arm64/efi: handle potential failure to remap memory map

When remapping the UEFI memory map using ioremap_cache(), we
have to deal with potential failure. Note that, even if the
common case is for ioremap_cache() to return the existing linear
mapping of the memory map, we cannot rely on that to be always the
case, e.g., in the presence of a mem= kernel parameter.

At the same time, remove a stale comment and move the memmap code
together.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index a98415b5979c2cff26d35d47d9ab3d57300b77d7..c9cb0fbe7aa45a5574960629bc22051ffb8f8e78 100644 (file)
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -229,19 +229,21 @@ static int __init arm64_enable_runtime_services(void)
                return -1;
        }
 
-       mapsize = memmap.map_end - memmap.map;
-
        if (efi_runtime_disabled()) {
                pr_info("EFI runtime services will be disabled.\n");
                return -1;
        }
 
        pr_info("Remapping and enabling EFI services.\n");
-       /* replace early memmap mapping with permanent mapping */
+
+       mapsize = memmap.map_end - memmap.map;
        memmap.map = (__force void *)ioremap_cache((phys_addr_t)memmap.phys_map,
                                                   mapsize);
+       if (!memmap.map) {
+               pr_err("Failed to remap EFI memory map\n");
+               return -1;
+       }
        memmap.map_end = memmap.map + mapsize;
-
        efi.memmap = &memmap;
 
        efi.systab = (__force void *)ioremap_cache(efi_system_table,