/* cpu_asm.s * * This file contains all assembly code for the MC68020 implementation * of RTEMS. * * COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994. * On-Line Applications Research Corporation (OAR). * All rights assigned to U.S. Government, 1994. * * This material may be reproduced by or for the U.S. Government pursuant * to the copyright license under the clause at DFARS 252.227-7013. This * notice must appear in all copies of this file and its derivatives. * * $Id$ */ #include .text /* void _CPU_Context_switch( run_context, heir_context ) * * This routine performs a normal non-FP context. */ .align 4 .global SYM (_CPU_Context_switch) .set RUNCONTEXT_ARG, 4 | save context argument .set HEIRCONTEXT_ARG, 8 | restore context argument SYM (_CPU_Context_switch): moval a7@(RUNCONTEXT_ARG),a0| a0 = running thread context movw sr,d1 | d1 = status register movml d1-d7/a2-a7,a0@ | save context moval a7@(HEIRCONTEXT_ARG),a0| a0 = heir thread context restore: movml a0@,d1-d7/a2-a7 | restore context movw d1,sr | restore status register rts /*PAGE * void __CPU_Context_save_fp_context( &fp_context_ptr ) * void __CPU_Context_restore_fp_context( &fp_context_ptr ) * * These routines are used to context switch a MC68881 or MC68882. * * NOTE: Context save and restore code is based upon the code shown * on page 6-38 of the MC68881/68882 Users Manual (rev 1). * * CPU_FP_CONTEXT_SIZE is higher than expected to account for the * -1 pushed at end of this sequence. */ .set FPCONTEXT_ARG, 4 | save FP context argument .align 4 .global SYM (_CPU_Context_save_fp) SYM (_CPU_Context_save_fp): #if ( M68K_HAS_FPU == 1 ) moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area moval a1@,a0 | a0 = Save context area fsave a0@- | save 68881/68882 state frame tstb a0@ | check for a null frame beq nosv | Yes, skip save of user model fmovem fp0-fp7,a0@- | save data registers (fp0-fp7) fmovem fpc/fps/fpi,a0@- | and save control registers movl #-1,a0@- | place not-null flag on stack nosv: movl a0,a1@ | save pointer to saved context #endif rts .align 4 .global SYM (_CPU_Context_restore_fp) SYM (_CPU_Context_restore_fp): #if ( M68K_HAS_FPU == 1 ) moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area moval a1@,a0 | a0 = address of saved context tstb a0@ | Null context frame? beq norst | Yes, skip fp restore addql #4,a0 | throwaway non-null flag fmovem a0@+,fpc/fps/fpi | restore control registers fmovem a0@+,fp0-fp7 | restore data regs (fp0-fp7) norst: frestore a0@+ | restore the fp state frame movl a0,a1@ | save pointer to saved context #endif rts /*PAGE * void _ISR_Handler() * * This routine provides the RTEMS interrupt management. * * NOTE: * Upon entry, the master stack will contain an interrupt stack frame * back to the interrupted thread and the interrupt stack will contain * a throwaway interrupt stack frame. If dispatching is enabled, this * is the outer most interrupt, and (a context switch is necessary or * the current thread has signals), then set up the master stack to * transfer control to the interrupt dispatcher. */ .set SR_OFFSET, 0 | Status register offset .set PC_OFFSET, 2 | Program Counter offset .set FVO_OFFSET, 6 | Format/vector offset .set SAVED, 16 | space for saved registers .align 4 .global SYM (_ISR_Handler) SYM (_ISR_Handler): moveml d0-d1/a0-a1,a7@- | save d0-d1,a0-a1 addql #1,SYM (_ISR_Nest_level) | one nest level deeper addql #1,SYM (_Thread_Dispatch_disable_level) | disable multitasking movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO andl #0x0fff,d0 | d0 = vector offset in vbr #if ( M68K_HAS_PREINDEXING == 1 ) movel @( SYM (_ISR_Vector_table),d0:w:1),a0| fetch the ISR #else movel # SYM (_ISR_Vector_table),a0 | a0 = base of RTEMS table addal d0,a0 | a0 = address of vector movel @(a0),a0 | a0 = address of user routine #warning "UNTESTED CODE!!!" #endif lsrl #2,d0 | d0 = vector number movel d0,a7@- | push vector number jbsr a0@ | invoke the user ISR addql #4,a7 | remove vector number subql #1,SYM (_ISR_Nest_level) | one less nest level subql #1,SYM (_Thread_Dispatch_disable_level) | unnest multitasking bne exit | If dispatch disabled, exit movew #0xf000,d0 | isolate format nibble andw a7@(SAVED+FVO_OFFSET),d0 | get F/VO cmpiw #0x1000,d0 | is it a throwaway isf? bne exit | NOT outer level, so branch tstl SYM (_Context_Switch_necessary) | Is thread switch necessary? bne bframe | Yes, invoke dispatcher tstl SYM (_ISR_Signals_to_thread_executing) | signals sent to Run_thread | while in interrupt handler? beq exit | No, then exit bframe: clrl SYM (_ISR_Signals_to_thread_executing) | If sent, will be processed #if ( M68K_HAS_SEPARATE_STACKS == 1 ) movec msp,a0 | a0 = master stack pointer movew #0,a0@- | push format word movel # SYM (_ISR_Dispatch),a0@- | push return addr movew a0@(6+SR_OFFSET),a0@- | push thread sr movec a0,msp | set master stack pointer #else #warning "FIX ME ... HOW DO I DISPATCH FROM AN INTERRUPT?" /* probably will simply need to push the _ISR_Dispatch frame */ #endif exit: moveml a7@+,d0-d1/a0-a1 | restore d0-d1,a0-a1 rte | return to thread | OR _Isr_dispatch /*PAGE * void _ISR_Dispatch() * * Entry point from the outermost interrupt service routine exit. * The current stack is the supervisor mode stack if this processor * has separate stacks. * * 1. save all registers not preserved across C calls. * 2. invoke the _Thread_Dispatch routine to switch tasks * or a signal to the currently executing task. * 3. restore all registers not preserved across C calls. * 4. return from interrupt */ .global SYM (_ISR_Dispatch) SYM (_ISR_Dispatch): movml d0-d1/a0-a1,a7@- jsr SYM (_Thread_Dispatch) movml a7@+,d0-d1/a0-a1 rte