# SPDX-FileCopyrightText: 2022 Andrius Štikonas # SPDX-FileCopyrightText: 2017 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 DEFINE add_eax,edi 01F8 DEFINE add_rbx, 4883C3 DEFINE add_rsp, 4883C4 DEFINE add_rbx,[rdi+BYTE] 48035F DEFINE call E8 DEFINE call_[rcx+BYTE] FF51 DEFINE call_[r14+BYTE] 41FF56 DEFINE call_[r14+DWORD] 41FF96 DEFINE cmp_al, 3C DEFINE cmp_rbx,rdx 4839D3 DEFINE dec_ebx FFCB DEFINE je 74 DEFINE jge 7D DEFINE jl 7C DEFINE jmp EB DEFINE jne 75 DEFINE lea_rdx,[rip+DWORD] 488D15 DEFINE mov_edi,eax 89C7 DEFINE mov_rbp,rsp 4889E5 DEFINE mov_rcx,rbx 4889D9 DEFINE mov_rcx,rsi 4889F1 DEFINE mov_rcx,r8 4C89C1 DEFINE mov_rcx,r9 4C89C9 DEFINE mov_rcx,r12 4C89E1 DEFINE mov_rcx,r13 4C89E9 DEFINE mov_rdx,rbx 4889DA DEFINE mov_rdx,rsp 4889E2 DEFINE mov_rsp,rbp 4889EC DEFINE mov_r8,rsp 4989E0 DEFINE mov_r8,r15 4D89F8 DEFINE mov_r9,r15 4D89F9 DEFINE mov_r13,rcx 4989CD DEFINE mov_r15,rcx 4989CF DEFINE mov_al,[rbx] 8A03 DEFINE mov_[rbx], C603 DEFINE mov_rbx,[rdi+BYTE] 488B5F DEFINE mov_rcx,[rdi+BYTE] 488B4F DEFINE mov_r14,[rdx+BYTE] 4C8B72 DEFINE pop_rax 58 DEFINE pop_rbx 5B DEFINE pop_rcx 59 DEFINE pop_rdi 5F DEFINE pop_rsi 5E DEFINE pop_r8 4158 DEFINE pop_r9 4159 DEFINE pop_r12 415C DEFINE pop_r13 415D DEFINE pop_r14 415E DEFINE pop_r15 415F DEFINE push 6A DEFINE push_rax 50 DEFINE push_rbx 53 DEFINE push_rdx 52 DEFINE push_rsi 56 DEFINE push_r13 4155 DEFINE push_r14 4156 DEFINE push_r15 4157 DEFINE ret C3 DEFINE ror_r9 49D1C9 DEFINE shl_edi, C1E7 DEFINE sub_al, 2C DEFINE sub_rbx, 4883EB DEFINE sub_rsp, 4883EC DEFINE test_eax,eax 85C0 DEFINE test_ebx,ebx 85DB DEFINE test_esi,esi 85F6 DEFINE xor_ebx,ebx 31DB DEFINE xor_edi,edi 31FF DEFINE xor_esi,esi 31F6 DEFINE xor_r9,r9 4D31C9 # efi_main(void *image_handle, struct efi_system_table *system) :_start mov_rbp,rsp # save stack pointer mov_r15,rcx # save image_handle mov_r14,[rdx+BYTE] !96 # system->boot # Open Loaded Image protocol mov_r9,r15 # arg4 = image_handle lea_rdx,[rip+DWORD] %LOADED_IMAGE_PROTOCOL # guid = &LOADED_IMAGE_PROTOCOL mov_rcx,r9 # arg1 = image_handle push_rax # allocate stack for image mov_r8,rsp # arg3 = &image push !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL push !0 # arg5 = NULL sub_rsp, !32 # allocate shadow stack space for UEFI function call_[r14+DWORD] %280 # system->boot->open_protocol(image_handle, &guid, &image, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) add_rsp, !48 # deallocate stack pop_rdi # get image # Get root file system mov_r9,r15 # arg4 = image_handle lea_rdx,[rip+DWORD] %SIMPLE_FS_PROTOCOL # guid = &SIMPLE_FS_PROTOCOL mov_rcx,[rdi+BYTE] !24 # arg1 = root_device = image->device mov_r13,rcx # save root_device push_rax # allocate stack for rootfs mov_r8,rsp # arg3 = &rootfs push !1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL push !0 # arg5 = NULL sub_rsp, !32 # allocate shadow stack space for UEFI function call_[r14+DWORD] %280 # system->boot->open_protocol(root_device, &guid, &rootfs, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) add_rsp, !48 # deallocate stack pop_rcx # get rootfs # Get root directory push_rax # allocate stack for rootdir mov_rdx,rsp # arg2 = &rootdir push_rax # allocate shadow stack space for UEFI function push_rax # allocate shadow stack space for UEFI function call_[rcx+BYTE] !8 # rootfs->open_volume(rootfs, &rootdir) pop_rax # deallocate stack pop_rax # deallocate stack pop_rsi # get rootdir # Push command line arguments onto stack mov_rbx,[rdi+BYTE] !56 # options = image->load_options mov_rdx,rbx # save beginning of load_options add_rbx,[rdi+BYTE] !48 # go to the end of load_options :loop_options cmp_rbx,rdx # Check if we are done je !loop_options_done # We are done sub_rbx, !2 # --options mov_al,[rbx] # *options cmp_al, !0x20 # if *options != ' ' jne !loop_options # then continue looping mov_[rbx], !0 # zero it add_rbx, !2 # ++options push_rbx # push another argument onto stack jmp !loop_options # next argument :loop_options_done # Open file for reading pop_r8 # arg3 = in push_rdx # allocate stack for fin mov_rdx,rsp # arg2 = &fin push !1 # arg5 = EFI_FILE_READ_ONLY push !1 # prepare to set arg4 to EFI_FILE_MODE_READ pop_r9 # arg4 = EFI_FILE_MODE_READ mov_rcx,rsi # arg1 = rootdir sub_rsp, !32 # allocate shadow stack space for UEFI function call_[rcx+BYTE] !8 # rootdir->open() add_rsp, !40 # deallocate stack pop_r12 # get fin # Open file for writing pop_r8 # arg3 = out push_r13 # save root_device push_rdx # allocate stack for fout mov_rdx,rsp # arg2 = &fout push !0 # arg5 = 0 push !7 # to get 0x8000000000000003 we set the rightmost 3 bits pop_r9 # and then do right rotation by 1 ror_r9 # arg4 = EFI_FILE_MODE_CREATE| EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ mov_rcx,rsi # arg1 = rootdir sub_rsp, !32 # allocate shadow stack space for UEFI function call_[rcx+BYTE] !8 # rootdir->open() add_rsp, !40 # deallocate stack pop_r13 # get fout # Save variables that are needed for cleanup push_r14 # save system->boot push_r15 # save image_handle push_rsi # save rootdir # Our flag for byte processing push !-1 pop_rbx # rbx = -1 # temp storage for the sum xor_edi,edi # rdi = 0 :loop # Read a byte call %read_byte # process byte call %hex # deal with -1 values test_eax,eax jl !loop # deal with toggle test_ebx,ebx # jump if ebx >= 0 jge !print # process first byte of pair mov_edi,eax xor_ebx,ebx # rbx = 0 jmp !loop # process second byte of pair :print # update the sum and store in output shl_edi, !4 add_eax,edi # flip the toggle dec_ebx # rbx = -1 call %write_byte jmp !loop :hex # Purge Comment Lines (#) cmp_al, !35 je !purge_comment # Purge Comment Lines (;) cmp_al, !59 je !purge_comment # deal all ascii less than '0' cmp_al, !48 jl !ascii_other # deal with 0-9 cmp_al, !58 jl !ascii_num # deal with all ascii less than 'A' cmp_al, !65 jl !ascii_other # deal with 'A'-'F' cmp_al, !71 jl !ascii_high # deal with all ascii less than 'a' cmp_al, !97 jl !ascii_other #deal with 'a'-'f' cmp_al, !103 jl !ascii_low # The rest that remains needs to be ignored jmp !ascii_other :purge_comment # Read a byte call %read_byte # Loop if not LF cmp_al, !10 jne !purge_comment # Otherwise return -1 :ascii_other push !-1 pop_rax # return = -1 ret :ascii_num sub_al, !48 ret :ascii_low sub_al, !32 # convert to uppercase :ascii_high sub_al, !55 ret # Writes byte stored in al :write_byte mov_rcx,r13 # arg1 = fout push !1 # size = 1 mov_rdx,rsp # arg2 = &size push_rax # allocate stack mov_r8,rsp # arg3 = &output push_rax # allocate shadow stack space for UEFI function push_rax # allocate shadow stack space for UEFI function push_rax # allocate shadow stack space for UEFI function call_[rcx+BYTE] !40 # fout->write() add_rsp, !40 # deallocate stack ret # return :read_byte mov_rcx,r12 # arg1 = fin push !1 # size = 1 mov_rdx,rsp # arg2 = &size xor_esi,esi # zero rsi push_rsi # allocate stack mov_r8,rsp # arg3 = &input push_rax # allocate shadow stack space for UEFI function push_rax # allocate shadow stack space for UEFI function push_rax # allocate shadow stack space for UEFI function call_[rcx+BYTE] !32 # fin->read() pop_rax # deallocate stack pop_rax # deallocate stack pop_rax # deallocate stack pop_rax # save input to rax pop_rsi # save size to rsi # If the file ended (0 bytes read) terminate test_esi,esi # if size = 0 je !terminate # then we are done ret # return :terminate pop_rax # remove last return address from stack pop_rsi # restore rootdir pop_r15 # restore image_handle pop_r14 # restore system->boot pop_rbx # restore root_device push_rbx # allocate stack mov_rcx,r12 # arg1 = fin call_[rcx+BYTE] !16 # fin->close() mov_rcx,r13 # arg1 = fout call_[rcx+BYTE] !16 # fout->close() mov_rcx,rsi # arg1 = rootdir call_[rcx+BYTE] !16 # rootdir->close() mov_r8,r15 # arg3 = image_handle lea_rdx,[rip+DWORD] %SIMPLE_FS_PROTOCOL # guid = &SIMPLE_FS_PROTOCOL mov_rcx,rbx # arg1 = root_device xor_r9,r9 # arg4 = NULL sub_rsp, !32 # allocate shadow stack space for UEFI function call_[r14+DWORD] %288 # system->boot->close_protocol(root_device, &guid, image_handle, 0) mov_r8,r15 # arg3 = image_handle lea_rdx,[rip+DWORD] %LOADED_IMAGE_PROTOCOL # guid = &LOADED_IMAGE_PROTOCOL mov_rcx,r8 # arg1 = image_handle xor_r9,r9 # arg4 = NULL call_[r14+DWORD] %288 # system->boot->close_protocol(image_handle, &guid, image_handle, 0) mov_rsp,rbp # restore stack ret # return to UEFI # Protocol GUIDs :LOADED_IMAGE_PROTOCOL %0x5b1b31a1 @0x9562 @0x11d2 !0x8e !0x3f !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b :SIMPLE_FS_PROTOCOL %0x0964e5b22 @0x6459 @0x11d2 !0x8e !0x39 !0 !0xa0 !0xc9 !0x69 !0x72 !0x3b :PE32_end