Update several example code for newer kernel

[fennecJ]

Known issues with current example code:
If you using newer kernel(e.g linux 5.11.x) to compile the example code,
you may meet following error:

1. syscall.c:83:50: error: ‘ksys_close’ undeclared;
2. cryptosk.c:17:24: error: field ‘sg’ has incomplete type
3. cryptosk.c:143:9: error: implicit declaration of function
   ‘get_random_bytes’
4. error: macro "DECLARE_TASKLET" passed 3 arguments, but takes just 2

Solutions/workaround:

1. In syscall.c, replace #include <linux/syscalls.h> with
   #include <linux/fdtable.h> and replace ksys_close with close_fd
   if the kernel version >= 5.11. [1][2]
2. Add #include <linux/scatterlist.h> into cryptosk.c
3. Add #include <linux/random.h> into cryptosk.c
4. In bottomhalf.c and example_tasklet.c, replace DECLARE_TASKLET
   with DECLARE_TASKLET_OLD and dispose third argument(0L). [3]

[1] - https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1572bfdf21d4d50e51941498ffe0b56c2289f783
[2] - https://www.mail-archive.com/meta-arago@arago-project.org//msg11939.html
[3] - https://patchwork.kernel.org/project/kernel-hardening/patch/20200716030847.1564131-3-keescook@chromium.org/

[fennecJ]

There are 2 things to worry about.

• Currently I'm not sure if all module worked correctly after above changes.
• Some function only worked on newer kernel (e.g. fd_close only worked in kernel >= 5.11) , I currently
  not sure if other version can compile the code via makefile smoothly after above changes.

My kernel version: 5.11.0-27-generic

[fennecJ]

The error/warning I've met with previous code:

syscall.c:

lkmpg/examples/syscall.c:83:50: error: ‘ksys_close’ undeclared (first use in this function); did you mean ‘ksys_chown’?
   83 |         if (sct[__NR_close] == (unsigned long *) ksys_close)

cryptosk.c:

lkmpg/examples/cryptosk.c:17:24: error: field ‘sg’ has incomplete type
   17 |     struct scatterlist sg;

lkmpg/examples/cryptosk.c:143:9: error: implicit declaration of function ‘get_random_bytes’ [-Werror=implicit-function-declaration]
  143 |         get_random_bytes(sk->ivdata, CIPHER_BLOCK_SIZE);

lkmpg/examples/cryptosk.c:156:5: error: implicit declaration of function ‘sg_init_one’ [-Werror=implicit-function-declaration]
  156 |     sg_init_one(&sk->sg, sk->scratchpad, CIPHER_BLOCK_SIZE);

bottomhalf.c:
example_tasklet.c:

error: macro "DECLARE_TASKLET" passed 3 arguments, but takes just 2

[fennecJ]

Seems like DECLARE_TASKLET_OLD is defined in include/linux/interrupt.h for kernel version >= v5.9
https://elixir.bootlin.com/linux/v5.9-rc1/C/ident/DECLARE_TASKLET_OLD

[jserv]

Modify the the description in TeX document about DECLARE_TASKLET_OLD transition.

[fennecJ]

There appears with a lot of *.dwo file after I using make in /example directory,
so I add *.dwo into .gitignore file.

[fennecJ]

"fn-in" in Makefile is intended to prevent make4ht from
excluding footnote into a new html file.

Output can be checked in https://fennecj.github.io/lkmpg/#tasklets

[jserv]

Thank @fennecJ for the great work!