如何使用内核头文件编译用户空间程序

Question

我需要使用ioctl 测试一个usbfs 设备。 我需要使用ioctl(fd, USBDEVFS_REAPURBNDELAY, &receive);。 但是USBDEVFS_REAPURBNDELAY 是在内核头文件中定义的，所以我包含了一些这样的内核文件：

#include <linux/usb.h>
#include <linux/usbdevice_fs.h>
#include <asm/byteorder.h>
#include <linux/usb/ch9.h>

并用gcc -g -I /usr/src/linux-3.4.4-2-pae/include/ -o /home/madper/kernel/usb/select_for_usb /home/madper/kernel/usb/select_for_usb.c编译它

上面写着#warning "Attempt to use kernel headers from user space, see http://kernelnewbies.org/KernelHeaders" [-Wcpp]

随之而来的是很多错误，那么，使用内核头文件的正确方法是什么？

/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:21:2: error: unknown type name ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:36:2: error: unknown type name ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:37:33: error: ‘kernel_ulong_t’ undeclared here (not in a function)
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:37:3: error: requested alignment is not an integer constant
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:119:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:141:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:154:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:168:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:179:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:187:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:195:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:200:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:227:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:260:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:314:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:341:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:366:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:413:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:433:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:444:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:479:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:508:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:540:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:551:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:566:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/usr/src/linux-3.4.4-2-pae/include/linux/mod_devicetable.h:582:2: error: expected specifier-qualifier-list before ‘kernel_ulong_t’
/home/madper/kernel/usb/select_for_usb.c: In function ‘main’:
/home/madper/kernel/usb/select_for_usb.c:46:30: error: expected expression before ‘void’

Answer 1

你真的不应该直接包含内核头文件。在某些情况下，处理它是必要的，并且可能是处理它的最佳方法是获取内核头文件的副本并仅删除您需要的部分。但在这种情况下，我不确定我是否理解你为什么需要内核头文件。为什么只包含<linux/usbdevice_fs.h> 不起作用？

在我查看的所有系统（几个不同的 Ubuntu 系统和一个 RHEL 6 系统）上，该文件可以从用户空间包含并具有USBDEVFS_REAPURBNDELAY 的定义。我试过了

#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/usbdevice_fs.h>

int main()
{
    printf("USBDEVFS_REAPURBNDELAY is %ld\n", USBDEVFS_REAPURBNDELAY);
    return 0;
}

我可以干净地构建它，当我运行它时，我得到了

USBDEVFS_REAPURBNDELAY is 1074287885

所以至少根据您上面写的内容，您不需要任何内核头文件来定义该 ioctl。我怀疑您认为用户空间 USB 内容所需的其他任何东西都以干净的标头类似地导出到用户空间。

Answer 2

您不能将内核头文件用于用户程序。即使您以某种方式这样做，也强烈建议您这样做。查看以下链接以获得更多说明。

http://lwn.net/Articles/113349/

如果您确实想从用户空间控制 USB 设备，请查看 libusb。