rdrand.asm
;; rdrand.asm - written and placed in public domain by Jeffrey Walton and Uri Blumenthal.
;; Copyright assigned to the Crypto++ project.
;; This ASM file provides RDRAND and RDSEED to downlevel Microsoft tool chains.
;; Everything "just works" under Visual Studio. Other platforms will have to
;; run MASM/MASM-64 and then link to the object files.
;; set ASFLAGS=/nologo /D_M_X86 /W3 /Cx /Zi /safeseh
;; set ASFLAGS64=/nologo /D_M_X64 /W3 /Cx /Zi
;; "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\ml.exe" %ASFLAGS% /Fo rdrand-x86.obj /c rdrand.asm
;; "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\amd64\ml64.exe" %ASFLAGS64% /Fo rdrand-x64.obj /c rdrand.asm
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TITLE MASM_RRA_GenerateBlock and MASM_RSA_GenerateBlock
SUBTITLE Microsoft specific ASM code to utilize RDRAND and RDSEED for down level Microsoft toolchains
PUBLIC MASM_RRA_GenerateBlock
PUBLIC MASM_RSA_GenerateBlock
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;; Naming convention used in rdrand.{h|cpp|asm}
;; MSC = Microsoft Compiler (and compatibles)
;; GCC = GNU Compiler (and compatibles)
;; ALL = MSC and GCC (and compatibles)
;; RRA = RDRAND, Assembly
;; RSA = RDSEED, Assembly
;; RRI = RDRAND, Intrinsic
;; RSA = RDSEED, Intrinsic
;; Caller/Callee Saved Registers
;; https://msdn.microsoft.com/en-us/library/6t169e9c.aspx
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;; C/C++ Function prototypes
;; X86:
;; extern "C" int MASM_RRA_GenerateBlock(byte* ptr, size_t size, unsigned int safety);
;; X64:
;; extern "C" int __fastcall MASM_RRA_GenerateBlock(byte* ptr, size_t size, unsigned int safety);
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;; Return values
RDRAND_SUCCESS EQU 1
RDRAND_FAILURE EQU 0
RDSEED_SUCCESS EQU 1
RDSEED_FAILURE EQU 0
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IFDEF _M_X86 ;; Set via the command line
.486
.MODEL FLAT
ENDIF
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IFDEF _M_X86 ;; Set via the command line
.CODE
ALIGN 8
OPTION LANGUAGE:C
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
;; Base relative (in): arg1, byte* buffer
;; Base relative (in): arg2, size_t bsize
;; Base relative (in): arg3, unsigned int safety
;; EAX (out): success (1), failure (0)
MASM_RRA_GenerateBlock PROC arg1:DWORD,arg2:DWORD,arg3:DWORD
MWSIZE EQU 04h ;; machine word size
buffer EQU edi
bsize EQU edx
safety EQU ecx
Load_Arguments:
mov buffer, arg1
mov bsize, arg2
mov safety, arg3
Validate_Pointer:
cmp buffer, 0
je GenerateBlock_PreRet
;; Top of While loop
GenerateBlock_Top:
;; Check remaining size
cmp bsize, 0
je GenerateBlock_Success
Call_RDRAND_EAX:
;; RDRAND is not available prior to VS2012. Just emit
;; the byte codes using DB. This is `rdrand eax`.
DB 0Fh, 0C7h, 0F0h
;; If CF=1, the number returned by RDRAND is valid.
;; If CF=0, a random number was not available.
jc RDRAND_succeeded
RDRAND_failed:
;; Exit if we've reached the limit
cmp safety, 0
je GenerateBlock_Failure
dec safety
jmp GenerateBlock_Top
RDRAND_succeeded:
cmp bsize, MWSIZE
jb Partial_Machine_Word
Full_Machine_Word:
mov DWORD PTR [buffer], eax
add buffer, MWSIZE ;; No need for Intel Core 2 slow workarounds, like
sub bsize, MWSIZE ;; `lea buffer,[buffer+MWSIZE]` for faster adds
;; Continue
jmp GenerateBlock_Top
;; 1,2,3 bytes remain
Partial_Machine_Word:
;; Test bit 1 to see if size is at least 2
test bsize, 2
jz Bit_1_Not_Set
mov WORD PTR [buffer], ax
shr eax, 16
add buffer, 2
Bit_1_Not_Set:
;; Test bit 0 to see if size is at least 1
test bsize, 1
jz GenerateBlock_Success
mov BYTE PTR [buffer], al
Bit_0_Not_Set:
;; We've hit all the bits
jmp GenerateBlock_Success
GenerateBlock_PreRet:
;; Test for success (was the request completely fulfilled?)
