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 #include <asm/crash.h>
  12
  13 struct real_mode_header *real_mode_header;
  14 u32 *trampoline_cr4_features;
  15
  16 /* Hold the pgd entry used on booting additional CPUs */
  17 pgd_t trampoline_pgd_entry;
  18
  19 void __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
  41 static 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  */
 124 static 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
 145 static 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 }
 155 early_initcall(init_real_mode);