blocks|key|962232|text|在专家看来，这不是一个在内核空间和用户空间之间进行数据通信的好方法。要么完全在内核空间工作，要么只在用户空间上工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|962233|但是一种解决方案可以在内核模块中使用read()和write()命令在用户空间和内核空间之间发送信息。|offset|length|style|BOLD|962234|entityMap^0|0|I|6|P|7|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|P|8|@]|9|@]|A|$]]]|I|$]]

In experts view , its NOT a good approach to communicate data between kernel space and user space. Either fully work on kernel space OR only on user space.

But one solution can, use read() and write() command in a kernel module to send the information between user space and kernel space.

blocks|key|4179684|text|你不能在内核模块中使用C库，对于数学库部分更是如此。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4179685|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You cannot use the C library in a kernel module, this is even more true for the math library part.

blocks|key|43569|text|您不能在内核空间中包含用户空间C模块。另外，您确定要这样做吗？这个线程可能会对http://kerneltrap.org/node/16570有所帮助。您可以在内核中执行数学函数，只需在http://lxr.linux.no/上搜索所需的函数即可。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|43570|entityMap|0|LINK|mutability|MUTABLE|url|http://kerneltrap.org/node/16570|1|http://lxr.linux.no/^0|13|W|0|2L|K|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

You can't include a userspace C module in kernel space. Also are you sure that you want to be doing this? This thread may help <a href="http://kerneltrap.org/node/16570" rel="nofollow noreferrer">http://kerneltrap.org/node/16570</a>. You can do math functions inside the kernel, just search around on <a href="http://lxr.linux.no/" rel="nofollow noreferrer">http://lxr.linux.no/</a> for the function you need.

blocks|key|4179861|text|标准库在内核中不可用。这包括libc、libm等。尽管这些库中的一些函数是在内核空间中实现的，但有些不是。如果不知道您尝试调用的是什么，就不可能确定您是否应该在内核空间中执行您正在尝试执行的操作。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|4179862|我应该进一步注意到，内核不能访问FPU。这是为了节省切换任务时的时间(因为在执行上下文切换时保存FPU寄存器会增加不必要的开销)。如果你真的想要，你可以通过从内核空间获得对的访问，但是你需要非常小心，在这样做的时候不要破坏用户空间的FPU寄存器。|4179863|编辑：This比我更好地总结了关于FPU的警告。|4179864|entityMap|0|LINK|mutability|MUTABLE|url|http://www.mail-archive.com/linuxppc-embedded@ozlabs.org/msg01260.html^0|U|G|0|26|8|2L|U|0|3|4|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@$9|10|A|11|1|12]]|E|$]]|$1|J|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]]]

Standard libraries are not available in the kernel. This includes libc, libm, etc. Although some of the functions in those libraries are implemented in kernel space, some are not. Without knowing what you're trying to call, it's impossible to say for sure whether or not you should be doing what you're trying to do in kernel space.

I should further note that the kernel does NOT have access to the FPU. This is to save time when switching tasks (since saving the FPU registers would add unnecessary overhead when performing context switches). You can get access to the FPU from kernel space if you really want it, but you need to be really careful not to trash the user space's FPU registers when doing so. 

Edit: <a href="http://www.mail-archive.com/linuxppc-embedded@ozlabs.org/msg01260.html" rel="nofollow noreferrer">This</a> summarizes the caveat about the FPU much better than I did.

blocks|key|962195|text|内核不支持浮点运算。这是因为当从内核上下文切换到用户上下文时，必须保存寄存器。如果内核使用浮点，那么还必须保存浮点寄存器，这将导致每个上下文切换的性能不佳。因此，由于浮点数很少需要，特别是在内核中，它不受支持。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|962196|如果你真的需要：|962197|962198|也许你可以编译你自己的具有浮点支持的内核|unordered-list-item|962199|你可以在你的浮点操作中阻止上下文切换|962200|最好是使用定点运算。|962201|962202|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|R|8|@]|9|@]|A|$]]|$1|H|3|I|5|G|7|S|8|@]|9|@]|A|$]]|$1|J|3|K|5|G|7|T|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Floating point operations is not supported in the kernel. This is because when switching from kernel context to user context, registers must be saved. If the kernel would make use of floating point, then also the floating point registers would have to be saved also, which would cause bad performance for each context switch. So because floating point is very rarely needed, especially in the kernel it is not supported.

