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, [esp + 12]
  50         mov     eax, [esp + 16]
  51         mov     ecx, [esp + 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.
  71         pushf
  72         pop     R_d(r)                  // current flags in d
  73
  74         or      R_d(r), EFLAGS_ID       // force the id bit on and check it
  75         push    R_d(r)
  76         popf
  77         pushf
  78         pop     R_d(r)
  79         test    edx, EFLAGS_ID
  80         jz      8f
  81
  82         and     R_d(r), ~EFLAGS_ID      // force the id bit off and check it
  83         push    R_d(r)
  84         popf
  85         pushf
  86         pop     R_d(r)
  87         test    edx, EFLAGS_ID
  88         jnz     8f
  89
  90         // OK, that seemed to work.
  91         cpuid
  92
  93         mov     [OUT + 0], eax
  94         mov     [OUT + 4], ebx
  95         mov     [OUT + 8], ecx
  96         mov     [OUT + 12], edx
  97         xor     eax, eax
  98
  99         // We're done.
 100 9:
 101 #if CPUFAM_X86
 102         popreg  edi
 103         popreg  ebx
 104 #endif
 105 #if CPUFAM_AMD64
 106         popreg  rbx
 107 #endif
 108         ret
 109
 110         // Failed.
 111 8:      xor     eax, eax
 112         mov     [OUT + 0], eax
 113         mov     [OUT + 4], eax
 114         mov     [OUT + 8], eax
 115         mov     [OUT + 12], eax
 116         mov     eax, -1
 117         jmp     9b
 118 ENDFUNC
 119
 120 ///--------------------------------------------------------------------------
 121 /// Probing for XMM register availability.
 122
 123 FUNC(dispatch_x86ish_xmmregisters_p)
 124         // Enter with no arguments.  Return nonzero if the XMM registers are
 125         // usable.
 126
 127         pushreg R_bp(r)
 128         setfp
 129         stalloc 512
 130         and     R_sp(r), ~15
 131   endprologue
 132
 133         // Save the floating point and SIMD registers, and try to clobber
 134         // xmm0.
 135         fxsave  [R_sp(r)]
 136         mov     eax, [R_sp(r) + 160]
 137         xor     dword ptr [R_sp(r) + 160], 0xaaaa5555
 138         fxrstor [R_sp(r)]
 139
 140         // Save them again, and read back the low word of xmm0.  Undo the
 141         // clobbering and restore.
 142         fxsave  [R_sp(r)]
 143         mov     ecx, [R_sp(r) + 160]
 144         mov     [R_sp(r) + 160], eax
 145         fxrstor [R_sp(r)]
 146
 147         // The register are live if we read different things.
 148         xor     eax, ecx
 149
 150         // Done.
 151         dropfp
 152         popreg  R_bp(r)
 153         ret
 154 ENDFUNC
 155
 156 ///----- That's all, folks --------------------------------------------------