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-rw-r--r--arch/x86/realmode/init.c220
1 files changed, 220 insertions, 0 deletions
diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
new file mode 100644
index 0000000000..788e555954
--- /dev/null
+++ b/arch/x86/realmode/init.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/memblock.h>
+#include <linux/cc_platform.h>
+#include <linux/pgtable.h>
+
+#include <asm/set_memory.h>
+#include <asm/realmode.h>
+#include <asm/tlbflush.h>
+#include <asm/crash.h>
+#include <asm/sev.h>
+
+struct real_mode_header *real_mode_header;
+u32 *trampoline_cr4_features;
+
+/* Hold the pgd entry used on booting additional CPUs */
+pgd_t trampoline_pgd_entry;
+
+void load_trampoline_pgtable(void)
+{
+#ifdef CONFIG_X86_32
+ load_cr3(initial_page_table);
+#else
+ /*
+ * This function is called before exiting to real-mode and that will
+ * fail with CR4.PCIDE still set.
+ */
+ if (boot_cpu_has(X86_FEATURE_PCID))
+ cr4_clear_bits(X86_CR4_PCIDE);
+
+ write_cr3(real_mode_header->trampoline_pgd);
+#endif
+
+ /*
+ * The CR3 write above will not flush global TLB entries.
+ * Stale, global entries from previous page tables may still be
+ * present. Flush those stale entries.
+ *
+ * This ensures that memory accessed while running with
+ * trampoline_pgd is *actually* mapped into trampoline_pgd.
+ */
+ __flush_tlb_all();
+}
+
+void __init reserve_real_mode(void)
+{
+ phys_addr_t mem;
+ size_t size = real_mode_size_needed();
+
+ if (!size)
+ return;
+
+ WARN_ON(slab_is_available());
+
+ /* Has to be under 1M so we can execute real-mode AP code. */
+ mem = memblock_phys_alloc_range(size, PAGE_SIZE, 0, 1<<20);
+ if (!mem)
+ pr_info("No sub-1M memory is available for the trampoline\n");
+ else
+ set_real_mode_mem(mem);
+
+ /*
+ * Unconditionally reserve the entire fisrt 1M, see comment in
+ * setup_arch().
+ */
+ memblock_reserve(0, SZ_1M);
+}
+
+static void __init sme_sev_setup_real_mode(struct trampoline_header *th)
+{
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+ if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+ th->flags |= TH_FLAGS_SME_ACTIVE;
+
+ if (cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
+ /*
+ * Skip the call to verify_cpu() in secondary_startup_64 as it
+ * will cause #VC exceptions when the AP can't handle them yet.
+ */
+ th->start = (u64) secondary_startup_64_no_verify;
+
+ if (sev_es_setup_ap_jump_table(real_mode_header))
+ panic("Failed to get/update SEV-ES AP Jump Table");
+ }
+#endif
+}
+
+static void __init setup_real_mode(void)
+{
+ u16 real_mode_seg;
+ const u32 *rel;
+ u32 count;
+ unsigned char *base;
+ unsigned long phys_base;
+ struct trampoline_header *trampoline_header;
+ size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
+#ifdef CONFIG_X86_64
+ u64 *trampoline_pgd;
+ u64 efer;
+ int i;
+#endif
+
+ base = (unsigned char *)real_mode_header;
+
+ /*
+ * If SME is active, the trampoline area will need to be in
+ * decrypted memory in order to bring up other processors
+ * successfully. This is not needed for SEV.
+ */
+ if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT))
+ set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
+
+ memcpy(base, real_mode_blob, size);
+
+ phys_base = __pa(base);
+ real_mode_seg = phys_base >> 4;
+
+ rel = (u32 *) real_mode_relocs;
+
+ /* 16-bit segment relocations. */
+ count = *rel++;
+ while (count--) {
+ u16 *seg = (u16 *) (base + *rel++);
+ *seg = real_mode_seg;
+ }
+
+ /* 32-bit linear relocations. */
+ count = *rel++;
+ while (count--) {
+ u32 *ptr = (u32 *) (base + *rel++);
+ *ptr += phys_base;
+ }
+
+ /* Must be performed *after* relocation. */
+ trampoline_header = (struct trampoline_header *)
+ __va(real_mode_header->trampoline_header);
+
+#ifdef CONFIG_X86_32
+ trampoline_header->start = __pa_symbol(startup_32_smp);
+ trampoline_header->gdt_limit = __BOOT_DS + 7;
+ trampoline_header->gdt_base = __pa_symbol(boot_gdt);
+#else
+ /*
+ * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
+ * so we need to mask it out.
+ */
+ rdmsrl(MSR_EFER, efer);
+ trampoline_header->efer = efer & ~EFER_LMA;
+
+ trampoline_header->start = (u64) secondary_startup_64;
+ trampoline_cr4_features = &trampoline_header->cr4;
+ *trampoline_cr4_features = mmu_cr4_features;
+
+ trampoline_header->flags = 0;
+
+ trampoline_lock = &trampoline_header->lock;
+ *trampoline_lock = 0;
+
+ trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
+
+ /* Map the real mode stub as virtual == physical */
+ trampoline_pgd[0] = trampoline_pgd_entry.pgd;
+
+ /*
+ * Include the entirety of the kernel mapping into the trampoline
+ * PGD. This way, all mappings present in the normal kernel page
+ * tables are usable while running on trampoline_pgd.
+ */
+ for (i = pgd_index(__PAGE_OFFSET); i < PTRS_PER_PGD; i++)
+ trampoline_pgd[i] = init_top_pgt[i].pgd;
+#endif
+
+ sme_sev_setup_real_mode(trampoline_header);
+}
+
+/*
+ * reserve_real_mode() gets called very early, to guarantee the
+ * availability of low memory. This is before the proper kernel page
+ * tables are set up, so we cannot set page permissions in that
+ * function. Also trampoline code will be executed by APs so we
+ * need to mark it executable at do_pre_smp_initcalls() at least,
+ * thus run it as a early_initcall().
+ */
+static void __init set_real_mode_permissions(void)
+{
+ unsigned char *base = (unsigned char *) real_mode_header;
+ size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
+
+ size_t ro_size =
+ PAGE_ALIGN(real_mode_header->ro_end) -
+ __pa(base);
+
+ size_t text_size =
+ PAGE_ALIGN(real_mode_header->ro_end) -
+ real_mode_header->text_start;
+
+ unsigned long text_start =
+ (unsigned long) __va(real_mode_header->text_start);
+
+ set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
+ set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
+ set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
+}
+
+void __init init_real_mode(void)
+{
+ if (!real_mode_header)
+ panic("Real mode trampoline was not allocated");
+
+ setup_real_mode();
+ set_real_mode_permissions();
+}
+
+static int __init do_init_real_mode(void)
+{
+ x86_platform.realmode_init();
+ return 0;
+}
+early_initcall(do_init_real_mode);