LXR linux/arch/hexagon/kernel/head.S

   1/*
   2 * Early kernel startup code for Hexagon
   3 *
   4 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   5 *
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 and
   9 * only version 2 as published by the Free Software Foundation.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, write to the Free Software
  18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 * 02110-1301, USA.
  20 */
  21
  22#include <linux/linkage.h>
  23#include <linux/init.h>
  24#include <asm/asm-offsets.h>
  25#include <asm/mem-layout.h>
  26#include <asm/vm_mmu.h>
  27#include <asm/page.h>
  28
  29        __INIT
  30ENTRY(stext)
  31        /*
  32         * VMM will already have set up true vector page, MMU, etc.
  33         * To set up initial kernel identity map, we have to pass
  34         * the VMM a pointer to some canonical page tables. In
  35         * this implementation, we're assuming that we've got
  36         * them precompiled. Generate value in R24, as we'll need
  37         * it again shortly.
  38         */
  39        r24.L = #LO(swapper_pg_dir)
  40        r24.H = #HI(swapper_pg_dir)
  41
  42        /*
  43         * Symbol is kernel segment address, but we need
  44         * the logical/physical address.
  45         */
  46        r24 = asl(r24, #2)
  47        r24 = lsr(r24, #2)
  48
  49        r0 = r24
  50
  51        /*
  52         * Initialize a 16MB PTE to make the virtual and physical
  53         * addresses where the kernel was loaded be identical.
  54         */
  55#define PTE_BITS ( __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X      \
  56                  | __HEXAGON_C_WB_L2 << 6                      \
  57                  | __HVM_PDE_S_4MB)
  58
  59        r1 = pc
  60        r2.H = #0xffc0
  61        r2.L = #0x0000
  62        r1 = and(r1,r2)         /* round PC to 4MB boundary     */
  63        r2 = lsr(r1, #22)       /* 4MB page number              */
  64        r2 = asl(r2, #2)        /* times sizeof(PTE) (4bytes)   */
  65        r0 = add(r0,r2)         /* r0 = address of correct PTE  */
  66        r2 = #PTE_BITS
  67        r1 = add(r1,r2)         /* r1 = 4MB PTE for the first entry     */
  68        r2.h = #0x0040
  69        r2.l = #0x0000          /* 4MB  */
  70        memw(r0 ++ #4) = r1
  71        r1 = add(r1, r2)
  72        memw(r0 ++ #4) = r1
  73
  74        r0 = r24
  75
  76        /*
  77         * The subroutine wrapper around the virtual instruction touches
  78         * no memory, so we should be able to use it even here.
  79         */
  80        call    __vmnewmap;
  81
  82        /*  Jump into virtual address range.  */
  83
  84        r31.h = #hi(__head_s_vaddr_target)
  85        r31.l = #lo(__head_s_vaddr_target)
  86        jumpr r31
  87
  88        /*  Insert trippy space effects.  */
  89
  90__head_s_vaddr_target:
  91        /*
  92         * Tear down VA=PA translation now that we are running
  93         * in the desgnated kernel segments.
  94         */
  95        r0 = #__HVM_PDE_S_INVALID
  96        r1 = r24
  97        loop0(1f,#0x100)
  981:
  99        {
 100                memw(R1 ++ #4) = R0
 101        }:endloop0
 102
 103        r0 = r24
 104        call __vmnewmap
 105
 106        /*  Go ahead and install the trap0 return so angel calls work  */
 107        r0.h = #hi(_K_provisional_vec)
 108        r0.l = #lo(_K_provisional_vec)
 109        call __vmsetvec
 110
 111        /*
 112         * OK, at this point we should start to be much more careful,
 113         * we're going to enter C code and start touching memory
 114         * in all sorts of places.
 115         * This means:
 116         *      SGP needs to be OK
 117         *      Need to lock shared resources
 118         *      A bunch of other things that will cause
 119         *      all kinds of painful bugs
 120         */
 121
 122        /*
 123         * Stack pointer should be pointed at the init task's
 124         * thread stack, which should have been declared in arch/init_task.c.
 125         * So uhhhhh...
 126         * It's accessible via the init_thread_union, which is a union
 127         * of a thread_info struct and a stack; of course, the top
 128         * of the stack is not for you.  The end of the stack
 129         * is simply init_thread_union + THREAD_SIZE.
 130         */
 131
 132        {r29.H = #HI(init_thread_union); r0.H = #HI(_THREAD_SIZE); }
 133        {r29.L = #LO(init_thread_union); r0.L = #LO(_THREAD_SIZE); }
 134
 135        /*  initialize the register used to point to current_thread_info */
 136        /*  Fixme:  THREADINFO_REG can't be R2 because of that memset thing. */
 137        {r29 = add(r29,r0); THREADINFO_REG = r29; }
 138
 139        /*  Hack:  zero bss; */
 140        { r0.L = #LO(__bss_start);  r1 = #0; r2.l = #LO(__bss_stop); }
 141        { r0.H = #HI(__bss_start);           r2.h = #HI(__bss_stop); }
 142
 143        r2 = sub(r2,r0);
 144        call memset;
 145
 146        /* Time to make the doughnuts.   */
 147        call start_kernel
 148
 149        /*
 150         * Should not reach here.
 151         */
 1521:
 153        jump 1b
 154
 155.p2align PAGE_SHIFT
 156ENTRY(external_cmdline_buffer)
 157        .fill _PAGE_SIZE,1,0
 158
 159.data
 160.p2align PAGE_SHIFT
 161ENTRY(empty_zero_page)
 162        .fill _PAGE_SIZE,1,0
 163