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 32-bit platform.
19;
20; Notes:
21;
22;------------------------------------------------------------------------------
23
24SECTION .text
25
26;------------------------------------------------------------------------------
27;  Generates a 16 bit random number through RDRAND instruction.
28;  Return TRUE if Rand generated successfully, or FALSE if not.
29;
30;  BOOLEAN EFIAPI InternalX86RdRand16 (UINT16 *Rand);
31;------------------------------------------------------------------------------
32global ASM_PFX(InternalX86RdRand16)
33ASM_PFX(InternalX86RdRand16):
34    ; rdrand   ax                  ; generate a 16 bit RN into ax
35                                   ; CF=1 if RN generated ok, otherwise CF=0
36    db     0xf, 0xc7, 0xf0         ; rdrand r16: "0f c7 /6  ModRM:r/m(w)"
37    jc     rn16_ok                 ; jmp if CF=1
38    xor    eax, eax                ; reg=0 if CF=0
39    ret                            ; return with failure status
40rn16_ok:
41    mov    edx, dword [esp + 4]
42    mov    [edx], ax
43    mov    eax,  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    eax, eax                ; reg=0 if CF=0
59    ret                            ; return with failure status
60rn32_ok:
61    mov    edx, dword [esp + 4]
62    mov    [edx], eax
63    mov    eax,  1
64    ret
65
66;------------------------------------------------------------------------------
67;  Generates a 64 bit random number through RDRAND instruction.
68;  Return TRUE if Rand generated successfully, or FALSE if not.
69;
70;  BOOLEAN EFIAPI InternalX86RdRand64 (UINT64 *Rand);
71;------------------------------------------------------------------------------
72global ASM_PFX(InternalX86RdRand64)
73ASM_PFX(InternalX86RdRand64):
74    ; rdrand   eax                 ; generate a 32 bit RN into eax
75                                   ; CF=1 if RN generated ok, otherwise CF=0
76    db     0xf, 0xc7, 0xf0         ; rdrand r32: "0f c7 /6  ModRM:r/m(w)"
77    jnc    rn64_ret                ; jmp if CF=0
78    mov    edx, dword [esp + 4]
79    mov    [edx], eax
80
81    db     0xf, 0xc7, 0xf0         ; generate another 32 bit RN
82    jnc    rn64_ret                ; jmp if CF=0
83    mov    [edx + 4], eax
84
85    mov    eax,  1
86    ret
87rn64_ret:
88    xor    eax, eax
89    ret                            ; return with failure status
90
91