arch/x86/realmode/init.c

   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
   7 #include <asm/set_memory.h>
   8 #include <asm/pgtable.h>
   9 #include <asm/realmode.h>
  10 #include <asm/tlbflush.h>
  11
  12 struct real_mode_header *real_mode_header;
  13 u32 *trampoline_cr4_features;
  14
  15 /* Hold the pgd entry used on booting additional CPUs */
  16 pgd_t trampoline_pgd_entry;
  17
  18 void __init set_real_mode_mem(phys_addr_t mem, size_t size)
  19 {
  20         void *base = __va(mem);
  21
  22         real_mode_header = (struct real_mode_header *) base;
  23         printk(KERN_DEBUG "Base memory trampoline at [%p] %llx size %zu\n",
  24                base, (unsigned long long)mem, size);
  25 }
  26
  27 void __init reserve_real_mode(void)
  28 {
  29         phys_addr_t mem;
  30         size_t size = real_mode_size_needed();
  31
  32         if (!size)
  33                 return;
  34
  35         WARN_ON(slab_is_available());
  36
  37         /* Has to be under 1M so we can execute real-mode AP code. */
  38         mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
  39         if (!mem) {
  40                 pr_info("No sub-1M memory is available for the trampoline\n");
  41                 return;
  42         }
  43
  44         memblock_reserve(mem, size);
  45         set_real_mode_mem(mem, size);
  46 }
  47
  48 static void __init setup_real_mode(void)
  49 {
  50         u16 real_mode_seg;
  51         const u32 *rel;
  52         u32 count;
  53         unsigned char *base;
  54         unsigned long phys_base;
  55         struct trampoline_header *trampoline_header;
  56         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
  57 #ifdef CONFIG_X86_64
  58         u64 *trampoline_pgd;
  59         u64 efer;
  60 #endif
  61
  62         base = (unsigned char *)real_mode_header;
  63
  64         /*
  65          * If SME is active, the trampoline area will need to be in
  66          * decrypted memory in order to bring up other processors
  67          * successfully. This is not needed for SEV.
  68          */
  69         if (sme_active())
  70                 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
  71
  72         memcpy(base, real_mode_blob, size);
  73
  74         phys_base = __pa(base);
  75         real_mode_seg = phys_base >> 4;
  76
  77         rel = (u32 *) real_mode_relocs;
  78
  79         /* 16-bit segment relocations. */
  80         count = *rel++;
  81         while (count--) {
  82                 u16 *seg = (u16 *) (base + *rel++);
  83                 *seg = real_mode_seg;
  84         }
  85
  86         /* 32-bit linear relocations. */
  87         count = *rel++;
  88         while (count--) {
  89                 u32 *ptr = (u32 *) (base + *rel++);
  90                 *ptr += phys_base;
  91         }
  92
  93         /* Must be perfomed *after* relocation. */
  94         trampoline_header = (struct trampoline_header *)
  95                 __va(real_mode_header->trampoline_header);
  96
  97 #ifdef CONFIG_X86_32
  98         trampoline_header->start = __pa_symbol(startup_32_smp);
  99         trampoline_header->gdt_limit = __BOOT_DS + 7;
 100         trampoline_header->gdt_base = __pa_symbol(boot_gdt);
 101 #else
 102         /*
 103          * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 104          * so we need to mask it out.
 105          */
 106         rdmsrl(MSR_EFER, efer);
 107         trampoline_header->efer = efer & ~EFER_LMA;
 108
 109         trampoline_header->start = (u64) secondary_startup_64;
 110         trampoline_cr4_features = &trampoline_header->cr4;
 111         *trampoline_cr4_features = mmu_cr4_features;
 112
 113         trampoline_header->flags = 0;
 114         if (sme_active())
 115                 trampoline_header->flags |= TH_FLAGS_SME_ACTIVE;
 116
 117         trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
 118         trampoline_pgd[0] = trampoline_pgd_entry.pgd;
 119         trampoline_pgd[511] = init_top_pgt[511].pgd;
 120 #endif
 121 }
 122
 123 /*
 124  * reserve_real_mode() gets called very early, to guarantee the
 125  * availability of low memory. This is before the proper kernel page
 126  * tables are set up, so we cannot set page permissions in that
 127  * function. Also trampoline code will be executed by APs so we
 128  * need to mark it executable at do_pre_smp_initcalls() at least,
 129  * thus run it as a early_initcall().
 130  */
 131 static void __init set_real_mode_permissions(void)
 132 {
 133         unsigned char *base = (unsigned char *) real_mode_header;
 134         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 135
 136         size_t ro_size =
 137                 PAGE_ALIGN(real_mode_header->ro_end) -
 138                 __pa(base);
 139
 140         size_t text_size =
 141                 PAGE_ALIGN(real_mode_header->ro_end) -
 142                 real_mode_header->text_start;
 143
 144         unsigned long text_start =
 145                 (unsigned long) __va(real_mode_header->text_start);
 146
 147         set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
 148         set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
 149         set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
 150 }
 151
 152 static int __init init_real_mode(void)
 153 {
 154         if (!real_mode_header)
 155                 panic("Real mode trampoline was not allocated");
 156
 157         setup_real_mode();
 158         set_real_mode_permissions();
 159
 160         return 0;
 161 }
 162 early_initcall(init_real_mode);