If you really have to:

<ul>
<li>maybe you could compile your own kernel with floating point support</li>
<li>you could block context switch within your floating point operations</li>
<li>the best would be to use fixed point arithmetics.</li>
</ul>

blocks|key|961708|text|AFAIK内核空间与用户空间是分开的，所以源代码也应该是分开的。/usr/include用于常规编程。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|961709|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

AFAIK kernel space is separated from user space, and so should the source code. /usr/include is for general programming.

blocks|key|4179654|text|This建议，在内核中进行浮点运算并不像在用户空间代码中那样简单。Another实例表明这很难。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4179655|仍然在寻找一个更明确的答案。|4179656|entityMap|0|LINK|mutability|MUTABLE|url|http://mail.rtai.org/pipermail/rtai/2007-August/017847.html|1|http://lwn.net/Articles/245291/^0|0|4|0|X|7|1|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]|$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

<a href="http://mail.rtai.org/pipermail/rtai/2007-August/017847.html" rel="nofollow noreferrer">This</a> suggests that doing floating point math in the kernel is not as simple is in user-space code. <a href="http://lwn.net/Articles/245291/" rel="nofollow noreferrer">Another</a> instance suggesting that this is hard.

Still looking for a more definitive answer.

blocks|key|4179813|text|非常感谢你的评论|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4179814|使用数学函数|4179815|是否有可能制作一个plane+C应用程序并从内核源文件中传递变量。因此，C应用程序将计算变量并发回信息。|4179816|内核源文件(内核空间)->+C应用程序(用户空间)|offset|length|style|BOLD|4179817|+++++++++++++++++++++++++++++++++++++++%7C

+++++++++++++++++++++++++++++++++++<---%7C|code-block|syntax|javascript|4179818|内核源文件|4179819|因此，我们可以在内核源代码中包含头文件。如果发生任何事件，它会将值传递给C应用程序(用户空间)|4179820|详细信息：我正在尝试修改我的HID操纵杆事件(绝对x，y)，这样它可能只会移动到改进的位置，这将由我的应用程序生成，并具有一些数学函数，如(pow，tan等)。|4179821|因此，我使用hid-input.c获取原始事件，并对其进行修改。它将通过hid内核模块用于输入子系统-|4179822|期待您的评论|4179823|致以问候。|4179824|entityMap^0|0|0|0|0|B|E|B|0|0|0|5|0|0|0|5|0|0|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|15|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|16|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|17|8|@$H|18|I|19|J|K]|$H|1A|I|1B|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|1C|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|1D|8|@$H|1E|I|1F|J|K]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1G|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1H|8|@$H|1I|I|1J|J|K]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|1L|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1M|8|@]|9|@]|A|$]]|$1|12|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]]|13|$]]

Thanks a lot for your comments

To use math functions

Is it possiable to make a plane C application and pass variables from kernel source file. So the C Application will compute the variables and sends back the information .

Kernel source file (kernel space) ---> C Application (user space)

<pre><code> |

 &lt;---|
</code></pre>

Kernel source file

So we may include header file in kernel source code. In case of any event, it pass the values to a C application (user space)

Details: 
I am trying to modify my HID joystick events(absolute x, y) So It may only move to the improved location, which will be genarated by my application, with some math functions like (pow, tan,etc).

So I used hid-input.c to get raw events, and modify them. which will be used for input subsystem through hid kernel module –

Looking for your comments

Regards.

blocks|key|4179894|text|你不能，你可以在你的模块中重写你需要的函数，它是脏的，但它应该可以工作…|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4179895|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

well you cannot, you can rewrite functions you need in your module, it's dirty but it should work...

