efi: libstub: install boot-time memory map as config table

Expose the EFI boot time memory map to the kernel via a configuration
table. This is arch agnostic and enables future changes that remove the
dependency on DT on architectures that don't otherwise rely on it.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 24 insertions, 3 deletions

diff --git a/drivers/firmware/efi/libstub/mem.c b/drivers/firmware/efi/libstub/mem.c
index c92b7dbc6dfe..45841ef55a9f 100644
--- a/drivers/firmware/efi/libstub/mem.c
+++ b/drivers/firmware/efi/libstub/mem.c
@@ -9,14 +9,20 @@
  * efi_get_memory_map() - get memory map
  * @map:		pointer to memory map pointer to which to assign the
  *			newly allocated memory map
+ * @install_cfg_tbl:	whether or not to install the boot memory map as a
+ *			configuration table
  *
  * Retrieve the UEFI memory map. The allocated memory leaves room for
  * up to EFI_MMAP_NR_SLACK_SLOTS additional memory map entries.
  *
  * Return:	status code
  */
-efi_status_t efi_get_memory_map(struct efi_boot_memmap **map)
+efi_status_t efi_get_memory_map(struct efi_boot_memmap **map,
+				bool install_cfg_tbl)
 {
+	int memtype = install_cfg_tbl ? EFI_ACPI_RECLAIM_MEMORY
+				      : EFI_LOADER_DATA;
+	efi_guid_t tbl_guid = LINUX_EFI_BOOT_MEMMAP_GUID;
 	struct efi_boot_memmap *m, tmp;
 	efi_status_t status;
 	unsigned long size;
@@ -28,20 +34,35 @@ efi_status_t efi_get_memory_map(struct efi_boot_memmap **map)
 		return EFI_LOAD_ERROR;
 
 	size = tmp.map_size + tmp.desc_size * EFI_MMAP_NR_SLACK_SLOTS;
-	status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, sizeof(*m) + size,
+	status = efi_bs_call(allocate_pool, memtype, sizeof(*m) + size,
 			     (void **)&m);
 	if (status != EFI_SUCCESS)
 		return status;
 
+	if (install_cfg_tbl) {
+		/*
+		 * Installing a configuration table might allocate memory, and
+		 * this may modify the memory map. This means we should install
+		 * the configuration table first, and re-install or delete it
+		 * as needed.
+		 */
+		status = efi_bs_call(install_configuration_table, &tbl_guid, m);
+		if (status != EFI_SUCCESS)
+			goto free_map;
+	}
+
 	m->buff_size = m->map_size = size;
 	status = efi_bs_call(get_memory_map, &m->map_size, m->map, &m->map_key,
 			     &m->desc_size, &m->desc_ver);
 	if (status != EFI_SUCCESS)
-		goto free_map;
+		goto uninstall_table;
 
 	*map = m;
 	return EFI_SUCCESS;
 
+uninstall_table:
+	if (install_cfg_tbl)
+		efi_bs_call(install_configuration_table, &tbl_guid, NULL);
 free_map:
 	efi_bs_call(free_pool, m);
 	return status;