[PATCH] arm/efi: fix ram base detection

[Vincent Stehlé]

On 32b Arm platforms, grub allocates memory for the initrd in the first
512MB of DRAM. To do so, the grub_efi_get_ram_base() function will be
called to compute the DRAM base. Currently this function returns the lowest
start address of all memory regions with attribute write-back.

However, if for example a small memory region with type reserved and
attribute write-back is present at the bottom of the memory map, it will be
chosen as DRAM base and initrd memory allocation will fail with:

  error: out of memory.

  Press any key to continue...

This is indeed the case with qemu arm machine virt when the secure world is
enabled and TF-A and OP-TEE are used. The secure world firmware will
reserve secure memory, resulting in the following EFI memory map:

  Type      Physical start  - end             #Pages        Size Attributes
  reserved  000000000e100000-000000000effffff 00000f00     15MiB WB
  conv-mem  0000000040000000-0000000047ef9fff 00007efa 130024KiB WB
  ACPI-rec  0000000047efa000-0000000047f05fff 0000000c     48KiB WB
  conv-mem  0000000047f06000-000000006d4f9fff 000255f4 612304KiB WB
  ldr-data  000000006d4fa000-000000006d4fafff 00000001      4KiB WB
 ...

In this case, the DRAM base is computed as 0xe100000, while it should be
0x40000000 instead.

Fix this issue by considering only conventional memory with attribute
write-back for DRAM base computation.

This is similar to what is done by Peter Jones in commit 3c1a5d940be5
("arm/arm64 loader: Better memory allocation and error messages.") in
Fedora's grub[1]. This patch reduces the modifications to a minimum.

[1]: https://github.com/rhboot/grub2.git

Fixes: bad144c60f66 ("efi: Add grub_efi_get_ram_base() function for arm64")
Suggested-by: Grant Likely <grant.likely@arm.com>
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Peter Jones <pjones@redhat.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
---
 grub-core/kern/efi/mm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index 0cdb063bb..abf8772bc 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -677,7 +677,8 @@ grub_efi_get_ram_base(grub_addr_t *base_addr)
   for (desc = memory_map, *base_addr = GRUB_EFI_MAX_USABLE_ADDRESS;
        (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)
+    if (desc->type == GRUB_EFI_CONVENTIONAL_MEMORY &&
+        desc->attribute & GRUB_EFI_MEMORY_WB)
       *base_addr = grub_min (*base_addr, desc->physical_start);
 
   grub_free(memory_map);
-- 
2.30.0