无法获得正确的Linux内核标头来构建内核模块

Question

I am trying to build a sample Linux kernel module using the following command in my makefile on my Raspberry Pi 3B+ running the latest Raspbian Buster OS updated with sudo apt-get dist-upgrade:

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

I get the following output:

make -C /lib/modules/4.19.57-v7+/build/ M=/home/pi/isr_test modules
make[1]: *** /lib/modules/4.19.57-v7+/build/: No such file or directory.  Stop.
make: *** [Makefile:4: all] Error 2

I tried installing linux headers using this command:

sudo apt-get install linux-headers-$(uname -r)
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package linux-headers-4.19.57-v7
E: Couldn't find any package by glob 'linux-headers-4.19.57-v7'
E: Couldn't find any package by regex 'linux-headers-4.19.57-v7'

I tried looking for Linux headers using this command, and it looks like they are installed:

dpkg -l | grep kernel-headers
ii  raspberrypi-kernel-headers            1.20190718-1                          armhf        Header files for the Raspberry Pi Linux kernel

I tried looking in the /lib/modules directory:

ls /lib/modules
4.19.58+  4.19.58-v7+  4.19.58-v7l+

See how there's no 4.19.57 there?

Also, under /usr/src, all I have is these directories:

ls /usr/src
linux-headers-4.19.58+  linux-headers-4.19.58-v7+  linux-headers-4.19.58-v7l+  sense-hat

Again, nothing for 4.19.57.

For the current OS, here's what I get when I run uname -r:

uname -r
4.19.57-v7+

When I change my makefile to point to the 4.19.58-v7+ instead of 4.19.57-v7+, I get my module to build with no issues.

I'm expecting to see folders with 4.19.57 in their names, but all I get is 4.19.58 (see the folders above). How can I get the Linux header files that match my Linux kernel version? Or does it not matter?

Answer 1

Turns out, all I had to do was to reboot my Raspberry Pi after updating the OS. Now it's at 4.19.58, and all the headers match the OS version and everything compiles just fine.