# SPDX-FileCopyrightText: 2022 Andrius Štikonas # SPDX-FileCopyrightText: 2022 Jeremiah Orians # # SPDX-License-Identifier: GPL-3.0-or-later # Usage: hex0 file.hex0 file # Does not validate the arguments or check for success # Calling convention: # First four arguments are passed via registers rcx, rdx, r8, r9 (if they fit in 64-bits) # but we need to leave stack space # rax, rcx, rdx, r8, r9, r10 and r11 are volatile and can be changed by called function # Registers: # r12 in/fin: input file name, later reused for handle # r13 out/fout: output file name, later reused for handle # r14 system->boot->open_protocol from UEFI, later reused for rootdir # r15 image_handle from UEFI # hex0 algorithm mostly follows stage0-posix version but uses rdi instead of rbp # DOS MZ header 4D 5A # Signature 00 00 # Number of bytes in the last page. 00 00 # Number of whole/partial pages 00 00 # Number of entries in the relocation table. 00 00 # Header size 00 00 # Minimum allocation 00 00 # Maximum allocation 00 00 # Relocatable segment address for SS 00 00 # Initial value for SP 00 00 # Checksum (I don't think is looked at) 00 00 # Initial value for IP (Seems ignored) 00 00 # Relocatable segment address for CS (Seems ignored) 00 00 # The (absolute) offset to the relocation table. 00 00 # Value used for overlay management. If zero, this is the main executable 00 00 00 00 00 00 00 00 # Reserved in PE 00 00 # OEM identifier 00 00 # OEM info 00 00 00 00 00 00 00 00 00 00 # The required reserved 20 bytes of NULLS 00 00 00 00 00 00 00 00 00 00 40 00 00 00 # Starting address of the PE header # [0x40] # PE header 50 45 00 00 # Signature "PE" 64 86 # Machine 01 00 # number of sections 00 00 00 00 # Timestamp supposedly 00 00 00 00 # PointerToSymbolTable 00 00 00 00 # number of symbols F0 00 # SizeOfOptionalHeader 00 00 # 'Characteristics' # [0x58] # COFF header bits 0B 02 # Magic PE32+ (64 bit) 00 00 # Linker version 00 00 00 00 # size of code 00 00 00 00 # sizeOfInitializedData 00 00 00 00 # SizeOfUninitializedData 00 10 00 00 # AddressOfEntryPoint 00 10 00 00 # BaseOfCode 00 00 00 80 01 00 00 00 # ImageBase 01 00 00 00 # SectionAlignment 01 00 00 00 # FileAlignment 00 00 00 00 # OperatingSystemVersion 00 00 00 00 # ImageVersion 00 00 00 00 # SubsystemVersion 00 00 00 00 # Win32VersionValue 00 20 00 00 # SizeOfImage 70 01 00 00 # SizeOfHeaders 00 00 00 00 # CheckSum (isn't used at all) 0A 00 # Subsystem 00 00 # DllCharacteristics 00 00 00 00 # SizeOfStackReserve 00 00 00 00 # SizeOfStackCommit 00 00 00 00 # SizeOfHeapReserve 00 00 00 00 # SizeOfHeapCommit 00 00 00 00 # LoaderFlags 00 00 00 00 # NumberOfRvaAndSizes # [0xB8] # Data directories (has to be 16 entries always 16bytes per entry) 00 00 00 00 # Export Table 00 00 00 00 # Size of Export Table 00 00 00 00 # Import Table 10 00 00 00 # Size of Import Table 00 00 00 00 # Resource Table 00 00 00 00 # Size of Resource Table 00 00 00 00 # Exception Table 00 00 00 00 # Size of Exception Table 00 00 00 00 # Certificate Table 00 00 00 00 # Size of Certificate Table 00 00 00 00 # Base Relocation Table 00 00 00 00 # Size of Base Relocation Table 00 00 00 00 # Debug Table 00 00 00 00 # Size of Debug Table 00 00 00 00 # Architecture Data Table 