diff options
| author | Kartik Agaram <vc@akkartik.com> | 2018-10-02 14:26:40 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2018-10-02 14:26:46 -0700 |
| commit | 871d2227c4a07b3be580d80894db40646fc59ca9 (patch) | |
| tree | 01ba684b5df8270ccbe01fc80579d3d46b17ffd9 /subx/053new_segment.subx | |
| parent | 66aa96ecc74140e0f2f920deb47c12a7f6f6e515 (diff) | |
| download | mu-871d2227c4a07b3be580d80894db40646fc59ca9.tar.gz | |
4652 - new subx helper: create new segment
Diffstat (limited to 'subx/053new_segment.subx')
| -rw-r--r-- | subx/053new_segment.subx | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/subx/053new_segment.subx b/subx/053new_segment.subx new file mode 100644 index 00000000..33522517 --- /dev/null +++ b/subx/053new_segment.subx @@ -0,0 +1,62 @@ +# Create a new segment (for data) using mmap(). + +== code + +# instruction effective address operand 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 + +# main: (manual test if this is the last file loaded) + # EAX = new_segment(0x1000) + # push arg + 68/push 0x1000/imm32 + # call + e8/call new_segment/disp32 + # discard arg + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + + # store to *EAX + c7/copy 0/mod/direct 0/rm32/EAX . . . . . 0x34/imm32 # copy to *EAX + + # exit(EAX) + 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # copy EAX to EBX + b8/copy . . . . . . . 1/imm32/exit # copy to EAX + cd/syscall 0x80/imm8 + +new_segment: # len : int -> address + # prolog + 55/push-EBP + 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP + 53/push-EBX + # copy len to mmap_new_segment.len + # TODO: compute mmap_new_segment+4 before runtime + 8b/copy 1/mod/*+disp8 4/rm32/SIB 5/base/EBP 4/index/none . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX + bb/copy . . . . . . . mmap_new_segment/imm32 # copy to EBX + 89/copy 1/mod/*+disp8 3/rm32/EBX . . . 0/r32/EAX 4/disp8 . # copy EAX to *(EBX+4) + # mmap(mmap_new_segment) + bb/copy . . . . . . . mmap_new_segment/imm32 # copy to EBX + b8/copy . . . . . . . 0x5a/imm32/mmap # copy to EAX + cd/syscall 0x80/imm8 + # epilog + 5b/pop-to-EBX + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +== data +# various constants used here were found in the Linux sources (search for file mman-common.h) +mmap_new_segment: # type mmap_arg_struct + # addr + 00 00 00 00 # null + # len + 00 00 00 00 # 0x1000 + # protection flags + 03 00 00 00 # PROT_READ | PROT_WRITE + # sharing flags + 22 00 00 00 # MAP_PRIVATE | MAP_ANONYMOUS + # fd + ff ff ff ff # -1 since MAP_ANONYMOUS is specified + # offset + 00 00 00 00 # 0 since MAP_ANONYMOUS is specified + +# vim:ft=subx:nowrap:tw& |