cmp bsize, 0
je GenerateBlock_Success
GenerateBlock_Failure:
xor eax, eax
mov al, RDRAND_FAILURE
ret
GenerateBlock_Success:
xor eax, eax
mov al, RDRAND_SUCCESS
ret
MASM_RRA_GenerateBlock ENDP
ENDIF ;; _M_X86
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IFDEF _M_X64 ;; Set via the command line
.CODE
ALIGN 16
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
;; RCX (in): arg1, byte* buffer
;; RDX (in): arg2, size_t bsize
;; R8d (in): arg3, unsigned int safety
;; RAX (out): success (1), failure (0)
MASM_RRA_GenerateBlock PROC
MWSIZE EQU 08h ;; machine word size
buffer EQU rcx
bsize EQU rdx
safety EQU r8d
;; No need for Load_Arguments due to fastcall
Validate_Pointer:
;; Validate pointer
cmp buffer, 0
je GenerateBlock_PreRet
;; Top of While loop
GenerateBlock_Top:
;; Check remaining size
cmp bsize, 0
je GenerateBlock_Success
Call_RDRAND_RAX:
;; RDRAND is not available prior to VS2012. Just emit
;; the byte codes using DB. This is `rdrand rax`.
DB 048h, 0Fh, 0C7h, 0F0h
;; If CF=1, the number returned by RDRAND is valid.
;; If CF=0, a random number was not available.
jc RDRAND_succeeded
RDRAND_failed:
;; Exit if we've reached the limit
cmp safety, 0
je GenerateBlock_Failure
dec safety
jmp GenerateBlock_Top
RDRAND_succeeded:
cmp bsize, MWSIZE
jb Partial_Machine_Word
Full_Machine_Word:
mov QWORD PTR [buffer], rax
add buffer, MWSIZE
sub bsize, MWSIZE
;; Continue
jmp GenerateBlock_Top
;; 1,2,3,4,5,6,7 bytes remain
Partial_Machine_Word:
;; Test bit 2 to see if size is at least 4
test bsize, 4
jz Bit_2_Not_Set
mov DWORD PTR [buffer], eax
shr rax, 32
add buffer, 4
Bit_2_Not_Set:
;; Test bit 1 to see if size is at least 2
test bsize, 2
jz Bit_1_Not_Set
mov WORD PTR [buffer], ax
shr eax, 16
add buffer, 2
Bit_1_Not_Set:
;; Test bit 0 to see if size is at least 1
test bsize, 1
jz GenerateBlock_Success
mov BYTE PTR [buffer], al
Bit_0_Not_Set:
;; We've hit all the bits
jmp GenerateBlock_Success
GenerateBlock_PreRet:
;; Test for success (was the request completely fulfilled?)
cmp bsize, 0
je GenerateBlock_Success
GenerateBlock_Failure:
xor rax, rax
mov al, RDRAND_FAILURE
ret
GenerateBlock_Success:
xor rax, rax
mov al, RDRAND_SUCCESS
ret
MASM_RRA_GenerateBlock ENDP
ENDIF ;; _M_X64
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IFDEF _M_X86 ;; Set via the command line
.CODE
ALIGN 8
OPTION LANGUAGE:C
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
;; Base relative (in): arg1, byte* buffer
;; Base relative (in): arg2, size_t bsize
;; Base relative (in): arg3, unsigned int safety
;; EAX (out): success (1), failure (0)
MASM_RSA_GenerateBlock PROC arg1:DWORD,arg2:DWORD,arg3:DWORD
MWSIZE EQU 04h ;; machine word size
buffer EQU edi
bsize EQU edx
safety EQU ecx
Load_Arguments:
mov buffer, arg1
mov bsize, arg2
mov safety, arg3
Validate_Pointer:
cmp buffer, 0
je GenerateBlock_PreRet
;; Top of While loop
GenerateBlock_Top:
;; Check remaining size
cmp bsize, 0
je GenerateBlock_Success
Call_RDSEED_EAX:
;; RDSEED is not available prior to VS2012. Just emit
;; the byte codes using DB. This is `rdseed eax`.
DB 0Fh, 0C7h, 0F8h
;; If CF=1, the number returned by RDSEED is valid.
