[RFC PATCH v3 10/20] Add support to access boot related data in the clear

[Tom Lendacky]

Boot data (such as EFI related data) is not encrypted when the system is
booted and needs to be accessed unencrypted.  Add support to apply the
proper attributes to the EFI page tables and to the early_memremap and
memremap APIs to identify the type of data being accessed so that the
proper encryption attribute can be applied.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/include/asm/e820.h    |    1 
 arch/x86/kernel/e820.c         |   16 +++++++
 arch/x86/mm/ioremap.c          |   89 ++++++++++++++++++++++++++++++++++++++++
 arch/x86/platform/efi/efi_64.c |   12 ++++-
 drivers/firmware/efi/efi.c     |   33 +++++++++++++++
 include/linux/efi.h            |    2 +
 kernel/memremap.c              |    8 +++-
 mm/early_ioremap.c             |   18 +++++++-
 8 files changed, 172 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/e820.h b/arch/x86/include/asm/e820.h
index 476b574..186f1d04 100644
--- a/arch/x86/include/asm/e820.h
+++ b/arch/x86/include/asm/e820.h
@@ -16,6 +16,7 @@ extern struct e820map *e820_saved;
 extern unsigned long pci_mem_start;
 extern int e820_any_mapped(u64 start, u64 end, unsigned type);
 extern int e820_all_mapped(u64 start, u64 end, unsigned type);
+extern unsigned int e820_get_entry_type(u64 start, u64 end);
 extern void e820_add_region(u64 start, u64 size, int type);
 extern void e820_print_map(char *who);
 extern int
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index b85fe5f..92fce4e 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -107,6 +107,22 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type)
 	return 0;
 }
 
+unsigned int e820_get_entry_type(u64 start, u64 end)
+{
+	int i;
+
+	for (i = 0; i < e820->nr_map; i++) {
+		struct e820entry *ei = &e820->map[i];
+
+		if (ei->addr >= end || ei->addr + ei->size <= start)
+			continue;
+
+		return ei->type;
+	}
+
+	return 0;
+}
+
 /*
  * Add a memory region to the kernel e820 map.
  */
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index ff542cd..ee347c2 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -20,6 +20,9 @@
 #include <asm/tlbflush.h>
 #include <asm/pgalloc.h>
 #include <asm/pat.h>
+#include <asm/e820.h>
+#include <asm/setup.h>
+#include <linux/efi.h>
 
 #include "physaddr.h"
 
@@ -418,6 +421,92 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
 	iounmap((void __iomem *)((unsigned long)addr & PAGE_MASK));
 }
 
+static bool memremap_setup_data(resource_size_t phys_addr,
+				unsigned long size)
+{
+	u64 paddr;
+
+	if (phys_addr == boot_params.hdr.setup_data)
+		return true;
+
+	paddr = boot_params.efi_info.efi_memmap_hi;
+	paddr <<= 32;
+	paddr |= boot_params.efi_info.efi_memmap;
+	if (phys_addr == paddr)
+		return true;
+
+	paddr = boot_params.efi_info.efi_systab_hi;
+	paddr <<= 32;
+	paddr |= boot_params.efi_info.efi_systab;
+	if (phys_addr == paddr)
+		return true;
+
+	if (efi_table_address_match(phys_addr))
+		return true;
+
+	return false;
+}
+
+static bool memremap_apply_encryption(resource_size_t phys_addr,
+				      unsigned long size)
+{
+	/* SME is not active, just return true */
+	if (!sme_me_mask)
+		return true;
+
+	/* Check if the address is part of the setup data */
+	if (memremap_setup_data(phys_addr, size))
+		return false;
+
+	/* Check if the address is part of EFI boot/runtime data */
+	switch (efi_mem_type(phys_addr)) {
+	case EFI_BOOT_SERVICES_DATA:
+	case EFI_RUNTIME_SERVICES_DATA:
+		return false;
+	}
+
+	/* Check if the address is outside kernel usable area */
+	switch (e820_get_entry_type(phys_addr, phys_addr + size - 1)) {
+	case E820_RESERVED:
+	case E820_ACPI:
+	case E820_NVS:
+	case E820_UNUSABLE:
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Architecure override of __weak function to prevent ram remap and use the
+ * architectural remap function.
+ */
+bool memremap_do_ram_remap(resource_size_t phys_addr, unsigned long size)
+{
+	if (!memremap_apply_encryption(phys_addr, size))
+		return false;
+
+	return true;
+}
+
+/*
+ * Architecure override of __weak function to adjust the protection attributes
+ * used when remapping memory.
+ */
+pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
+					     unsigned long size,
+					     pgprot_t prot)
+{
+	unsigned long prot_val = pgprot_val(prot);
+
+	if (memremap_apply_encryption(phys_addr, size))
+		prot_val |= _PAGE_ENC;
+	else
+		prot_val &= ~_PAGE_ENC;
+
+	return __pgprot(prot_val);
+}
+
 /* Remap memory with encryption */
 void __init *early_memremap_enc(resource_size_t phys_addr,
 				unsigned long size)
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 58b0f80..3f89179 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -221,7 +221,13 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	if (efi_enabled(EFI_OLD_MEMMAP))
 		return 0;
 
