C++ 内核模块，调用 get_futex_key

我正在开发一个Linux内核模块，我想调用函数get_futex_key.我怎么能这样做呢？最终目标是使用内核函数返回包含给定Futex的线程列表.

我按照这个tutorial创建了一个"Hello World"模块.它使用printk函数.我理解使用printk是可能的，因为它是内核可见的符号之一.

# cat /proc/kallsyms | grep printk
...
ffffffff9ebb9c32 T printk
...

功能get_futex_key在/proc/kallsyms中也可见.它是在futex.c，而不是futex.h中定义的.例如，请看这个source.

# cat /proc/kallsyms | grep "get_futex_key"
ffffffff9e3223c0 t get_futex_key_refs.isra.11
ffffffff9e322a30 t get_futex_key

假设0x20566a0是用strace得到的uaddr.

# strace -p  117589
strace: Process 117589 attached
futex(0x20566a0, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 0, NULL, 0xffffffff^Cstrace: Process 117589 detached

我以fut.c的身份try 了以下代码.

#include <linux/module.h>    // included for all kernel modules
#include <linux/kernel.h>    // included for KERN_INFO
#include <linux/init.h>      // included for __init and __exit macros
#include <linux/futex.h>
#include <kernel/futex.c>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("FutexTestAuthor");
MODULE_DESCRIPTION("Futex Examiner");

static int __init hello_init(void)
{
    union futex_key key1 = FUTEX_KEY_INIT;
    printk(KERN_INFO "Get futex key\n");
    //futex_key key1 = FUTEX_KEY_INIT;
    get_futex_key(0x20566a0, 0, &key1, VERIFY_READ);
    printk(KERN_INFO "key1 = %p\n", &key1);
    return 0;    // Non-zero return means that the module couldn't be loaded.
}

static void __exit hello_cleanup(void)
{
    printk(KERN_INFO "Cleaning up futex module.\n");
}

module_init(hello_init);
module_exit(hello_cleanup);

The 100

obj-m += fut.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Output of 100

# make
make -C /lib/modules/4.15.0-204-generic/build M=/home/myusername/git/LinuxExamples/kernel/fut modules
make[1]: Entering directory '/usr/src/linux-headers-4.15.0-204-generic'
  CC [M]  /home/myusername/git/LinuxExamples/kernel/fut/fut.o
/home/myusername/git/LinuxExamples/kernel/fut/fut.c:5:10: fatal error: kernel/futex.c: No such file or directory
 #include <kernel/futex.c>
          ^~~~~~~~~~~~~~~~
compilation terminated.
scripts/Makefile.build:340: recipe for target '/home/myusername/git/LinuxExamples/kernel/fut/fut.o' failed
make[2]: *** [/home/myusername/git/LinuxExamples/kernel/fut/fut.o] Error 1
Makefile:1596: recipe for target '_module_/home/myusername/git/LinuxExamples/kernel/fut' failed
make[1]: *** [_module_/home/myusername/git/LinuxExamples/kernel/fut] Error 2
make[1]: Leaving directory '/usr/src/linux-headers-4.15.0-204-generic'
Makefile:4: recipe for target 'all' failed
make: *** [all] Error 2