libx86 -- C++ interface to x86/x86-64 registers and data structures

This library provides C++ interfaces for manipulating x86 and x86_64 register types and data structures. For example, to set the direction flag in the hardware rflags register, you can use the following code:

using namespace x86_64;
rflags::write(rflags::read().direction_flag(true));

You can chain multiple changes like this:

rflags::write(rflags::read()
	.direction_flag(true)
	.zero_flag(false)
	.overflow_flag(false));

If you simply want to read different parts of the register (without actually reading it from the hardware more than once), you can store the value in a variable:

rflags x = rflags::read();
printf("carry flag = %d\n", x.carry_flag());
printf("parity flag = %d\n", x.parity_flag());

If you're an operating system kernel, you may wish to inspect a (paused) thread's rflags that were pushed to the stack during interrupt or system call entry. Then you would typically have a struct like this:

struct task_state {
	...
	uint64_t rsp;
	uint64_t rflags;
	uint64_t rip;
	...
};

Since x86_64::rflags is always a 64-bit POD (XXX: should be, anyway), you can embed it in other structs and manipulate it as if it was the actual hardware register:

struct task_state {
	...
	uint64_t rsp;
	x86_64::rflags rflags;
	uint64_t rip;
	...
};

...

void interrupt(struct task_state &current_task)
{
	...
	printf("interrupted task:\n");
	printf("carry flag = %d\n", current_task.rflags.carry_flag());
	printf("parity flag = %d\n", current_task.rflags.parity_flag());
	...
}

Contact

Please send ideas, suggestions, patches, etc. to Vegard Nossum [email protected].

Disclaimer: The library is in a very early stage. Don't expect it to be able to do anything that I haven't needed to do with it myself already.