285 lines
11 KiB
ArmAsm
285 lines
11 KiB
ArmAsm
# SPDX-FileCopyrightText: 2022 Andrius Štikonas <andrius@stikonas.eu>
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# SPDX-FileCopyrightText: 2017 Jeremiah Orians <jeremiah@pdp10.guru>
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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# Usage: hex0 file.hex0 file
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# Does not validate the arguments or check for success
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# Calling convention:
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# First four arguments are passed via registers rcx, rdx, r8, r9 (if they fit in 64-bits)
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# but we need to leave stack space
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# rax, rcx, rdx, r8, r9, r10 and r11 are volatile and can be changed by called function
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# Registers:
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# r12 in/fin: input file name, later reused for handle
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# r13 out/fout: output file name, later reused for handle
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# r14 system->boot->open_protocol from UEFI, later reused for rootdir
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# r15 image_handle from UEFI
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# hex0 algorithm mostly follows stage0-posix version but uses rdi instead of rbp
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.global _start
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.text
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# efi_main(void *image_handle, struct efi_system_table *system)
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_start:
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mov rbp, rsp # save stack pointer
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mov r15, rcx # save image_handle
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mov r14, [rdx+96] # system->boot
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mov r14, [r14+280] # system->boot->open_protocol
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# Open Loaded Image protocol
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push rax # allocate stack for image
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mov r8, rsp # arg3 = &image
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mov rdx, [rip+LOADED_IMAGE_PROTOCOL+8] # EFI_LOADED_IMAGE_PROTOCOL_GUID (last 64 bits)
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push rdx # push last 64 bits onto stack
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mov rdx, [rip+LOADED_IMAGE_PROTOCOL] # EFI_LOADED_IMAGE_PROTOCOL_GUID (first 64 bits)
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push rdx # push first 64 bits onto stack
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mov rdx, rsp # arg2 = &guid
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push 1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL
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push 0 # arg5 = NULL
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mov r9, rcx # arg4 = image_handle
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# arg1 = ImageHandle (already set)
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sub rsp, 32 # allocate shadow stack space for UEFI function
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call r14 # system->boot->open_protocol(image_handle, &guid, &image, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL)
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mov rax, [rsp+64] # get image
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mov rcx, rax # save image
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# Command line args
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mov rbx, [rax+56] # options = image->load_options
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loop_options1: # Skip application name
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add rbx, 2 # ++options
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mov al, [rbx] # *options
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cmp al, 0x20 # if *options != ' '
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jne loop_options1 # then jump
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add rbx, 2 # ++options
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mov r12, rbx # save input file
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loop_options2: # Skip argv[1]
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add rbx, 2 # ++options
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mov al, [rbx] # *options
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cmp al, 0x20 # if *options != ' '
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jne loop_options2 # then jump
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mov byte ptr [rbx], 0 # *options = 0
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add rbx, 2 # ++options
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mov r13, rbx # save output file
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# Get root file system
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push rax # allocate stack for rootfs
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mov r8, rsp # arg3 = &rootfs
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mov rdx, [rip+SIMPLE_FS_PROTOCOL+8] # EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID (last 64 bits)
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push rdx # push last 64 bits onto stack
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mov rdx, [rip+SIMPLE_FS_PROTOCOL] # EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID (first 64 bits)
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push rdx # push first 64 bits onto stack
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mov rdx, rsp # arg2 = &guid
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push 1 # arg6 = EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL
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push 0 # arg5 = NULL
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mov r9, r15 # arg4 = image_handle
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mov rcx, [rcx+24] # arg1 = root_device = image->device
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sub rsp, 32 # allocate shadow stack space for UEFI function
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call r14 # system->boot->open_protocol(root_device, &guid, &rootfs, image_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL)
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mov rcx, [rsp+64] # get rootfs
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# Get root directory
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push rdx # allocate stack for rootdir
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mov rdx, rsp # arg2 = &rootdir
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push rax # allocate shadow stack space for UEFI function
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push rax # allocate shadow stack space for UEFI function
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call [rcx+8] # rootfs->open_volume(rootfs, &rootdir)
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pop rax # deallocate stack
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pop rax # deallocate stack
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pop r14 # save &rootdir
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# Open file for writing
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push rdx # allocate stack for fout
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mov rdx, rsp # arg2 = &fout
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push 0 # arg5 = 0
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push 7 # to get 0x8000000000000003 we set the rightmost 3 bits
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pop r9 # and then do right rotation by 1
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ror r9 # arg4 = EFI_FILE_MODE_CREATE| EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ
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mov r8, r13 # arg3 = out
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mov rcx, r14 # arg1 = rootdir
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sub rsp, 32 # allocate shadow stack space for UEFI function
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call [rcx+8] # rootdir->open()
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mov r13, [rsp+40] # get fout
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# Open file for reading
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push rdx # allocate stack for fin
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mov rdx, rsp # arg2 = &fin
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push 1 # arg5 = EFI_FILE_READ_ONLY
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push 1 # prepare to set arg4 to EFI_FILE_MODE_READ
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pop r9 # arg4 = EFI_FILE_MODE_READ
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mov r8, r12 # arg3 = in
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mov rcx, r14 # arg1 = rootdir
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sub rsp, 32 # allocate shadow stack space for UEFI function
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call [rcx+8] # rootdir->open()
