efi: Refactor efi_memmap_init_early() into arch-neutral code

Every EFI architecture apart from ia64 needs to setup the EFI memory
map at efi.memmap, and the code for doing that is essentially the same
across all implementations. Therefore, it makes sense to factor this
out into the common code under drivers/firmware/efi/.

The only slight variation is the data structure out of which we pull
the initial memory map information, such as physical address, memory
descriptor size and version, etc. We can address this by passing a
generic data structure (struct efi_memory_map_data) as the argument to
efi_memmap_init_early() which contains the minimum info required for
initialising the memory map.

In the process, this patch also fixes a few undesirable implementation
differences:

 - ARM and arm64 were failing to clear the EFI_MEMMAP bit when
   unmapping the early EFI memory map. EFI_MEMMAP indicates whether
   the EFI memory map is mapped (not the regions contained within) and
   can be traversed.  It's more correct to set the bit as soon as we
   memremap() the passed in EFI memmap.

 - Rename efi_unmmap_memmap() to efi_memmap_unmap() to adhere to the
   regular naming scheme.

This patch also uses a read-write mapping for the memory map instead
of the read-only mapping currently used on ARM and arm64. x86 needs
the ability to update the memory map in-place when assigning virtual
addresses to regions (efi_map_region()) and tagging regions when
reserving boot services (efi_reserve_boot_services()).

There's no way for the generic fake_mem code to know which mapping to
use without introducing some arch-specific constant/hook, so just use
read-write since read-only is of dubious value for the EFI memory map.

Tested-by: Dave Young <dyoung@redhat.com> [kexec/kdump]
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [arm]
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Peter Jones <pjones@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 7f5a582253853..d862d49985804 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -669,6 +669,18 @@ typedef struct {
 	unsigned long tables;
 } efi_system_table_t;
 
+/*
+ * Architecture independent structure for describing a memory map for the
+ * benefit of efi_memmap_init_early(), saving us the need to pass four
+ * parameters.
+ */
+struct efi_memory_map_data {
+	phys_addr_t phys_map;
+	unsigned long size;
+	unsigned long desc_version;
+	unsigned long desc_size;
+};
+
 struct efi_memory_map {
 	phys_addr_t phys_map;
 	void *map;
@@ -900,6 +912,10 @@ static inline efi_status_t efi_query_variable_store(u32 attributes,
 }
 #endif
 extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
+
+extern int __init efi_memmap_init_early(struct efi_memory_map_data *data);
+extern void __init efi_memmap_unmap(void);
+
 extern int efi_config_init(efi_config_table_type_t *arch_tables);
 #ifdef CONFIG_EFI_ESRT
 extern void __init efi_esrt_init(void);