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-es.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_find_in_range(0, 1<<20, size, PAGE_SIZE);
  32         if (!mem) {
  33                 pr_info("No sub-1M memory is available for the trampoline\n");
  34                 return;
  35         }
  36
  37         memblock_reserve(mem, size);
  38         set_real_mode_mem(mem);
  39         crash_reserve_low_1M();
  40 }
  41
  42 static void sme_sev_setup_real_mode(struct trampoline_header *th)
  43 {
  44 #ifdef CONFIG_AMD_MEM_ENCRYPT
  45         if (sme_active())
  46                 th->flags |= TH_FLAGS_SME_ACTIVE;
  47
  48         if (sev_es_active()) {
  49                 /*
  50                  * Skip the call to verify_cpu() in secondary_startup_64 as it
  51                  * will cause #VC exceptions when the AP can't handle them yet.
  52                  */
  53                 th->start = (u64) secondary_startup_64_no_verify;
  54
  55                 if (sev_es_setup_ap_jump_table(real_mode_header))
  56                         panic("Failed to get/update SEV-ES AP Jump Table");
  57         }
  58 #endif
  59 }
  60
  61 static void __init setup_real_mode(void)
  62 {
  63         u16 real_mode_seg;
  64         const u32 *rel;
  65         u32 count;
  66         unsigned char *base;
  67         unsigned long phys_base;
  68         struct trampoline_header *trampoline_header;
  69         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
  70 #ifdef CONFIG_X86_64
  71         u64 *trampoline_pgd;
  72         u64 efer;
  73 #endif
  74
  75         base = (unsigned char *)real_mode_header;
  76
  77         /*
  78          * If SME is active, the trampoline area will need to be in
  79          * decrypted memory in order to bring up other processors
  80          * successfully. This is not needed for SEV.
  81          */
  82         if (sme_active())
  83                 set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
  84
  85         memcpy(base, real_mode_blob, size);
  86
  87         phys_base = __pa(base);
  88         real_mode_seg = phys_base >> 4;
  89
  90         rel = (u32 *) real_mode_relocs;
  91
  92         /* 16-bit segment relocations. */
  93         count = *rel++;
  94         while (count--) {
  95                 u16 *seg = (u16 *) (base + *rel++);
  96                 *seg = real_mode_seg;
  97         }
  98
  99         /* 32-bit linear relocations. */
 100         count = *rel++;
 101         while (count--) {
 102                 u32 *ptr = (u32 *) (base + *rel++);
 103                 *ptr += phys_base;
 104         }
 105
 106         /* Must be perfomed *after* relocation. */
 107         trampoline_header = (struct trampoline_header *)
 108                 __va(real_mode_header->trampoline_header);
 109
 110 #ifdef CONFIG_X86_32
 111         trampoline_header->start = __pa_symbol(startup_32_smp);
 112         trampoline_header->gdt_limit = __BOOT_DS + 7;
 113         trampoline_header->gdt_base = __pa_symbol(boot_gdt);
 114 #else
 115         /*
 116          * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 117          * so we need to mask it out.
 118          */
 119         rdmsrl(MSR_EFER, efer);
 120         trampoline_header->efer = efer & ~EFER_LMA;
 121
 122         trampoline_header->start = (u64) secondary_startup_64;
 123         trampoline_cr4_features = &trampoline_header->cr4;
 124         *trampoline_cr4_features = mmu_cr4_features;
 125
 126         trampoline_header->flags = 0;
 127
 128         trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
 129         trampoline_pgd[0] = trampoline_pgd_entry.pgd;
 130         trampoline_pgd[511] = init_top_pgt[511].pgd;
 131 #endif
 132
 133         sme_sev_setup_real_mode(trampoline_header);
 134 }
 135
 136 /*
 137  * reserve_real_mode() gets called very early, to guarantee the
 138  * availability of low memory. This is before the proper kernel page
 139  * tables are set up, so we cannot set page permissions in that
 140  * function. Also trampoline code will be executed by APs so we
 141  * need to mark it executable at do_pre_smp_initcalls() at least,
 142  * thus run it as a early_initcall().
 143  */
 144 static void __init set_real_mode_permissions(void)
 145 {
 146         unsigned char *base = (unsigned char *) real_mode_header;
 147         size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 148
 149         size_t ro_size =
 150                 PAGE_ALIGN(real_mode_header->ro_end) -
 151                 __pa(base);
 152
 153         size_t text_size =
 154                 PAGE_ALIGN(real_mode_header->ro_end) -
 155                 real_mode_header->text_start;
 156
 157         unsigned long text_start =
 158                 (unsigned long) __va(real_mode_header->text_start);
 159
 160         set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
 161         set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
 162         set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
 163 }
 164
 165 static int __init init_real_mode(void)
 166 {
 167         if (!real_mode_header)
 168                 panic("Real mode trampoline was not allocated");
 169
 170         setup_real_mode();
 171         set_real_mode_permissions();
 172
 173         return 0;
 174 }
 175 early_initcall(init_real_mode);