *regs,
 134 +                                  struct mm_decoded_insn dec_insn,
 135 +                                  unsigned long *contpc)
 136 +{
 137 +       return 0;
 138 +}
 139 +#endif /* CONFIG_MIPS_FPU_EMU */
 140
 141  /*
 142   * Instruction inserted following the badinst to further tag the sequence
 143 --- a/arch/mips/kernel/traps.c
 144 +++ b/arch/mips/kernel/traps.c
 145 @@ -684,6 +684,7 @@ asmlinkage void do_ov(struct pt_regs *re
 146         force_sig_info(SIGFPE, &info, current);
 147  }
 148
 149 +#ifdef CONFIG_MIPS_FPU_EMU
 150  int process_fpemu_return(int sig, void __user *fault_addr)
 151  {
 152         if (sig == SIGSEGV || sig == SIGBUS) {
 153 @@ -707,6 +708,7 @@ int process_fpemu_return(int sig, void _
 154                 return 0;
 155         }
 156  }
 157 +#endif /* CONFIG_MIPS_FPU_EMU */
 158
 159  /*
 160   * XXX Delayed fp exceptions when doing a lazy ctx switch XXX