ヒープバッファオーバーフロー-AddressSanitizer出力-この状態を悪用するには何が必要ですか？
これはAddressSanitizerの出力です。さまざまな入力に対して、READおよびWRITEエラーが発生します。ヒープバッファオーバーフローの観点から、より興味深いのはどれですか。シェルコードを実行したい。誰かがこのAndressSanitizerの出力をより「人間的な」理解可能な方法で解釈できますか？
例を読む：
==24222== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000010000 at pc 0x4022bd bp 0x7fff9b142e90 sp 0x7fff9b142e88
READ of size 1 at 0x602000010000 thread T0
#0 0x4022bc (/home/user/final/apngdis-2.5.orig/apngdis+0x4022bc)
#1 0x40619a (/home/user/final/apngdis-2.5.orig/apngdis+0x40619a)
#2 0x4012cd (/home/user/final/apngdis-2.5.orig/apngdis+0x4012cd)
#3 0x7f677aadfec4 (/lib/x86_64-linux-gnu/libc-2.19.so+0x21ec4)
#4 0x401734 (/home/user/final/apngdis-2.5.orig/apngdis+0x401734)
0x602000010000 is located 0 bytes to the right of 192-byte region [0x60200000ff40,0x602000010000)
allocated by thread T0 here:
#0 0x7f677b0b141a (/usr/lib/x86_64-linux-gnu/libasan.so.0.0.0+0x1541a)
#1 0x4059bb (/home/user/final/apngdis-2.5.orig/apngdis+0x4059bb)
Shadow bytes around the buggy address:
0x0c047fff9fb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fe0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c047fff9ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fffa000:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap righ redzone: fb
Freed Heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
ASan internal: fe
==24222== ABORTING
以下はGDB出力です
このヒープオーバーフローは悪用可能ですか？コードで何を探す必要がありますか？コードスニペットの例を挙げられますか？
Starting program: /home/user/final/apngdis-2.5.orig/apngdis crash.png
APNG Disassembler 2.5
Reading 'crash.png'...
Breakpoint 2, unpack (zstream=..., dst=dst@entry=0x6e1910 "", dst_size=dst_size@entry=192, src=src@entry=0x6e19e0 "x\332b\356\317\300", src_size=src_size@entry=14, h=2147483651,
rowbytes=rowbytes@entry=63, bpp=1 '\001') at apngdis.c:171
171 {
(gdb)
(gdb)
(gdb) l
166 row[i] += row[i-bpp];
167 }
168 }
169
170 void unpack(z_stream zstream, unsigned char * dst, unsigned int dst_size, unsigned char * src, unsigned int src_size, unsigned int h, unsigned int rowbytes, unsigned char bpp)
171 {
172 unsigned int j;
173 unsigned char * row = dst;
174 unsigned char * prev_row = NULL;
175
(gdb) l
176 zstream.next_out = dst;
177 zstream.avail_out = dst_size;
178 zstream.next_in = src;
179 zstream.avail_in = src_size;
180 inflate(&zstream, Z_FINISH);
181 inflateReset(&zstream);
182
183 for (j=0; j<h; j++)
184 {
185 switch (*row++)
(gdb) l
186 {
187 case 0: break;
188 case 1: read_sub_row(row, rowbytes, bpp); break;
189 case 2: read_up_row(row, prev_row, rowbytes, bpp); break;
190 case 3: read_average_row(row, prev_row, rowbytes, bpp); break;
191 case 4: read_paeth_row(row, prev_row, rowbytes, bpp); break;
192 }
193 prev_row = row;
194 row += rowbytes;
195 }
(gdb) cont
Continuing.
