# SPDX-FileCopyrightText: 2022 Andrius Štikonas # SPDX-FileCopyrightText: 2017 Jeremiah Orians # # SPDX-License-Identifier: GPL-3.0-or-later # Some of the functions are deliberately inlined at the slight expense of # binary size to avoid tricky jump calculations in hex0 code. .global _start .text # 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+96] # system->boot # Open Loaded Image protocol mov r9, r15 # arg4 = image_handle lea rdx, [rip+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+280] # system->boot->open_protocol(image_handle, &guid, &image, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) mov rdi, [rsp+48] # save image # Get root file system mov r9, r15 # arg4 = image_handle lea rdx, [rip+SIMPLE_FS_PROTOCOL] # guid = &SIMPLE_FS_PROTOCOL mov rcx, [rdi+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+280] # system->boot->open_protocol(root_device, &guid, &rootfs, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL) mov rcx, [rsp+48] # 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+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+56] # options = image->load_options mov rdx, rbx # save beginning of load_options add rbx, [rdi+48] # go to the end of load_options push 0 # Save end of arguments (NULL) onto stack 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 BYTE PTR [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+8] # rootdir->open() add rsp, 40 # deallocate stack pop rdi # get fin # Open file for writing pop r8 # arg3 = out 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+8] # rootdir->open() add rsp, 40 # deallocate stack pop rbx # get fout # Save variables that are needed for cleanup push r13 # save root_device push r14 # save system->boot push r15 # save image_handle push rsi # save rootdir # Allocate pool for single-character label table # pointer to table will be stored at the top of the stack push rdx # allocate stack for table mov r8, rsp # arg3 = &table xor edx, edx # zero rdx mov dh, 0x8 # arg2 = 256 * 8 = 2048 = 0x800 push 2 pop rcx # arg1 = EFI_LOADER_DATA sub rsp, 24 # allocate shadow stack space for UEFI call [r14+64] # system->boot->allocate_pool(EFI_LOADER_DATA, 2048, &table) add rsp, 24 # deallocate stack mov r15, -1 # Our flag for byte processing mov r14, 0 # temp storage for the sum mov r13, 0 # Our starting IP call First_pass # Process it # rewind input file mov rcx, rdi # Using our input file xor edx, edx # Offset Zero push rax # allocate shadow stack space for UEFI function push rax # allocate shadow stack space for UEFI function call [rcx+56] # fin->set_position(fin, 0) pop rax # deallocate stack pop rax # deallocate stack mov r15, -1 # Our flag for byte processing mov r14, 0 # temp storage for the sum mov r13, 0 # Our starting IP call Second_pass # Process it jmp Done First_pass: call Read_byte # Deal with EOF cmp rax, -4 je First_pass_done # Check for : cmp rax, 0x3a jne First_pass_0 # Deal with label call StoreLabel First_pass_0: # Check for % cmp rax, 0x25 je First_pass_pointer # Deal with everything else call hex # Process our char # Deal with EOF cmp rax, -4 je First_pass_done # deal with -1 values cmp rax, 0 jl First_pass # deal with toggle cmp r15, 0 je First_pass_1 add r13, 1 # Increment IP First_pass_1: not r15 jmp First_pass First_pass_pointer: # Deal with Pointer to label call Read_byte # Drop the char add r13, 4 # Increment IP jmp First_pass # Loop again First_pass_done: RET hex: # deal with EOF cmp rax, -4 je EOF # deal with line comments starting with # cmp rax, 0x23 je ascii_comment # deal with line comments starting with ; cmp rax, 0x3b je ascii_comment # deal all ascii less than 0 cmp rax, 0x30 