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繞過linux driver vermagic檢查

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。

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。

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

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。

#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。

#include
#include

/* Simply sanity version stamp for modules. */
#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

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
 
 
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