Linux内核模块-在源文件之间共享变量 [英] Linux Kernel Module - Sharing variables between source files

问题描述

我正在尝试将内核模块链接到非LKM源文件.问题是，我遇到了一些问题.这两个文件的名称是chardev.c(LKM)和foo.c.

I'm trying to link a kernel module to a non-LKM source file. The problem is, I'm running into some issues. The names of the two files are chardev.c (the LKM) and foo.c.

我的Makefile:

My Makefile:

obj-m += chardev.o
obj-y += foo.o

all:
    make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
    $(CC) test.c -o test
clean:
    make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean
    rm test 

在chardev.c内部，我有以下代码行:extern int foo;，在foo内部，我有以下代码行:int foo = 123;. (这两行都在文件范围内.)

Inside of chardev.c I've the following line of code: extern int foo;, and inside foo I've the following line of code: int foo = 123;. (Both lines are at file-scope.)

运行make时，我得到以下输出:

When running make I'm getting the following output:

make -C /lib/modules/4.4.0-31-generic/build/ M=/home/kylemart/Desktop/Device-Driver modules
make[1]: Entering directory `/usr/src/linux-headers-4.4.0-31-generic'
  CC [M]  /home/kylemart/Desktop/Device-Driver/chardev.o
  Building modules, stage 2.
  MODPOST 1 modules
WARNING: "foo" [/home/kylemart/Desktop/Device-Driver/chardev.ko] undefined!
  CC      /home/kylemart/Desktop/Device-Driver/chardev.mod.o
  LD [M]  /home/kylemart/Desktop/Device-Driver/chardev.ko
make[1]: Leaving directory `/usr/src/linux-headers-4.4.0-31-generic'
cc test.c -o test

似乎无法正确链接.我在做什么错了?

Seems things aren't linking properly. What am I doing wrong?

这似乎可行，但是有一个问题:

This seems to work, but there's a problem:

obj-m += chardev.o
chardev-objs += foo.o

all:
    make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
    $(CC) test.c -o test
clean:
    make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean
    rm test  

尽管它编译时没有警告，但是在安装编译后的模块(即sudo insmod chardev.ko)之后，/dev中没有新设备.以前，在不尝试链接源文件的情况下，如前所述安装内核模块会创建一个设备文件.也就是说，运行lsmod时该设备存在.

Although it compiles without warnings, after installing the compiled module (i.e. sudo insmod chardev.ko) there isn't a new device present in /dev. Previously, without trying to link source files, installing kernel modules as previously stated created a device file. That said, the device is present when running lsmod.

推荐答案

您的all目标仅构建模块，而不构建内核，因此foo符号在那里不存在.

Your all target builds only the module, but not the kernel so that the foo symbol does not exist there.

在将源代码(此处为foo.c)编译到内核时，必须将makefile集成到内核源代码中.例如.您必须添加

When compiling a source (here: foo.c) into the kernel, you have to integrate the makefile into the kernel source. E.g. you have to add

obj-y += my-driver/

到先前目录中的makefile并构建整个内核.您可能应该从makefile中删除all:和clean:目标，以避免与内核内置规则冲突.

to the makefile in the previous directory and build the whole kernel. You should probably remove your all: and clean: targets from the makefile to avoid conflicts with kernel builtin rules.

foo.c必须包含

EXPORT_SYMBOL(foo);

或

EXPORT_SYMBOL_GPL(foo);

第二个生成文件...

将仅生成仅由foo.c构建的chardev.ko模块； chardev.c不会被使用.当您确实需要此功能时，必须更改文件名.例如

The second makefile...

will generate only the chardev.ko module which is built from only foo.c; chardev.c will not be used for it. When you really want this, you have to change file names; e.g.

obj-m += chardev.o
chardev-objs = chardev-core.o foo.o

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