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.TH ARCH 9 2023-12-18 "Osmora" "Hyra Operating System"
.Sh NAME
.Nm arch - hyra arch information
.Sh SYNOPSIS
.In sys/machdep.h
.In machine/cpu.h
.In machine/pmap.h
.Sh DESCRIPTION
NOTE: All examples will be for x86_64 but can be applied to others


Information about how Hyra and architectures work together. This
will describe headers and .c files that need to exist for all
architectures and things they should include. The
.Ft machine/cpu.h
file contains information about the CPU for the specific
architecture. Required structures in this header include the
.Ft cpu_info
struct which contains CPU specific fields.

Example
.Ft cpu_info
structure shown below:

.Bd -literal
struct cpu_info {
    /* Per-arch fields */
    void *pmap;                     /* Current pmap */
    uint32_t id;
    struct spinlock lock;
    /* AMD64 */
    ...
};
.Ed

There will be some per-architecture fields that, for the sake
of keeping things tidy, should remain at the top of the struct.
These fields will be described below.

The
.Ft pmap
field points to the current virtual memory context
which shall be NULL if not used.

The
.Ft id
field simply identifies the CPU with a specific "ID".

The
.Ft lock
field is a spinlock to prevent race conditions
while accessing this structure. This must be acquired
when accessing a
.Ft cpu_info
instance.

There are also some common helper macros that shall
be implemented, these are described below.

The macro
.Ft this_cpu()
calls an internal function that fetches the
cpu_info structure for the current CPU.

The macro
.Ft get_bsp()
calls an internal function that fetches the
cpu_info structure for the BSP.

The function these macros call must return a pointer
to a
.Ft cpu_info
structure.

In the
.Ft machine/pmap.h
header, should be a struct containing information
about the address space. This header MUST be implemented
or compiler errors will occur.

.Sh AUTHORS
.An Ian Moffett Aq Mt ian@osmora.org