[RFC PATCH 2/3] efi: mm: extract function to add memory regions

[Patrick Steinhardt]

In preparation of support for runtime-allocating additional memory
region, this patch extracts the function to retrieve the EFI memory map
and add a subset of it to GRUB's own memory regions.

Note that this commit also changes how many bytes we request by default.
Previously, we would've tried to allocate a quarter of available system
memory, bounded by a minimum/maximum value. As we're about to implement
runtime allocation of memory, we now instead always request the minimum
amount of bytes and let the memory allocator call out to our callback.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 grub-core/kern/efi/mm.c | 57 ++++++++++++++---------------------------
 1 file changed, 19 insertions(+), 38 deletions(-)

diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c
index 457772d57..76f0f6a0f 100644
--- a/grub-core/kern/efi/mm.c
+++ b/grub-core/kern/efi/mm.c
@@ -38,9 +38,8 @@
    a multiplier of 4KB.  */
 #define MEMORY_MAP_SIZE        0x3000
 
-/* The minimum and maximum heap size for GRUB itself.  */
-#define MIN_HEAP_SIZE  0x100000
-#define MAX_HEAP_SIZE  (1600 * 0x100000)
+/* The default heap size for GRUB itself in bytes.  */
+#define DEFAULT_HEAP_SIZE      0x100000
 
 static void *finish_mmap_buf = 0;
 static grub_efi_uintn_t finish_mmap_size = 0;
@@ -464,23 +463,6 @@ filter_memory_map (grub_efi_memory_descriptor_t 
*memory_map,
   return filtered_desc;
 }
 
-/* Return the total number of pages.  */
-static grub_efi_uint64_t
-get_total_pages (grub_efi_memory_descriptor_t *memory_map,
-                grub_efi_uintn_t desc_size,
-                grub_efi_memory_descriptor_t *memory_map_end)
-{
-  grub_efi_memory_descriptor_t *desc;
-  grub_efi_uint64_t total = 0;
-
-  for (desc = memory_map;
-       desc < memory_map_end;
-       desc = NEXT_MEMORY_DESCRIPTOR (desc, desc_size))
-    total += desc->num_pages;
-
-  return total;
-}
-
 /* Add memory regions.  */
 static void
 add_memory_regions (grub_efi_memory_descriptor_t *memory_map,
@@ -508,7 +490,7 @@ add_memory_regions (grub_efi_memory_descriptor_t 
*memory_map,
 
       addr = grub_efi_allocate_pages_real (start, pages,
                                           GRUB_EFI_ALLOCATE_ADDRESS,
-                                          GRUB_EFI_LOADER_CODE);      
+                                          GRUB_EFI_LOADER_CODE);
       if (! addr)
        grub_fatal ("cannot allocate conventional memory %p with %u pages",
                    (void *) ((grub_addr_t) start),
@@ -560,8 +542,8 @@ print_memory_map (grub_efi_memory_descriptor_t *memory_map,
 }
 #endif
 
-void
-grub_efi_mm_init (void)
+static grub_err_t
+grub_efi_mm_add_regions (grub_efi_uint64_t required_bytes)
 {
   grub_efi_memory_descriptor_t *memory_map;
   grub_efi_memory_descriptor_t *memory_map_end;
@@ -569,14 +551,12 @@ grub_efi_mm_init (void)
   grub_efi_memory_descriptor_t *filtered_memory_map_end;
   grub_efi_uintn_t map_size;
   grub_efi_uintn_t desc_size;
-  grub_efi_uint64_t total_pages;
-  grub_efi_uint64_t required_pages;
   int mm_status;
 
   /* Prepare a memory region to store two memory maps.  */
   memory_map = grub_efi_allocate_any_pages (2 * BYTES_TO_PAGES 
(MEMORY_MAP_SIZE));
   if (! memory_map)
-    grub_fatal ("cannot allocate memory");
+    return grub_error (GRUB_ERR_OUT_OF_MEMORY, "cannot allocate memory");
 
   /* Obtain descriptors for available memory.  */
   map_size = MEMORY_MAP_SIZE;
@@ -594,14 +574,14 @@ grub_efi_mm_init (void)
 
       memory_map = grub_efi_allocate_any_pages (2 * BYTES_TO_PAGES (map_size));
       if (! memory_map)
-       grub_fatal ("cannot allocate memory");
+       return grub_error (GRUB_ERR_OUT_OF_MEMORY, "cannot allocate memory");
 
       mm_status = grub_efi_get_memory_map (&map_size, memory_map, 0,
                                           &desc_size, 0);
     }
 
   if (mm_status < 0)
-    grub_fatal ("cannot get memory map");
+    return grub_error (GRUB_ERR_OUT_OF_MEMORY, "cannot get memory map");
 
   memory_map_end = NEXT_MEMORY_DESCRIPTOR (memory_map, map_size);
 
@@ -610,22 +590,14 @@ grub_efi_mm_init (void)
   filtered_memory_map_end = filter_memory_map (memory_map, filtered_memory_map,
                                               desc_size, memory_map_end);
 
-  /* By default, request a quarter of the available memory.  */
-  total_pages = get_total_pages (filtered_memory_map, desc_size,
-                                filtered_memory_map_end);
-  required_pages = (total_pages >> 2);
-  if (required_pages < BYTES_TO_PAGES (MIN_HEAP_SIZE))
-    required_pages = BYTES_TO_PAGES (MIN_HEAP_SIZE);
-  else if (required_pages > BYTES_TO_PAGES (MAX_HEAP_SIZE))
-    required_pages = BYTES_TO_PAGES (MAX_HEAP_SIZE);
-
   /* Sort the filtered descriptors, so that GRUB can allocate pages
      from smaller regions.  */
   sort_memory_map (filtered_memory_map, desc_size, filtered_memory_map_end);
 
   /* Allocate memory regions for GRUB's memory management.  */
   add_memory_regions (filtered_memory_map, desc_size,
-                     filtered_memory_map_end, required_pages);
+                     filtered_memory_map_end,
+                     BYTES_TO_PAGES (required_bytes));
 
 #if 0
   /* For debug.  */
@@ -643,6 +615,15 @@ grub_efi_mm_init (void)
   /* Release the memory maps.  */
   grub_efi_free_pages ((grub_addr_t) memory_map,
                       2 * BYTES_TO_PAGES (MEMORY_MAP_SIZE));
+
+  return GRUB_ERR_NONE;
+}
+
+void
+grub_efi_mm_init (void)
+{
+  if (grub_efi_mm_add_regions (DEFAULT_HEAP_SIZE) != GRUB_ERR_NONE)
+    grub_fatal (grub_errmsg);
 }
 
 #if defined (__aarch64__) || defined (__arm__) || defined (__riscv)
-- 
2.26.2

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