From what I've read, seems like there are 9 different flags. Is it possible to read/change them directly? I know I can know for example if the zero flag is set after doing a cmp/jmp instruction, but I'm asking if it's possible to do something like
mov eax, flags
or something.
Also, for writing, is it possible to set them by hand?
Simplest way is using pushfd/pushfw and pop (r16/r32).
If you want to move eflags into eax, use code below.
pushfd # push eflags into stack
pop %eax # pop it into %eax
Or, if you only want the first 16 bits from eflags:
pushfw
pop %ax
In most assemblers (at least GAS and NASM, likely others), pushf without an explicit operand-size defaults to the mode you're in. e.g. pushfq in 64-bit mode. You'd normally only need an explicit operand-size if you wanted to use pushfd in 16-bit mode to match a 32-bit pop. But it doesn't hurt.