diff options
Diffstat (limited to 'linux/apps/ex5.subx')
| -rw-r--r-- | linux/apps/ex5.subx | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/linux/apps/ex5.subx b/linux/apps/ex5.subx new file mode 100644 index 00000000..220a4246 --- /dev/null +++ b/linux/apps/ex5.subx @@ -0,0 +1,40 @@ +# Read a character from stdin, save it to a local on the stack, write it to stdout. +# +# To run: +# $ bootstrap/bootstrap translate apps/ex5.subx -o ex5 +# $ bootstrap/bootstrap run ex5 + +== 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: + + # allocate x on the stack + 81 5/subop/subtract 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # subtract from esp + + # read(stdin, x, 1) + # . fd = 0 (stdin) + bb/copy-to-ebx 0/imm32 + # . data = x (location to write result to) + 8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none 1/r32/ecx 4/disp8 . # copy esp+4 to ecx + # . size = 1 character + ba/copy-to-edx 1/imm32 + # . syscall + e8/call syscall_read/disp32 + + # syscall(write, stdout, x, 1) + # . fd = 1 (stdout) + bb/copy-to-ebx 1/imm32 + # . data = x (location to read from) + 8d/copy-address 1/mod/*+disp8 4/rm32/sib 4/base/esp 4/index/none 1/r32/ecx 4/disp8 . # copy esp+4 to ecx + # . size = 1 character + ba/copy-to-edx 1/imm32 + # . syscall + e8/call syscall_write/disp32 + + # exit(ebx) + e8/call syscall_exit/disp32 + +# . . vim:nowrap:textwidth=0 |