arch/x86/kernel/head32.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/arch/i386/kernel/head32.c -- prepare to run common code
   4  *
   5  *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
   6  *  Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com>
   7  */
   8
   9 #include <linux/init.h>
  10 #include <linux/start_kernel.h>
  11 #include <linux/mm.h>
  12 #include <linux/memblock.h>
  13
  14 #include <asm/desc.h>
  15 #include <asm/setup.h>
  16 #include <asm/sections.h>
  17 #include <asm/e820/api.h>
  18 #include <asm/page.h>
  19 #include <asm/apic.h>
  20 #include <asm/io_apic.h>
  21 #include <asm/bios_ebda.h>
  22 #include <asm/tlbflush.h>
  23 #include <asm/bootparam_utils.h>
  24
  25 static void __init i386_default_early_setup(void)
  26 {
  27         /* Initialize 32bit specific setup functions */
  28         x86_init.resources.reserve_resources = i386_reserve_resources;
  29         x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
  30 }
  31
  32 asmlinkage __visible void __init i386_start_kernel(void)
  33 {
  34         /* Make sure IDT is set up before any exception happens */
  35         idt_setup_early_handler();
  36
  37         cr4_init_shadow();
  38
  39         sanitize_boot_params(&boot_params);
  40         x86_verify_bootdata_version();
  41
  42         x86_early_init_platform_quirks();
  43
  44         /* Call the subarch specific early setup function */
  45         switch (boot_params.hdr.hardware_subarch) {
  46         case X86_SUBARCH_INTEL_MID:
  47                 x86_intel_mid_early_setup();
  48                 break;
  49         case X86_SUBARCH_CE4100:
  50                 x86_ce4100_early_setup();
  51                 break;
  52         default:
  53                 i386_default_early_setup();
  54                 break;
  55         }
  56
  57         start_kernel();
  58 }
  59
  60 /*
  61  * Initialize page tables.  This creates a PDE and a set of page
  62  * tables, which are located immediately beyond __brk_base.  The variable
  63  * _brk_end is set up to point to the first "safe" location.
  64  * Mappings are created both at virtual address 0 (identity mapping)
  65  * and PAGE_OFFSET for up to _end.
  66  *
  67  * In PAE mode initial_page_table is statically defined to contain
  68  * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
  69  * entries). The identity mapping is handled by pointing two PGD entries
  70  * to the first kernel PMD. Note the upper half of each PMD or PTE are
  71  * always zero at this stage.
  72  */
  73 void __init mk_early_pgtbl_32(void)
  74 {
  75 #ifdef __pa
  76 #undef __pa
  77 #endif
  78 #define __pa(x)  ((unsigned long)(x) - PAGE_OFFSET)
  79         pte_t pte, *ptep;
  80         int i;
  81         unsigned long *ptr;
  82         /* Enough space to fit pagetables for the low memory linear map */
  83         const unsigned long limit = __pa(_end) +
  84                 (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
  85 #ifdef CONFIG_X86_PAE
  86         pmd_t pl2, *pl2p = (pmd_t *)__pa(initial_pg_pmd);
  87 #define SET_PL2(pl2, val)    { (pl2).pmd = (val); }
  88 #else
  89         pgd_t pl2, *pl2p = (pgd_t *)__pa(initial_page_table);
  90 #define SET_PL2(pl2, val)   { (pl2).pgd = (val); }
  91 #endif
  92
  93         ptep = (pte_t *)__pa(__brk_base);
  94         pte.pte = PTE_IDENT_ATTR;
  95
  96         while ((pte.pte & PTE_PFN_MASK) < limit) {
  97
  98                 SET_PL2(pl2, (unsigned long)ptep | PDE_IDENT_ATTR);
  99                 *pl2p = pl2;
 100 #ifndef CONFIG_X86_PAE
 101                 /* Kernel PDE entry */
 102                 *(pl2p +  ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
 103 #endif
 104                 for (i = 0; i < PTRS_PER_PTE; i++) {
 105                         *ptep = pte;
 106                         pte.pte += PAGE_SIZE;
 107                         ptep++;
 108                 }
 109
 110                 pl2p++;
 111         }
 112
 113         ptr = (unsigned long *)__pa(&max_pfn_mapped);
 114         /* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
 115         *ptr = (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;
 116
 117         ptr = (unsigned long *)__pa(&_brk_end);
 118         *ptr = (unsigned long)ptep + PAGE_OFFSET;
 119 }
 120