1// SPDX-License-Identifier: GPL-2.0
  2#include <linux/io.h>
  3#include <linux/slab.h>
  4#include <linux/memblock.h>
  5#include <linux/mem_encrypt.h>
  6#include <linux/pgtable.h>
  7
  8#include <asm/set_memory.h>
  9#include <asm/realmode.h>
 10#include <asm/tlbflush.h>
 11#include <asm/crash.h>
 12
 13struct real_mode_header *real_mode_header;
 14u32 *trampoline_cr4_features;
 15
 16/* Hold the pgd entry used on booting additional CPUs */
 17pgd_t trampoline_pgd_entry;
 18
 19void __init reserve_real_mode(void)
 20{
 21	phys_addr_t mem;
 22	size_t size = real_mode_size_needed();
 23
 24	if (!size)
 25		return;
 26
 27	WARN_ON(slab_is_available());
 28
 29	/* Has to be under 1M so we can execute real-mode AP code. */
 30	mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
 31	if (!mem) {
 32		pr_info("No sub-1M memory is available for the trampoline\n");
 33		return;
 34	}
 35
 36	memblock_reserve(mem, size);
 37	set_real_mode_mem(mem);
 38	crash_reserve_low_1M();
 39}
 40
 41static void __init setup_real_mode(void)
 42{
 43	u16 real_mode_seg;
 44	const u32 *rel;
 45	u32 count;
 46	unsigned char *base;
 47	unsigned long phys_base;
 48	struct trampoline_header *trampoline_header;
 49	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 50#ifdef CONFIG_X86_64
 51	u64 *trampoline_pgd;
 52	u64 efer;
 53#endif
 54
 55	base = (unsigned char *)real_mode_header;
 56
 57	/*
 58	 * If SME is active, the trampoline area will need to be in
 59	 * decrypted memory in order to bring up other processors
 60	 * successfully. This is not needed for SEV.
 61	 */
 62	if (sme_active())
 63		set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
 64
 65	memcpy(base, real_mode_blob, size);
 66
 67	phys_base = __pa(base);
 68	real_mode_seg = phys_base >> 4;
 69
 70	rel = (u32 *) real_mode_relocs;
 71
 72	/* 16-bit segment relocations. */
 73	count = *rel++;
 74	while (count--) {
 75		u16 *seg = (u16 *) (base + *rel++);
 76		*seg = real_mode_seg;
 77	}
 78
 79	/* 32-bit linear relocations. */
 80	count = *rel++;
 81	while (count--) {
 82		u32 *ptr = (u32 *) (base + *rel++);
 83		*ptr += phys_base;
 84	}
 85
 86	/* Must be perfomed *after* relocation. */
 87	trampoline_header = (struct trampoline_header *)
 88		__va(real_mode_header->trampoline_header);
 89
 90#ifdef CONFIG_X86_32
 91	trampoline_header->start = __pa_symbol(startup_32_smp);
 92	trampoline_header->gdt_limit = __BOOT_DS + 7;
 93	trampoline_header->gdt_base = __pa_symbol(boot_gdt);
 94#else
 95	/*
 96	 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 97	 * so we need to mask it out.
 98	 */
 99	rdmsrl(MSR_EFER, efer);
100	trampoline_header->efer = efer & ~EFER_LMA;
101
102	trampoline_header->start = (u64) secondary_startup_64;
103	trampoline_cr4_features = &trampoline_header->cr4;
104	*trampoline_cr4_features = mmu_cr4_features;
105
106	trampoline_header->flags = 0;
107	if (sme_active())
108		trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;
109
110	trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
111	trampoline_pgd[0] = trampoline_pgd_entry.pgd;
112	trampoline_pgd[511] = init_top_pgt[511].pgd;
113#endif
114}
115
116/*
117 * reserve_real_mode() gets called very early, to guarantee the
118 * availability of low memory. This is before the proper kernel page
119 * tables are set up, so we cannot set page permissions in that
120 * function. Also trampoline code will be executed by APs so we
121 * need to mark it executable at do_pre_smp_initcalls() at least,
122 * thus run it as a early_initcall().
123 */
124static void __init set_real_mode_permissions(void)
125{
126	unsigned char *base = (unsigned char *) real_mode_header;
127	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
128
129	size_t ro_size =
130		PAGE_ALIGN(real_mode_header->ro_end) -
131		__pa(base);
132
133	size_t text_size =
134		PAGE_ALIGN(real_mode_header->ro_end) -
135		real_mode_header->text_start;
136
137	unsigned long text_start =
138		(unsigned long) __va(real_mode_header->text_start);
139
140	set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
141	set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
142	set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
143}
144
145static int __init init_real_mode(void)
146{
147	if (!real_mode_header)
148		panic("Real mode trampoline was not allocated");
149
150	setup_real_mode();
151	set_real_mode_permissions();
152
153	return 0;
154}
155early_initcall(init_real_mode);