[PATCH v2] Grab the EFI System Resource Table and check it

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

The EFI System Resource Table (ESRT) is necessary for fwupd to identify
firmware updates to install.  According to the UEFI specification §23.4,
the table shall be stored in memory of type EfiBootServicesData.
Therefore, Xen must avoid reusing that memory for other purposes, so
that Linux can access the ESRT.  Additionally, Xen must mark the memory
as reserved, so that Linux knows accessing it is safe.

See https://lore.kernel.org/xen-devel/20200818184018.GN1679@mail-itl/T/
for details.

Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/arm/efi/efi-boot.h |  9 +++--
 xen/arch/x86/efi/efi-boot.h |  5 ++-
 xen/common/efi/boot.c       | 77 +++++++++++++++++++++++++++++++++++--
 xen/common/efi/efi.h        |  2 +-
 xen/common/efi/runtime.c    |  5 ++-
 xen/include/efi/efiapi.h    |  3 ++
 6 files changed, 89 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index 458cfbbed4..398a2411a1 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -187,7 +187,8 @@ static bool __init meminfo_add_bank(struct meminfo *mem,
 
 static EFI_STATUS __init efi_process_memory_map_bootinfo(EFI_MEMORY_DESCRIPTOR 
*map,
                                                 UINTN mmap_size,
-                                                UINTN desc_size)
+                                                UINTN desc_size,
+                                                const EFI_MEMORY_DESCRIPTOR 
*const esrt_desc)
 {
     int Index;
     EFI_MEMORY_DESCRIPTOR *desc_ptr = map;
@@ -199,6 +200,7 @@ static EFI_STATUS __init 
efi_process_memory_map_bootinfo(EFI_MEMORY_DESCRIPTOR *
               desc_ptr->Type == EfiLoaderCode ||
               desc_ptr->Type == EfiLoaderData ||
               (!map_bs &&
+               desc != esrt_desc &&
                (desc_ptr->Type == EfiBootServicesCode ||
                 desc_ptr->Type == EfiBootServicesData))) )
         {
@@ -404,11 +406,12 @@ static void __init 
efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
                                                void *map,
                                                UINTN map_size,
                                                UINTN desc_size,
-                                               UINT32 desc_ver)
+                                               UINT32 desc_ver,
+                                               const EFI_MEMORY_DESCRIPTOR 
*const esrt_desc)
 {
     EFI_STATUS status;
 
-    status = efi_process_memory_map_bootinfo(map, map_size, desc_size);
+    status = efi_process_memory_map_bootinfo(map, map_size, desc_size, 
esrt_desc);
     if ( EFI_ERROR(status) )
         blexit(L"EFI memory map processing failed");
 
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 9b0cc29aae..fb1e9d5eef 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -154,7 +154,8 @@ static void __init 
efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
                                                void *map,
                                                UINTN map_size,
                                                UINTN desc_size,
-                                               UINT32 desc_ver)
+                                               UINT32 desc_ver,
+                                               const EFI_MEMORY_DESCRIPTOR 
*const esrt_desc)
 {
     struct e820entry *e;
     unsigned int i;
@@ -171,7 +172,7 @@ static void __init 
efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
         {
         case EfiBootServicesCode:
         case EfiBootServicesData:
-            if ( map_bs )
+            if ( map_bs || desc == esrt_desc )
             {
         default:
                 type = E820_RESERVED;
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 8fd5e2d078..04024b7e99 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -93,6 +93,23 @@ typedef struct _EFI_LOAD_OPTION {
     CHAR16 Description[];
 } EFI_LOAD_OPTION;
 
+struct esrt_entry {
+    EFI_GUID fw_class;
+    UINT32 fw_type;
+    UINT32 fw_version;
+    UINT32 fw_lowest_supported_version;
+    UINT32 fw_capsule_flags;
+    UINT32 fw_last_attempt_version;
+    UINT32 fw_last_attempt_status;
+};
+
+struct esrt {
+    UINT32 esrt_count;
+    UINT32 esrt_max;
+    UINT64 esrt_version;
+    struct esrt_entry esrt_entries[];
+};
+
 #define LOAD_OPTION_ACTIVE              0x00000001
 
 union string {
@@ -175,6 +192,38 @@ static int __init efi_check_dt_boot(EFI_LOADED_IMAGE 
*loaded_image)
 }
 #endif
 
