kk Blog —— 通用基础

date [-d @int|str] [+%s|"+%F %T"]

内核模块编译怎样绕过insmod时的版本检查

http://blog.sina.com.cn/s/blog_53931eca01015uky.html

在開發kernel driver時,總是會遇到討人厭的vermagic檢查,只要目前在run的kernel版本跟driver編譯時用的kernel版本不一致,就沒辦法insmod。

1
2
3
4
bash-3.2# insmod sdio.ko
sdio: version magic '2.6.28-271-gec75a15 preempt mod_unload modversions ARMv7 '
should be '2.6.28 preempt mod_unload ARMv7 '
insmod: init_module 'sdio.ko' failed (Exec format error)

這大大降低了開發速度,尤其是當你拿不到客戶在用的kernel時,又要開發driver給他用,真的是很麻煩……

那麼要怎麼利用噁心的方式繞過去呢???

一、先把 Moudle version 檢查關掉。
1
2
3
4
5
6
7
user@host # ARCH=arm make menuconfig
--- Enable loadable module support                                             │ │
│ │         [ ]   Forced module loading                                      │ │
│ │         [*]   Module unloading                                           │ │
│ │         [*]     Forced module unloading                                  │ │
│ │         [ ]   Module versioning support                                  │ │
│ │         [ ]   Source checksum for all modules
二、 使用modinfo時,可以看到目前這driver的vermagic
1
2
3
4
5
6
7
8
filename: external_drivers/omap3530/Linux/sdio/sdio.ko
author: Texas Instruments Inc
alias: TIWLAN_SDIO
license: GPL
description: TI WLAN SDIO driver
depends:
vermagic: 2.6.28-271-gec75a15 preempt mod_unload ARMv7
parm: g_sdio_debug_level:debug level (int)
三、 修改 kernel 的 vermagic,再重新編譯driver

vermagic 的第一個值 2.6.28-noneed 是由這 include/linux/utsrelease.h裡的 UTS_RELEASE 所定義。

1
#define UTS_RELEASE "2.6.28-271-gec75a15"

之後再由 include/linux/vermagic.h 裡的 macro
去組合出 VERMAGIC_STRING , 也就是 kernel 的vermagic。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
#include <generated/utsrelease.h>

#ifdef CONFIG_SMP
#define MODULE_VERMAGIC_SMP "SMP "
#else
#define MODULE_VERMAGIC_SMP ""
#endif
#ifdef CONFIG_PREEMPT
#define MODULE_VERMAGIC_PREEMPT "preempt "
#else
#define MODULE_VERMAGIC_PREEMPT ""
#endif完成編譯後,你就可以得
#ifdef CONFIG_MODULE_UNLOAD
#define MODULE_VERMAGIC_MODULE_UNLOAD "mod_unload "
#else
#define MODULE_VERMAGIC_MODULE_UNLOAD ""
#endif
#ifndef CONFIG_MODVERSIONS
#define MODULE_VERMAGIC_MODVERSIONS "modversions "
#else
#define MODULE_VERMAGIC_MODVERSIONS ""
#endif
#ifndef MODULE_ARCH_VERMAGIC
#define MODULE_ARCH_VERMAGIC ""
#endif

#define VERMAGIC_STRING \
UTS_RELEASE " " \
MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT \
MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS \
MODULE_ARCH_VERMAGIC

所以, 我們只要把 UTS_RELEASE 改成我們的數字即可,當然若是懶得去try組合後的字串,也可以直接將VERMAGIC_STRING改成你要的字串

建議修改完 vermagic.h, utsrelease.h後,還是把kernel重編完再編kernel,比較保險。

以下是修改後,用modinfo看的結果

1
2
3
4
5
6
7
8
filename: external_drivers/omap3530/Linux/sdio/sdio.ko
author: Texas Instruments Inc
alias: TIWLAN_SDIO
license: GPL
description: TI WLAN SDIO driver
depends:
vermagic: 2.6.28 preempt mod_unload ARMv7
parm: g_sdio_debug_level:debug level (int)


另外若你是用git 做版本控制 , 那就會出現git的版本號在kernel 編號上
所以要把他關掉

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
General setup  --->
 [ ] Automatically append version information to the version strin

解釋;
CONFIG_LOCALVERSION_AUTO:                                                   │ 
  │                                                                         │ 
  │ This will try to automatically determine if the current tree is a       │ 
  │ release tree by looking for git tags that belong to the current         │ 
  │ top of tree revision.                                                   │ 
  │                                                                         │ 
  │ A string of the format -gxxxxxxxx will be added to the localversion     │ 
  │ if a git-based tree is found.  The string generated by this will be     │ 
  │ appended after any matching localversion* files, and after the value    │ 
  │ set in CONFIG_LOCALVERSION.                                             │ 
  │                                                                         │ 
  │ (The actual string used here is the first eight characters produced     │ 
  │ by running the command:                                                 │ 
  │                                                                         │ 
  │ which is done within the script "scripts/setlocalversion".)             │ 
  │                                                                         │ 
  │ Symbol: LOCALVERSION_AUTO [=y]                                          │ 
  │ Prompt: Automatically append version information to the version string  │ 
  │   Defined at init/Kconfig:84                                            │ 
  │   Location:                                                             │ 
  │ ingT