# Linux Kernel Module Cheat
The perfect emulation setup to study and develop the <<linux-kernel>> v5.9.2, kernel modules, <<qemu-buildroot-setup,QEMU>>, <<gem5-buildroot-setup,gem5>> and x86_64, ARMv7 and ARMv8 <<userland-assembly,userland>> and <<baremetal-setup,baremetal>> assembly, <<c,ANSI C>>, <<cpp,C++>> and <<posix,POSIX>>. <<gdb>> and <<kgdb>> just work. Powered by <<about-the-qemu-buildroot-setup,Buildroot>> and <<about-the-baremetal-setup,crosstool-NG>>. Highly automated. Thoroughly documented. Automated <<test-this-repo,tests>>.

#### 29.3.2. x86 PUSH and POP instructions

userland/arch/x86_64/push.S

`push %rax` is basically equivalent to:

    sub $8, %rsp
    mov %rax, (%rsp)

and `pop %rax`:

    mov (%rsp), %rax
    add $8, %rsp

Why do those instructions exist at all vs MOV / ADD / SUB: https://stackoverflow.com/questions/4584089/what-is-the-function-of-push-pop-registers-in-x86-assembly/33583134#33583134