+static UINTN __initdata esrt;
+
+static bool __init is_esrt_valid(
+    const EFI_MEMORY_DESCRIPTOR *const desc)
+{
+    size_t available_len, esrt_len, len;
+    const UINTN physical_start = desc->PhysicalStart;
+    const struct esrt *esrt_ptr;
+
+    len = desc->NumberOfPages << EFI_PAGE_SHIFT;
+    if ( esrt == EFI_INVALID_TABLE_ADDR )
+        return false;
+    if ( physical_start > esrt || esrt - physical_start >= len )
+        return false;
+    /*
+     * The specification requires EfiBootServicesData, but accept
+     * EfiRuntimeServicesData for compatibility
+     */
+    if ( (desc->Type != EfiRuntimeServicesData) &&
+         (desc->Type != EfiBootServicesData) )
+        return false;
+    available_len = len - (esrt - physical_start);
+    if ( available_len < sizeof(*esrt_ptr) )
+        return false;
+    esrt_ptr = (const struct esrt *)esrt;
+    if ( esrt_ptr->esrt_version != 1 || esrt_ptr->esrt_count <= 0 )
+        return false;
+    esrt_len = esrt_ptr->esrt_count * sizeof(esrt_ptr->esrt_entries[0]);
+
+    return esrt_len > available_len - sizeof(*esrt_ptr);
+}
+
 /*
  * Include architecture specific implementation here, which references the
  * static globals defined above.
@@ -844,6 +893,10 @@ static void __init efi_tables(void)
 {
     unsigned int i;
 
+    BUILD_BUG_ON(sizeof(struct esrt_entry) != 40);
+    BUILD_BUG_ON(__alignof(struct esrt_entry) != 4);
+    BUILD_BUG_ON(sizeof(struct esrt) != 16);
+
     /* Obtain basic table pointers. */
     for ( i = 0; i < efi_num_ct; ++i )
     {
@@ -852,6 +905,7 @@ static void __init efi_tables(void)
         static EFI_GUID __initdata mps_guid = MPS_TABLE_GUID;
         static EFI_GUID __initdata smbios_guid = SMBIOS_TABLE_GUID;
         static EFI_GUID __initdata smbios3_guid = SMBIOS3_TABLE_GUID;
+        static EFI_GUID __initdata esrt_guid = ESRT_GUID;
 
         if ( match_guid(&acpi2_guid, &efi_ct[i].VendorGuid) )
               efi.acpi20 = (long)efi_ct[i].VendorTable;
@@ -863,6 +917,8 @@ static void __init efi_tables(void)
               efi.smbios = (long)efi_ct[i].VendorTable;
         if ( match_guid(&smbios3_guid, &efi_ct[i].VendorGuid) )
               efi.smbios3 = (long)efi_ct[i].VendorTable;
+        if ( match_guid(&esrt_guid, &efi_ct[i].VendorGuid) )
+              esrt = (long)efi_ct[i].VendorTable;
     }
 
 #ifndef CONFIG_ARM /* TODO - disabled until implemented on ARM */
@@ -1051,19 +1107,19 @@ static void __init efi_exit_boot(EFI_HANDLE 
ImageHandle, EFI_SYSTEM_TABLE *Syste
     EFI_STATUS status;
     UINTN info_size = 0, map_key;
     bool retry;
-#ifdef CONFIG_EFI_SET_VIRTUAL_ADDRESS_MAP
     unsigned int i;
-#endif
 
     efi_bs->GetMemoryMap(&info_size, NULL, &map_key,
                          &efi_mdesc_size, &mdesc_ver);
-    info_size += 8 * efi_mdesc_size;
+    info_size += 8 * (efi_mdesc_size + 1);
     efi_memmap = efi_arch_allocate_mmap_buffer(info_size);
     if ( !efi_memmap )
         blexit(L"Unable to allocate memory for EFI memory map");
 
     for ( retry = false; ; retry = true )
     {
+        esrt_desc = (EFI_MEMORY_DESCRIPTOR*)EFI_INVALID_TABLE_ADDR;
+
         efi_memmap_size = info_size;
         status = SystemTable->BootServices->GetMemoryMap(&efi_memmap_size,
                                                          efi_memmap, &map_key,
@@ -1072,8 +1128,21 @@ static void __init efi_exit_boot(EFI_HANDLE ImageHandle, 
EFI_SYSTEM_TABLE *Syste
         if ( EFI_ERROR(status) )
             PrintErrMesg(L"Cannot obtain memory map", status);
 
