99 lines
3.5 KiB
Plaintext
99 lines
3.5 KiB
Plaintext
# Example showing file syscalls.
|
|
#
|
|
# Create a file, open it for writing, write a character to it, close it, open
|
|
# it for reading, read a character from it, close it, delete it, and return
|
|
# the character read.
|
|
#
|
|
# To run:
|
|
# $ bootstrap/bootstrap translate ex7.subx -o ex7
|
|
# $ bootstrap/bootstrap run ex7
|
|
# Expected result:
|
|
# $ echo $?
|
|
# 97
|
|
|
|
== code
|
|
# instruction effective address register displacement immediate
|
|
# . op subop mod rm32 base index scale r32
|
|
# . 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes
|
|
|
|
Entry:
|
|
# creat(Filename)
|
|
bb/copy-to-ebx Filename/imm32
|
|
b9/copy-to-ecx 0x180/imm32/fixed-perms
|
|
e8/call syscall_creat/disp32
|
|
|
|
# stream = open(Filename, O_WRONLY, 0) # we can't use 'fd' because it looks like a hex byte
|
|
bb/copy-to-ebx Filename/imm32
|
|
b9/copy-to-ecx 1/imm32/wronly
|
|
ba/copy-to-edx 0x180/imm32/fixed-perms
|
|
e8/call syscall_open/disp32
|
|
# save stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
89/copy 0/mod/indirect 3/rm32/ebx . . . 0/r32/eax . . # copy eax to *ebx
|
|
|
|
# write(Stream, "a", 1)
|
|
# . load stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 3/r32/ebx . . # copy *ebx to ebx
|
|
# .
|
|
b9/copy-to-ecx A/imm32
|
|
ba/copy-to-edx 1/imm32/size
|
|
e8/call syscall_write/disp32
|
|
|
|
# close(Stream)
|
|
# . load stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 3/r32/ebx . . # copy *ebx to ebx
|
|
# .
|
|
e8/call syscall_close/disp32
|
|
|
|
# stream = open(Filename, O_RDONLY, 0)
|
|
bb/copy-to-ebx Filename/imm32
|
|
b9/copy-to-ecx 0/imm32/rdonly
|
|
ba/copy-to-edx 0x180/imm32/fixed-perms
|
|
e8/call syscall_open/disp32
|
|
# . save Stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
89/copy 0/mod/indirect 3/rm32/ebx . . . 0/r32/eax . . # copy eax to *ebx
|
|
|
|
# read(Stream, B, 1)
|
|
# . load stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 3/r32/ebx . . # copy *ebx to ebx
|
|
# .
|
|
b9/copy-to-ecx B/imm32
|
|
ba/copy-to-edx 1/imm32/size
|
|
e8/call syscall_read/disp32
|
|
|
|
# close(Stream)
|
|
# . load stream
|
|
bb/copy-to-ebx Stream/imm32
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 3/r32/ebx . . # copy *ebx to ebx
|
|
#
|
|
e8/call syscall_close/disp32
|
|
|
|
# unlink(filename)
|
|
bb/copy-to-ebx Filename/imm32
|
|
e8/call syscall_unlink/disp32
|
|
|
|
# exit(b)
|
|
# . load b
|
|
bb/copy-to-ebx B/imm32
|
|
8b/copy 0/mod/indirect 3/rm32/ebx . . . 3/r32/ebx . . # copy *ebx to ebx
|
|
#
|
|
e8/call syscall_exit/disp32
|
|
|
|
== data
|
|
|
|
Stream:
|
|
0/imm32
|
|
A:
|
|
61/imm32/A
|
|
B:
|
|
0/imm32
|
|
Filename:
|
|
2e 66 6f 6f 00 00 00 00
|
|
# . f o o null
|
|
|
|
# . . vim:nowrap:textwidth=0
|