Program received signal SIGSEGV, Segmentation fault.
unpack (zstream=..., dst=dst@entry=0x6e1910 "\003\217\257\277\307\313\315\316", '\317' <repeats 17 times>, "ϗ{mfca```\200\220H$\022\t\004\002\001", dst_size=dst_size@entry=192,
src=src@entry=0x6e19e0 "x\332b\356\317\300", src_size=src_size@entry=14, h=2147483651, rowbytes=rowbytes@entry=63, bpp=1 '\001') at apngdis.c:185
185 switch (*row++)
(gdb)
ここにシンボルがあります：
root@user-lap:~/final/apngdis-2.5.orig# export ASAN_SYMBOLIZER_PATH=/usr/bin/llvm-symbolizer-3.4
root@user-lap:~/final/apngdis-2.5.orig# ASAN_OPTIONS=symbolize=1 ./apngdis crash.png
APNG Disassembler 2.5
Reading 'crash.png'...
=================================================================
==25265== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000010000 at pc 0x41c07d bp 0x7ffc560b3f20 sp 0x7ffc560b3f18
READ of size 1 at 0x602000010000 thread T0
#0 0x41c07c in unpack /home/user/final/apngdis-2.5.orig/apngdis.c:185
#1 0x41ff5a in LoadAPNG /home/user/final/apngdis-2.5.orig/apngdis.c:846
#2 0x40281d in main /home/user/final/apngdis-2.5.orig/apngdis.c:1208
#3 0x7fb4ca7e4ec4 (/lib/x86_64-linux-gnu/libc.so.6+0x21ec4)
#4 0x402c84 in _start (/home/user/final/apngdis-2.5.orig/apngdis+0x402c84)
0x602000010000 is located 0 bytes to the right of 192-byte region [0x60200000ff40,0x602000010000)
allocated by thread T0 here:
#0 0x412c0a in __interceptor_malloc (/home/user/final/apngdis-2.5.orig/apngdis+0x412c0a)
#1 0x41f77b in LoadAPNG /home/user/final/apngdis-2.5.orig/apngdis.c:635
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/user/final/apngdis-2.5.orig/apngdis.c:185 unpack
Shadow bytes around the buggy address:
0x0c047fff9fb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9fe0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c047fff9ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fffa000:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fffa050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap righ redzone: fb
Freed Heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
ASan internal: fe
==25265== ABORTING
最後ですが、Linuxでのヒープバッファオーバーフローに関する優れたチュートリアルへのリンクは、実際のところすばらしいものです。
問題のプログラムの完全なコードは次のとおりです。
アップデート29.02.2016
4バイトの書き込みが見つかりました。 LoadAPNGにユーザーが制御した値のmalloc呼び出しがあるようです。 「力の家」というテクニックは使えますか？
==2720== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60ae0003a81c at pc 0x41ee70 bp 0x7ffc84d157d0 sp 0x7ffc84d157c8
WRITE of size 4 at 0x60ae0003a81c thread T0
#0 0x41ee6f in compose6 /home/user/final/apngdis-2.5.orig/apngdis.c:475
#1 0x420025 in LoadAPNG /home/user/final/apngdis-2.5.orig/apngdis.c:853
#2 0x40281d in main /home/user/final/apngdis-2.5.orig/apngdis.c:1208
#3 0x7f4942135ec4 (/lib/x86_64-linux-gnu/libc.so.6+0x21ec4)
#4 0x402c84 in _start (/home/user/final/apngdis-2.5.orig/apngdis+0x402c84)
0x60ae0003a81c is located 0 bytes to the right of 114716-byte region [0x60ae0001e800,0x60ae0003a81c)
allocated by thread T0 here:
#0 0x412c0a in __interceptor_malloc (/home/user/final/apngdis-2.5.orig/apngdis+0x412c0a)
#1 0x41f746 in LoadAPNG /home/user/final/apngdis-2.5.orig/apngdis.c:633
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/user/final/apngdis-2.5.orig/apngdis.c:474 compose6
Shadow bytes around the buggy address:
0x0c163ffff4b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c163ffff4c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c163ffff4d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c163ffff4e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c163ffff4f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c163ffff500: 00 00 00[04]fa fa fa fa fa fa fa fa fa fa fa fa
0x0c163ffff510: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c163ffff520: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c163ffff530: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c163ffff540: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c163ffff550: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap righ redzone: fb
Freed Heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
ASan internal: fe
==2720== ABORTING
アップデート07.02.2017
@grepNstepNの要求どおり
root@laptop:~/security/apngfuzz/apngdis-2.5.orig# gdb ./apngdis crash/crash.png
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos Word" to search for commands related to "Word"...