00 00 00 00 # Size of Architecture Data Table 00 00 00 00 # Global Pointer 00 00 00 00 # NULL 00 00 00 00 # TLS Table 00 00 00 00 # Size of TLS Table 00 00 00 00 # Load Config Table 00 00 00 00 # Size of Load Config Table 00 00 00 00 # Bound Import Table 00 00 00 00 # Size of Bound Import Table 00 00 00 00 # Import Address Table 00 00 00 00 # Size of Import Address Table 00 00 00 00 # Delay Import Descriptor Table 00 00 00 00 # Size of Delay Import Descriptor Table 00 00 00 00 # CLR Runtime header table 00 00 00 00 # Size of CLR Runtime Header table 00 00 00 00 00 00 00 00 # MUST BE NULL # no idea what it is yet 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # [0x148] # Start of section headers 00 00 00 00 00 00 00 00 ; Name of the section (empty) but could set to ".text" A3 01 00 00 ; VirtualSize 00 10 00 00 ; VirtualAddress A3 01 00 00 ; SizeOfRawData 70 01 00 00 ; PointerToRawData 00 00 00 00 ; PointerToRelocations 00 00 00 00 ; PointerToLinenumbers 00 00 ; NumberOfRelocations 00 00 ; NumberOfLinenumbers 00 00 00 00 ; 'Characteristics' # [0x170] # Our actual program # efi_main(void *image_handle, struct efi_system_table *system) # :_start 4889E5 ; COPY_RSP_to_RBP # save stack pointer 4989CF ; COPY_RCX_to_R15 # save image_handle 4C8B72 60 ; LOAD64_into_R14_from_Address_RDX_Immediate8 !96 # system->boot 4D8BB6 18010000 ; LOAD64_into_R14_from_Address_R14_Immediate32 %280 # system->boot->open_protocol # Open Loaded Image protocol 50 ; PUSH_RAX # allocate stack for image 4989E0 ; COPY_RSP_to_R8 # arg3 = &image 488B15 6F010000 ; LOAD64_rel_RDX !LOADED_IMAGE_PROTOCOL_8 # EFI_LOADED_IMAGE_PROTOCOL_GUID (last 64 bits) # [_start+0x1C] 52 ; PUSH_RDX # push last 64 bits onto stack 488B15 5F010000 ; LOAD64_rel_RDX !LOADED_IMAGE_PROTOCOL # EFI_LOADED_IMAGE_PROTOCOL_GUID (first 64 bits) # [_start+0x24] 52 ; PUSH_RDX # push first 64 bits onto stack 4889E2 ; COPY_RSP_to_RDX # arg2 = &guid 6A 01 ; PUSH !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL 6A 00 ; PUSH !0 # arg5 = NULL 4989C9 ; COPY_RCX_to_R9 # arg4 = image_handle # arg1 = ImageHandle (already set) 4883EC 20 ; SUBI8_RSP !32 # allocate shadow stack space for UEFI function 41FFD6 ; CALL_R14 # system->boot->open_protocol(image_handle, &guid, &image, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) 488B4424 40 ; LOAD64_into_RAX_from_Address_RSP_Immediate8 !64 # get_image 4889C1 ; COPY_RCX_to_RAX # save image # Command line args 488B58 38 ; LOAD64_into_RBX_from_Address_RAX_Immediate8 !56 # options = image->load_options # :loop_options1 [_start+0x42] # Skip application name 4883C3 02 ; ADDI8_RBX !2 # ++options 8A03 ; LOAD8_AL_from_Address_RBX # *options 3C 20 ; CMPI8_AL !0x20 # if *options != ' ' 75 F6 ; JNE8 !loop_options1 # then jump 4883C3 02 ; ADDI8_RBX !2 # ++options 4989DC ; COPY_RBX_to_R12 # save input file # :loop_options2 [_start+0x53] # Skip argv[1] 4883C3 02 ; ADDI8_RBX !2 # ++options 8A03 ; LOAD8_AL_from_Address_RBX # *options 3C 20 ; CMPI8_AL !0x20 # if *options != ' ' 75 F6 ; JNE8 !loop_options2 # then jump C603 00 ; STOREI8_into_Address_RBX !0 # *options = 0; 4883C3 02 ; ADDI8_RBX !2 # ++options 4989DD ; COPY_RBX_to_R13 # save output file # Get root file system [_start+0x67] 50 ; PUSH_RAX # allocate stack for rootfs 4989E0 ; COPY_R8_to_RSP # arg3 = &rootfs 488B15 29010000 ; LOAD64_rel_RDX %SIMPLE_FS_PROTOCOL_8 # EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID (last 64 bits) 52 ; PUSH_RDX # push last 64 bits onto stack 488B15 19010000 ; LOAD64_rel_RDX %SIMPLE_FS_PROTOCOL # EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID (first 64 bits) 52 ; PUSH_RDX # push first 64 bits onto stack 4889E2 ; COPY_RSP_to_RDX # arg2 = &guid 6A 01 ; PUSH !