1// SPDX-License-Identifier: GPL-2.0
2#include <linux/module.h>
3#include <linux/kernel.h>
4#include <linux/slab.h>
5#include <linux/mm_types.h>
6#include <linux/pgtable.h>
7
8#include <asm/cputype.h>
9#include <asm/idmap.h>
10#include <asm/hwcap.h>
11#include <asm/pgalloc.h>
12#include <asm/sections.h>
13#include <asm/system_info.h>
14
15/*
16 * Note: accesses outside of the kernel image and the identity map area
17 * are not supported on any CPU using the idmap tables as its current
18 * page tables.
19 */
20pgd_t *idmap_pgd __ro_after_init;
21long long arch_phys_to_idmap_offset __ro_after_init;
22
23#ifdef CONFIG_ARM_LPAE
24static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
25	unsigned long prot)
26{
27	pmd_t *pmd;
28	unsigned long next;
29
30	if (pud_none_or_clear_bad(pud) || (pud_val(*pud) & L_PGD_SWAPPER)) {
31		pmd = pmd_alloc_one(&init_mm, addr);
32		if (!pmd) {
33			pr_warn("Failed to allocate identity pmd.\n");
34			return;
35		}
36		/*
37		 * Copy the original PMD to ensure that the PMD entries for
38		 * the kernel image are preserved.
39		 */
40		if (!pud_none(*pud))
41			memcpy(pmd, pmd_offset(pud, 0),
42			       PTRS_PER_PMD * sizeof(pmd_t));
43		pud_populate(&init_mm, pud, pmd);
44		pmd += pmd_index(addr);
45	} else
46		pmd = pmd_offset(pud, addr);
47
48	do {
49		next = pmd_addr_end(addr, end);
50		*pmd = __pmd((addr & PMD_MASK) | prot);
51		flush_pmd_entry(pmd);
52	} while (pmd++, addr = next, addr != end);
53}
54#else	/* !CONFIG_ARM_LPAE */
55static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
56	unsigned long prot)
57{
58	pmd_t *pmd = pmd_offset(pud, addr);
59
60	addr = (addr & PMD_MASK) | prot;
61	pmd[0] = __pmd(addr);
62	addr += SECTION_SIZE;
63	pmd[1] = __pmd(addr);
64	flush_pmd_entry(pmd);
65}
66#endif	/* CONFIG_ARM_LPAE */
67
68static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
69	unsigned long prot)
70{
71	p4d_t *p4d = p4d_offset(pgd, addr);
72	pud_t *pud = pud_offset(p4d, addr);
73	unsigned long next;
74
75	do {
76		next = pud_addr_end(addr, end);
77		idmap_add_pmd(pud, addr, next, prot);
78	} while (pud++, addr = next, addr != end);
79}
80
81static void identity_mapping_add(pgd_t *pgd, const char *text_start,
82				 const char *text_end, unsigned long prot)
83{
84	unsigned long addr, end;
85	unsigned long next;
86
87	addr = virt_to_idmap(text_start);
88	end = virt_to_idmap(text_end);
89	pr_info("Setting up static identity map for 0x%lx - 0x%lx\n", addr, end);
90
91	prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
92
93	if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale_family())
94		prot |= PMD_BIT4;
95
96	pgd += pgd_index(addr);
97	do {
98		next = pgd_addr_end(addr, end);
99		idmap_add_pud(pgd, addr, next, prot);
100	} while (pgd++, addr = next, addr != end);
101}
102
103extern char  __idmap_text_start[], __idmap_text_end[];
104
105static int __init init_static_idmap(void)
106{
107	idmap_pgd = pgd_alloc(&init_mm);
108	if (!idmap_pgd)
109		return -ENOMEM;
110
111	identity_mapping_add(idmap_pgd, __idmap_text_start,
112			     __idmap_text_end, 0);
113
114	/* Flush L1 for the hardware to see this page table content */
115	if (!(elf_hwcap & HWCAP_LPAE))
116		flush_cache_louis();
117
118	return 0;
119}
120early_initcall(init_static_idmap);
121
122/*
123 * In order to soft-boot, we need to switch to a 1:1 mapping for the
124 * cpu_reset functions. This will then ensure that we have predictable
125 * results when turning off the mmu.
126 */
127void setup_mm_for_reboot(void)
128{
129	/* Switch to the identity mapping. */
130	cpu_switch_mm(idmap_pgd, &init_mm);
131	local_flush_bp_all();
132
133#ifdef CONFIG_CPU_HAS_ASID
134	/*
135	 * We don't have a clean ASID for the identity mapping, which
136	 * may clash with virtual addresses of the previous page tables
137	 * and therefore potentially in the TLB.
138	 */
139	local_flush_tlb_all();
140#endif
141}
142