text: /*
   *   Save/restore CPU state macros
   *
   *   Copyright (C) 2015 Mark Cave-Ayland (mark.cave-ayland@ilande.co.uk>)
   *
   *   This program is free software; you can redistribute it and/or
   *   modify it under the terms of the GNU General Public License
   *   version 2
   *
   */
  
  #include "autoconf.h"
  
  /* State size for context (see below) */
  #define CONTEXT_STATE_SIZE 0x570
  
  /* Stack size for context (allocated inline of the context stack) */
  #define CONTEXT_STACK_SIZE 0x2000
  
  /* %cwp save/restore direction */
  #if defined(CONFIG_QEMU)
      /* QEMU SPARCv9 %cwp save/restore direction is reversed compared to real hardware */
      #define CWP_DIRECTION -1
  #else
      #define CWP_DIRECTION  1
  #endif
  
  /*
   * SAVE_CPU_STATE and RESTORE_CPU_STATE are macros used to enable a context switch
   * to C to occur within the MMU I/D TLB miss handlers.
   *
   * Because these handlers are called on a TLB miss, we cannot use flushw to store
   * processor window state on the stack, as the memory areas used by each window's
   * stack pointer may not be in the TLB, causing recursive TLB miss traps.
   *
   * For this reason, we save window state by manually rotating the window registers
   * and saving their contents (along with other vital registers) into a special
   * tlb_handler_stack defined above which is guaranteed to be locked in the TLB, and
   * so won't cause issues with trap recursion.
   *
   * Once this process is complete, we remain in a TL=0, CWP=0 state (with IE=1 to allow
   * window fill/spill traps if required), switch to our safe tlb_handler_stack and 
   * invoke the miss handler.
   */
  
  #define SAVE_CPU_GENERAL_STATE(type) \
  	/* Save generate state into context at %g1 */ \
  	rdpr	%pstate, %g7; \
  	stx	%g7, [%g1 + 0xb0]; \
  	rd	%y, %g7; \
  	stx	%g7, [%g1 + 0xb8]; \
  	rd	%fprs, %g7; \
  	stx	%g7, [%g1 + 0xc0]; \
  	rdpr    %tl, %g7; \
  	stx     %g7, [%g1 + 0xc8];
  
  
  #define SAVE_CPU_WINDOW_STATE(type) \
  	/* Save window state into context at %g1 */ \
  	rdpr	%cwp, %g7; \
  	stx	%g7, [%g1]; \
  	rdpr	%cansave, %g7; \
  	stx	%g7, [%g1 + 0x8]; \
  	rdpr	%canrestore, %g7; \
  	stx	%g7, [%g1 + 0x10]; \
  	rdpr	%otherwin, %g7; \
  	stx	%g7, [%g1 + 0x18]; \
  	rdpr	%wstate, %g7; \
  	stx	%g7, [%g1 + 0x20]; \
  	rdpr	%cleanwin, %g7; \
  	stx	%g7, [%g1 + 0x28]; \
  	\
  	/* %g1-%g7 stored at 0x30 - 0x68 */ \
  	\
  	stx	%o0, [%g1 + 0x70]; \
  	stx	%o1, [%g1 + 0x78]; \
  	stx	%o2, [%g1 + 0x80]; \
  	stx	%o3, [%g1 + 0x88]; \
  	stx	%o4, [%g1 + 0x90]; \
  	stx	%o5, [%g1 + 0x98]; \
  	stx	%o6, [%g1 + 0xa0]; \
  	stx	%o7, [%g1 + 0xa8]; \
  	\
  	/* Now iterate through all of the windows saving all l and i registers */ \
  	add	%g1, 0xd0, %g5; \
  	\
  	/* Get the number of windows in %g6 */ \
  	rdpr	%ver, %g6; \
  	and	%g6, 0xf, %g6; \
  	\
  	mov     %g6, %g4; \
  	inc     %g4; \
  	\
  	/* Starting cwp in g7 */ \
  	rdpr    %cwp, %g7; \
  	\
  save_cpu_window_##type: \
  	wrpr    %g7, %cwp; \
  	stx	%l0, [%g5]; \
  	stx	%l1, [%g5 + 0x8]; \
  	stx	%l2, [%g5 + 0x10]; \
  	stx	%l3, [%g5 + 0x18]; \
  	stx	%l4, [%g5 + 0x20]; \
  	stx	%l5, [%g5 + 0x28]; \
  	stx	%l6, [%g5 + 0x30]; \
  	stx	%l7, [%g5 + 0x38]; \
  	stx	%i0, [%g5 + 0x40]; \
  	stx	%i1, [%g5 + 0x48]; \
  	stx	%i2, [%g5 + 0x50]; \
  	stx	%i3, [%g5 + 0x58]; \
  	stx	%i4, [%g5 + 0x60]; \
  	stx	%i5, [%g5 + 0x68]; \
  	stx	%i6, [%g5 + 0x70]; \
  	stx	%i7, [%g5 + 0x78]; \
  	add	%g7, CWP_DIRECTION, %g7; \
  	and	%g7, %g6, %g7; \
  	subcc	%g4, 1, %g4; \
  	bne	save_cpu_window_##type; \
  	 add	%g5, 0x80, %g5; \
  	\
  	/* For 8 windows with 16 registers to save in the window, memory required \
  	is 16*8*8 = 0x400 bytes */
  