Reading symbols from ./apngdis...done.
"/home/user/security/apngfuzz/apngdis-2.5.orig/crash/crash.png" is not a core dump: File format not recognized
(gdb) r crash/crash.png
Starting program: /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis crash/crash.png
[Thread debugging using libthread_db enabled]
Using Host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
APNG Disassembler 2.5
Reading 'crash/crash.png'...
=================================================================
==14864==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000ef91 at pc 0x00000040b1b4 bp 0x7fffffffd9b0 sp 0x7fffffffd9a0
READ of size 1 at 0x60200000ef91 thread T0
#0 0x40b1b3 in compose6 /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis.c:469
#1 0x40ca5f in LoadAPNG /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis.c:850
#2 0x4017be in main /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis.c:1202
#3 0x7ffff68a782f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
#4 0x402048 in _start (/home/user/security/apngfuzz/apngdis-2.5.orig/apngdis+0x402048)
0x60200000ef91 is located 0 bytes to the right of 1-byte region [0x60200000ef90,0x60200000ef91)
allocated by thread T0 here:
#0 0x7ffff6f02602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
#1 0x40bb97 in LoadAPNG /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis.c:632
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis.c:469 compose6
Shadow bytes around the buggy address:
0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa 00 06
=>0x0c047fff9df0: fa fa[01]fa fa fa 04 fa fa fa 01 fa fa fa 01 fa
0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
==14864==ABORTING
[Inferior 1 (process 14864) exited with code 01]
(gdb) disass crash/crash.pngQuit
(gdb) dis
disable disassemble disconnect display
(gdb) disass 0x40b1b3
Dump of assembler code for function compose6:
0x000000000040a990 <+0>: lea -0x98(%rsp),%rsp
0x000000000040a998 <+8>: mov %rdx,(%rsp)
0x000000000040a99c <+12>: mov %rcx,0x8(%rsp)
0x000000000040a9a1 <+17>: mov %rax,0x10(%rsp)
0x000000000040a9a6 <+22>: mov $0xbb3f,%rcx
0x000000000040a9ad <+29>: callq 0x4112e0 <__afl_maybe_log>
0x000000000040a9b2 <+34>: mov 0x10(%rsp),%rax
0x000000000040a9b7 <+39>: mov 0x8(%rsp),%rcx
0x000000000040a9bc <+44>: mov (%rsp),%rdx
0x000000000040a9c0 <+48>: lea 0x98(%rsp),%rsp
0x000000000040a9c8 <+56>: Push %r15
0x000000000040a9ca <+58>: Push %r14
0x000000000040a9cc <+60>: Push %r13
0x000000000040a9ce <+62>: Push %r12
0x000000000040a9d0 <+64>: Push %rbp
0x000000000040a9d1 <+65>: Push %rbx
0x000000000040a9d2 <+66>: sub $0x48,%rsp
0x000000000040a9d6 <+70>: movzbl 0x88(%rsp),%r13d
0x000000000040a9df <+79>: mov %rdi,0x18(%rsp)
0x000000000040a9e4 <+84>: mov %r8d,0x28(%rsp)
0x000000000040a9e9 <+89>: mov %r9d,0x2c(%rsp)
0x000000000040a9ee <+94>: add $0x7,%r13d
---Type <return> to continue, or q <return> to quit---q
Quit
(gdb) i r
The program has no registers now.