+        for ( i = 0; i < efi_memmap_size; i += efi_mdesc_size )
+        {
+            if ( is_esrt_valid(efi_memmap + i) )
+            {
+                esrt_desc = efi_memmap + i;
+                break;
+            }
+        }
+
+        /*
+         * We cannot pass esrt because we need to explicitly compare the
+         * descriptor pointers for equality.
+         */
         efi_arch_process_memory_map(SystemTable, efi_memmap, efi_memmap_size,
-                                    efi_mdesc_size, mdesc_ver);
+                                    efi_mdesc_size, mdesc_ver, esrt_desc);
 
         efi_arch_pre_exit_boot();
 
diff --git a/xen/common/efi/efi.h b/xen/common/efi/efi.h
index c9aa65d506..498c8dc1fa 100644
--- a/xen/common/efi/efi.h
+++ b/xen/common/efi/efi.h
@@ -27,7 +27,7 @@ extern const CHAR16 *efi_fw_vendor;
 extern const EFI_RUNTIME_SERVICES *efi_rs;
 
 extern UINTN efi_memmap_size, efi_mdesc_size;
-extern void *efi_memmap;
+extern void *efi_memmap, *esrt_desc;
 
 #ifdef CONFIG_X86
 extern mfn_t efi_l4_mfn;
diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c
index 375b94229e..c45c7cee77 100644
--- a/xen/common/efi/runtime.c
+++ b/xen/common/efi/runtime.c
@@ -51,6 +51,7 @@ static unsigned int efi_rs_on_cpu = NR_CPUS;
 UINTN __read_mostly efi_memmap_size;
 UINTN __read_mostly efi_mdesc_size;
 void *__read_mostly efi_memmap;
+void *__read_mostly esrt_desc;
 
 UINT64 __read_mostly efi_boot_max_var_store_size;
 UINT64 __read_mostly efi_boot_remain_var_store_size;
@@ -251,14 +252,14 @@ int efi_get_info(uint32_t idx, union xenpf_efi_info *info)
     case XEN_FW_EFI_MEM_INFO:
         for ( i = 0; i < efi_memmap_size; i += efi_mdesc_size )
         {
-            EFI_MEMORY_DESCRIPTOR *desc = efi_memmap + i;
+            const EFI_MEMORY_DESCRIPTOR *desc = efi_memmap + i;
             u64 len = desc->NumberOfPages << EFI_PAGE_SHIFT;
 
             if ( info->mem.addr >= desc->PhysicalStart &&
                  info->mem.addr < desc->PhysicalStart + len )
             {
                 info->mem.type = desc->Type;
-                info->mem.attr = desc->Attribute;
+                info->mem.attr = desc == esrt_desc ? EFI_MEMORY_RUNTIME : 
desc->Attribute;
                 if ( info->mem.addr + info->mem.size < info->mem.addr ||
                      info->mem.addr + info->mem.size >
                      desc->PhysicalStart + len )
diff --git a/xen/include/efi/efiapi.h b/xen/include/efi/efiapi.h
index a616d1238a..42ef3e1c8c 100644
--- a/xen/include/efi/efiapi.h
+++ b/xen/include/efi/efiapi.h
@@ -882,6 +882,9 @@ typedef struct _EFI_BOOT_SERVICES {
 #define SAL_SYSTEM_TABLE_GUID    \
     { 0xeb9d2d32, 0x2d88, 0x11d3, {0x9a, 0x16, 0x0, 0x90, 0x27, 0x3f, 0xc1, 
0x4d} }
 
+#define ESRT_GUID    \
+    { 0xb122a263, 0x3661, 0x4f68, {0x99, 0x29, 0x78, 0xf8, 0xb0, 0xd6, 0x21, 
0x80} }
+
 
 typedef struct _EFI_CONFIGURATION_TABLE {
     EFI_GUID                VendorGuid;
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab

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