LXR linux/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
  14struct real_mode_header *real_mode_header;
  15u32 *trampoline_cr4_features;
  16
  17/* Hold the pgd entry used on booting additional CPUs */
  18pgd_t trampoline_pgd_entry;
  19
  20void __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
  44static 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
  63static 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#endif
  76
  77        base = (unsigned char *)real_mode_header;
  78
  79        /*
  80         * If SME is active, the trampoline area will need to be in
  81         * decrypted memory in order to bring up other processors
  82         * successfully. This is not needed for SEV.
  83         */
  84        if (sme_active())
  85                set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
  86
  87        memcpy(base, real_mode_blob, size);
  88
  89        phys_base = __pa(base);
  90        real_mode_seg = phys_base >> 4;
  91
  92        rel = (u32 *) real_mode_relocs;
  93
  94        /* 16-bit segment relocations. */
  95        count = *rel++;
  96        while (count--) {
  97                u16 *seg = (u16 *) (base + *rel++);
  98                *seg = real_mode_seg;
  99        }
 100
 101        /* 32-bit linear relocations. */
 102        count = *rel++;
 103        while (count--) {
 104                u32 *ptr = (u32 *) (base + *rel++);
 105                *ptr += phys_base;
 106        }
 107
 108        /* Must be performed *after* relocation. */
 109        trampoline_header = (struct trampoline_header *)
 110                __va(real_mode_header->trampoline_header);
 111
 112#ifdef CONFIG_X86_32
 113        trampoline_header->start = __pa_symbol(startup_32_smp);
 114        trampoline_header->gdt_limit = __BOOT_DS + 7;
 115        trampoline_header->gdt_base = __pa_symbol(boot_gdt);
 116#else
 117        /*
 118         * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 119         * so we need to mask it out.
 120         */
 121        rdmsrl(MSR_EFER, efer);
 122        trampoline_header->efer = efer & ~EFER_LMA;
 123
 124        trampoline_header->start = (u64) secondary_startup_64;
 125        trampoline_cr4_features = &trampoline_header->cr4;
 126        *trampoline_cr4_features = mmu_cr4_features;
 127
 128        trampoline_header->flags = 0;
 129
 130        trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
 131        trampoline_pgd[0] = trampoline_pgd_entry.pgd;
 132        trampoline_pgd[511] = init_top_pgt[511].pgd;
 133#endif
 134
 135        sme_sev_setup_real_mode(trampoline_header);
 136}
 137
 138/*
 139 * reserve_real_mode() gets called very early, to guarantee the
 140 * availability of low memory. This is before the proper kernel page
 141 * tables are set up, so we cannot set page permissions in that
 142 * function. Also trampoline code will be executed by APs so we
 143 * need to mark it executable at do_pre_smp_initcalls() at least,
 144 * thus run it as a early_initcall().
 145 */
 146static void __init set_real_mode_permissions(void)
 147{
 148        unsigned char *base = (unsigned char *) real_mode_header;
 149        size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 150
 151        size_t ro_size =
 152                PAGE_ALIGN(real_mode_header->ro_end) -
 153                __pa(base);
 154
 155        size_t text_size =
 156                PAGE_ALIGN(real_mode_header->ro_end) -
 157                real_mode_header->text_start;
 158
 159        unsigned long text_start =
 160                (unsigned long) __va(real_mode_header->text_start);
 161
 162        set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
 163        set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
 164        set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
 165}
 166
 167static int __init init_real_mode(void)
 168{
 169        if (!real_mode_header)
 170                panic("Real mode trampoline was not allocated");
 171
 172        setup_real_mode();
 173        set_real_mode_permissions();
 174
 175        return 0;
 176}
 177early_initcall(init_real_mode);
 178