linux显示git commit id，同时解决insmod模块时版本不一致导致无法加载问题

时间：2022-08-19 01:53:06

　　linux内核默认会包含git的commit ID。

　　而linux的内核在insmod模块时，会对模块和内核本身的版本做严格的校验。在开发产品时，改动内核后，由于commit ID变更，会导致linux内核变更，之前已编译发布的模块与升级后的linux版本不一致，必须重新编译，非常麻烦。

为了解决这个问题，很多开发者通过配置make menuconfig，去掉CONFIG_LOCALVERSION_AUTO选项，从而不再包含git commit ID。

　　关于linux包含git commit的实现原理，可以参考博文：

　　转： linux内核版本本地版本号的检查——setlocalversion

　　http://www.cnblogs.com/liuwanpeng/p/6148572.html

　　但是git的commit ID对于版本追溯又很有帮助，能够帮助我们追溯到特定的内核版本，本文通过以下方法，把git

 commit ID包含到内核中，但是不属于内核版本的一部分，从而解决上述问题。

　　1.make menuconfig，去掉CONFIG_LOCALVERSION_AUTO选项，不自动包含git commit ID

　　2. 修改 /scripts/setlocalverison脚本，把git commit ID导出到一个单独的文件，命名为git_ver.h

#!/bin/sh

#

# This scripts adds local version information from the version

# control systems git, mercurial (hg) and subversion (svn).

#

# If something goes wrong, send a mail the kernel build mailinglist

# (see MAINTAINERS) and CC Nico Schottelius

# <nico-linuxsetlocalversion -at- schottelius.org>.

#

#

usage() {

    echo "Usage: $0 [--save-scmversion] [srctree]" >&

    exit

}

scm_only=false

srctree=.

if test "$1" = "--save-scmversion"; then

    scm_only=true

    shift

fi

if test $# -gt ; then

    srctree=$

    shift

fi

if test $# -gt  -o ! -d "$srctree"; then

    usage

fi

scm_version()

{

    local short

    short=false

    cd "$srctree"

    if test -e .scmversion; then

        cat .scmversion

        return

    fi

    if test "$1" = "--short"; then

        short=true

    fi

    # Check for git and a git repo.

    if test -z "$(git rev-parse --show-cdup 2>/dev/null)" &&

       head=`git rev-parse --verify --short HEAD >/dev/null`; then

        # If we are at a tagged commit (like "v2.6.30-rc6"), we ignore

        # it, because this version is defined in the top level Makefile.

        if [ -z "`git describe --exact-match 2>/dev/null`" ]; then

            # If only the short version is requested, don't bother

            # running further git commands

            if $short; then

                #echo "+"    // modify by *，不要+号了，没啥意义

                return

            fi

            # If we are past a tagged commit (like

            # "v2.6.30-rc5-302-g72357d5"), we pretty print it.

            if atag="`git describe 2>/dev/null`"; then

                echo "$atag" | awk -F- '{printf("-%05d-%s", $(NF-1),$(NF))}'

            # If we don't have a tag at all we print -g{commitish}.

            else

                #printf '%s%s' -g $head    // modify by *

                printf '%s%s'  $head

            fi

        fi

        # Is this git on svn?

        if git config --get svn-remote.svn.url >/dev/null; then

            printf -- '-svn%s' "`git svn find-rev $head`"

        fi

        # Check for uncommitted changes

        if git diff-index --name-only HEAD | grep -qv "^scripts/package"; then

            printf '%s' -dirty

        fi

        # All done with git

        return

    fi

    # Check for mercurial and a mercurial repo.

    if test -d .hg && hgid=`hg id >/dev/null`; then

        # Do we have an tagged version?  If so, latesttagdistance ==

        if [ "`hg log -r . --template '{latesttagdistance}'`" == "" ]; then

            id=`hg log -r . --template '{latesttag}'`

            printf '%s%s' -hg "$id"

        else

            tag=`printf '%s' "$hgid" | cut -d' ' -f2`

            if [ -z "$tag" -o "$tag" = tip ]; then

                id=`printf '%s' "$hgid" | sed 's/[+ ].*//'`

                printf '%s%s' -hg "$id"

            fi

        fi

        # Are there uncommitted changes?

        # These are represented by + after the changeset id.

        case "$hgid" in

            *+|*+\ *) printf '%s' -dirty ;;

        esac

        # All done with mercurial

        return

    fi

    # Check for svn and a svn repo.

    if rev=`LANG= LC_ALL= LC_MESSAGES=C svn info >/dev/null | grep '^Last Changed Rev'`; then

        rev=`echo $rev | awk '{print $NF}'`

        printf -- '-svn%s' "$rev"

        # All done with svn

        return

    fi

}

collect_files()

{

    local file res

    for file; do

        case "$file" in

        *\~*)

            continue

            ;;

        esac

        if test -e "$file"; then

            res="$res$(cat "$file")"

        fi

    done

    echo "$res"

