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 #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 #include <asm/sev.h>
  13
  14 struct real_mode_header *real_mode_header;
  15 u32 *trampoline_cr4_features;
  16
  17 /* Hold the pgd entry used on booting additional CPUs */
  18 pgd_t trampoline_pgd_entry;
  19
  20 void __init reserve_real_mode(void)
  21 {
  22         phys_addr_t mem;
  23         size_t size = real_mode_size_needed();
  24
  25         if (!size)
  26                 return;
  27
  28         WARN_ON(slab_is_available());
  29
  30         /* Has to be under 1M so we can execute real-mode AP code. */
  31         mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20);
  32         if (!mem)
  33                 pr_info("No sub-1M memory is available for the trampoline\n");
  34         else
  35                 set_real_mode_mem(mem);
  36
  37         /*
  38          * Unconditionally reserve the entire fisrt 1M, see comment in
  39          * setup_arch().
  40          */
  41         memblock_reserve(0, SZ_1M);
  42 }
  43
  44 static void sme_sev_setup_real_mode(struct trampoline_header *th)
  45 {
  46 #ifdef CONFIG_AMD_MEM_ENCRYPT
  47         if (sme_active())
  48                 th->flags |= TH_FLAGS_SME_ACTIVE;
  49
  50         if (sev_es_active()) {
  51                 /*
  52                  * Skip the call to verify_cpu() in secondary_startup_64 as it
  53                  * will cause #VC exceptions when the AP can't handle them yet.
  54                  */
  55                 th->start = (u64) secondary_startup_64_no_verify;
  56
  57                 if (sev_es_setup_ap_jump_table(real_mode_header))
  58                         panic("Failed to get/update SEV-ES AP Jump Table");
  59         }
  60 #endif
  61 }
  62
  63 static void __init setup_real_mode(void)
  64 {
  65         u16 real_mode_seg;
  66         const u32 *rel;
  67         u32 count;
  68         unsigned char *base;
  69         unsigned long phys_base;
  70         struct trampoline_header *trampoline_header;
  71         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
  72 #ifdef CONFIG_X86_64
  73         u64 *trampoline_pgd;
  74         u64 efer;
  75         int i;
  76 #endif
  77
  78         base = (unsigned char *)real_mode_header;
  79
  80         /*
  81          * If SME is active, the trampoline area will need to be in
  82          * decrypted memory in order to bring up other processors
  83          * successfully. This is not needed for SEV.
  84          */
  85         if (sme_active())
  86                 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
  87
  88         memcpy(base, real_mode_blob, size);
  89
  90         phys_base = __pa(base);
  91         real_mode_seg = phys_base >> 4;
  92
  93         rel = (u32 *) real_mode_relocs;
  94
  95         /* 16-bit segment relocations. */
  96         count = *rel++;
  97         while (count--) {
  98                 u16 *seg = (u16 *) (base + *rel++);
  99                 *seg = real_mode_seg;
 100         }
 101
 102         /* 32-bit linear relocations. */
 103         count = *rel++;
 104         while (count--) {
 105                 u32 *ptr = (u32 *) (base + *rel++);
 106                 *ptr += phys_base;
 107         }
 108
 109         /* Must be performed *after* relocation. */
 110         trampoline_header = (struct trampoline_header *)
 111                 __va(real_mode_header->trampoline_header);
 112
 113 #ifdef CONFIG_X86_32
 114         trampoline_header->start = __pa_symbol(startup_32_smp);
 115         trampoline_header->gdt_limit = __BOOT_DS + 7;
 116         trampoline_header->gdt_base = __pa_symbol(boot_gdt);
 117 #else
 118         /*
 119          * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 120          * so we need to mask it out.
 121          */
 122         rdmsrl(MSR_EFER, efer);
 123         trampoline_header->efer = efer & ~EFER_LMA;
 124
 125         trampoline_header->start = (u64) secondary_startup_64;
 126         trampoline_cr4_features = &trampoline_header->cr4;
 127         *trampoline_cr4_features = mmu_cr4_features;
 128
 129         trampoline_header->flags = 0;
 130
 131         trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
 132
 133         /* Map the real mode stub as virtual == physical */
 134         trampoline_pgd[0] = trampoline_pgd_entry.pgd;
 135
 136         /*
 137          * Include the entirety of the kernel mapping into the trampoline
 138          * PGD.  This way, all mappings present in the normal kernel page
 139          * tables are usable while running on trampoline_pgd.
 140          */
 141         for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
 142                 trampoline_pgd[i] = init_top_pgt[i].pgd;
 143 #endif
 144
 145         sme_sev_setup_real_mode(trampoline_header);
 146 }
 147
 148 /*
 149  * reserve_real_mode() gets called very early, to guarantee the
 150  * availability of low memory. This is before the proper kernel page
 151  * tables are set up, so we cannot set page permissions in that
 152  * function. Also trampoline code will be executed by APs so we
 153  * need to mark it executable at do_pre_smp_initcalls() at least,
 154  * thus run it as a early_initcall().
 155  */
 156 static void __init set_real_mode_permissions(void)
 157 {
 158         unsigned char *base = (unsigned char *) real_mode_header;
 159         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 160
 161         size_t ro_size =
 162                 PAGE_ALIGN(real_mode_header->ro_end) -
 163                 __pa(base);
 164
 165         size_t text_size =
 166                 PAGE_ALIGN(real_mode_header->ro_end) -
 167                 real_mode_header->text_start;
 168
 169         unsigned long text_start =
 170                 (unsigned long) __va(real_mode_header->text_start);
 171
 172         set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
 173         set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
 174         set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
 175 }
 176
 177 static int __init init_real_mode(void)
 178 {
 179         if (!real_mode_header)
 180                 panic("Real mode trampoline was not allocated");
 181
 182         setup_real_mode();
 183         set_real_mode_permissions();
 184
 185         return 0;
 186 }
 187 early_initcall(init_real_mode);