  #define RESET_CPU_WINDOW_STATE(type) \
  	wrpr	%g0, %cwp; \
  	/* Now we should be in window 0 so update the other window registers */ \
  	rdpr	%ver, %g6; \
  	and	%g6, 0xf, %g6; \
  	dec	%g6; \
  	wrpr	%g6, %cansave; \
  	\
  	wrpr	%g0, %cleanwin; \
  	wrpr	%g0, %canrestore; \
  	wrpr	%g0, %otherwin;
  
  #define SAVE_CPU_TRAP_STATE(type) \
  	/* Save trap state into context at %g1 */ \
  	rdpr	%tba, %g5; \
  	stx	%g5, [%g1 + 0x4e0]; \
  	add	%g1, 0x4f0, %g5; \
  	mov	4, %g6; \
  	\
  	/* Save current trap level */ \
  	rdpr	%tl, %g4; \
  	\
  save_trap_state_##type: \
  	deccc	%g6; \
  	wrpr	%g6, %tl; \
  	rdpr	%tpc, %g7; \
  	stx	%g7, [%g5]; \
  	rdpr	%tnpc, %g7; \
  	stx	%g7, [%g5 + 0x8]; \
  	rdpr	%tstate, %g7; \
  	stx	%g7, [%g5 + 0x10]; \
  	rdpr	%tt, %g7; \
  	stx	%g7, [%g5 + 0x18]; \
  	bne	save_trap_state_##type; \
  	 add	%g5, 0x20, %g5; \
  	\
  	/* For 4 trap levels with 4 registers, memory required is \
  	4*8*4 = 0x80 bytes */ \
  	\
  	/* Switch back to original trap level */ \
  	wrpr	%g4, %tl;
  
  /* Save all state into context at %g1 */
  #define SAVE_CPU_STATE(type) \
  	SAVE_CPU_GENERAL_STATE(type); \
  	SAVE_CPU_WINDOW_STATE(type); \
  	SAVE_CPU_TRAP_STATE(type);
  
  
  #define RESTORE_CPU_GENERAL_STATE(type) \
  	/* Restore general state from context at %g1 */ \
  	ldx	[%g1 + 0xb0], %g7; \
  	wrpr	%g7, %pstate; \
  	ldx	[%g1 + 0xb8], %g7; \
  	wr	%g7, 0, %y; \
  	ldx	[%g1 + 0xc0], %g7; \
  	wr	%g7, 0, %fprs;
  	
