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/microcode.h>
23 #include <asm/tlbflush.h>
24 #include <asm/bootparam_utils.h>
25
26 static void __init i386_default_early_setup(void)
27 {
28 /* Initialize 32bit specific setup functions */
29 x86_init.resources.reserve_resources = i386_reserve_resources;
30 x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
31 }
32
33 #ifdef CONFIG_MICROCODE_INITRD32
34 unsigned long __initdata initrd_start_early;
35 static pte_t __initdata *initrd_pl2p_start, *initrd_pl2p_end;
36
37 static void zap_early_initrd_mapping(void)
38 {
39 pte_t *pl2p = initrd_pl2p_start;
40
41 for (; pl2p < initrd_pl2p_end; pl2p++) {
42 *pl2p = (pte_t){ .pte = 0 };
43
44 if (!IS_ENABLED(CONFIG_X86_PAE))
45 *(pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = (pte_t) {.pte = 0};
46 }
47 }
48 #else
49 static inline void zap_early_initrd_mapping(void) { }
50 #endif
51
52 asmlinkage __visible void __init __noreturn i386_start_kernel(void)
53 {
54 /* Make sure IDT is set up before any exception happens */
55 idt_setup_early_handler();
56
57 load_ucode_bsp();
58 zap_early_initrd_mapping();
59
60 cr4_init_shadow();
61
62 sanitize_boot_params(&boot_params);
63
64 x86_early_init_platform_quirks();
65
66 /* Call the subarch specific early setup function */
67 switch (boot_params.hdr.hardware_subarch) {
68 case X86_SUBARCH_INTEL_MID:
69 x86_intel_mid_early_setup();
70 break;
71 case X86_SUBARCH_CE4100:
72 x86_ce4100_early_setup();
73 break;
74 default:
75 i386_default_early_setup();
76 break;
77 }
78
79 start_kernel();
80 }
81
82 /*
83 * Initialize page tables. This creates a PDE and a set of page
84 * tables, which are located immediately beyond __brk_base. The variable
85 * _brk_end is set up to point to the first "safe" location.
86 * Mappings are created both at virtual address 0 (identity mapping)
87 * and PAGE_OFFSET for up to _end.
88 *
89 * In PAE mode initial_page_table is statically defined to contain
90 * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
91 * entries). The identity mapping is handled by pointing two PGD entries
92 * to the first kernel PMD. Note the upper half of each PMD or PTE are
93 * always zero at this stage.
94 */
95 #ifdef CONFIG_X86_PAE
96 typedef pmd_t pl2_t;
97 #define pl2_base initial_pg_pmd
98 #define SET_PL2(val) { .pmd = (val), }
99 #else
100 typedef pgd_t pl2_t;
101 #define pl2_base initial_page_table
102 #define SET_PL2(val) { .pgd = (val), }
103 #endif
104
105 static __init __no_stack_protector pte_t init_map(pte_t pte, pte_t **ptep, pl2_t **pl2p,
106 const unsigned long limit)
107 {
108 while ((pte.pte & PTE_PFN_MASK) < limit) {
109 pl2_t pl2 = SET_PL2((unsigned long)*ptep | PDE_IDENT_ATTR);
110 int i;
111
112 **pl2p = pl2;
113 if (!IS_ENABLED(CONFIG_X86_PAE)) {
114 /* Kernel PDE entry */
115 *(*pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
116 }
117
118 for (i = 0; i < PTRS_PER_PTE; i++) {
119 **ptep = pte;
120 pte.pte += PAGE_SIZE;
121 (*ptep)++;
122 }
123 (*pl2p)++;
124 }
125 return pte;
126 }
127
128 void __init __no_stack_protector mk_early_pgtbl_32(void)
129 {
130 /* Enough space to fit pagetables for the low memory linear map */
131 unsigned long limit = __pa_nodebug(_end) + (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
132 pte_t pte, *ptep = (pte_t *)__pa_nodebug(__brk_base);
133 struct boot_params __maybe_unused *params;
134 pl2_t *pl2p = (pl2_t *)__pa_nodebug(pl2_base);
135 unsigned long *ptr;
136
137 pte.pte = PTE_IDENT_ATTR;
138 pte = init_map(pte, &ptep, &pl2p, limit);
139
140 ptr = (unsigned long *)__pa_nodebug(&max_pfn_mapped);
141 /* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
142 *ptr = (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;
143
144 ptr = (unsigned long *)__pa_nodebug(&_brk_end);
145 *ptr = (unsigned long)ptep + PAGE_OFFSET;
146
147 #ifdef CONFIG_MICROCODE_INITRD32
148 /* Running on a hypervisor? */
149 if (native_cpuid_ecx(1) & BIT(31))
150 return;
151
152 params = (struct boot_params *)__pa_nodebug(&boot_params);
153 if (!params->hdr.ramdisk_size || !params->hdr.ramdisk_image)
154 return;
155
156 /* Save the virtual start address */
157 ptr = (unsigned long *)__pa_nodebug(&initrd_start_early);
158 *ptr = (pte.pte & PTE_PFN_MASK) + PAGE_OFFSET;
159 *ptr += ((unsigned long)params->hdr.ramdisk_image) & ~PAGE_MASK;
160
161 /* Save PLP2 for cleanup */
162 ptr = (unsigned long *)__pa_nodebug(&initrd_pl2p_start);
163 *ptr = (unsigned long)pl2p + PAGE_OFFSET;
164
165 limit = (unsigned long)params->hdr.ramdisk_image;
166 pte.pte = PTE_IDENT_ATTR | PFN_ALIGN(limit);
167 limit = (unsigned long)params->hdr.ramdisk_image + params->hdr.ramdisk_size;
168
169 init_map(pte, &ptep, &pl2p, limit);
170
171 ptr = (unsigned long *)__pa_nodebug(&initrd_pl2p_end);
172 *ptr = (unsigned long)pl2p + PAGE_OFFSET;
173 #endif
174 }
175
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