head.S (5545B)
1/* SPDX-License-Identifier: GPL-2.0-only */ 2/* 3 * Early kernel startup code for Hexagon 4 * 5 * Copyright (c) 2010-2013, The Linux Foundation. All rights reserved. 6 */ 7 8#include <linux/linkage.h> 9#include <linux/init.h> 10#include <asm/asm-offsets.h> 11#include <asm/mem-layout.h> 12#include <asm/vm_mmu.h> 13#include <asm/page.h> 14#include <asm/hexagon_vm.h> 15 16#define SEGTABLE_ENTRIES #0x0e0 17 18 __INIT 19ENTRY(stext) 20 /* 21 * VMM will already have set up true vector page, MMU, etc. 22 * To set up initial kernel identity map, we have to pass 23 * the VMM a pointer to some canonical page tables. In 24 * this implementation, we're assuming that we've got 25 * them precompiled. Generate value in R24, as we'll need 26 * it again shortly. 27 */ 28 r24.L = #LO(swapper_pg_dir) 29 r24.H = #HI(swapper_pg_dir) 30 31 /* 32 * Symbol is kernel segment address, but we need 33 * the logical/physical address. 34 */ 35 r25 = pc; 36 r2.h = #0xffc0; 37 r2.l = #0x0000; 38 r25 = and(r2,r25); /* R25 holds PHYS_OFFSET now */ 39 r1.h = #HI(PAGE_OFFSET); 40 r1.l = #LO(PAGE_OFFSET); 41 r24 = sub(r24,r1); /* swapper_pg_dir - PAGE_OFFSET */ 42 r24 = add(r24,r25); /* + PHYS_OFFSET */ 43 44 r0 = r24; /* aka __pa(swapper_pg_dir) */ 45 46 /* 47 * Initialize page dir to make the virtual and physical 48 * addresses where the kernel was loaded be identical. 49 * Done in 4MB chunks. 50 */ 51#define PTE_BITS ( __HVM_PTE_R | __HVM_PTE_W | __HVM_PTE_X \ 52 | __HEXAGON_C_WB_L2 << 6 \ 53 | __HVM_PDE_S_4MB) 54 55 /* 56 * Get number of VA=PA entries; only really needed for jump 57 * to hyperspace; gets blown away immediately after 58 */ 59 60 { 61 r1.l = #LO(_end); 62 r2.l = #LO(stext); 63 r3 = #1; 64 } 65 { 66 r1.h = #HI(_end); 67 r2.h = #HI(stext); 68 r3 = asl(r3, #22); 69 } 70 { 71 r1 = sub(r1, r2); 72 r3 = add(r3, #-1); 73 } /* r1 = _end - stext */ 74 r1 = add(r1, r3); /* + (4M-1) */ 75 r26 = lsr(r1, #22); /* / 4M = # of entries */ 76 77 r1 = r25; 78 r2.h = #0xffc0; 79 r2.l = #0x0000; /* round back down to 4MB boundary */ 80 r1 = and(r1,r2); 81 r2 = lsr(r1, #22) /* 4MB page number */ 82 r2 = asl(r2, #2) /* times sizeof(PTE) (4bytes) */ 83 r0 = add(r0,r2) /* r0 = address of correct PTE */ 84 r2 = #PTE_BITS 85 r1 = add(r1,r2) /* r1 = 4MB PTE for the first entry */ 86 r2.h = #0x0040 87 r2.l = #0x0000 /* 4MB increments */ 88 loop0(1f,r26); 891: 90 memw(r0 ++ #4) = r1 91 { r1 = add(r1, r2); } :endloop0 92 93 /* Also need to overwrite the initial 0xc0000000 entries */ 94 /* PAGE_OFFSET >> (4MB shift - 4 bytes per entry shift) */ 95 R1.H = #HI(PAGE_OFFSET >> (22 - 2)) 96 R1.L = #LO(PAGE_OFFSET >> (22 - 2)) 97 98 r0 = add(r1, r24); /* advance to 0xc0000000 entry */ 99 r1 = r25; 100 r2.h = #0xffc0; 101 r2.l = #0x0000; /* round back down to 4MB boundary */ 102 r1 = and(r1,r2); /* for huge page */ 103 r2 = #PTE_BITS 104 r1 = add(r1,r2); 105 r2.h = #0x0040 106 r2.l = #0x0000 /* 4MB increments */ 107 108 loop0(1f,SEGTABLE_ENTRIES); 1091: 110 memw(r0 ++ #4) = r1; 