You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
79 lines
2.5 KiB
79 lines
2.5 KiB
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
|
|
From: Daniel Axtens <dja@axtens.net>
|
|
Date: Thu, 25 Nov 2021 02:22:45 +1100
|
|
Subject: [PATCH] mm: Document GRUB internal memory management structures
|
|
|
|
I spent more than a trivial quantity of time figuring out pre_size and
|
|
whether a memory region's size contains the header cell or not.
|
|
|
|
Document the meanings of all the properties. Hopefully now no-one else
|
|
has to figure it out!
|
|
|
|
Signed-off-by: Daniel Axtens <dja@axtens.net>
|
|
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
|
|
(cherry picked from commit a6c5c52ccffd2674d43db25fb4baa9c528526aa0)
|
|
---
|
|
include/grub/mm_private.h | 28 ++++++++++++++++++++++++++++
|
|
1 file changed, 28 insertions(+)
|
|
|
|
diff --git a/include/grub/mm_private.h b/include/grub/mm_private.h
|
|
index c2c4cb1511..203533cc3d 100644
|
|
--- a/include/grub/mm_private.h
|
|
+++ b/include/grub/mm_private.h
|
|
@@ -21,15 +21,27 @@
|
|
|
|
#include <grub/mm.h>
|
|
|
|
+/* For context, see kern/mm.c */
|
|
+
|
|
/* Magic words. */
|
|
#define GRUB_MM_FREE_MAGIC 0x2d3c2808
|
|
#define GRUB_MM_ALLOC_MAGIC 0x6db08fa4
|
|
|
|
+/* A header describing a block of memory - either allocated or free */
|
|
typedef struct grub_mm_header
|
|
{
|
|
+ /*
|
|
+ * The 'next' free block in this region's circular free list.
|
|
+ * Only meaningful if the block is free.
|
|
+ */
|
|
struct grub_mm_header *next;
|
|
+ /* The block size, not in bytes but the number of cells of
|
|
+ * GRUB_MM_ALIGN bytes. Includes the header cell.
|
|
+ */
|
|
grub_size_t size;
|
|
+ /* either free or alloc magic, depending on the block type. */
|
|
grub_size_t magic;
|
|
+ /* pad to cell size: see the top of kern/mm.c. */
|
|
#if GRUB_CPU_SIZEOF_VOID_P == 4
|
|
char padding[4];
|
|
#elif GRUB_CPU_SIZEOF_VOID_P == 8
|
|
@@ -48,11 +60,27 @@ typedef struct grub_mm_header
|
|
|
|
#define GRUB_MM_ALIGN (1 << GRUB_MM_ALIGN_LOG2)
|
|
|
|
+/* A region from which we can make allocations. */
|
|
typedef struct grub_mm_region
|
|
{
|
|
+ /* The first free block in this region. */
|
|
struct grub_mm_header *first;
|
|
+
|
|
+ /*
|
|
+ * The next region in the linked list of regions. Regions are initially
|
|
+ * sorted in order of increasing size, but can grow, in which case the
|
|
+ * ordering may not be preserved.
|
|
+ */
|
|
struct grub_mm_region *next;
|
|
+
|
|
+ /*
|
|
+ * A grub_mm_region will always be aligned to cell size. The pre-size is
|
|
+ * the number of bytes we were given but had to skip in order to get that
|
|
+ * alignment.
|
|
+ */
|
|
grub_size_t pre_size;
|
|
+
|
|
+ /* How many bytes are in this region? (free and allocated) */
|
|
grub_size_t size;
|
|
}
|
|
*grub_mm_region_t;
|