offsets_target.h File Reference

X86-32 address space sizes and offsets. More...

Macros
#define	X86_32_VADDR_SPACE_SIZE   ((genpaddr_t)1 << 32)
#define	X86_32_PADDR_SPACE_SIZE   ((genpaddr_t)1 << 32)
#define	X86_32_START_KERNEL_PHYS   0x100000
#define	X86_32_PADDR_SPACE_LIMIT   ((genpaddr_t)1 << 31)
#define	X86_32_DEVICE_SPACE_LIMIT   (1 * X86_32_MEM_PAGE_SIZE)
#define	X86_32_INIT_SPACE_LIMIT   (32 * 1024 * 1024)
#define	X86_32_PDE_ALIGN(addr)   ((addr) & ~(((genpaddr_t)1 << 22) - 1))
#define	X86_32_MEMORY_OFFSET   X86_32_PDE_ALIGN((genpaddr_t)2 * 1024 * 1024 * 1024)
#define	X86_32_KERNEL_STACK_SIZE   0x4000
#define	X86_32_REAL_MODE_SEGMENT   0x0600
#define	X86_32_REAL_MODE_OFFSET   0x0000
#define	X86_32_REAL_MODE_LINEAR_OFFSET   (X86_32_REAL_MODE_SEGMENT << 4)

Variables
uintptr_t	x86_32_kernel_stack [X86_32_KERNEL_STACK_SIZE/sizeof(uintptr_t)]
	The kernel stack. More...

Detailed Description

X86-32 address space sizes and offsets.

The layout of the x86-32 virtual address space can be summarized as follows:

 +--------------------------------+------------------------------------+
 | User-space                     | Physical memory                    |
 | PDPTE entries: 0 1             | PDPTE entries: 2 3                 |
 +--------------------------------+------------------------------------+

User-space maps user-space programs. Physical memory maps all available physical memory (up to PADDR_SPACE_LIMIT).

This partition is static and can only be changed at compile-time.

Macro Definition Documentation

#define X86_32_DEVICE_SPACE_LIMIT   (1 * X86_32_MEM_PAGE_SIZE)

Maximum device address space mappable by the kernel. Adjust this for a bigger device address space. We set this to one page, so the APIC driver can do its job.

#define X86_32_INIT_SPACE_LIMIT   (32 * 1024 * 1024)

Static virtual address space limit for the init user-space domain. init's virtual address space always starts at address zero. The static space is used to map in code and static data of the init module, as well as all loaded multiboot modules, the dispatcher frame and bootinfo structure. init can freely allocate dynamic memory as soon as it is running. This is 32 MBytes right now.

You should make this constant a multiple of #BASE_PAGE_SIZE * #PTABLE_SIZE or you'll restrict init's static address space unneccessarily. init's lowest segment should also be based at these multiples or it restricts itself.

#define X86_32_KERNEL_STACK_SIZE   0x4000

Kernel stack size – 16KB

#define X86_32_MEMORY_OFFSET   X86_32_PDE_ALIGN((genpaddr_t)2 * 1024 * 1024 * 1024)

Absolute offset of mapped physical memory within virtual address space. This occupies one or more PDE slots directly before the kernel. This needs to be aligned to PADDR_SPACE_LIMIT.

#define X86_32_PADDR_SPACE_LIMIT   ((genpaddr_t)1 << 31)

Maximum physical address space mappable by the kernel. Adjust this for a bigger physical address space. We set this to 32-bit, i.e. 4 GBytes.

#define X86_32_PADDR_SPACE_SIZE   ((genpaddr_t)1 << 32)

Absolute size of physical address space. This is 48-bit.

#define X86_32_PDE_ALIGN

(

addr

)

((addr) & ~(((genpaddr_t)1 << 22) - 1))

Aligns an address to the nearest PDE entry by masking out lower 21 bits.

#define X86_32_REAL_MODE_LINEAR_OFFSET   (X86_32_REAL_MODE_SEGMENT << 4)

The linear offset of the real-mode segment

#define X86_32_REAL_MODE_OFFSET   0x0000

The real-mode offset has to be 0000!!

#define X86_32_REAL_MODE_SEGMENT   0x0600

The real-mode addressesThe real-mode segment

#define X86_32_START_KERNEL_PHYS   0x100000

Start address of kernel image in physical memory. This is passed to the linker also. The bootloader will load us there.

#define X86_32_VADDR_SPACE_SIZE   ((genpaddr_t)1 << 32)

Absolute size of virtual address space. This is 32-bit on x86-32, which equals 4 GBytes and allows for 1024 PDE slots, each of which can map 4 MBytes.

Variable Documentation

uintptr_t x86_32_kernel_stack[X86_32_KERNEL_STACK_SIZE/sizeof(uintptr_t)]

The kernel stack.

The kernel stack.

This is the one and only kernel stack for a kernel instance.