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
  41         x86_early_init_platform_quirks();
  42
  43         /* Call the subarch specific early setup function */
  44         switch (boot_params.hdr.hardware_subarch) {
  45         case X86_SUBARCH_INTEL_MID:
  46                 x86_intel_mid_early_setup();
  47                 break;
  48         case X86_SUBARCH_CE4100:
  49                 x86_ce4100_early_setup();
  50                 break;
  51         default:
  52                 i386_default_early_setup();
  53                 break;
  54         }
  55
  56         start_kernel();
  57 }
  58
  59 /*
  60  * Initialize page tables.  This creates a PDE and a set of page
  61  * tables, which are located immediately beyond __brk_base.  The variable
  62  * _brk_end is set up to point to the first "safe" location.
  63  * Mappings are created both at virtual address 0 (identity mapping)
  64  * and PAGE_OFFSET for up to _end.
  65  *
  66  * In PAE mode initial_page_table is statically defined to contain
  67  * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
  68  * entries). The identity mapping is handled by pointing two PGD entries
  69  * to the first kernel PMD. Note the upper half of each PMD or PTE are
  70  * always zero at this stage.
  71  */
  72 void __init mk_early_pgtbl_32(void)
  73 {
  74 #ifdef __pa
  75 #undef __pa
  76 #endif
  77 #define __pa(x)  ((unsigned long)(x) - PAGE_OFFSET)
  78         pte_t pte, *ptep;
  79         int i;
  80         unsigned long *ptr;
  81         /* Enough space to fit pagetables for the low memory linear map */
  82         const unsigned long limit = __pa(_end) +
  83                 (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
  84 #ifdef CONFIG_X86_PAE
  85         pmd_t pl2, *pl2p = (pmd_t *)__pa(initial_pg_pmd);
  86 #define SET_PL2(pl2, val)    { (pl2).pmd = (val); }
  87 #else
  88         pgd_t pl2, *pl2p = (pgd_t *)__pa(initial_page_table);
  89 #define SET_PL2(pl2, val)   { (pl2).pgd = (val); }
  90 #endif
  91
  92         ptep = (pte_t *)__pa(__brk_base);
  93         pte.pte = PTE_IDENT_ATTR;
  94
  95         while ((pte.pte & PTE_PFN_MASK) < limit) {
  96
  97                 SET_PL2(pl2, (unsigned long)ptep | PDE_IDENT_ATTR);
  98                 *pl2p = pl2;
  99 #ifndef CONFIG_X86_PAE
 100                 /* Kernel PDE entry */
 101                 *(pl2p +  ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
 102 #endif
 103                 for (i = 0; i < PTRS_PER_PTE; i++) {
 104                         *ptep = pte;
 105                         pte.pte += PAGE_SIZE;
 106                         ptep++;
 107                 }
 108
 109                 pl2p++;
 110         }
 111
 112         ptr = (unsigned long *)__pa(&max_pfn_mapped);
 113         /* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
 114         *ptr = (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;
 115
 116         ptr = (unsigned long *)__pa(&_brk_end);
 117         *ptr = (unsigned long)ptep + PAGE_OFFSET;
 118 }
 119