1;------------------------------------------------------------------------------
2;
3; Copyright (c) 2015 - 2016, Intel Corporation. All rights reserved.<BR>
4; This program and the accompanying materials
5; are licensed and made available under the terms and conditions of the BSD License
6; which accompanies this distribution.  The full text of the license may be found at
7; http://opensource.org/licenses/bsd-license.php.
8;
9; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
10; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
11;
12; Module Name:
13;
14;   RdRand.nasm
15;
16; Abstract:
17;
18;   Generates random number through CPU RdRand instruction under 64-bit platform.
19;
20; Notes:
21;
22;------------------------------------------------------------------------------
23
24    DEFAULT REL
25    SECTION .text
26
27;------------------------------------------------------------------------------
28;  Generates a 16 bit random number through RDRAND instruction.
29;  Return TRUE if Rand generated successfully, or FALSE if not.
30;
31;  BOOLEAN EFIAPI InternalX86RdRand16 (UINT16 *Rand);
32;------------------------------------------------------------------------------
33global ASM_PFX(InternalX86RdRand16)
34ASM_PFX(InternalX86RdRand16):
35    ; rdrand   ax                  ; generate a 16 bit RN into eax,
36                                   ; CF=1 if RN generated ok, otherwise CF=0
37    db     0xf, 0xc7, 0xf0         ; rdrand r16: "0f c7 /6  ModRM:r/m(w)"
38    jc     rn16_ok                 ; jmp if CF=1
39    xor    rax, rax                ; reg=0 if CF=0
40    ret                            ; return with failure status
41rn16_ok:
42    mov    [rcx], ax
43    mov    rax,  1
44    ret
45
46;------------------------------------------------------------------------------
47;  Generates a 32 bit random number through RDRAND instruction.
48;  Return TRUE if Rand generated successfully, or FALSE if not.
49;
50;  BOOLEAN EFIAPI InternalX86RdRand32 (UINT32 *Rand);
51;------------------------------------------------------------------------------
52global ASM_PFX(InternalX86RdRand32)
53ASM_PFX(InternalX86RdRand32):
54    ; rdrand   eax                 ; generate a 32 bit RN into eax,
55                                   ; CF=1 if RN generated ok, otherwise CF=0
56    db     0xf, 0xc7, 0xf0         ; rdrand r32: "0f c7 /6  ModRM:r/m(w)"
57    jc     rn32_ok                 ; jmp if CF=1
58    xor    rax, rax                ; reg=0 if CF=0
59    ret                            ; return with failure status
60rn32_ok:
61    mov    [rcx], eax
62    mov    rax,  1
63    ret
64
65;------------------------------------------------------------------------------
66;  Generates a 64 bit random number through one RDRAND instruction.
67;  Return TRUE if Rand generated successfully, or FALSE if not.
68;
69;  BOOLEAN EFIAPI InternalX86RdRand64 (UINT64 *Random);
70;------------------------------------------------------------------------------
71global ASM_PFX(InternalX86RdRand64)
72ASM_PFX(InternalX86RdRand64):
73    ; rdrand   rax                 ; generate a 64 bit RN into rax,
74                                   ; CF=1 if RN generated ok, otherwise CF=0
75    db     0x48, 0xf, 0xc7, 0xf0   ; rdrand r64: "REX.W + 0f c7 /6 ModRM:r/m(w)"
76    jc     rn64_ok                 ; jmp if CF=1
77    xor    rax, rax                ; reg=0 if CF=0
78    ret                            ; return with failure status
79rn64_ok:
80    mov    [rcx], rax
81    mov    rax, 1
82    ret
83
84