[PATCH 3/4] efi: Support GRUB_MMAP_MALLOC_LOW in the EFI firmware allocator

[Josh Triplett]

EFI supports allocating memory below a specified address; use that to
implement GRUB_MMAP_MALLOC_LOW by requesting memory below 1M.
---

ChangeLog entry:

2013-11-13  Josh Triplett  <address@hidden>

        * include/grub/efi/memory.h (GRUB_MMAP_MALLOC_LOW): Define.
        * grub-core/mmap/efi/mmap.c (grub_mmap_malign_and_register): Add
          support for GRUB_MMAP_MALLOC_LOW, to allocate memory below 1M via the
          EFI firmware.

 grub-core/mmap/efi/mmap.c | 15 ++++++++++-----
 include/grub/efi/memory.h |  2 ++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/grub-core/mmap/efi/mmap.c b/grub-core/mmap/efi/mmap.c
index e6cd185..64ad05c 100644
--- a/grub-core/mmap/efi/mmap.c
+++ b/grub-core/mmap/efi/mmap.c
@@ -239,9 +239,9 @@ void *
 grub_mmap_malign_and_register (grub_uint64_t align __attribute__ ((unused)),
                               grub_uint64_t size,
                               int *handle, int type,
-                              int flags __attribute__ ((unused)))
+                              int flags)
 {
-  grub_efi_physical_address_t address;
+  grub_efi_physical_address_t address, max_address;
   grub_efi_boot_services_t *b;
   grub_efi_uintn_t pages;
   grub_efi_status_t status;
@@ -254,13 +254,18 @@ grub_mmap_malign_and_register (grub_uint64_t align 
__attribute__ ((unused)),
 
   b = grub_efi_system_table->boot_services;
 
-  address = 0xffffffff;
+  if (flags & GRUB_MMAP_MALLOC_LOW)
+      max_address = 0xfffff;
+  else
+      max_address = 0xffffffff;
+  address = max_address;
 
 #if GRUB_TARGET_SIZEOF_VOID_P < 8
   /* Limit the memory access to less than 4GB for 32-bit platforms.  */
   atype = GRUB_EFI_ALLOCATE_MAX_ADDRESS;
 #else
-  atype = GRUB_EFI_ALLOCATE_ANY_PAGES;
+  atype = (flags & GRUB_MMAP_MALLOC_LOW) ? GRUB_EFI_ALLOCATE_MAX_ADDRESS
+                                         : GRUB_EFI_ALLOCATE_ANY_PAGES;
 #endif
 
   pages = (size + 0xfff) >> 12;
@@ -276,7 +281,7 @@ grub_mmap_malign_and_register (grub_uint64_t align 
__attribute__ ((unused)),
     {
       /* Uggh, the address 0 was allocated... This is too annoying,
         so reallocate another one.  */
-      address = 0xffffffff;
+      address = max_address;
       status = efi_call_4 (b->allocate_pages, atype,
                           make_efi_memtype (type), pages, &address);
       grub_efi_free_pages (0, pages);
diff --git a/include/grub/efi/memory.h b/include/grub/efi/memory.h
index 20526b1..b4940af 100644
--- a/include/grub/efi/memory.h
+++ b/include/grub/efi/memory.h
@@ -24,6 +24,8 @@
 
 #define GRUB_MMAP_REGISTER_BY_FIRMWARE  1
 
+#define GRUB_MMAP_MALLOC_LOW 1
+
 grub_err_t grub_machine_mmap_register (grub_uint64_t start, grub_uint64_t size,
                                       int type, int handle);
 grub_err_t grub_machine_mmap_unregister (int handle);
-- 
1.8.4.3