arch/mn10300/kernel/switch_to.S

   1 ###############################################################################
   2 #
   3 # MN10300 Context switch operation
   4 #
   5 # Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   6 # Written by David Howells (dhowells@redhat.com)
   7 #
   8 # This program is free software; you can redistribute it and/or
   9 # modify it under the terms of the GNU General Public Licence
  10 # as published by the Free Software Foundation; either version
  11 # 2 of the Licence, or (at your option) any later version.
  12 #
  13 ###############################################################################
  14 #include <linux/sys.h>
  15 #include <linux/linkage.h>
  16 #include <asm/thread_info.h>
  17 #include <asm/cpu-regs.h>
  18 #ifdef CONFIG_SMP
  19 #include <proc/smp-regs.h>
  20 #endif /* CONFIG_SMP */
  21
  22         .text
  23
  24 ###############################################################################
  25 #
  26 # struct task_struct *__switch_to(struct thread_struct *prev,
  27 #                                 struct thread_struct *next,
  28 #                                 struct task_struct *prev_task)
  29 #
  30 ###############################################################################
  31 ENTRY(__switch_to)
  32         movm    [d2,d3,a2,a3,exreg1],(sp)
  33         or      EPSW_NMID,epsw
  34
  35         mov     (44,sp),d2
  36
  37         mov     d0,a0
  38         mov     d1,a1
  39
  40         # save prev context
  41         mov     __switch_back,d0
  42         mov     sp,a2
  43         mov     a2,(THREAD_SP,a0)
  44         mov     a3,(THREAD_A3,a0)
  45
  46 #ifdef CONFIG_KGDB
  47         btst    0xff,(kgdb_single_step)
  48         bne     __switch_to__lift_sstep_bp
  49 __switch_to__continue:
  50 #endif
  51         mov     d0,(THREAD_PC,a0)
  52
  53         mov     (THREAD_A3,a1),a3
  54         mov     (THREAD_SP,a1),a2
  55
  56         # switch
  57         mov     a2,sp
  58
  59         # load next context
  60         GET_THREAD_INFO a2
  61         mov     a2,(__current_ti)
  62         mov     (TI_task,a2),a2
  63         mov     a2,(__current)
  64 #ifdef CONFIG_MN10300_CURRENT_IN_E2
  65         mov     a2,e2
  66 #endif
  67
  68         mov     (THREAD_PC,a1),a2
  69         mov     d2,d0                   # for ret_from_fork
  70         mov     d0,a0                   # for __switch_to
  71
  72         jmp     (a2)
  73
  74 __switch_back:
  75         and     ~EPSW_NMID,epsw
  76         ret     [d2,d3,a2,a3,exreg1],32
  77
  78 #ifdef CONFIG_KGDB
  79 ###############################################################################
  80 #
  81 # Lift the single-step breakpoints when the task being traced is switched out
  82 # A0 = prev
  83 # A1 = next
  84 #
  85 ###############################################################################
  86 __switch_to__lift_sstep_bp:
  87         add     -12,sp
  88         mov     a0,e4
  89         mov     a1,e5
  90
  91         # Clear the single-step flag to prevent us coming this way until we get
  92         # switched back in
  93         bclr    0xff,(kgdb_single_step)
  94
  95         # Remove first breakpoint
  96         mov     (kgdb_sstep_bp_addr),a2
  97         cmp     0,a2
  98         beq     1f
  99         movbu   (kgdb_sstep_bp),d0
 100         movbu   d0,(a2)
 101 #if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
 102         mov     a2,d0
 103         mov     a2,d1
 104         add     1,d1
 105         calls   flush_icache_range
 106 #endif
 107 1:
 108
 109         # Remove second breakpoint
 110         mov     (kgdb_sstep_bp_addr+4),a2
 111         cmp     0,a2
 112         beq     2f
 113         movbu   (kgdb_sstep_bp+1),d0
 114         movbu   d0,(a2)
 115 #if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
 116         mov     a2,d0
 117         mov     a2,d1
 118         add     1,d1
 119         calls   flush_icache_range
 120 #endif
 121 2:
 122
 123         # Change the resumption address and return
 124         mov     __switch_back__reinstall_sstep_bp,d0
 125         mov     e4,a0
 126         mov     e5,a1
 127         add     12,sp
 128         bra     __switch_to__continue
 129
 130 ###############################################################################
 131 #
 132 # Reinstall the single-step breakpoints when the task being traced is switched
 133 # back in (A1 points to the new thread_struct).
 134 #
 135 ###############################################################################
 136 __switch_back__reinstall_sstep_bp:
 137         add     -12,sp
 138         mov     a0,e4                   # save the return value
 139         mov     0xff,d3
 140
 141         # Reinstall first breakpoint
 142         mov     (kgdb_sstep_bp_addr),a2
 143         cmp     0,a2
 144         beq     1f
 145         movbu   (a2),d0
 146         movbu   d0,(kgdb_sstep_bp)
 147         movbu   d3,(a2)
 148 #if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
 149         mov     a2,d0
 150         mov     a2,d1
 151         add     1,d1
 152         calls   flush_icache_range
 153 #endif
 154 1:
 155
 156         # Reinstall second breakpoint
 157         mov     (kgdb_sstep_bp_addr+4),a2
 158         cmp     0,a2
 159         beq     2f
 160         movbu   (a2),d0
 161         movbu   d0,(kgdb_sstep_bp+1)
 162         movbu   d3,(a2)
 163 #if defined(CONFIG_MN10300_CACHE_FLUSH_ICACHE) || defined(CONFIG_MN10300_CACHE_INV_ICACHE)
 164         mov     a2,d0
 165         mov     a2,d1
 166         add     1,d1
 167         calls   flush_icache_range
 168 #endif
 169 2:
 170
 171         mov     d3,(kgdb_single_step)
 172
 173         # Restore the return value (the previous thread_struct pointer)
 174         mov     e4,a0
 175         mov     a0,d0
 176         add     12,sp
 177         bra     __switch_back
 178
 179 #endif /* CONFIG_KGDB */