[PATCH v2 02/19] mmap: Add grub_mmap_get_lowest() and grub_mmap_get_highest()

[Sergii Dmytruk]

From: Daniel Kiper <daniel.kiper@oracle.com>

The functions find the lowest and highest values with regard to the
passed in limit.  Passing a low limit of 0 or a high limit of ~0
calculates lowest and highest available RAM addresses respectively.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
---
 grub-core/mmap/mmap.c | 83 +++++++++++++++++++++++++++++++++++++++++++
 include/grub/memory.h |  3 ++
 2 files changed, 86 insertions(+)

diff --git a/grub-core/mmap/mmap.c b/grub-core/mmap/mmap.c
index c8c8312c5..80d6c60b8 100644
--- a/grub-core/mmap/mmap.c
+++ b/grub-core/mmap/mmap.c
@@ -26,6 +26,7 @@
 #include <grub/command.h>
 #include <grub/dl.h>
 #include <grub/i18n.h>
+#include <grub/safemath.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -343,6 +344,88 @@ grub_mmap_unregister (int handle)
 
 #endif /* ! GRUB_MMAP_REGISTER_BY_FIRMWARE */
 
+typedef struct
+{
+  grub_uint64_t addr;
+  grub_uint64_t limit;
+} addr_limit_t;
+
+/* Helper for grub_mmap_get_lowest(). */
+static int
+lowest_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
+             void *data)
+{
+  addr_limit_t *al = data;
+  grub_uint64_t end;
+
+  if (type != GRUB_MEMORY_AVAILABLE)
+    return 0;
+
+  if (grub_add (addr, size, &end))
+    return 0;
+
+  if (addr >= al->limit)
+    al->addr = grub_min (al->addr, addr);
+
+  if ((addr < al->limit) && (end > al->limit))
+    al->addr = al->limit;
+
+  return 0;
+}
+
+/*
+ * This function calculates lowest available RAM address that is at or above
+ * the passed limit.  If no RAM exists above the limit, ~0 is returned.
+ */
+grub_uint64_t
+grub_mmap_get_lowest (grub_uint64_t limit)
+{
+  addr_limit_t al = {~0, limit};
+
+  grub_mmap_iterate (lowest_hook, &al);
+
+  return al.addr;
+}
+
+/* Helper for grub_mmap_get_highest(). */
+static int
+highest_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
+              void *data)
+{
+  addr_limit_t *al = data;
+  grub_uint64_t end;
+
+  if (type != GRUB_MEMORY_AVAILABLE)
+    return 0;
+
+  if (grub_add (addr, size, &end))
+    return 0;
+
+  if (end < al->limit)
+    al->addr = grub_max (al->addr, end);
+
+  if ((addr < al->limit) && (end >= al->limit))
+    al->addr = al->limit;
+
+  return 0;
+}
+
+/*
+ * This function calculates highest available RAM address that is below the
+ * passed limit.  Returned address is either one byte after last byte of RAM or
+ * equal to limit, whichever is lower.  If no RAM exists below limit, 0 is
+ * returned.
+ */
+grub_uint64_t
+grub_mmap_get_highest (grub_uint64_t limit)
+{
+  addr_limit_t al = {0, limit};
+
+  grub_mmap_iterate (highest_hook, &al);
+
+  return al.addr;
+}
+
 #define CHUNK_SIZE     0x400
 
 struct badram_entry {
diff --git a/include/grub/memory.h b/include/grub/memory.h
index 6da114a1b..8f22f7525 100644
--- a/include/grub/memory.h
+++ b/include/grub/memory.h
@@ -69,6 +69,9 @@ void *grub_mmap_malign_and_register (grub_uint64_t align, 
grub_uint64_t size,
 
 void grub_mmap_free_and_unregister (int handle);
 
+extern grub_uint64_t grub_mmap_get_lowest (grub_uint64_t limit);
+extern grub_uint64_t grub_mmap_get_highest (grub_uint64_t limit);
+
 #ifndef GRUB_MMAP_REGISTER_BY_FIRMWARE
 
 struct grub_mmap_region
-- 
2.47.0