[PATCH 1/7] efi: add grub_efi_get_dram_base() function for arm*

[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 arm/arm64 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 | 42 ++++++++++++++++++++++++++++++++++++++++++
 include/grub/efi/efi.h  |  1 +
 2 files changed, 43 insertions(+)

diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index 20a47aaf5..460a4b763 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -525,3 +525,45 @@ grub_efi_mm_init (void)
   grub_efi_free_pages ((grub_addr_t) memory_map,
                       2 * BYTES_TO_PAGES (MEMORY_MAP_SIZE));
 }
+
+#if defined (__arm__) || defined (__aarch64__)
+grub_err_t
+grub_efi_get_dram_base(grub_addr_t *base_addr)
+{
+  grub_efi_memory_descriptor_t *memory_map;
+  grub_efi_memory_descriptor_t *desc;
+  grub_efi_uintn_t mmap_size;
+  grub_efi_uintn_t desc_size;
+
+  mmap_size = (1 << GRUB_EFI_PAGE_SHIFT);
+  while (1)
+    {
+      int ret;
+
+      memory_map = grub_malloc (mmap_size);
+      if (! memory_map)
+        return GRUB_ERR_OUT_OF_MEMORY;
+      ret = grub_efi_get_memory_map (&mmap_size, memory_map, NULL,
+                                    &desc_size, NULL);
+      if (ret > 0)
+       break;
+
+      grub_free (memory_map);
+      if (ret == 0)
+       return GRUB_ERR_BUG;
+
+      mmap_size += (1 << GRUB_EFI_PAGE_SHIFT);
+    }
+
+  for (desc = memory_map, *base_addr = GRUB_UINT_MAX;
+       (grub_addr_t) desc < ((grub_addr_t) memory_map + mmap_size);
+       desc = NEXT_MEMORY_DESCRIPTOR (desc, desc_size))
+    {
+      if (desc->attribute & GRUB_EFI_MEMORY_WB)
+       if (desc->physical_start < *base_addr)
+         *base_addr = desc->physical_start;
+    }
+
+  return GRUB_ERR_NONE;
+}
+#endif
diff --git a/include/grub/efi/efi.h b/include/grub/efi/efi.h
index e9c601f34..845fc2438 100644
--- a/include/grub/efi/efi.h
+++ b/include/grub/efi/efi.h
@@ -83,6 +83,7 @@ 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);
+grub_err_t EXPORT_FUNC(grub_efi_get_dram_base)(grub_addr_t *);
 #endif
 
 grub_addr_t grub_efi_modules_addr (void);
-- 
2.11.0