diff options
Diffstat (limited to 'linux/ex7.subx')
| -rw-r--r-- | linux/ex7.subx | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/linux/ex7.subx b/linux/ex7.subx new file mode 100644 index 00000000..73cb2720 --- /dev/null +++ b/linux/ex7.subx @@ -0,0 +1,98 @@ +# 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 translate init.linux apps/ex7.subx -o apps/ex7 +# $ ./bootstrap run apps/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 |