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 #  define OUT edi
  48         pushreg ebx
  49         pushreg edi
  50         mov     OUT, [SP + 12]
  51         mov     eax, [SP + 16]
  52         mov     ecx, [SP + 20]
  53 #endif
  54 #if CPUFAM_AMD64 && ABI_SYSV
  55 #  define OUT rdi
  56         pushreg rbx
  57         mov     eax, esi
  58         mov     ecx, edx
  59 #endif
  60 #if CPUFAM_AMD64 && ABI_WIN
  61 #  define OUT r9
  62         pushreg rbx
  63         mov     OUT, rcx
  64         mov     eax, edx
  65         mov     ecx, r8d
  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
 124 #undef OUT
 125 ENDFUNC
 126
 127 ///--------------------------------------------------------------------------
 128 /// Probing for XMM register availability.
 129
 130 FUNC(dispatch_x86ish_xmmregisters_p)
 131         // Enter with no arguments.  Return nonzero if the XMM registers are
 132         // usable.
 133
 134         pushreg BP
 135         setfp
 136         stalloc 512
 137         and     SP, ~15
 138   endprologue
 139
 140         // Save the floating point and SIMD registers, and try to clobber
 141         // xmm0.
 142         lea     DX, [SP + 160]
 143         fxsave  [SP]
 144         mov     eax, [DX]
 145         xor     dword ptr [DX], 0xaaaa5555
 146         fxrstor [SP]
 147
 148         // Save them again, and read back the low word of xmm0.  Undo the
 149         // clobbering and restore.
 150         fxsave  [SP]
 151         mov     ecx, [DX]
 152         mov     [DX], eax
 153         fxrstor [SP]
 154
 155         // The register are live if we read different things.
 156         xor     eax, ecx
 157
 158         // Done.
 159         dropfp
 160         popreg  BP
 161         ret
 162 ENDFUNC
 163
 164 ///--------------------------------------------------------------------------
 165 /// Checking extended control registers.
 166
 167 FUNC(dispatch_x86ish_xgetbv)
 168         // Call with two arguments: a pointer Z_OUT to 8 bytes of output space, and
 169         // a 32-bit integer C.  Read the 64-bit value of XCR(C), and store it
 170         // at Z_OUT.
 171
 172 #if CPUFAM_X86
 173 #  define Z_OUT edi
 174         pushreg edi
 175         mov     Z_OUT, [esp + 8]
 176         mov     ecx, [esp + 12]
 177 #endif
 178 #if CPUFAM_AMD64 && ABI_SYSV
 179 #  define Z_OUT rdi
 180         mov     ecx, esi
 181 #endif
 182 #if CPUFAM_AMD64 && ABI_WIN
 183 #  define Z_OUT r8
 184         mov     r8, rcx
 185         mov     ecx, edx
 186 #endif
 187   endprologue
 188
 189         xgetbv
 190         mov     [Z_OUT + 0], eax
 191         mov     [Z_OUT + 4], edx
 192
 193 #if CPUFAM_X86
 194         popreg  edi
 195 #endif
 196         ret
 197
 198 #undef Z_OUT
 199 ENDFUNC
 200
 201 ///--------------------------------------------------------------------------
 202 /// Checking `rdrand'.
 203
 204 FUNC(dispatch_x86ish_rdrand)
 205         // Enter with two arguments: a code OP requesting either `rdrand' (0)
 206         // or `rdseed' (1), and a pointer X_OUT to a 32-bit word.  Try to
 207         // generate a random word using the requested instruction'.  If
 208         // successful, set *X_OUT to the generated word, and return zero;
 209         // otherwise, return -1.
 210
 211 #if CPUFAM_X86
 212 #  define OP eax
 213 #  define X_OUT edx
 214 #  define COUNT ecx
 215         mov     OP, [SP + 4]
 216         mov     X_OUT, [SP + 8]
 217 #endif
 218 #if CPUFAM_AMD64 && ABI_SYSV
 219 #  define OP edi
 220 #  define X_OUT rsi
 221 #  define COUNT ecx
 222 #endif
 223 #if CPUFAM_AMD64 && ABI_WIN
 224 #  define OP rcx
 225 #  define X_OUT rdx
 226 #  define COUNT r8d
 227 #endif
 228   endprologue
 229
 230         cmp     OP, 0
 231         mov     COUNT, 16               // fairly persistent
 232         jne     1f
 233
 234 0:      rdrand  eax
 235         jc      9f
 236         dec     COUNT
 237         jnz     0b
 238         jmp     8f
 239
 240 1:      rdseed  eax
 241         jc      9f
 242         dec     COUNT
 243         jnz     1b
 244         jmp     8f
 245
 246         // Failed to come up with a random value.
 247 8:      mov     eax, -1
 248         ret
 249
 250         // Success.
 251 9:      mov     [X_OUT], eax
 252         xor     eax, eax
 253         ret
 254
 255 #undef X_OUT
 256 #undef COUNT
 257
 258 ENDFUNC
 259
 260 ///----- That's all, folks --------------------------------------------------