;; If CF=0, a random number was not available.
jc RDSEED_succeeded
RDSEED_failed:
;; Exit if we've reached the limit
cmp safety, 0
je GenerateBlock_Failure
dec safety
jmp GenerateBlock_Top
RDSEED_succeeded:
cmp bsize, MWSIZE
jb Partial_Machine_Word
Full_Machine_Word:
mov DWORD PTR [buffer], eax
add buffer, MWSIZE ;; No need for Intel Core 2 slow workarounds, like
sub bsize, MWSIZE ;; `lea buffer,[buffer+MWSIZE]` for faster adds
;; Continue
jmp GenerateBlock_Top
;; 1,2,3 bytes remain
Partial_Machine_Word:
;; Test bit 1 to see if size is at least 2
test bsize, 2
jz Bit_1_Not_Set
mov WORD PTR [buffer], ax
shr eax, 16
add buffer, 2
Bit_1_Not_Set:
;; Test bit 0 to see if size is at least 1
test bsize, 1
jz GenerateBlock_Success
mov BYTE PTR [buffer], al
Bit_0_Not_Set:
;; We've hit all the bits
jmp GenerateBlock_Success
GenerateBlock_PreRet:
;; Test for success (was the request completely fulfilled?)
cmp bsize, 0
je GenerateBlock_Success
GenerateBlock_Failure:
xor eax, eax
mov al, RDSEED_FAILURE
ret
GenerateBlock_Success:
xor eax, eax
mov al, RDSEED_SUCCESS
ret
MASM_RSA_GenerateBlock ENDP
ENDIF ;; _M_X86
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IFDEF _M_X64 ;; Set via the command line
.CODE
ALIGN 16
OPTION PROLOGUE:NONE
OPTION EPILOGUE:NONE
;; RCX (in): arg1, byte* buffer
;; RDX (in): arg2, size_t bsize
;; R8d (in): arg3, unsigned int safety
;; RAX (out): success (1), failure (0)
MASM_RSA_GenerateBlock PROC ;; arg1:QWORD,arg2:QWORD,arg3:DWORD
MWSIZE EQU 08h ;; machine word size
buffer EQU rcx
bsize EQU rdx
safety EQU r8d
;; No need for Load_Arguments due to fastcall
Validate_Pointer:
;; Validate pointer
cmp buffer, 0
je GenerateBlock_PreRet
;; Top of While loop
GenerateBlock_Top:
;; Check remaining size
cmp bsize, 0
je GenerateBlock_Success
Call_RDSEED_RAX:
;; RDSEED is not available prior to VS2012. Just emit
;; the byte codes using DB. This is `rdseed rax`.
DB 048h, 0Fh, 0C7h, 0F8h
;; If CF=1, the number returned by RDSEED is valid.
;; If CF=0, a random number was not available.
jc RDSEED_succeeded
RDSEED_failed:
;; Exit if we've reached the limit
cmp safety, 0
je GenerateBlock_Failure
dec safety
jmp GenerateBlock_Top
RDSEED_succeeded:
cmp bsize, MWSIZE
jb Partial_Machine_Word
Full_Machine_Word:
mov QWORD PTR [buffer], rax
add buffer, MWSIZE
sub bsize, MWSIZE
;; Continue
jmp GenerateBlock_Top
;; 1,2,3,4,5,6,7 bytes remain
Partial_Machine_Word:
;; Test bit 2 to see if size is at least 4
test bsize, 4
jz Bit_2_Not_Set
mov DWORD PTR [buffer], eax
shr rax, 32
add buffer, 4
Bit_2_Not_Set:
;; Test bit 1 to see if size is at least 2
test bsize, 2
jz Bit_1_Not_Set
mov WORD PTR [buffer], ax
shr eax, 16
add buffer, 2
Bit_1_Not_Set:
;; Test bit 0 to see if size is at least 1
test bsize, 1
jz GenerateBlock_Success
mov BYTE PTR [buffer], al
Bit_0_Not_Set:
;; We've hit all the bits
jmp GenerateBlock_Success
GenerateBlock_PreRet:
;; Test for success (was the request completely fulfilled?)
cmp bsize, 0
je GenerateBlock_Success
GenerateBlock_Failure:
xor rax, rax
mov al, RDSEED_FAILURE
ret
GenerateBlock_Success:
xor rax, rax
mov al, RDSEED_SUCCESS
ret
MASM_RSA_GenerateBlock ENDP
ENDIF ;; _M_X64
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END