  	
  #define RESTORE_CPU_WINDOW_STATE(type) \
  	/* Restore window state from context at %g1 */ \
  	\
  	/* Get the number of windows in %g6 */ \
  	rdpr	%ver, %g6; \
  	and	%g6, 0xf, %g6; \
  	\
  	mov	%g6, %g4; \
  	inc	%g4; \
  	\
  	/* Set starting window */ \
  	ldx	[%g1], %g7; \
  	\
  	/* Now iterate through all of the windows restoring all l and i registers */ \
  	add	%g1, 0xd0, %g5; \
  	\
  restore_cpu_window_##type: \
  	wrpr	%g7, %cwp; \
  	ldx	[%g5], %l0; \
  	ldx	[%g5 + 0x8], %l1; \
  	ldx	[%g5 + 0x10], %l2; \
  	ldx	[%g5 + 0x18], %l3; \
  	ldx	[%g5 + 0x20], %l4; \
  	ldx	[%g5 + 0x28], %l5; \
  	ldx	[%g5 + 0x30], %l6; \
  	ldx	[%g5 + 0x38], %l7; \
  	ldx	[%g5 + 0x40], %i0; \
  	ldx	[%g5 + 0x48], %i1; \
  	ldx	[%g5 + 0x50], %i2; \
  	ldx	[%g5 + 0x58], %i3; \
  	ldx	[%g5 + 0x60], %i4; \
  	ldx	[%g5 + 0x68], %i5; \
  	ldx	[%g5 + 0x70], %i6; \
  	ldx	[%g5 + 0x78], %i7; \
  	add	%g7, CWP_DIRECTION, %g7; \
  	and	%g7, %g6, %g7; \
  	subcc	%g4, 1, %g4; \
  	bne	restore_cpu_window_##type; \
  	 add	%g5, 0x80, %g5; \
  	\
  	/* Restore the window registers to their original value */ \
  	ldx	[%g1], %g7; \
  	wrpr	%g7, %cwp; \
  	ldx	[%g1 + 0x8], %g7; \
  	wrpr	%g7, %cansave; \
  	ldx	[%g1 + 0x10], %g7; \
  	wrpr	%g7, %canrestore; \
  	ldx	[%g1 + 0x18], %g7; \
  	wrpr	%g7, %otherwin; \
  	ldx	[%g1 + 0x20], %g7; \
  	wrpr	%g7, %wstate; \
  	ldx	[%g1 + 0x28], %g7; \
  	wrpr	%g7, %cleanwin; \
  	\
  	/* %g1-%g7 stored at 0x30 - 0x68 */ \
  	\
  	ldx	[%g1 + 0x70], %o0; \
  	ldx	[%g1 + 0x78], %o1; \
  	ldx	[%g1 + 0x80], %o2; \
  	ldx	[%g1 + 0x88], %o3; \
  	ldx	[%g1 + 0x90], %o4; \
  	ldx	[%g1 + 0x98], %o5; \
  	ldx	[%g1 + 0xa0], %o6; \
  	ldx	[%g1 + 0xa8], %o7;
  
  
  #define RESTORE_CPU_TRAP_STATE(type) \
  	/* Restore trap state from context at %g1 */ \
  	add	%g1, 0x4f0, %g5; \
  	mov	4, %g6; \
  	\
  restore_trap_state_##type: \
  	deccc	%g6; \
  	wrpr	%g6, %tl; \
  	ldx	[%g5], %g7; \
  	wrpr	%g7, %tpc; \
  	ldx	[%g5 + 0x8], %g7; \
  	wrpr	%g7, %tnpc; \
  	ldx	[%g5 + 0x10], %g7; \
  	wrpr	%g7, %tstate; \
  	ldx	[%g5 + 0x18], %g7; \
  	wrpr	%g7, %tt; \
  	bne	restore_trap_state_##type; \
  	 add	%g5, 0x20, %g5; \
  	\
  	ldx	[%g1 + 0xc8], %g7; \
  	wrpr	%g7, %tl; \
  	ldx	[%g1 + 0x4e0], %g7; \
  	wrpr	%g7, %tba
  
  
  /* Restore all state from context at %g1 */
  #define RESTORE_CPU_STATE(type) \
  	RESTORE_CPU_GENERAL_STATE(type); \
  	RESTORE_CPU_WINDOW_STATE(type); \
  	RESTORE_CPU_TRAP_STATE(type);
  