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Tools for Device Driver Development
In this page, I will explain on various ways and commands to retrieve the information about the modules (device drivers) running on your system. You will find these methods useful when you are developing and testing your own drivers (modules).
How to get information about modules ?
First try following command and see if the /proc/modules exists. As you see here, this is a read-only file.
-r--r--r-- 1 root root 0 Jan 27 17:33 /proc/modules
you can see the contents of this file as shown below. This file contains the list of all the modules installed on your system and the execution of the status of each drivers.
binfmt_misc 20480 1 - Live 0x0000000000000000 vboxsf 49152 1 - Live 0x0000000000000000 intel_powerclamp 16384 0 - Live 0x0000000000000000 crct10dif_pclmul 16384 0 - Live 0x0000000000000000 crc32_pclmul 16384 0 - Live 0x0000000000000000 ghash_clmulni_intel 16384 0 - Live 0x0000000000000000 ...... hid 118784 2 hid_generic,usbhid, Live 0x0000000000000000 e1000 143360 0 - Live 0x0000000000000000 psmouse 139264 0 - Live 0x0000000000000000 ahci 36864 2 - Live 0x0000000000000000 libahci 32768 1 ahci, Live 0x0000000000000000 fjes 77824 0 - Live 0x0000000000000000 video 40960 0 - Live 0x0000000000000000 pata_acpi 16384 0 - Live 0x0000000000000000
Even though you can get the list of modules and information from /proc/modules file, it will be easier to use lsmod command as shown below to find the same information. Actually, lsmod command extracts the information from /proc/modules.
$ lsmod
Module Size Used by binfmt_misc 20480 1 vboxsf 49152 1 intel_powerclamp 16384 0 crct10dif_pclmul 16384 0 crc32_pclmul 16384 0 ghash_clmulni_intel 16384 0 pcbc 16384 0 aesni_intel 167936 0 aes_x86_64 20480 1 aesni_intel crypto_simd 16384 1 aesni_intel glue_helper 16384 1 aesni_intel ..... parport 49152 3 lp,parport_pc,ppdev autofs4 40960 2 hid_generic 16384 0 usbhid 53248 0 hid 118784 2 hid_generic,usbhid e1000 143360 0 psmouse 139264 0 ahci 36864 2 libahci 32768 1 ahci fjes 77824 0 video 40960 0 pata_acpi 16384 0
Once you find a specific module from the list shown above, you can find more detailed information about a specific module as shown below using modinfo command.
filename: /lib/modules/4.10.0-28-generic/kernel/drivers/video/fbdev/core/fb_sys_fops.ko license: GPL description: Generic file read (fb in system RAM) author: Antonino Daplas <adaplas@pol.net> srcversion: 208A81F7665624BC72DCB7D depends: intree: Y vermagic: 4.10.0-28-generic SMP mod_unload
Now you may look into /lib/module/(your linux version) as shown below. As shown here, these files are located in a specific directory name as linux kernel version on your system. If you are not sure about the kernel version on your Linux, the second method would work better.
$ ls -al /lib/modules/4.10.0-28-generic or $ ls -al /lib/modules/$(uname -r)
total 4964 drwxr-xr-x 5 root root 4096 Jan 27 03:12 . drwxr-xr-x 3 root root 4096 Aug 1 07:23 .. lrwxrwxrwx 1 root root 40 Jan 27 02:54 build -> /usr/src/linux-headers-4.10.0-28-generic drwxr-xr-x 2 root root 4096 Jul 20 2017 initrd drwxr-xr-x 14 root root 4096 Aug 1 07:23 kernel -rw-r--r-- 1 root root 1166411 Jan 27 03:12 modules.alias -rw-r--r-- 1 root root 1149737 Jan 27 03:12 modules.alias.bin -rw-r--r-- 1 root root 7317 Jul 20 2017 modules.builtin -rw-r--r-- 1 root root 9142 Jan 27 03:12 modules.builtin.bin -rw-r--r-- 1 root root 523389 Jan 27 03:12 modules.dep -rw-r--r-- 1 root root 741387 Jan 27 03:12 modules.dep.bin -rw-r--r-- 1 root root 285 Jan 27 03:12 modules.devname -rw-r--r-- 1 root root 196852 Jul 20 2017 modules.order -rw-r--r-- 1 root root 429 Jan 27 03:12 modules.softdep -rw-r--r-- 1 root root 558199 Jan 27 03:12 modules.symbols -rw-r--r-- 1 root root 680971 Jan 27 03:12 modules.symbols.bin drwxr-xr-x 3 root root 4096 Aug 1 07:23 vdso
Among the various files listed above, a file especially helpful would be modules.dep. This file contains the location of binary files for each module and its dependencies.
$ cat /lib/modules/4.10.0-28-generic/modules.dep
kernel/arch/x86/events/intel/intel-rapl-perf.ko: kernel/arch/x86/events/intel/intel-cstate.ko: ... kernel/arch/x86/crypto/des3_ede-x86_64.ko: kernel/crypto/des_generic.ko kernel/arch/x86/crypto/camellia-x86_64.ko: kernel/crypto/lrw.ko kernel/arch/x86/crypto/glue_helper.ko kernel/arch/x86/crypto/blowfish-x86_64.ko: kernel/crypto/blowfish_common.ko kernel/arch/x86/crypto/twofish-x86_64.ko: kernel/crypto/twofish_common.ko .... kernel/crypto/crypto_simd.ko kernel/arch/x86/crypto/glue_helper.ko kernel/crypto/cryptd.ko kernel/arch/x86/crypto/ghash-clmulni-intel.ko: kernel/crypto/cryptd.ko kernel/arch/x86/crypto/sha1-ssse3.ko: kernel/arch/x86/crypto/crc32-pclmul.ko: kernel/arch/x86/crypto/sha256-ssse3.ko:
How to find a location of a specific header file ?
In device driver programming, you need to include various header files as shown below and sometimes you want to look into the contents of these header files.
#include <linux/module.h> #include <linux/version.h> #include <linux/kernel.h> #include <linux/types.h> #include <linux/kdev_t.h> #include <linux/fs.h>
To see the contents of these files, you first need to figure out the location of a specific header files. You may use various ways to find the location of the file. Following is how I do to find the header file location that I want.
$ sudo find / -name *.h | grep 'linux/module.h'
/usr/src/linux-headers-4.10.0-28/include/uapi/linux/module.h /usr/src/linux-headers-4.10.0-28/include/linux/module.h
How to find header file or c source file containing a specific string ?
Following command search all the *.c and *.h files starting from /usr/src directory to all the sub directories to search for the string "module_init(x)".
$ sudo grep --include=\*.{c,h} -rn /usr/src -e "module_init(x)"
/usr/src/linux-headers-4.10.0-28/include/linux/module.h:86:#define module_init(x) ..;
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