# ELF header
# e_ident: u128
# Magic number: 0x7f454c46 = "\x7fELF"
7f 45 4c 46
02 # EI_CLASS: u8 = ELFCLASS64
01 # EI_DATA: u8 = ELFDATA2LSB
01 # EI_VERSION: u8 = EV_CURRENT
00 # EI_OSABI: u8 = ELFOSABI_NONE
00 # EI_ABIVERSION: u8 = 0
00 00 00 00 00 00 00 # EI_PAD: [u8; 7]
# e_type: u16 = E_EXEC
02 00
# e_machine: u16 = EM_X86_64
3e 00
# e_version: u32 = EV_CURRENT
01 00 00 00
# e_entry: u64 = 0x400000
00 00 40 00 00 00 00 00
# e_phoff: u64 = 0x40
40 00 00 00 00 00 00 00
# e_shoff: u64 = 0x0
00 00 00 00 00 00 00 00
# e_flags: u32 = 0
00 00 00 00
# e_ehsize: u16 = 64
40 00
# e_phentsize: u16 = 56
38 00
# e_phnum: u16 = 1
01 00
# e_shentsize: u16 = 0
00 00
# e_shnum: u16 = 0
00 00
# e_shstrndx: u16 = 0
00 00
# End of ELF header
#
# Program header
# p_type: u32 = PT_LOAD
01 00 00 00
# p_flags: u32 = PF_R | PF_X
05 00 00 00
# p_offset: u64 = 0
00 00 00 00 00 00 00 00
# p_vaddr: u64 = 0x400000
00 00 40 00 00 00 00 00
# p_paddr: u64 = 0x0
00 00 00 00 00 00 00 00
# p_filesz: u64 = 0x164
64 01 00 00 00 00 00 00
# p_memsz: u64 = 0x1000
00 10 00 00 00 00 00 00
# p_align: u64 = 0x1000
00 10 00 00 00 00 00 00
# End of program header
#
# Code segment (offset 0x40, virtual address 0x400000)
#
# _start:
# ; alloca 0x1000 bytes on the stack
# mov rbp, rsp
48 89 e5
# sub rsp, 0x1000
48 81 ec 00 10 00 00
# ; read 0x800 bytes from stdin into the stack
# .READ: (_start+10)
# xor rax, rax
48 31 c0
# mov edi, 0 (stdin)
48 c7 c7 00 00 00 00
# mov rsi, rsp
48 89 e6
# mov rdx, 0x800
48 c7 c2 00 08 00 00
# syscall (sys_read)
0f 05
# cmp rax, 0
48 83 f8 00
# jle die
0f 8e a1 00 00 00 # 203 - 42 = 161 = 0xa1
## (_start+42)
# ; end = r8
# mov r8, rax
49 89 c0
# add r8, rsp
49 01 e0
# ; pos = r9
# mov r9, rsp
49 89 e1
# ; dst = r10
# mov r10, rsp
49 89 e2
# add r10, 0x800
49 81 c2 00 08 00 00
# ; while (pos < end) {
# ; .L0: (_start+61)
# cmp r9, r8
4d 39 c1
# jge .L3
0f 8d 60 00 00 00 ; 166 - 70 = 96 = 0x60
# (_start+70)
#
# ; if (*pos == '#') {
# mov al , byte [r9]
41 8a 41 00
# cmp al, '#'
3c 23
# jne .L1 ; 100 - 82 = 18 = 0x12
0f 85 12 00 00 00
# (_start+82)
# ; while (*pos != '\n') pos++;
# ; .L2: (_start+82)
# inc r9
49 ff c1
# cmp byte [r9], '\n'
41 80 39 0a
# jne .L2 ; 82 - 95 = -13 = 0xfffffffffffffff3 = 0xf3
0f 85 f3 ff ff ff
# (_start+95)
# jmp .L0 ; 61 - 100 = -39 = 0xfffffffffffffd89 = 0xfd89
e9 89 fd ff ff
# (_start+100)
# ; .L1: (_start+100)
# ; convert *pos to high word
# mov bl, al
88 c3
# sub bl, 'a'
80 eb 61
# add bl, 10
80 c3 0a
# sub al, '0'
2c 30
# cmp al, 10
3c 0a
# cmovge eax, ebx
0f 43 c3
# shl al, 4
c0 e0 04
# ; pos++
# inc r9
49 ff c1
# ; convert *pos to low word
# mov bl, byte [r9]
41 8a 19
# mov cl, bl
88 d9
# sub cl, 'a'
80 e9 61
# add cl, 10
80 c1 0a
# sub bl, '0'
80 eb 30
# cmp bl, 10
80 fb 0a
# cmovge ebx, ecx
0f 4d d9
# ; combine high and low word
# or al, bl
08 d8
# ; write the byte to dst
# mov byte [r10], al
41 88 02
# inc r10
41 ff c2
# ; if (*pos != '\n') pos++;
# cmp byte [r9], '\n'
41 80 39 0a
# inc r9
49 ff c1
# je .L0 ; 61 - 161 = -100 = 0xffffffffffffff9c = 0x9c
0f 84 9c ff ff ff
## (_start+161)
# jmp .L1 ; 100 - 166 = -66 = 0xffffffffffffffbe = 0xbe
e9 be ff ff ff
## (_start+166)
# ; }
# .L3: (_start+166)
# ; write the decoded bytes to stdout
# mov rax, 1 (sys_write)
48 c7 c0 01 00 00 00
# mov rdi, 1 (stdout)
48 c7 c7 01 00 00 00
# mov rsi, rsp
48 89 e6
# add rsi, 0x800
48 81 c6 00 08 00 00
# mov rdx, r10
4c 89 d2
# sub rdx, rsi
48 29 f2
# syscall
0f 05
# jmp .READ ; 10 - 203 = -193 = 0xffffffffffffff3f = 0x3f
e9 3f ff ff ff
## (_start+203)
#
# die: (_start+203)
# mov rax, 60 (sys_exit)
48 c7 c0 3c 00 00 00
# xor rdi, rdi
48 31 ff
# syscall
0f 05
# _start+215