-	efi_scratch.efi_pgt = (pgd_t *)__pa(efi_pgd);
+	/*
+	 * Since the PGD is encrypted, set the encryption mask so that when
+	 * this value is loaded into cr3 the PGD will be decrypted during
+	 * the pagetable walk.
+	 */
+	efi_scratch.efi_pgt = (pgd_t *)__sme_pa(efi_pgd);
+
 	pgd = efi_pgd;
 
 	/*
@@ -231,7 +237,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	 * phys_efi_set_virtual_address_map().
 	 */
 	pfn = pa_memmap >> PAGE_SHIFT;
-	if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, _PAGE_NX | _PAGE_RW)) {
+	if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, _PAGE_NX | _PAGE_RW | _PAGE_ENC)) {
 		pr_err("Error ident-mapping new memmap (0x%lx)!\n", pa_memmap);
 		return 1;
 	}
@@ -258,7 +264,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	text = __pa(_text);
 	pfn = text >> PAGE_SHIFT;
 
-	if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, _PAGE_RW)) {
+	if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, _PAGE_RW | _PAGE_ENC)) {
 		pr_err("Failed to map kernel text 1:1\n");
 		return 1;
 	}
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 1ac199c..91c06ec 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -51,6 +51,25 @@ struct efi __read_mostly efi = {
 };
 EXPORT_SYMBOL(efi);
 
+static unsigned long *efi_tables[] = {
+	&efi.mps,
+	&efi.acpi,
+	&efi.acpi20,
+	&efi.smbios,
+	&efi.smbios3,
+	&efi.sal_systab,
+	&efi.boot_info,
+	&efi.hcdp,
+	&efi.uga,
+	&efi.uv_systab,
+	&efi.fw_vendor,
+	&efi.runtime,
+	&efi.config_table,
+	&efi.esrt,
+	&efi.properties_table,
+	&efi.mem_attr_table,
+};
+
 static bool disable_runtime;
 static int __init setup_noefi(char *arg)
 {
@@ -822,3 +841,17 @@ int efi_status_to_err(efi_status_t status)
 
 	return err;
 }
+
+bool efi_table_address_match(unsigned long phys_addr)
+{
+	int i;
+
+	if (phys_addr == EFI_INVALID_TABLE_ADDR)
+		return false;
+
+	for (i = 0; i < ARRAY_SIZE(efi_tables); i++)
+		if (*(efi_tables[i]) == phys_addr)
+			return true;
+
+	return false;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 2d08948..72d89bf 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1070,6 +1070,8 @@ efi_capsule_pending(int *reset_type)
 
 extern int efi_status_to_err(efi_status_t status);
 
+extern bool efi_table_address_match(unsigned long phys_addr);
+
 /*
  * Variable Attributes
  */
diff --git a/kernel/memremap.c b/kernel/memremap.c
index b501e39..ac1437e 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -34,12 +34,18 @@ static void *arch_memremap_wb(resource_size_t offset, unsigned long size)
 }
 #endif
 
+bool __weak memremap_do_ram_remap(resource_size_t offset, size_t size)
+{
+	return true;
+}
+
 static void *try_ram_remap(resource_size_t offset, size_t size)
 {
 	unsigned long pfn = PHYS_PFN(offset);
 
 	/* In the simple case just return the existing linear address */
-	if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)))
+	if (pfn_valid(pfn) && !PageHighMem(pfn_to_page(pfn)) &&
+	    memremap_do_ram_remap(offset, size))
 		return __va(offset);
 	return NULL; /* fallback to arch_memremap_wb */
 }
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index d71b98b..34af5b6 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -30,6 +30,13 @@ early_param("early_ioremap_debug", early_ioremap_debug_setup);
 
 static int after_paging_init __initdata;
 
+pgprot_t __init __weak early_memremap_pgprot_adjust(resource_size_t phys_addr,
+						    unsigned long size,
+						    pgprot_t prot)
+{
+	return prot;
+}
+
 void __init __weak early_ioremap_shutdown(void)
 {
 }
@@ -215,14 +222,19 @@ early_ioremap(resource_size_t phys_addr, unsigned long size)
 void __init *
 early_memremap(resource_size_t phys_addr, unsigned long size)
 {
-	return (__force void *)__early_ioremap(phys_addr, size,
-					       FIXMAP_PAGE_NORMAL);
+	pgprot_t prot = early_memremap_pgprot_adjust(phys_addr, size,
+						     FIXMAP_PAGE_NORMAL);
+
+	return (__force void *)__early_ioremap(phys_addr, size, prot);
 }
 #ifdef FIXMAP_PAGE_RO
 void __init *
 early_memremap_ro(resource_size_t phys_addr, unsigned long size)
 {
-	return (__force void *)__early_ioremap(phys_addr, size, FIXMAP_PAGE_RO);
+	pgprot_t prot = early_memremap_pgprot_adjust(phys_addr, size,
+						     FIXMAP_PAGE_RO);
+
+	return (__force void *)__early_ioremap(phys_addr, size, prot);
 }
 #endif