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL 6A 00 ; PUSH !0 # arg5 = NULL 4D89F9 ; COPY_R15_to_R9 # arg4 = image_handle 488B49 18 ; LOAD64_into_RCX_from_Address_RCX_Immediate8 !24 # arg1 = root_device = image->device 4883EC 20 ; SUBI8_RSP !32 # allocate shadow stack space for UEFI function 41FFD6 ; CALL_R14 # system->boot->open_protocol(root_device, &guid, &rootfs, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) 488B4C24 40 ; LOAD64_into_RCX_from_Address_RSP_Immediate8 !64 # get rootfs # Get root directory 52 ; PUSH_RDX # allocate stack for rootdir 4889E2 ; COPY_RSP_to_RDX # arg2 = &rootdir 50 ; PUSH_RAX # allocate shadow stack space for UEFI function 50 ; PUSH_RAX # allocate shadow stack space for UEFI function FF51 08 ; CALL_RCX_Immediate8 !8 # rootfs->open_volume(rootfs, &rootdir) 58 ; POP_RAX # deallocate stack 58 ; POP_RAX # deallocate stack 415E ; POP_R14 # save &rootdir # Open file for writing 52 ; PUSH_RDX # allocate stack for fout 4889E2 ; COPY_RSP_to_RDX # arg2 = &fout 6A 00 ; PUSH !0 # arg5 = 0 6A 07 ; PUSH !7 # to get 0x8000000000000003 we set the rightmost 3 bits 4159 ; POP_R9 # and then do right rotation by 1 49D1C9 ; ROR_R9 # arg4 = EFI_FILE_MODE_CREATE| EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ 4D89E8 ; COPY_R13_to_R8 # arg3 = out 4C89F1 ; COPY_R14_to_RCX # arg1 = rootdir 4883EC 20 ; SUBI8_RSP !32 # allocate shadow stack space for UEFI function FF51 08 ; CALL_RCX_Immediate8 !8 # rootdir->open() 4C8B6C24 28 ; LOAD64_into_R13_from_Address_RSP_Immediate8 !40 # get fout # Open file for reading 52 ; PUSH_RDX # allocate stack for fin 4889E2 ; COPY_RSP_to_RDX # arg2 = &fin 6A 01 ; PUSH !1 # arg5 = EFI_FILE_READ_ONLY 6A 01 ; PUSH !1 # prepare to set arg4 to EFI_FILE_MODE_READ 4159 ; POP_R9 # arg4 = EFI_FILE_MODE_READ 4D89E0 ; COPY_R12_to_R8 # arg3 = in 4C89F1 ; COPY_R14_to_RCX # arg1 = rootdir 4883EC 20 ; SUBI8_RSP !32 # allocate shadow stack space for UEFI function FF51 08 ; CALL_RCX_Immediate8 !8 # rootdir->open() 4C8B6424 28 ; LOAD64_into_R12_from_Address_RSP_Immediate8 !40 # get fin # Our flag for byte processing 6A FF ; PUSH !-1 5B ; POP_RBX # rbx = -1 # temp storage for the sum 31FF ; XOR_EDI_EDI # rdi = 0 # :loop [_start+0xE2] # Read a byte E8 6F000000 ; CALLI32 %read_byte # process byte E8 1C000000 ; CALLI32 %hex # deal with -1 values 85C0 ; TEST_EAX_EAX 7C F2 ; JL8 !loop # deal with toggle 85DB ; TEST_EBX_EBX # jump if ebx >= 0 7D 06 ; JGE8 !print # process first byte of pair 89C7 ; COPY_EAX_to_EDI 31DB ; XOR_EBX_EBX # rbx = 0 EB E8 ; JMP8 !loop # process second byte of pair # :print [_start+0xFA] # update the sum and store in output C1E7 04 ; SHL_EDI_Immediate8 !4 01F8 ; ADD_EAX_EDI # flip the toggle FFCB ; DEC_EBX # rbx = -1 E8 39000000 ; CALLI32 %write_byte EB DA ; JMP8 !loop # :hex [_start+0x108] # Purge Comment Lines (#) 3C 23 ; CMPI8_AL !35 74 1E ; JE8 !purge_comment # Purge Comment Lines (;) 3C 3B ; CMPI8_AL !59 74 1A ; JE8 !purge_comment # deal all ascii less than '0' 3C 30 ; CMPI8_AL !48 7C 1F ; JL8 !ascii_other # deal with 0-9 3C 3A ; CMPI8_AL !58 7C 1F ; JL8 !ascii_num # deal with all ascii less than 'A' 3C 41 ; CMPI8_AL !65 7C 17 ; JL8 !ascii_other # deal with 'A'-'F' 3C 47 ; CMPI8_AL !71 7C 1C ; JL8 !ascii_high # deal with all ascii less than 'a' 3C 61 ; CMPI8_AL !97 7C 0F ; JL8 !ascii_other #deal with 'a'-'f' 3C 67 ; CMPI8_AL !103 7C 12 ; JL8 !ascii_low # The rest that remains needs to be ignored EB 09 ; JMP8 !ascii_other # :purge_comment [_start+0x12A] # Read a byte E8 27000000 ; CALLI32 %read_byte # Loop if not LF 3C 0A ; CMPI8_AL !10 75 F7 ; JNE8 !purge_comment # Otherwise return -1 # :ascii_other [_start+0x133] 6A FF ; PUSH !-1 58 ; POP_RAX # return = -1 C3 ; RET # :ascii_num [_start+0x137] 2C 30 ; SUBI8_AL !48 C3 ; RET # :ascii_low [_start+0x13A] 2C 20 ; SUBI8_AL !32 # convert to uppercase # :ascii_high [_start+0x13C] 2C 37 ; SUBI8_AL !55 C3 ; RET # Writes byte stored in al # :write_byte [_start+0x13F] 4C89E9 ; COPY_R13_to_RCX # arg1 = fout 6A 01 ; PUSH !1 # size = 1 4889E2 ; COPY_RSP_to_RDX # arg2 = &size 50 ; PUSH_RAX # allocate stack 4989E0 ; COPY_RSP_to_R8 # arg3 = &output 50 ; PUSH_RAX # allocate shadow stack space for UEFI function 50 ; PUSH_RAX # allocate shadow stack space for UEFI function 50 ; PUSH_RAX # allocate shadow stack space for UEFI function FF51 28 ; CALL_RCX_Immediate8 !40 # fout->write() 4883C4 28 ; ADDI8_RSP !40 # deallocate stack C3 ; RET # return # :read_byte [_start+0x156] 4C89E1 ; COPY_R12_to_RCX # arg1 = fin 6A 01 ; PUSH !1 # size = 1 4889E2 ; COPY_RSP_to_RDX # arg2 = &size 56 ; PUSH_RSI # allocate stack 4989E0 ; COPY_RSP_to_R8 # arg3 = &input 50 ; PUSH_RAX # allocate shadow stack space for UEFI function 50 ; PUSH_RAX # allocate shadow stack space for UEFI function 50 ; PUSH_RAX # allocate shadow stack space for UEFI function FF51 20 ; CALL_RCX_Immediate8 !32 # fin->read() 58 ; POP_RAX # deallocate stack 58 ; POP_RAX # deallocate stack 58 ; POP_RAX # deallocate stack 58 ; POP_RAX # save input to rax 5E ; POP_RSI # save size to rsi # If the file ended (0 bytes read) terminate 85F6 ; TEST_ESI_ESI # if size = 0 74 01 ; JE8 !terminate # then we are done C3 ; RET # return # :terminate [_start+0x172] 53 ; PUSH_RBX # allocate stack 4C89E1 ; COPY_R12_to_RCX # arg1 = fin FF51 10 ; CALL_RCX_Immediate8 !16 # fin->close() 4C89E9 ; COPY_R13_to_RCX # arg1 = fout FF51 10 ; CALL_RCX_Immediate8 !16 # fout->close() 4889EC ; COPY_RBP_to_RSP # restore stack C3 ; RET # return to UEFI # Protocol GUIDs # :LOADED_IMAGE_PROTOCOL [_start+0x183] A1 31 1B 5B ; %0x5b1b31a1 62 95 ; @0x9562 D2 11 ; @0x11d2 # :LOADED_IMAGE_PROTOCOL_8 [_start+0x18B] 8E 3F 00 A0 C9 69 72 3B ; !0x8e !0x3f !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b # :SIMPLE_FS_PROTOCOL [_start+0x193] 22 5B 4E 96 ; %0x0964e5b22 59 64 ; @0x6459 D2 11 ; @0x11d2 # :SIMPLE_FS_PROTOCOL_8 [_start+0x19B] 8E 39 00 A0 C9 69 72 3B ; !0x8e !0x39 !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b # :PE32_end [_start+0x1A3]