(gdb) b *0x40b1b3
Breakpoint 1 at 0x40b1b3: file apngdis.c, line 469.
(gdb) r crash/crash.png
Starting program: /home/user/security/apngfuzz/apngdis-2.5.orig/apngdis crash/crash.png
[Thread debugging using libthread_db enabled]
Using Host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
APNG Disassembler 2.5
Reading 'crash/crash.png'...
Program received signal SIGSEGV, Segmentation fault.
0xffffffffcd4013e0 in ?? ()
(gdb) i r
rax 0x1 1
rbx 0x1 1
rcx 0x60210000efd0 105694850248656
rdx 0xc0400001df2 13211319410162
rsi 0x60200000ef92 105690555281298
rdi 0x60200000ef91 105690555281297
rbp 0x2 0x2
rsp 0x7fffffffd9b8 0x7fffffffd9b8
r8 0x0 0
r9 0x1 1
r10 0x60200000eff0 105690555281392
r11 0x60200000ef91 105690555281297
r12 0x40000000 1073741824
r13 0x1 1
r14 0x1 1
r15 0x4 4
rip 0xffffffffcd4013e0 0xffffffffcd4013e0
eflags 0x10202 [ IF RF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
---Type <return> to continue, or q <return> to quit---
gs 0x0 0
(gdb) info registers rip
rip 0xffffffffcd4013e0 0xffffffffcd4013e0
私はあなたがどこから来たのか理解しています、私はさまざまな製品（とりわけ、クロム、フラッシュなど）をファジングしています。あなたがしたい最後のことは、可能性のある報奨金または助言を与えることです（私は formermorethanthe をサポートしています） = 後半 、特に アーロンシュワルツに起こったこと を考慮してください。
考えてみてください：この場合、apngdisは libpng でパーサーまたはファイル形式の脆弱性をもたらす可能性があり、Chrome、Firefox、Webkit（iOS、OSX）で使用されます、など。前述のすべてにバグの報奨金があります。少なくとも Googleはオープンソースプロジェクトを保護するための報奨金を提供しています 。 apngdisが製品で直接使用されているかどうかはわかりません。
前述のことを考慮して、助けが必要な場合は、私が見つけたいくつかの脆弱性に関してこれまでに行ったことを行うことができます。
- 賞金や助言を盗むにはあまりにも評判が高い人に助けを求めます（＃corelan /ピーターヴァンイーコットが頭に浮かびます）。動機
- 誰かにNDA=に署名して盗難が発生しないようにします。ただし、見返りとして、報奨金/栄光の一部を提供する必要があります（アドバイザリーでは一言、または著者）
- 以前のチュートリアルを確認し、記述を活用して類似点を探します
- Stackexchangeの見返りに何も提供しないように助けを求めます。これはかなり無礼です。少なくとも、それが公開されている場合は、助けてくれた人に感謝を...
＃4を選択した場合、次のものが必要です。
[apngdis + 0x4022bc]での読み取り、前の命令、および呼び出しスタックの逆アセンブリが必要です。同じことが書き込みにも当てはまります（RIP、RIP-1命令、呼び出しスタックの逆アセンブリ）
考慮：ASanの出力を解釈しても、前述の説明がないと、必ずしも悪用可能性に役立つわけではありません。例えば：
==24222== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000010000 at pc 0x4022bd bp 0x7fff9b142e90 sp 0x7fff9b142e88
READ of size 1 at 0x602000010000 thread T0
#0 0x4022bc (/home/user/final/apngdis-2.5.orig/apngdis+0x4022bc)
...