111 { r1 = add(r1,r2); } :endloop0 112 113 r0 = r24; 114 115 /* 116 * The subroutine wrapper around the virtual instruction touches 117 * no memory, so we should be able to use it even here. 118 * Note that in this version, R1 and R2 get "clobbered"; see 119 * vm_ops.S 120 */ 121 r1 = #VM_TRANS_TYPE_TABLE 122 call __vmnewmap; 123 124 /* Jump into virtual address range. */ 125 126 r31.h = #hi(__head_s_vaddr_target) 127 r31.l = #lo(__head_s_vaddr_target) 128 jumpr r31 129 130 /* Insert trippy space effects. */ 131 132__head_s_vaddr_target: 133 /* 134 * Tear down VA=PA translation now that we are running 135 * in kernel virtual space. 136 */ 137 r0 = #__HVM_PDE_S_INVALID 138 139 r1.h = #0xffc0; 140 r1.l = #0x0000; 141 r2 = r25; /* phys_offset */ 142 r2 = and(r1,r2); 143 144 r1.l = #lo(swapper_pg_dir) 145 r1.h = #hi(swapper_pg_dir) 146 r2 = lsr(r2, #22) /* 4MB page number */ 147 r2 = asl(r2, #2) /* times sizeof(PTE) (4bytes) */ 148 r1 = add(r1,r2); 149 loop0(1f,r26) 150 1511: 152 { 153 memw(R1 ++ #4) = R0 154 }:endloop0 155 156 r0 = r24 157 r1 = #VM_TRANS_TYPE_TABLE 158 call __vmnewmap 159 160 /* Go ahead and install the trap0 return so angel calls work */ 161 r0.h = #hi(_K_provisional_vec) 162 r0.l = #lo(_K_provisional_vec) 163 call __vmsetvec 164 165 /* 166 * OK, at this point we should start to be much more careful, 167 * we're going to enter C code and start touching memory 168 * in all sorts of places. 169 * This means: 170 * SGP needs to be OK 171 * Need to lock shared resources 172 * A bunch of other things that will cause 173 * all kinds of painful bugs 174 */ 175 176 /* 177 * Stack pointer should be pointed at the init task's 178 * thread stack, which should have been declared in arch/init_task.c. 179 * So uhhhhh... 180 * It's accessible via the init_thread_union, which is a union 181 * of a thread_info struct and a stack; of course, the top 182 * of the stack is not for you. The end of the stack 183 * is simply init_thread_union + THREAD_SIZE. 184 */ 185 186 {r29.H = #HI(init_thread_union); r0.H = #HI(_THREAD_SIZE); } 187 {r29.L = #LO(init_thread_union); r0.L = #LO(_THREAD_SIZE); } 188 189 /* initialize the register used to point to current_thread_info */ 190 /* Fixme: THREADINFO_REG can't be R2 because of that memset thing. */ 191 {r29 = add(r29,r0); THREADINFO_REG = r29; } 192 193 /* Hack: zero bss; */ 194 { r0.L = #LO(__bss_start); r1 = #0; r2.l = #LO(__bss_stop); } 195 { r0.H = #HI(__bss_start); r2.h = #HI(__bss_stop); } 196 197 r2 = sub(r2,r0); 198 call memset; 199 200 /* Set PHYS_OFFSET; should be in R25 */ 201#ifdef CONFIG_HEXAGON_PHYS_OFFSET 202 r0.l = #LO(__phys_offset); 203 r0.h = #HI(__phys_offset); 204 memw(r0) = r25; 205#endif 206 207 /* Time to make the doughnuts. */ 208 call start_kernel 209 210 /* 211 * Should not reach here. 212 */ 2131: 214 jump 1b 215 216.p2align PAGE_SHIFT 217ENTRY(external_cmdline_buffer) 218 .fill _PAGE_SIZE,1,0 219 220.data 221.p2align PAGE_SHIFT 222ENTRY(empty_zero_page) 223 .fill _PAGE_SIZE,1,0