root/arch/mips/kernel/head.S

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994, 1995 Waldorf Electronics
   7  * Written by Ralf Baechle and Andreas Busse
   8  * Copyright (C) 1994 - 99, 2003, 06 Ralf Baechle
   9  * Copyright (C) 1996 Paul M. Antoine
  10  * Modified for DECStation and hence R3000 support by Paul M. Antoine
  11  * Further modifications by David S. Miller and Harald Koerfgen
  12  * Copyright (C) 1999 Silicon Graphics, Inc.
  13  * Kevin Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
  14  * Copyright (C) 2000 MIPS Technologies, Inc.  All rights reserved.
  15  */
  16 #include <linux/init.h>
  17 #include <linux/threads.h>
  18 
  19 #include <asm/addrspace.h>
  20 #include <asm/asm.h>
  21 #include <asm/asmmacro.h>
  22 #include <asm/irqflags.h>
  23 #include <asm/regdef.h>
  24 #include <asm/mipsregs.h>
  25 #include <asm/stackframe.h>
  26 
  27 #include <kernel-entry-init.h>
  28 
  29         /*
  30          * For the moment disable interrupts, mark the kernel mode and
  31          * set ST0_KX so that the CPU does not spit fire when using
  32          * 64-bit addresses.  A full initialization of the CPU's status
  33          * register is done later in per_cpu_trap_init().
  34          */
  35         .macro  setup_c0_status set clr
  36         .set    push
  37         mfc0    t0, CP0_STATUS
  38         or      t0, ST0_CU0|\set|0x1f|\clr
  39         xor     t0, 0x1f|\clr
  40         mtc0    t0, CP0_STATUS
  41         .set    noreorder
  42         sll     zero,3                          # ehb
  43         .set    pop
  44         .endm
  45 
  46         .macro  setup_c0_status_pri
  47 #ifdef CONFIG_64BIT
  48         setup_c0_status ST0_KX 0
  49 #else
  50         setup_c0_status 0 0
  51 #endif
  52         .endm
  53 
  54         .macro  setup_c0_status_sec
  55 #ifdef CONFIG_64BIT
  56         setup_c0_status ST0_KX ST0_BEV
  57 #else
  58         setup_c0_status 0 ST0_BEV
  59 #endif
  60         .endm
  61 
  62 #ifndef CONFIG_NO_EXCEPT_FILL
  63         /*
  64          * Reserved space for exception handlers.
  65          * Necessary for machines which link their kernels at KSEG0.
  66          */
  67         .fill   0x400
  68 #endif
  69 
  70 EXPORT(_stext)
  71 
  72 #ifdef CONFIG_BOOT_RAW
  73         /*
  74          * Give us a fighting chance of running if execution beings at the
  75          * kernel load address.  This is needed because this platform does
  76          * not have a ELF loader yet.
  77          */
  78 FEXPORT(__kernel_entry)
  79         j       kernel_entry
  80 #endif /* CONFIG_BOOT_RAW */
  81 
  82         __REF
  83 
  84 NESTED(kernel_entry, 16, sp)                    # kernel entry point
  85 
  86         kernel_entry_setup                      # cpu specific setup
  87 
  88         setup_c0_status_pri
  89 
  90         /* We might not get launched at the address the kernel is linked to,
  91            so we jump there.  */
  92         PTR_LA  t0, 0f
  93         jr      t0
  94 0:
  95 
  96 #ifdef CONFIG_USE_OF
  97 #if defined(CONFIG_MIPS_RAW_APPENDED_DTB) || \
  98         defined(CONFIG_MIPS_ELF_APPENDED_DTB)
  99 
 100         PTR_LA          t2, __appended_dtb
 101 
 102 #ifdef CONFIG_CPU_BIG_ENDIAN
 103         li              t1, 0xd00dfeed
 104 #else  /* !CONFIG_CPU_BIG_ENDIAN */
 105         li              t1, 0xedfe0dd0
 106 #endif /* !CONFIG_CPU_BIG_ENDIAN */
 107         lw              t0, (t2)
 108         beq             t0, t1, dtb_found
 109 #endif /* CONFIG_MIPS_RAW_APPENDED_DTB || CONFIG_MIPS_ELF_APPENDED_DTB */
 110         li              t1, -2
 111         move            t2, a1
 112         beq             a0, t1, dtb_found
 113 
 114         li              t2, 0
 115 dtb_found:
 116 #endif /* CONFIG_USE_OF */
 117         PTR_LA          t0, __bss_start         # clear .bss
 118         LONG_S          zero, (t0)
 119         PTR_LA          t1, __bss_stop - LONGSIZE
 120 1:
 121         PTR_ADDIU       t0, LONGSIZE
 122         LONG_S          zero, (t0)
 123         bne             t0, t1, 1b
 124 
 125         LONG_S          a0, fw_arg0             # firmware arguments
 126         LONG_S          a1, fw_arg1
 127         LONG_S          a2, fw_arg2
 128         LONG_S          a3, fw_arg3
 129 
 130 #ifdef CONFIG_USE_OF
 131         LONG_S          t2, fw_passed_dtb
 132 #endif
 133 
 134         MTC0            zero, CP0_CONTEXT       # clear context register
 135         PTR_LA          $28, init_thread_union
 136         /* Set the SP after an empty pt_regs.  */
 137         PTR_LI          sp, _THREAD_SIZE - 32 - PT_SIZE
 138         PTR_ADDU        sp, $28
 139         back_to_back_c0_hazard
 140         set_saved_sp    sp, t0, t1
 141         PTR_SUBU        sp, 4 * SZREG           # init stack pointer
 142 
 143 #ifdef CONFIG_RELOCATABLE
 144         /* Copy kernel and apply the relocations */
 145         jal             relocate_kernel
 146 
 147         /* Repoint the sp into the new kernel image */
 148         PTR_LI          sp, _THREAD_SIZE - 32 - PT_SIZE
 149         PTR_ADDU        sp, $28
 150         set_saved_sp    sp, t0, t1
 151         PTR_SUBU        sp, 4 * SZREG           # init stack pointer
 152 
 153         /*
 154          * relocate_kernel returns the entry point either
 155          * in the relocated kernel or the original if for
 156          * some reason relocation failed - jump there now
 157          * with instruction hazard barrier because of the
 158          * newly sync'd icache.
 159          */
 160         jr.hb           v0
 161 #else  /* !CONFIG_RELOCATABLE */
 162         j               start_kernel
 163 #endif /* !CONFIG_RELOCATABLE */
 164         END(kernel_entry)
 165 
 166 #ifdef CONFIG_SMP
 167 /*
 168  * SMP slave cpus entry point.  Board specific code for bootstrap calls this
 169  * function after setting up the stack and gp registers.
 170  */
 171 NESTED(smp_bootstrap, 16, sp)
 172         smp_slave_setup
 173         setup_c0_status_sec
 174         j       start_secondary
 175         END(smp_bootstrap)
 176 #endif /* CONFIG_SMP */