Context

Thread execution state and accessors More...

Data Structures
struct	irq_context_t
	Architecture-specific structure for holding the processor state. More...

Macros
#define	REG_BYTE_CNT   256
	The number of bytes required to save thread context.

Functions
void	irq_set_context (irq_context_t *regbank)
	Switch out contexts (for interrupt return).
irq_context_t *	irq_get_context (void)
	Get the current IRQ context.
void	irq_create_context (irq_context_t *context, uint32_t stack_pointer, uint32_t routine, const uint32_t *args, bool usermode)
	Fill a newly allocated context block.

Register Accessors
Convenience macros for accessing context registers
#define	CONTEXT_PC(c)   ((c).pc)
	Fetch the program counter from an irq_context_t.
#define	CONTEXT_FP(c)   ((c).r[14])
	Fetch the frame pointer from an irq_context_t.
#define	CONTEXT_SP(c)   ((c).r[15])
	Fetch the stack pointer from an irq_context_t.
#define	CONTEXT_RET(c)   ((c).r[0])
	Fetch the return value from an irq_context_t.

Detailed Description

Thread execution state and accessors

This API includes the structure and accessors for a thread's context state, which contains the registers that are stored and loaded upon thread context switches, which are passed back to interrupt handlers.

Macro Definition Documentation

CONTEXT_FP

#define CONTEXT_FP

(

c

)

((c).r[14])

Fetch the frame pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The frame pointer value.

CONTEXT_PC

#define CONTEXT_PC

(

c

)

((c).pc)

Fetch the program counter from an irq_context_t.

Parameters

c	The context to read from.

Returns

The program counter value.

CONTEXT_RET

#define CONTEXT_RET

(

c

)

((c).r[0])

Fetch the return value from an irq_context_t.

Parameters

c	The context to read from.

Returns

The return value.

CONTEXT_SP

#define CONTEXT_SP

(

c

)

((c).r[15])

Fetch the stack pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The stack pointer value.

REG_BYTE_CNT

#define REG_BYTE_CNT   256

The number of bytes required to save thread context.

This should include all general CPU registers, FP registers, and status regs (even if not all of these are actually used).

Note

On the Dreamcast, we need 228 bytes for all of that, but we round it up to a nicer number for sanity.

Function Documentation

irq_create_context()

void irq_create_context	(	irq_context_t *	context,
		uint32_t	stack_pointer,
		uint32_t	routine,
		const uint32_t *	args,
		bool	usermode )

Fill a newly allocated context block.

The given parameters will be passed to the called routine (up to the architecture maximum). For the Dreamcast, this maximum is 4.

Parameters

context	The IRQ context to fill in.
stack_pointer	The value to set in the stack pointer.
routine	The address of the program counter for the context.
args	Any arguments to set in the registers. This cannot be NULL, and must have enough values to fill in up to the architecture maximum.
usermode	true to run the routine in user mode, false for supervisor.

irq_get_context()

irq_context_t * irq_get_context

(

void

)

Get the current IRQ context.

This will fetch the processor context prior to the exception handling during an IRQ service routine.

Returns

The current IRQ context.

See also

irq_set_context()

irq_set_context()

void irq_set_context

(

irq_context_t *

regbank

)

Switch out contexts (for interrupt return).

This function will set the processor state that will be restored when the exception returns.

Parameters

regbank

The values of all registers to be restored.

See also

irq_get_context()