未解决 [原创] MASM伪指令Offset的使用问题

发表于: 2020-10-23 19:15 2933

未解决 [原创] MASM伪指令Offset的使用问题

baolongshou 活跃值

2020-10-23 19:15

2933

伪指令Offset指令使用问题

定义

大致讲:使用该伪指令将获取expression相对于当前段的偏移.
offset

一个例子 demo.asm

.386
.model flat, stdcall
option casemap  :none           ;forces your labels to be case sensitive, which means Hello and hello are treated differently.
 
include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\masm32.inc
 
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\masm32.lib
 
.data
    HelloWorld db "Hello, World!", 0
 
.code
start:
    mov eax, offset CC_Position
    invoke StdOut, addr HelloWorld
    invoke ExitProcess, 0
 
CC_Position:
    int 3
    int 3
    int 3
    int 3
end start

编译 & 运行

1 2	`ml` `/c` `/Zd` `/coff demo.asm` `link` `/subsystem:console demo.obj`

问题

offset返回一个偏移，但链接之后的exe程序中使用的却是一个有效地址地址

如下图:
offset

如何在运行时获取标号的偏移呢，即CC_Position相对.code的偏移

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最后于 2020-10-23 19:16 被baolongshou编辑，原因：

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Alfik 雪币： 897 活跃值： (5906) 能力值： ( LV2，RANK：10 ) 在线值：发帖 46 回帖 367 粉丝 129 关注私信	Alfik 2 楼 6efK9s2c8@1M7s2y4Q4x3@1q4Q4x3V1k6Q4x3V1k6U0z5i4S2Q4x3X3g2E0k6g2)9J5c8Y4R3^5y4W2)9J5c8X3S2@1L8h3I4Q4x3V1k6X3K9h3I4W2i4K6g2X3L8h3!0V1N6h3I4W2i4K6g2X3P5o6R3$3i4K6g2X3K9h3c8Q4y4h3j5I4y4K6k6Q4x3X3g2Z5N6r3#2D9 codestart0: jmp codestart1 someVar dd 0 codestart1: mov eax,[rip+($-someVar)] Position-Independent Code 56eK9s2c8@1M7s2y4Q4x3@1q4Q4x3V1k6Q4x3V1k6%4N6%4N6Q4x3X3g2G2M7X3g2A6L8r3I4&6i4K6u0W2j5$3!0E0i4K6u0r3L8r3W2T1M7X3q4J5P5g2)9J5c8Y4k6A6k6i4N6Q4x3V1k6H3M7X3q4U0N6r3W2U0j5h3I4Q4x3X3c8E0j5h3I4%4j5i4u0W2i4K6u0V1j5h3&6S2L8s2W2K6K9i4y4Q4x3V1j5&6y4K6R3I4y4e0V1K6x3U0M7J5z5e0l9$3i4K6u0r3j5$3R3J5x3s2x3H3x3W2)9J5k6h3S2@1L8h3H3`. How RIP/EIP relative addressing works in 32-bit mode 4caK9s2c8@1M7q4)9K6b7g2)9J5c8W2)9J5c8Y4N6%4N6#2)9J5k6h3y4G2k6r3g2Y4N6i4u0#2M7#2)9J5k6h3u0W2i4K6u0r3f1s2u0G2k6%4u0S2L8h3#2A6L8X3N6Q4x3V1k6J5K9i4m8J5k6h3I4S2N6r3W2$3k6h3q4V1k6s2u0W2M7%4y4A6L8X3N6Q4y4h3k6W2L8W2)9J5k6h3S2@1L8g2)9J5x3@1#2G2k6r3f1K6x3R3`.`. 2020-10-24 19:17 0
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最新回复 (1)

Alfik

雪币： 897

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( LV2，RANK：10 )

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Alfik: 2 楼

6efK9s2c8@1M7s2y4Q4x3@1q4Q4x3V1k6Q4x3V1k6U0z5i4S2Q4x3X3g2E0k6g2)9J5c8Y4R3^5y4W2)9J5c8X3S2@1L8h3I4Q4x3V1k6X3K9h3I4W2i4K6g2X3L8h3!0V1N6h3I4W2i4K6g2X3P5o6R3$3i4K6g2X3K9h3c8Q4y4h3j5I4y4K6k6Q4x3X3g2Z5N6r3#2D9

codestart0:
jmp codestart1

someVar dd 0

codestart1:
mov eax,[rip+($-someVar)]

Position-Independent Code
56eK9s2c8@1M7s2y4Q4x3@1q4Q4x3V1k6Q4x3V1k6%4N6%4N6Q4x3X3g2G2M7X3g2A6L8r3I4&6i4K6u0W2j5$3!0E0i4K6u0r3L8r3W2T1M7X3q4J5P5g2)9J5c8Y4k6A6k6i4N6Q4x3V1k6H3M7X3q4U0N6r3W2U0j5h3I4Q4x3X3c8E0j5h3I4%4j5i4u0W2i4K6u0V1j5h3&6S2L8s2W2K6K9i4y4Q4x3V1j5&6y4K6R3I4y4e0V1K6x3U0M7J5z5e0l9$3i4K6u0r3j5$3R3J5x3s2x3H3x3W2)9J5k6h3S2@1L8h3H3`.

How RIP/EIP relative addressing works in 32-bit mode
4caK9s2c8@1M7q4)9K6b7g2)9J5c8W2)9J5c8Y4N6%4N6#2)9J5k6h3y4G2k6r3g2Y4N6i4u0#2M7#2)9J5k6h3u0W2i4K6u0r3f1s2u0G2k6%4u0S2L8h3#2A6L8X3N6Q4x3V1k6J5K9i4m8J5k6h3I4S2N6r3W2$3k6h3q4V1k6s2u0W2M7%4y4A6L8X3N6Q4y4h3k6W2L8W2)9J5k6h3S2@1L8g2)9J5x3@1#2G2k6r3f1K6x3R3`.`.

2020-10-24 19:17

baolongshou

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