}

if $scm_only; then

    if test ! -e .scmversion; then

        res=$(scm_version)

        echo "$res" >.scmversion

    fi

    exit

fi

if test -e include/config/auto.conf; then

    . include/config/auto.conf

else

    echo "Error: kernelrelease not valid - run 'make prepare' to update it"

    exit

fi

# localversion* files in the build and source directory

res="$(collect_files localversion*)"

if test ! "$srctree" -ef .; then

    res="$res$(collect_files "$srctree"/localversion*)"

fi

# CONFIG_LOCALVERSION and LOCALVERSION (if set)

res="${res}${CONFIG_LOCALVERSION}${LOCALVERSION}"

# scm version string if not at a tagged commit

if test "$CONFIG_LOCALVERSION_AUTO" = "y"; then

    # full scm version string

    res="$res$(scm_version)"

else

    # append a plus sign if the repository is not in a clean

    # annotated or signed tagged state (as git describe only

    # looks at signed or annotated tags - git tag -a/-s) and

    # LOCALVERSION= is not specified

    if test "${LOCALVERSION+set}" != "set"; then

        scm=$(scm_version --short)

        res="$res${scm:++}"

    fi

fi

# add by *,save git commit id to ./include/generated/git_ver.h

rm -rf "$srctree"/include/generated/git_ver.h

GIT_VER_INC_PATH="$srctree/include/generated/git_ver.h"　　// 将git commit ID导出到git_ver.h中

echo "/*" >> $GIT_VER_INC_PATH

echo "* auto generate. Don't edit!" >> $GIT_VER_INC_PATH

echo "*/" >> $GIT_VER_INC_PATH

echo "#ifndef __GIT_VERSION_H__" >> $GIT_VER_INC_PATH

echo >> $GIT_VER_INC_PATH

echo "#define __GIT_VERSION_H__" >> $GIT_VER_INC_PATH

echo  >> $GIT_VER_INC_PATH

echo "#define GIT_COMMIT_ID_STR    \"$(scm_version)\" ">> $GIT_VER_INC_PATH

echo  >> $GIT_VER_INC_PATH

echo "#endif" >> $GIT_VER_INC_PATH

echo "$res"

上述代码红色部分是修改的地方，编译linux内核以后，自动生成的git_ver.h如下：

/*

* auto generate. Don't edit!

*/

#ifndef __GIT_VERSION_H__

#define __GIT_VERSION_H__

#define GIT_COMMIT_ID_STR    "afb275c" 　　　// 可以通过git show afb275c，方便的查询这个版本的log

#endif

　　

3. 从git_ver.h中获取git commit ID，并打印，且存放到到 /proc/version文件系统中

linux启动时，start_kernel()函数会打印版本号

init/main.c:

asmlinkage void __init start_kernel(void)

{

    ......

    boot_cpu_init();

    page_address_init();

    pr_notice("%s", linux_banner);

        ......

}
linux_banner的定义：
init/version.c:

/* FIXED STRINGS! Don't touch! */

const char linux_banner[] =

    "Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"

    LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\nGit commit id: " GIT_COMMIT_ID_STR "\n";　　// 再次全局变量中增加git commit ID用于显示

const char linux_proc_banner[] =　

    "%s version %s"

    " (" LINUX_COMPILE_BY "@" LINUX_COMPILE_HOST ")"

    " (" LINUX_COMPILER ") %s\n""Git commit id: " GIT_COMMIT_ID_STR"\n";

除了初始化打印，/proc/version文件系统中也提供版本相关的信息，正好用到linux_proc_banner变量，也添加上git commit ID

fs/proc/version.c:

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/proc_fs.h>

#include <linux/seq_file.h>

#include <linux/utsname.h>

static int version_proc_show(struct seq_file *m, void *v)

{

    seq_printf(m, linux_proc_banner,

        utsname()->sysname,

        utsname()->release,

        utsname()->version);

    return ;

}

static int version_proc_open(struct inode *inode, struct file *file)

{

    return single_open(file, version_proc_show, NULL);

}

static const struct file_operations version_proc_fops = {

    .open        = version_proc_open,

    .read        = seq_read,

    .llseek        = seq_lseek,

    .release    = single_release,

};

static int __init proc_version_init(void)

{

    proc_create("version", , NULL, &version_proc_fops);

    return ;

}

fs_initcall(proc_version_init);

4.修改后的结果

（1）串口打印：

Starting kernel ...

machid 0, r2(bi_boot_params): 16ffa000
gd 1fb8df38, bd 1fb8dfe0 bi_arch_number: 0
kernel entry 00008000
Booting Linux on physical CPU 0x0
Linux version 3.14.0-xilinx (****@ubuntu) (gcc version 4.8.3 20140320 (prerelease) (Sourcery CodeBench Lite 2014.05-23) ) #8 SMP PREEMPT Mon Dec 12 11:28:17 CST 2016
Git commit id: afb275c

（2）/proc/version

zynq> cat /proc/version
Linux version 3.14.0-xilinx (liuwanpeng@ubuntu) (gcc version 4.8.3 20140320 (prerelease) (Sourcery CodeBench Lite 2014.05-23) ) #8 SMP PREEMPT Mon Dec 12 11:28:17 CST 2016
Git commit id: afb275c

OK，job‘s done !

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