[PATCH v4 2/6] efi: add grub_efi_get_ram_base() function for arm64

[Leif Lindholm]

Since ARM platforms do not have a common memory map, add a helper
function that finds the lowest address region with the EFI_MEMORY_WB
attribute set in the UEFI memory map.

Required for the arm64 efi linux loader to restrict the initrd
location to where it will be accessible by the kernel at runtime.

Signed-off-by: Leif Lindholm <address@hidden>
---
 grub-core/kern/efi/mm.c | 31 +++++++++++++++++++++++++++++++
 include/grub/efi/efi.h  |  3 +++
 2 files changed, 34 insertions(+)

diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index fd39d23b4..b7cf144e5 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -629,3 +629,34 @@ grub_efi_mm_init (void)
   grub_efi_free_pages ((grub_addr_t) memory_map,
                       2 * BYTES_TO_PAGES (MEMORY_MAP_SIZE));
 }
+
+#if defined (__aarch64__)
+grub_err_t
+grub_efi_get_ram_base(grub_addr_t *base_addr)
+{
+  grub_efi_memory_descriptor_t *memory_map, *desc;
+  grub_efi_uintn_t memory_map_size, desc_size;
+  int ret;
+
+  memory_map_size = grub_efi_find_mmap_size();
+
+  memory_map = grub_malloc (memory_map_size);
+  if (! memory_map)
+    return GRUB_ERR_OUT_OF_MEMORY;
+  ret = grub_efi_get_memory_map (&memory_map_size, memory_map, NULL,
+                                &desc_size, NULL);
+
+  if (ret < 1)
+    return GRUB_ERR_BUG;
+
+  for (desc = memory_map, *base_addr = GRUB_UINT_MAX;
+       (grub_addr_t) desc < ((grub_addr_t) memory_map + memory_map_size);
+       desc = NEXT_MEMORY_DESCRIPTOR (desc, desc_size))
+    if (desc->attribute & GRUB_EFI_MEMORY_WB)
+      *base_addr = grub_min (*base_addr, desc->physical_start);
+
+  grub_free(memory_map);
+
+  return GRUB_ERR_NONE;
+}
+#endif
diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index 1021273c1..57db74b57 100644
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -93,6 +93,9 @@ extern void (*EXPORT_VAR(grub_efi_net_config)) 
(grub_efi_handle_t hnd,
 #if defined(__arm__) || defined(__aarch64__)
 void *EXPORT_FUNC(grub_efi_get_firmware_fdt)(void);
 #endif
+#if defined(__aarch64__)
+grub_err_t EXPORT_FUNC(grub_efi_get_ram_base)(grub_addr_t *);
+#endif
 
 grub_addr_t grub_efi_modules_addr (void);
 
-- 
2.11.0