mdw@git.distorted.org.uk Git - catacomb/blob - base/dispatch-x86ish.S

   1 /// -*- mode: asm; asm-comment-char: ?/ -*-
   2 ///
   3 /// CPU dispatch support for x86
   4 ///
   5 /// (c) 2019 Straylight/Edgeware
   6 ///
   7
   8 ///----- Licensing notice ---------------------------------------------------
   9 ///
  10 /// This file is part of Catacomb.
  11 ///
  12 /// Catacomb is free software: you can redistribute it and/or modify it
  13 /// under the terms of the GNU Library General Public License as published
  14 /// by the Free Software Foundation; either version 2 of the License, or
  15 /// (at your option) any later version.
  16 ///
  17 /// Catacomb is distributed in the hope that it will be useful, but
  18 /// WITHOUT ANY WARRANTY; without even the implied warranty of
  19 /// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20 /// Library General Public License for more details.
  21 ///
  22 /// You should have received a copy of the GNU Library General Public
  23 /// License along with Catacomb.  If not, write to the Free Software
  24 /// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  25 /// USA.
  26
  27 ///--------------------------------------------------------------------------
  28 /// Preliminaries.
  29
  30 #include "config.h"
  31 #include "asm-common.h"
  32
  33         EFLAGS_ID = 1 << 21
  34
  35         .text
  36
  37 ///--------------------------------------------------------------------------
  38 /// Probing for CPUID.
  39
  40 FUNC(dispatch_x86ish_cpuid)
  41         // Enter with a pointer to 16 bytes of storage for the output A, B,
  42         // C, D values in the first argument, and input A and C values in the
  43         // second and third.  Fill the output buffer with `cpuid' results and
  44         // return zero if we can; otherwise fill with zero and return -1.
  45
  46 #if CPUFAM_X86
  47         pushreg ebx
  48         pushreg edi
  49         mov     edi, [SP + 12]
  50         mov     eax, [SP + 16]
  51         mov     ecx, [SP + 20]
  52 #  define OUT edi
  53 #endif
  54 #if CPUFAM_AMD64 && ABI_SYSV
  55         pushreg rbx
  56         mov     eax, esi
  57         mov     ecx, edx
  58 #  define OUT rdi
  59 #endif
  60 #if CPUFAM_AMD64 && ABI_WIN
  61         pushreg rbx
  62         mov     r9, rcx
  63         mov     eax, edx
  64         mov     ecx, r8d
  65 #  define OUT r9
  66 #endif
  67   endprologue
  68
  69         // First, check that this is even a thing, using the complicated
  70         // dance with the flags register.  This is unnecessary on AMD64,
  71         // which postdates the introduction of `cpuid'.
  72 #if CPUFAM_X86
  73         pushf
  74         pop     DX                      // current flags in d
  75
  76         or      DX, EFLAGS_ID           // force the id bit on and check it
  77         push    DX
  78         popf
  79         pushf
  80         pop     DX
  81         test    edx, EFLAGS_ID
  82         jz      8f
  83
  84         and     DX, ~EFLAGS_ID          // force the id bit off and check it
  85         push    DX
  86         popf
  87         pushf
  88         pop     DX
  89         test    edx, EFLAGS_ID
  90         jnz     8f
  91 #endif
  92
  93         // OK, that seemed to work.
  94         cpuid
  95
  96         mov     [OUT + 0], eax
  97         mov     [OUT + 4], ebx
  98         mov     [OUT + 8], ecx
  99         mov     [OUT + 12], edx
 100         xor     eax, eax
 101
 102         // We're done.
 103 9:
 104 #if CPUFAM_X86
 105         popreg  edi
 106         popreg  ebx
 107 #endif
 108 #if CPUFAM_AMD64
 109         popreg  rbx
 110 #endif
 111         ret
 112
 113         // Failed.
 114 #if CPUFAM_X86
 115 8:      xor     eax, eax
 116         mov     [OUT + 0], eax
 117         mov     [OUT + 4], eax
 118         mov     [OUT + 8], eax
 119         mov     [OUT + 12], eax
 120         mov     eax, -1
 121         jmp     9b
 122 #endif
 123 ENDFUNC
 124
 125 ///--------------------------------------------------------------------------
 126 /// Probing for XMM register availability.