blocks|key|962278|text|你不能在内核中使用浮点寄存器(通常，如果没有足够的内核知识来锁定和保留这些寄存器，同时又不会影响其他关键部分)，而且在内核中进行“处理”当然也是不合适的。其他许多人也提到过这一点。性能将会很糟糕。因此，没有为内核模块提供math.h。我们接受这一点，继续前进……|type|unstyled|depth|inlineStyleRanges|entityRanges|data|962279|然而，由于我也是别人强加给我们的疯狂要求和完全疯狂的设计的受害者，这是一个合理的问题。在减少math.h+API的使用以最小化对性能的影响之后，您可以通过正确的编译器设置使用浮点仿真(软浮点)来实现所需的函数，而无需使用浮点寄存器。内核代码应该已经使用这些软浮点设置进行了编译。|962280|为了实现math.h功能，您可以查看glibc或uClibc等。这两个库都有通用的libm的"C“实现，它们实现了math.h，而不使用特殊的内部函数或特定于平台的类型，因此应该可以在内核中很好地编译。|offset|length|style|CODE|962281|libm+:上面的链接直接将您带到uClibc的uClibc部分。|962282|glibc:在"git"-ing+glibc之后，你会在glibc/sysdeps/ieee754/flt-32中找到你想要的东西。|962283|C89可能更难理解，因为它更复杂，内部有更多的相互依赖性，但glibc+(目前)只提供glibc+math.h。如果您想要像C99%2B中那样的单精度(读取:更快)或复杂的数学功能，那么您必须考虑使用glibc。|962284|entityMap|0|LINK|mutability|MUTABLE|url|https://sourceware.org/glibc/wiki/HomePage|1|http://git.uclibc.org/uClibc/tree/libm^0|0|0|4|6|1L|6|I|5|0|O|6|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|10|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|11|8|@$F|12|G|13|H|I]|$F|14|G|15|H|I]]|9|@$F|16|G|17|1|18]|$F|19|G|1A|1|1B]]|A|$]]|$1|J|3|K|5|6|7|1C|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1D|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|1E|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]|X|$5|S|T|U|A|$V|Y]]]]

You cannot (often, without lots of kernel know-how to lock and preserve these registers while not impacting other critical sections) use floating point registers in the kernel, and besides it is of course inappropriate to do "processing" in the kernel. Many others have mentioned this. Performance will be terrible. Thus, math.h is not provided for kernel modules. We accept this and move on...

However, as I am also a victim of crazy requirements and completely insane designs forced on us by others, this is a legitimate question. After reducing the usage of the math.h API to minimize the performance impact, you can use floating point emulation (soft-float) via correct compiler settings to implement your required functions without using floating point registers. Kernel code should already compile with these soft-float settings.

In order to implement <code>math.h</code> functionality, you can look at <a href="https://sourceware.org/glibc/wiki/HomePage" rel="nofollow">glibc</a> or <a href="http://git.uclibc.org/uClibc/tree/libm" rel="nofollow">uClibc</a> and perhaps others. Both of these libraries have generic "C" implementations of libm which implement <code>math.h</code> without the use of special intrinsics or platform specific types and should therefore compile just fine in the kernel. 

uClibc: The above link takes you directly to the libm section of uClibc.

glibc: After "git"-ing glibc, you'll find what you're looking for in glibc/sysdeps/ieee754/flt-32.

glibc may be more difficult to understand because it is more sophisticated and has more inter-dependencies within itself, but uClibc only provides (at the moment) C89 math.h. If you want single precision (read: faster) or complex math functionality as in C99+, you'll have to look at glibc.

blocks|key|1345500|text|也许可以尝试使用双引号(")而不是单引号？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1345501|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Maybe try using double quotes (") instead of single quotes?

I am trying to include math.h in my Linux kernel module. If I use,

<pre><code>#include '/usr/include/math.h'
</code></pre>

It give me theses errors:

<pre><code>error: features.h: No such file or directory
error: bits/huge_val.h: No such file or directory
error: bits/mathdef.h: No such file or directory
error: bits/mathcalls.h: No such file or directory
</code></pre>

Why is this?

How to include math.h #include <math.h> on kernel source file?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在尝试将math.h包含在我的Linux内核模块中。如果我用了，#include '/usr/include/math.h'它给了我以下错误：error: features.h: No such file or directoryerror: bits/huge_val.h: No such file or directoryerror: bits/mathdef.h: No such fil

问如何在内核源文件中包含math.h #include <math.h>？
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问如何在内核源文件中包含math.h #include <math.h>？
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