# 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 # 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" D1 01 00 00 ; VirtualSize 00 10 00 00 ; VirtualAddress D1 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 ; mov_rbp,rsp # save stack pointer 4989CF ; mov_r15,rcx # save image_handle 4C8B72 60 ; mov_r14,[rdx+BYTE] !96 # system->boot # Open Loaded Image protocol 4D89F9 ; mov_r9,r15 # arg4 = image_handle 488D15 9D010000 ; lea_rdx,[rip+DWORD] %LOADED_IMAGE_PROTOCOL # guid = &LOADED_IMAGE_PROTOCOL 4C89C9 ; mov_rcx,r9 # arg1 = image_handle 50 ; push_rax # allocate stack for image 4989E0 ; mov_r8,rsp # arg3 = &image 6A 01 ; push !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL 6A 00 ; push !0 # arg5 = NULL 4883EC 20 ; sub_rsp, !32 # allocate shadow stack space for UEFI function 41FF96 18010000 ; call_[r14+DWORD] %280 # system->boot->open_protocol(image_handle, &guid, &image, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) 4883C4 30 ; add_rsp, !48 # deallocate stack 5F ; pop_rdi # get image # Get root file system 4D89F9 ; mov_r9,r15 # arg4 = image_handle 488D15 88010000 ; lea_rdx,[rip+DWORD] %SIMPLE_FS_PROTOCOL # guid = &SIMPLE_FS_PROTOCOL 488B4F 18 ; mov_rcx,[rdi+BYTE] !24 # arg1 = root_device = image->device 4989CD ; mov_r13,rcx # save root_device 50 ; push_rax # allocate stack for rootfs 4989E0 ; mov_r8,rsp # arg3 = &rootfs 6A 01 ; push !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL 6A 00 ; push !0 # arg5 = NULL 4883EC 20 ; sub_rsp, !32 # allocate shadow stack space for UEFI function 41FF96 18010000 ; call_[r14+DWORD] %280 # system->boot->open_protocol(root_device, &guid, &rootfs, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) 4883C4 30 ; add_rsp, !48 # deallocate stack 59 ; pop rcx # get rootfs # Get root directory 50 ; push_rax # allocate stack for rootdir 4889E2 ; mov_rdx,rsp # 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+BYTE] !8 # rootfs->open_volume(rootfs, &rootdir) 58 ; pop_rax # deallocate stack 58 ; pop_rax # deallocate stack 5E ; pop_rsi # save rootdir # Push command line arguments onto stack 488B5F 38 ; mov_rbx,[rdi+BYTE] !56 # options = image->load_options 4889DA ; mov_rdx,rbx # save beginning of load_options 48035F 30 ; add_rbx,[rdi+BYTE] !48 # go to the end of load_options # :loop_options [_start + 0x6F] 4839D3 ; cmp_rbx,rdx # Check if we are done 74 14 ; je !loop_options_done # We are done 4883EB 02 ; sub_rbx, !2 # --options 8A03 ; mov_al,[rbx] # *options 3C 20 ; cmp_al, !0x20 # if *options != ' ' 75 F1 ; jne !loop_options # then continue looping C603 00 ; mov_[rbx], !0 # zero it 4883C3 02 ; add_rbx, !2 # ++options 53 ; push_rbx # push another argument onto stack EB E7 ; jmp !loop_options # next argument # :loop_options_done [_start + 0x88] # Open file for reading 4158 ; pop_r8 # arg3 = in 52 ; push_rdx # allocate stack for fin 4889E2 ; mov_rdx,rsp # 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 4889F1 ; mov_rcx,rsi # arg1 = rootdir 4883EC 20 ; sub_rsp, !32 # allocate shadow stack space for UEFI function FF51 08 ; call_[rcx+BYTE] !8 # rootdir->open() 4883C4 28 ; add_rsp, !40 # deallocate stack 415C ; pop_r12 # get fin # Open file for writing 4158 ; pop_r8 # arg3 = out 4155 ; push_r13 # save root_device 52 ; push_rdx # allocate stack for fout 4889E2 ; mov_rdx,rsp # 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 4889F1 ; mov_rcx,rsi # arg1 = rootdir 4883EC 20 ; sub_rsp, !32 # allocate shadow stack space for UEFI function FF51 08 ; call_[rcx+BYTE] !8 # rootdir->open() 4883C4 28 ; add_rsp, !40 # deallocate stack 415D ; pop_r13 # get fout # Save variables that are needed for cleanup 4156 ; push_r14 # save system->boot 4157 ; push_r15 # save image_handle 56 ; push_rsi # save rootdir # 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+0xCF] # Read a byte E8 6F000000 ; call %read_byte # process byte E8 1C000000 ; call %hex # deal with -1 values 85C0 ; test_eax,eax 