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mov r12, [rsp+40] # get fin
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# Our flag for byte processing
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push -1
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pop rbx # rbx = -1
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# temp storage for the sum
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xor edi, edi # rdi = 0
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loop:
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# Read a byte
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call read_byte
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# process byte
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call hex
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# Deal with -1 values
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test eax, eax
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jl loop
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# deal with toggle
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test ebx, ebx # jump if ebx >= 0
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jge print
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# process first byte of pair
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mov edi, eax
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xor ebx, ebx # rbx = 0
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jmp loop
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# process second byte of pair
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print:
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# update the sum and store in output
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shl edi, 4
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add eax, edi
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# flip the toggle
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dec ebx # rbx = -1
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call write_byte
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jmp loop
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hex:
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# Purge Comment Lines (#)
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cmp al, 35
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je purge_comment
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# Purge Comment Lines (;)
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cmp al, 59
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je purge_comment
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# deal all ascii less than 0
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cmp al, 48
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jl ascii_other
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# deal with 0-9
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cmp al, 58
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jl ascii_num
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# deal with all ascii less than A
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cmp al, 65
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jl ascii_other
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# deal with A-F
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cmp al, 71
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jl ascii_high
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# deal with all ascii less than a
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cmp al, 97
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jl ascii_other
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# deal with a-f
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cmp al, 103
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jl ascii_low
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# The rest that remains needs to be ignored
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jmp ascii_other
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purge_comment:
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# Read a byte
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call read_byte
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# Loop if not LF (works for CR/LF and LF/CR endings too)
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cmp al, 10
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jne purge_comment
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# Otherwise return -1
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ascii_other:
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push -1
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pop rax # return = -1
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ret
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ascii_num:
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sub al, 48
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ret
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ascii_low:
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sub al, 32 # convert to uppercase
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ascii_high:
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sub al, 55
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ret
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# Writes byte stored in al
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write_byte:
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mov rcx, r13 # arg1 = fout
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push 1 # size = 1
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mov rdx, rsp # arg2 = &size
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push rax # allocate stack
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mov r8, rsp # arg3 = &output
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push rax # allocate shadow stack space for UEFI function
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push rax # allocate shadow stack space for UEFI function
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push rax # allocate shadow stack space for UEFI function
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call [rcx+40] # fout->write()
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add rsp, 40 # deallocate stack
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ret # return
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read_byte:
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mov rcx, r12 # arg1 = fin
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push 1 # size = 1
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mov rdx, rsp # arg2 = &size
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push rsi # allocate stack
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mov r8, rsp # arg3 = &input
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push rax # allocate shadow stack space for UEFI function
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push rax # allocate shadow stack space for UEFI function
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push rax # allocate shadow stack space for UEFI function
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call [rcx+32] # fin->read()
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pop rax # deallocate stack
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pop rax # deallocate stack
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pop rax # deallocate stack
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pop rax # save input to rax
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pop rsi # save size to rsi
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# If the file ended (0 bytes read) terminate
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test esi, esi # if size == 0
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je terminate # then we are done
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ret # return
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terminate:
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push rbx # allocate stack
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mov rcx, r12 # arg1 = fin
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call [rcx+16] # fin->close()
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mov rcx, r13 # arg1 = fout
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call [rcx+16] # fout->close()
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abort: # used for debugging only
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mov rsp, rbp # restore stack
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ret # return to UEFI
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.data
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# Protocol GUIDs
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LOADED_IMAGE_PROTOCOL:
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.long 0x5b1b31a1
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.short 0x9562
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.short 0x11d2
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.byte 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b
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SIMPLE_FS_PROTOCOL:
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.long 0x0964e5b22
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.short 0x6459
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.short 0x11d2
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.byte 0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b
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