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Subject[PATCH 1/2] x86: reserve range near the ram
From: Linus Torvalds <torvalds@linux-foundation.org>


The point is to take all RAM resources we have, and
_after_ we've added all the resources we've seen in the E820 tree, we then
_also_ try to add fake reserved entries for any "round up to X" at the end
of the RAM resources.

[ Impact: protect stolen RAM ]

Acked-by: Jesse Barnes <jesse.barnes@intel.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
arch/x86/kernel/e820.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)

Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -1370,6 +1370,23 @@ void __init e820_reserve_resources(void)
}
}

+/* How much should we pad RAM ending depending on where it is? */
+static unsigned long ram_alignment(resource_size_t pos)
+{
+ unsigned long mb = pos >> 20;
+
+ /* To 64kB in the first megabyte */
+ if (!mb)
+ return 64*1024;
+
+ /* To 1MB in the first 16MB */
+ if (mb < 16)
+ return 1024*1024;
+
+ /* To 32MB for anything above that */
+ return 32*1024*1024;
+}
+
void __init e820_reserve_resources_late(void)
{
int i;
@@ -1381,6 +1398,24 @@ void __init e820_reserve_resources_late(
insert_resource_expand_to_fit(&iomem_resource, res);
res++;
}
+
+ /*
+ * Try to bump up RAM regions to reasonable boundaries to
+ * avoid stolen RAM
+ */
+ for (i = 0; i < e820.nr_map; i++) {
+ struct e820entry *entry = &e820_saved.map[i];
+ resource_size_t start, end;
+
+ if (entry->type != E820_RAM)
+ continue;
+ start = entry->addr + entry->size;
+ end = round_up(start, ram_alignment(start));
+ if (start == end)
+ continue;
+ reserve_region_with_split(&iomem_resource, start,
+ end - 1, "RAM buffer");
+ }
}

char *__init default_machine_specific_memory_setup(void)

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