Linux Kernel init fails in encrypted filesystem

Question

I am trying to make a linux os with encrypted filesystem for the whole OS (boot,kernel,root,...)

I modified EXT4 filesystem's read and write functions. after running a lot of tests everything read and write work fine.

EDIT:

my change is a simple XOR to file contents.

my tests include reading/writing text files, tar archive creation/deletion, sound and videofile creation/copying/deletion and some stress tests.

this is dmesg says when trying to run a binary:

traps: a.out[2765] trap invalid opcode ip:400e73 sp:7ffc9f3d6f10 error:0 in a.out[400000+b4000]

next step was to boot a simple linux based OS on this encrypted filesystem, I modified GRUB 2 bootloader so it cat boot the kernel from encrypted disk. then I faced this problem:

• grub can load linux kernel and kernel boots, but when it tries to run the init proccess I get kernel panic with the message: "init Not tained".

I can see from previous messages that filesystem is loaded by kernel and it is actually reading init file but refuses to run init.

my question is: is kernel reading init file in any other way than using standard read system call? is there something I am doing wrong here?

Any help would be greatly appreciated

EDIT:

now the question is:

how can I decrypt the data that kernel uses by mapping memory?

Answer 1

The kernel will map the init binary to memory (i.e, using mmap()) to execute it. If you have only tested read(), this is quite possibly where your filesystem is failing.