jl ascii_other # deal with 0-9 cmp rax, 0x3a jl ascii_num # deal with all ascii less than A cmp rax, 0x41 jl ascii_other # deal with A-F cmp rax, 0x47 jl ascii_high # deal with all ascii less than a cmp rax, 0x61 jl ascii_other # deal with a-f cmp rax, 0x67 jl ascii_low # The rest that remains needs to be ignored jmp ascii_other Second_pass: call Read_byte # Deal with EOF cmp rax, -4 je Second_pass_done # Simply drop the label cmp rax, 0x3a jne Second_pass_0 call Read_byte jmp Second_pass Second_pass_0: # Deal with pointer cmp rax, 0x25 jne Second_pass_1 call StorePointer jmp Second_pass Second_pass_1: # Deal with everything else call hex # Process our char # Deal with EOF cmp rax, -4 je Second_pass_done # deal with -1 values cmp rax, 0 jl Second_pass # deal with toggle cmp r15, 0 je print # process first byte of pair mov r14, rax mov r15, 0 jmp Second_pass Second_pass_done: EOF: ret ascii_num: sub rax, 0x30 ret ascii_low: sub rax, 0x57 ret ascii_high: sub rax, 0x37 ret ascii_other: mov rax, -1 ret ascii_comment: call Read_byte cmp rax, 0xd je ascii_comment_cr cmp rax, 0xa jne ascii_comment ascii_comment_cr: mov rax, -1 ret # process second byte of pair print: # update the sum and store in output shl r14, 4 add rax, r14 # flip the toggle not r15 # r15 = -1 mov rdx, 1 # set the size of chars we want call print_chars add r13, 1 # Increment IP jmp Second_pass Read_byte: mov rcx, rdi # 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+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) return EOF test esi, esi # if size == 0 jne Read_byte_1 mov rax, -4 # Put EOF in rax Read_byte_1: ret # return # Writes bytes stored in rax print_chars: mov rcx, rbx # arg1 = fout push rdx # set size 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+40] # fout->write() add rsp, 40 # deallocate stack ret # return Get_table_target: call Read_byte # Get single char label shl rax, 3 # Each label in table takes 8 bytes to store mov rcx, [rsp+24] # Get table add rax, rcx # Calculate offset ret StoreLabel: call Get_table_target mov [rax], r13 # Write out pointer to table ret StorePointer: add r13, 4 # Increment IP call Get_table_target # Get address of pointer mov rax, [rax] # Get pointer sub rax, r13 # target - ip mov rdx, 4 # set the size of chars we want call print_chars ret Done: pop rcx # restore table pop rsi # restore rootdir pop r15 # restore image_handle pop r14 # restore system->boot pop r13 # restore root_device # Free pool # arg1 = table push rax # allocate shadow stack space for UEFI function call [r14+72] # system->boot->free_pool(table) mov rcx, rdi # arg1 = fin call [rcx+16] # fin->close() mov rcx, rbx # arg1 = fout call [rcx+16] # fout->close() mov rcx, rsi # arg1 = rootdir call [rcx+16] # rootdir->close() mov r8, r15 # arg3 = image_handle lea rdx, [rip+SIMPLE_FS_PROTOCOL] # guid = &SIMPLE_FS_PROTOCOL mov rcx, r13 # arg1 = root_device xor r9, r9 # arg4 = NULL sub rsp, 32 # allocate shadow stack space for UEFI function call [r14+288] # system->boot->close_protocol(root_device, &guid, image_handle, 0) mov r8, r15 # arg3 = image_handle lea rdx, [rip+LOADED_IMAGE_PROTOCOL] # guid = &LOADED_IMAGE_PROTOCOL mov rcx, r8 # arg1 = image_handle xor r9, r9 # arg4 = NULL call [r14+288] # system->boot->close_protocol(image_handle, &guid, image_handle, 0) abort: # used for debugging only mov rsp, rbp # restore stack ret # return to UEFI # Protocol GUIDs LOADED_IMAGE_PROTOCOL: .long 0x5b1b31a1 .short 0x9562 .short 0x11d2 .byte 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b SIMPLE_FS_PROTOCOL: .long 0x0964e5b22 .short 0x6459 .short 0x11d2 .byte 0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b