[英]error in kernel source code of linux?
I modified the kernel source code r8169.c
and calculating the timestamp
as below: 我修改了内核源代码r8169.c
并计算timestamp
如下:
s64 a;
EXPORT_SYMBOL(a);
a = time();
I did not add the original timestamp function call 我没有添加原始时间戳函数调用
I am using the variable a in another source file in kernel: ip_input.c
我在内核中的另一个源文件中使用变量a: ip_input.c
extern s64 a;
s64 b,c;
b= time();
c = b-a;
I receive this error: 我收到此错误:
ERROR: undefined reference to a
How to solve it? 怎么解决?
From the incomplete source code, I guess that 从不完整的源代码,我猜
s64 a;
EXPORT_SYMBOL(a);
a = time();
is inside a function and therefore, a
cannot be exported, because it is local to that function. 是在函数内部,因此, a
不能出口,因为它是局部的功能。
To use a
outside of this module, you must define it with file scope, eg 要使用此模块a
外部,必须使用文件范围定义它,例如
s64 a;
EXPORT_SYMBOL(a);
void some_function()
{
a = time();
}
This allows the symbol for a
to be exported and then used in another module. 这允许导出a
的符号,然后在另一个模块中使用。
r8169.c is a module, whereas ip_input.c is in the main kernel. r8169.c是一个模块,而ip_input.c在主内核中。 The main kernel cannot import symbols from a module. 主内核无法从模块导入符号。 The fix for this is to declare your variable within ip_input.c, and import it from r8169.c. 解决此问题的方法是在ip_input.c中声明您的变量,并从r8169.c导入它。 You also have to use file scope as Olaf mentioned. 您还必须使用Olaf提到的文件范围。
ip_input.c: ip_input.c:
s64 a, b, c;
EXPORT_SYMBOL(a);
void someFunc() {
b=time();
c=b-a;
}
r8169.c: r8169.c:
extern s64 a;
void someFunc() {
a=time();
}
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