;; 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 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 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; TITLE MASM_RDRAND_GenerateBlock source file SUBTITLE Microsoft specific ASM code to utilize RDRAND for down level Microsoft toolchains PUBLIC MASM_RDRAND_GenerateBlock ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; C/C++ Function prototypes (both are fastcall) ;; X86: ;; extern "C" void __fastcall MASM_RDRAND_GenerateBlock(byte* ptr, size_t size); ;; X64: ;; extern "C" void __fastcall MASM_RDRAND_GenerateBlock(byte* ptr, size_t size); ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; IFDEF _M_X86 ;; Set via the command line .486 .MODEL FLAT ;; Fastcall calling conventions exports ALIAS <@MASM_RDRAND_GenerateBlock@8> = ENDIF ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; IFDEF _M_X86 ;; Set via the command line .CODE ALIGN 8 OPTION PROLOGUE:NONE OPTION EPILOGUE:NONE ;; No need for Load_Arguments due to fastcall ;; ECX (in): arg1, byte* buffer ;; EDX (in): arg2, size_t bsize MASM_RDRAND_GenerateBlock PROC ;; arg1:DWORD, arg2:DWORD MWSIZE EQU 04h ;; machine word size buffer EQU ecx bsize EQU edx ;; Top of While loop RDRAND_GenerateBlock_Top: ;; Check remaining size cmp bsize, 0 je RDRAND_GenerateBlock_Return RDRAND_Call_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. ;; Retry immediately jnc RDRAND_Call_EAX RDRAND_succeeded: cmp bsize, MWSIZE jb RDRAND_Partial_Machine_Word RDRAND_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 RDRAND_GenerateBlock_Top ;; 1,2,3 bytes remain RDRAND_Partial_Machine_Word: ;; Test bit 1 to see if size is at least 2 test bsize, 2 jz RDRAND_Bit_1_Not_Set mov WORD PTR [buffer], ax shr eax, 16 add buffer, 2 RDRAND_Bit_1_Not_Set: ;; Test bit 0 to see if size is at least 1 test bsize, 1 jz RDRAND_Bit_0_Not_Set mov BYTE PTR [buffer], al ;; shr ax, 8 ;; add buffer, 1 RDRAND_Bit_0_Not_Set: ;; We've hit all the bits RDRAND_GenerateBlock_Return: ;; Clear artifacts xor eax, eax ret MASM_RDRAND_GenerateBlock ENDP ENDIF ;; _M_X86 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; IFDEF _M_X64 ;; Set via the command line .CODE ALIGN 16 OPTION PROLOGUE:NONE OPTION EPILOGUE:NONE ;; No need for Load_Arguments due to fastcall ;; RCX (in): arg1, byte* buffer ;; RDX (in): arg2, size_t bsize MASM_RDRAND_GenerateBlock PROC ;; arg1:QWORD, arg2:QWORD MWSIZE EQU 08h ;; machine word size buffer EQU rcx bsize EQU rdx ;; Top of While loop RDRAND_GenerateBlock_Top: ;; Check remaining size cmp bsize, 0 je RDRAND_GenerateBlock_Return RDRAND_Call_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. ;; Retry immediately jnc RDRAND_Call_RAX RDRAND_succeeded: cmp bsize, MWSIZE jb RDRAND_Partial_Machine_Word RDRAND_Full_Machine_Word: mov QWORD PTR [buffer], rax add buffer, MWSIZE sub bsize, MWSIZE ;; Continue jmp RDRAND_GenerateBlock_Top ;; 1,2,3,4,5,6,7 bytes remain RDRAND_Partial_Machine_Word: ;; Test bit 2 to see if size is at least 4 test bsize, 4 jz RDRAND_Bit_2_Not_Set mov DWORD PTR [buffer], eax shr rax, 32 add buffer, 4 RDRAND_Bit_2_Not_Set: ;; Test bit 1 to see if size is at least 2 test bsize, 2 jz RDRAND_Bit_1_Not_Set mov WORD PTR [buffer], ax shr eax, 16 add buffer, 2 RDRAND_Bit_1_Not_Set: ;; Test bit 0 to see if size is at least 1 test bsize, 1 jz RDRAND_Bit_0_Not_Set mov BYTE PTR [buffer], al ;; shr ax, 8 ;; add buffer, 1 RDRAND_Bit_0_Not_Set: ;; We've hit all the bits RDRAND_GenerateBlock_Return: ;; Clear artifacts xor rax, rax ret MASM_RDRAND_GenerateBlock ENDP ENDIF ;; _M_X64 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; END