7C F2 ; jl !loop # deal with toggle 85DB ; test_ebx,ebx # jump if ebx >= 0 7D 06 ; jge !print # process first byte of pair 89C7 ; mov_edi,eax 31DB ; xor_ebx,ebx # rbx = 0 EB E8 ; jmp !loop # process second byte of pair # :print [_start+0xE7] # update the sum and store in output C1E7 04 ; shl_edi, !4 01F8 ; add_eax,edi # flip the toggle FFCB ; dec_ebx # rbx = -1 E8 39000000 ; call %write_byte EB DA ; jmp !loop # :hex [_start+0xF5] # Purge Comment Lines (#) 3C 23 ; cmp_al, !35 74 1E ; je !purge_comment # Purge Comment Lines (;) 3C 3B ; cmp_al, !59 74 1A ; je !purge_comment # deal all ascii less than '0' 3C 30 ; cmp_al, !48 7C 1F ; jl !ascii_other # deal with 0-9 3C 3A ; cmp_al, !58 7C 1F ; jl !ascii_num # deal with all ascii less than 'A' 3C 41 ; cmp_al, !65 7C 17 ; jl !ascii_other # deal with 'A'-'F' 3C 47 ; cmp_al, !71 7C 1C ; jl !ascii_high # deal with all ascii less than 'a' 3C 61 ; cmp_al, !97 7C 0F ; jl !ascii_other #deal with 'a'-'f' 3C 67 ; cmp_al, !103 7C 12 ; jl !ascii_low # The rest that remains needs to be ignored EB 09 ; jmp !ascii_other # :purge_comment [_start+0x117] # Read a byte E8 27000000 ; call %read_byte # Loop if not LF 3C 0A ; cmp_al, !10 75 F7 ; jne !purge_comment # Otherwise return -1 # :ascii_other [_start+0x120] 6A FF ; push !-1 58 ; pop_rax # return = -1 C3 ; ret # :ascii_num [_start+0x124] 2C 30 ; sub_al, !48 C3 ; ret # :ascii_low [_start+0x127] 2C 20 ; sub_al, !32 # convert to uppercase # :ascii_high [_start+0x129] 2C 37 ; sub_al, !55 C3 ; ret # Writes byte stored in al # :write_byte [_start+0x12C] 4C89E9 ; mov_rcx,r13 # arg1 = fout 6A 01 ; push !1 # size = 1 4889E2 ; mov_rdx,rsp # arg2 = &size 50 ; push_rax # allocate stack 4989E0 ; mov_r8,rsp # 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+BYTE] !40 # fout->write() 4883C4 28 ; add_rsp, !40 # deallocate stack C3 ; ret # return # :read_byte [_start+0x143] 4C89E1 ; mov_rcx,r12 # arg1 = fin 6A 01 ; push !1 # size = 1 4889E2 ; mov_rdx,rsp # arg2 = &size 31F6 ; xor_esi,esi # zero rsi 56 ; push_rsi # allocate stack 4989E0 ; mov_r8,rsp # 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+BYTE] !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 ; je !terminate # then we are done C3 ; ret # return # :terminate [_start+0x161] 58 ; pop_rax # remove last return address from stack 5E ; pop_rsi # restore rootdir 415F ; pop_r15 # restore image_handle 415E ; pop_r14 # restore system->boot 5B ; pop_rbx # restore root_device 53 ; push_rbx # allocate stack 4C89E1 ; mov_rcx,r12 # arg1 = fin FF51 10 ; call_[rcx+BYTE] !16 # fin->close() 4C89E9 ; mov_rcx,r13 # arg1 = fout FF51 10 ; call_[rcx+BYTE] !16 # fout->close() 4889F1 ; mov_rcx,rsi # arg1 = rootdir FF51 10 ; call_[rcx+BYTE] !16 # rootdir->close() 4D89F8 ; mov_r8,r15 # arg3 = image_handle 488D15 3C000000 ; lea_rdx,[rip+DWORD] %SIMPLE_FS_PROTOCOL # guid = &SIMPLE_FS_PROTOCOL 4889D9 ; mov_rcx,rbx # arg1 = root_device 4D31C9 ; xor_r9,r9 # arg4 = NULL 4883EC 20 ; sub_rsp, !32 # allocate shadow stack space for UEFI function 41FF96 20010000 ; call_[r14+DWORD] %288 # system->boot->close_protocol(root_device, &guid, image_handle, 0) 4D89F8 ; mov_r8,r15 # arg3 = image_handle 488D15 11000000 ; lea_rdx,[rip+DWORD] %LOADED_IMAGE_PROTOCOL # guid = &LOADED_IMAGE_PROTOCOL 4C89C1 ; mov_rcx,r8 # arg1 = image_handle 4D31C9 ; xor_r9,r9 # arg4 = NULL 41FF96 20010000 ; call_[r14+DWORD] %288 # system->boot->close_protocol(image_handle, &guid, image_handle, 0) 4889EC ; mov_rsp,rbp # restore stack C3 ; ret # return to UEFI # Protocol GUIDs # :LOADED_IMAGE_PROTOCOL [_start+0x1B1] A1 31 1B 5B ; %0x5b1b31a1 62 95 ; @0x9562 D2 11 ; @0x11d2 8E 3F 00 A0 C9 69 72 3B ; !0x8e !0x3f !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b # :SIMPLE_FS_PROTOCOL [_start+0x1C1] 22 5B 4E 96 ; %0x0964e5b22 59 64 ; @0x6459 D2 11 ; @0x11d2 8E 39 00 A0 C9 69 72 3B ; !0x8e !0x39 !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b # :PE32_end [_start+0x1D1]