CVE-2017-619 は、この特定の脆弱性（バージョン2.8に存在）のために予約されています。あなたの名前は、発見者および共同貢献者として。
明日、この投稿は1年間オンラインになり、執筆時点ではほぼ2000回閲覧されています。したがって、誰もがこれを誤用しないように、詳細がまだ公開されていることを確認するために、afl-fuzzクラスターでapngdisを自由に実行して、問題を報告用に再構築しました。
これらのメモリ破損の再発見の中で、ファイル名パラメータの処理における教科書のオーバーフローは言うまでもなく、チャンクサイズ記述子にも1つありました。
問題をデバッグし、開発者に通知しました。背後で起こった状況の深刻さを説明した後、彼は非常に反応がよく、バージョン2.9で作業するのに十分親切になりました。
Compose_frame関数のメモリ破損は最新バージョン2.8にも存在しており、簡単に説明できます。 memcpy（）は、いくつかの制約内で、攻撃者が指定した長さの一連のゼロに対して呼び出されます。
まず、それが実際にPNGであり、IHDRサイズフィールドであることを確認した後、値はファイルから読み込まれます。
w0 = w = png_get_uint_32(chunkIHDR.p + 8);
h0 = h = png_get_uint_32(chunkIHDR.p + 12);
次に、値がconst unsigned long cMaxPNGSize = 1000000UL;未満であることを確認した後、次のものが呼び出されます。
compose_frame(frameCur.rows, frameRaw.rows, bop, x0, y0, w0, h0);
で構成されています：
void compose_frame(unsigned char ** rows_dst, unsigned char ** rows_src, unsigned char bop, unsigned int x, unsigned int y, unsigned int w, unsigned int h)
{
unsigned int i, j;
int u, v, al;
for (j=0; j<h; j++)
{
unsigned char * sp = rows_src[j];
unsigned char * dp = rows_dst[j+y] + x*4;
if (bop == 0)
memcpy(dp, sp, w*4);
Memcpyが呼び出され、数百万のゼロのコピーを開始してから、マップされていないメモリに実行されます。
Breakpoint 1, compose_frame (rows_dst=0x7fffef54f010, rows_src=0x7ffff3150010, bop=0 '\000', x=0, y=0, w=983040, h=983040) at apngdis.cpp:77
77 if (bop == 0)
(gdb) n
78 memcpy(dp, sp, w*4);
(gdb) print dp
$1 = (unsigned char *) 0x55555576f910 ""
(gdb) print sp
$2 = (unsigned char *) 0x55555576f2a0 ""
(gdb) print w
Windows x86では、これは次のアセンブリにコンパイルされ、ESIからEDIへのコピーが行われることがわかります。
.text:011FFA90 loc_11FFA90: ; CODE XREF: .text:011FFAEBj .text:011FFA90 movdqa xmm0, oword ptr [esi] .text:011FFA94 movdqa xmm1, oword ptr [esi+10h] .text:011FFA99 movdqa xmm2, oword ptr [esi+20h] .text:011FFA9E movdqa xmm3, oword ptr [esi+30h] .text:011FFAA3 movdqa oword ptr [edi], xmm0 .text:011FFAA7 movdqa oword ptr [edi+10h], xmm1 .text:011FFAAC movdqa oword ptr [edi+20h], xmm2 .text:011FFAB1 movdqa oword ptr [edi+30h], xmm3 .text:011FFAB6 movdqa xmm4, oword ptr [esi+40h] .text:011FFABB movdqa xmm5, oword ptr [esi+50h] .text:011FFAC0 movdqa xmm6, oword ptr [esi+60h] .text:011FFAC5 movdqa xmm7, oword ptr [esi+70h] .text:011FFACA movdqa oword ptr [edi+40h], xmm4 .text:011FFACF movdqa oword ptr [edi+50h], xmm5 .text:011FFAD4 movdqa oword ptr [edi+60h], xmm6 .text:011FFAD9 movdqa oword ptr [edi+70h], xmm7 .text:011FFADE lea esi, [esi+80h] .text:011FFAE4 lea edi, [edi+80h] .text:011FFAEA dec edx .text:011FFAEB jnz short loc_11FFA90