 127
 128 FUNC(dispatch_x86ish_xmmregisters_p)
 129         // Enter with no arguments.  Return nonzero if the XMM registers are
 130         // usable.
 131
 132         pushreg BP
 133         setfp
 134         stalloc 512
 135         and     SP, ~15
 136   endprologue
 137
 138         // Save the floating point and SIMD registers, and try to clobber
 139         // xmm0.
 140         lea     DX, [SP + 160]
 141         fxsave  [SP]
 142         mov     eax, [DX]
 143         xor     dword ptr [DX], 0xaaaa5555
 144         fxrstor [SP]
 145
 146         // Save them again, and read back the low word of xmm0.  Undo the
 147         // clobbering and restore.
 148         fxsave  [SP]
 149         mov     ecx, [DX]
 150         mov     [DX], eax
 151         fxrstor [SP]
 152
 153         // The register are live if we read different things.
 154         xor     eax, ecx
 155
 156         // Done.
 157         dropfp
 158         popreg  BP
 159         ret
 160 ENDFUNC
 161
 162 ///--------------------------------------------------------------------------
 163 /// Checking extended control registers.
 164
 165 FUNC(dispatch_x86ish_xgetbv)
 166         // Call with two arguments: a pointer Z_OUT to 8 bytes of output space, and
 167         // a 32-bit integer C.  Read the 64-bit value of XCR(C), and store it
 168         // at Z_OUT.
 169
 170 #if CPUFAM_X86
 171 #  define Z_OUT edi
 172         pushreg edi
 173         mov     edi, [esp + 8]
 174         mov     ecx, [esp + 12]
 175 #endif
 176 #if CPUFAM_AMD64 && ABI_SYSV
 177 #  define Z_OUT rdi
 178         mov     ecx, esi
 179 #endif
 180 #if CPUFAM_AMD64 && ABI_WIN
 181 #  define Z_OUT r8
 182         mov     r8, rcx
 183         mov     ecx, edx
 184 #endif
 185   endprologue
 186
 187         xgetbv
 188         mov     [Z_OUT + 0], eax
 189         mov     [Z_OUT + 4], edx
 190
 191 #if CPUFAM_X86
 192         popreg  edi
 193 #endif
 194         ret
 195
 196 #undef Z_OUT
 197 ENDFUNC
 198
 199 ///--------------------------------------------------------------------------
 200 /// Checking `rdrand'.
 201
 202 FUNC(dispatch_x86ish_rdrand)
 203         // Enter with two arguments: a code OP requesting either `rdrand' (0)
 204         // or `rdseed' (1), and a pointer X_OUT to a 32-bit word.  Try to
 205         // generate a random word using the requested instruction'.  If
 206         // successful, set *X_OUT to the generated word, and return zero;
 207         // otherwise, return -1.
 208
 209 #if CPUFAM_X86
 210 #  define OP eax
 211 #  define X_OUT edx
 212 #  define COUNT ecx
 213         mov     OP, [SP + 4]
 214         mov     X_OUT, [SP + 8]
 215 #endif
 216 #if CPUFAM_AMD64 && ABI_SYSV
 217 #  define OP edi
 218 #  define X_OUT rsi
 219 #  define COUNT ecx
 220 #endif
 221 #if CPUFAM_AMD64 && ABI_WIN
 222 #  define OP rcx
 223 #  define X_OUT rdx
 224 #  define COUNT r8d
 225 #endif
 226   endprologue
 227
 228         cmp     OP, 0
 229         mov     COUNT, 16               // fairly persistent
 230         jne     1f
 231
 232 0:      rdrand  eax
 233         jc      9f
 234         dec     COUNT
 235         jnz     0b
 236         jmp     8f
 237
 238 1:      rdseed  eax
 239         jc      9f
 240         dec     COUNT
 241         jnz     1b
 242         jmp     8f
 243
 244         // Failed to come up with a random value.
 245 8:      mov     eax, -1
 246         ret
 247
 248         // Success.
 249 9:      mov     [X_OUT], eax
 250         xor     eax, eax
 251         ret
 252
 253 #undef X_OUT
 254 #undef COUNT
 255
 256 ENDFUNC
 257
 258 ///----- That's all, folks --------------------------------------------------