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.section .constants, "a"
c_elf_header:
.byte 0x7f # Magic Number
.ascii "ELF" #
.byte 0x2 # 64-Bit
.byte 0x1 # little-endian
.byte 0x1 # ELFv1
.byte 0x0 # System V ABI
.quad 0x0 #
.hword 0x02 # Executable
.hword 0x3e # AMD x86-64
.int 0x1 # ELFv1
.quad 0x401000 # Entry
.quad 0x40 # Program Header Offset
.quad 0x100 # TODO: Section Header Offset
.int 0x0 #
.hword 0x40 # ELF Header Size
.hword 0x38 # Program Header Table Entry Size
.hword 0x3 # TODO: Number Of Entries in Program Header Table
.hword 0x40 # Section Header Table Entry Size
.hword 0x3 # TODO: Number Of Entries in Section Header Table
.hword 0x2 # TODO: Index of Section Header Table Entry containing section names
c_usage_message:
.asciz "bfc [input file] [output file]\n"
.section .variables, "aw"
v_input_fd:
.int 0x0
v_output_fd:
.int 0x0
v_buffer_start:
.quad 0x0
v_buffer_end:
.quad 0x0
v_buffer_cursor:
.quad 0x0
v_input_char:
.byte 0x0
.section .code, "ax"
.global _start
_start:
mov %rsp, %rbp
call f_check_args
call f_open_files
call f_init_buffer
l_read_loop:
call f_read_next_character
cmp $0, %rax
je l_read_loop_end
mov $1, %rax
mov $1, %rdi
mov $v_input_char, %rsi
mov $1, %rdx
syscall
jmp l_read_loop
l_read_loop_end:
# ----
call f_close_files
mov $0, %rdi
jmp f_exit
f_exit:
mov $60, %rax
syscall
f_check_args:
mov (%rbp), %rax
cmp $3, %rax
je l_check_args_success
mov $1, %rax
mov $2, %rdi
mov $c_usage_message, %rsi
mov $32, %rdx
syscall
mov $-1, %rdi
jmp f_exit
l_check_args_success:
ret
f_open_files:
mov $2, %rax
mov 16(%rbp), %rdi
mov $0, %rsi
mov $0, %rdx
syscall
mov $v_input_fd, %rbx
mov %eax, (%rbx)
mov $2, %rax
mov 24(%rbp), %rdi
mov $0x41, %rsi
mov $0744, %rdx
syscall
mov $v_output_fd, %rbx
mov %eax, (%rbx)
ret
f_close_files:
mov $3, %rax
mov %rbx, %rsi
syscall
mov $3, %rax
mov %rcx, %rsi
syscall
ret
f_init_buffer:
mov $12, %rax
mov $0, %rdi
syscall
mov $v_buffer_start, %rbx
mov %rax, (%rbx)
mov $v_buffer_end, %rbx
mov %rax, (%rbx)
mov $v_buffer_cursor, %rbx
mov %rax, (%rbx)
/*
* We directly skip to f_resize_buffer
* since we want to resize it to a usable amount
*/
f_resize_buffer:
mov $12, %rax
mov $v_buffer_end, %rbx
mov (%rbx), %rdi
add $0x400, %rdi
syscall
mov %rax, (%rbx)
ret
/* %rsi = needed end */
f_check_buffer:
mov $v_buffer_end, %rbx
mov (%rbx), %rax
cmp %rax, %rsi
jl l_check_buffer_large_enough
call f_resize_buffer
l_check_buffer_large_enough:
ret
f_read_next_character:
mov $0, %rax
mov $v_input_fd, %rbx
mov (%rbx), %rdi
mov $v_input_char, %rsi
mov $1, %rdx
syscall
ret
|
