247 lines
11 KiB
ArmAsm
247 lines
11 KiB
ArmAsm
# SPDX-FileCopyrightText: 2022 Andrius Štikonas <andrius@stikonas.eu>
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# SPDX-FileCopyrightText: 2019 Jeremiah Orians
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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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 r12, rcx # save image_handle
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mov r14, [rdx+96] # save system->boot
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# Open Loaded Image protocol
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mov r9, r12 # arg4 = image_handle
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lea rdx, [rip+LOADED_IMAGE_PROTOCOL] # guid = &LOADED_IMAGE_PROTOCOL
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mov rcx, r12 # arg1 = image_handle
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call open_protocol # open protocol
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mov rdi, rax # save image
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# Get root file system
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mov r9, r12 # arg4 = image_handle
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lea rdx, [rip+SIMPLE_FS_PROTOCOL] # guid = &SIMPLE_FS_PROTOCOL
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mov rcx, [rdi+24] # arg1 = root_device = image->device
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mov [rip+root_device], rcx # save root_device
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call open_protocol # open protocol
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mov rcx, rax # get rootfs
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# Get root directory
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lea rdx, [rip+rootdir] # 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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# Push command line arguments onto stack
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mov rbx, [rdi+56] # options = image->load_options
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mov rdx, rbx # save beginning of load_options
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add rbx, [rdi+48] # go to the end of load_options
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push 0 # Save end of arguments (NULL) onto stack
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loop_options:
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cmp rbx, rdx # Check if we are done
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je loop_options_done # We are done
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sub 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_options # then continue looping
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mov BYTE PTR [rbx], 0 # zero it
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add rbx, 2 # ++options
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push rbx # push another argument onto stack
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jmp loop_options # next argument
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loop_options_done:
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pop r8 # get output file
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test r8, r8 # if no output file
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je exit_early # then exit
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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 rcx, [rip+rootdir] # 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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add rsp, 40 # deallocate stack
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pop r15 # get fout
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mov rdx, 0x100000 # Allocate 1MiB
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call allocate_pool # Get memory pool
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mov rbx, rax # Save it
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core:
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pop r8 # Get the actual input name
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cmp r8, 0 # Check for null string
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je done # We are done if null string
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call open_file # Open file as read only
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test eax, eax # check if successfully opened
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jne core # Else go to another file
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mov r13, rsi # Protect fin
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keep:
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mov rdx, 0x100000 # set the size of chars we want
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call read # read them
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push rax # Protect the number of bytes read
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mov rdx, rax # number of bytes to write
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call write # write them
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pop rax # Get bytes read
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cmp rax, 0x100000 # Check if buffer was fully used
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je keep # Keep looping if it was full
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mov rcx, r13 # fin
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call close_file # close file
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jmp core # Move to next file
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done:
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mov rcx, r15 # Get output file
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call close_file # close it
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mov rcx, rbx # Get buffer
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call free_pool # release it
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exit_early:
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mov rcx, [rip+rootdir] # Get rootdir
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call close_file # close it
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mov r8, r12 # arg3 = image_handle
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lea rdx, [rip+SIMPLE_FS_PROTOCOL] # EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID
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mov rcx, [rip+root_device] # arg1 = root_device
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call close_protocol # close protocol
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mov r8, r12 # arg3 = image_handle
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lea rdx, [rip+LOADED_IMAGE_PROTOCOL] # EFI_LOADED_IMAGE_PROTOCOL_GUID
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mov rcx, r12 # arg1 = image_handle
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call close_protocol # close protocol
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mov rsp, rbp # restore stack pointer
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ret # return to UEFI
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# r8: input file name
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# returns input file handle in rsi, status in rax
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open_file:
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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 rcx, [rip+rootdir] # 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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add rsp, 40 # deallocate stack
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pop rsi # get fin
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ret
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# rcx: file handle
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close_file:
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push rax # allocate shadow stack space for UEFI function
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call [rcx+16] # file_handle->close(file_handle)
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pop rax # deallocate stack
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ret
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# rcx: handle
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# rdx: &guid
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# r9: agent_handle
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# returns interface
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open_protocol:
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push rax # allocate stack for interface
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mov r8, rsp # arg3 = &interface
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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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sub rsp, 32 # allocate shadow stack space for UEFI function
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call [r14+280] # system->boot->open_protocol(handle, &guid, &interface, agent_handle, 0, EFI_OPEN_PROTOCOL_BY_HANDLE_PROTOCOL)
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add rsp, 48 # deallocate stack
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pop rax # get image
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ret
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# rcx: handle
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# rdx: &guid
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# r8: agent_handle
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close_protocol:
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xor r9, r9 # arg4 = NULL
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sub rsp, 32 # allocate shadow stack space for UEFI function
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call [r14+288] # system->boot->close_protocol(handle, &guid, agent_handle, 0)
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add rsp, 32 # deallocate stack
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ret
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# rdx: number of bytes to allocate
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# r14: system->boot
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# returns pointer in rax
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allocate_pool:
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push rdx # allocate stack for pool pointer
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mov r8, rsp # arg3 = &pool
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push 2
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pop rcx # arg1 = EFI_LOADER_DATA
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sub rsp, 24 # allocate shadow stack space for UEFI
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call [r14+64] # system->boot->allocate_pool(EFI_LOADER_DATA, 2048, &pool)
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add rsp, 24 # deallocate stack
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pop rax # get pool
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ret
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# rcx: memory pool
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# r14: system->boot
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free_pool:
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push rax # allocate shadow stack space for UEFI function
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call [r14+72] # system->boot->free_pool(pool)
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pop rax # deallocate stack
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ret
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# rdx: number of bytes to read
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# rbx: buffer
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# r13: input file handle
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# returns number of bytes read in rax
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read:
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mov rcx, r13 # arg1 = fin
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push rdx # set size
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mov rdx, rsp # arg2 = &size
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mov r8, rbx # arg3 = buffer
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sub rsp, 24 # allocate shadow stack space for UEFI
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call [rcx+32] # fin->read()
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add rsp, 24 # deallocate stack
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pop rax # save size to rax
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ret
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# rdx: number of bytes to write
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# rbx: buffer
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# r14: output file handle
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# returns number of bytes written in rax
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write:
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mov rcx, r15 # arg1 = fout
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push rdx # set size
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mov rdx, rsp # arg2 = &size
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mov r8, rbx # arg3 = buffer
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sub rsp, 24 # allocate shadow stack space for UEFI
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call [rcx+40] # fin->write()
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add rsp, 24 # deallocate stack
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pop rax # save size to rax
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ret
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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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rootdir:
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.long 0, 0
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root_device:
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.long 0, 0
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