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Diffstat (limited to 'arch/x86/platform/efi/quirks.c')
-rw-r--r--arch/x86/platform/efi/quirks.c79
1 files changed, 62 insertions, 17 deletions
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 2d66db8f80f9..ed30e79347e8 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -131,6 +131,27 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
EXPORT_SYMBOL_GPL(efi_query_variable_store);
/*
+ * Helper function for efi_reserve_boot_services() to figure out if we
+ * can free regions in efi_free_boot_services().
+ *
+ * Use this function to ensure we do not free regions owned by somebody
+ * else. We must only reserve (and then free) regions:
+ *
+ * - Not within any part of the kernel
+ * - Not the BIOS reserved area (E820_RESERVED, E820_NVS, etc)
+ */
+static bool can_free_region(u64 start, u64 size)
+{
+ if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end))
+ return false;
+
+ if (!e820_all_mapped(start, start+size, E820_RAM))
+ return false;
+
+ return true;
+}
+
+/*
* The UEFI specification makes it clear that the operating system is free to do
* whatever it wants with boot services code after ExitBootServices() has been
* called. Ignoring this recommendation a significant bunch of EFI implementations
@@ -147,26 +168,50 @@ void __init efi_reserve_boot_services(void)
efi_memory_desc_t *md = p;
u64 start = md->phys_addr;
u64 size = md->num_pages << EFI_PAGE_SHIFT;
+ bool already_reserved;
if (md->type != EFI_BOOT_SERVICES_CODE &&
md->type != EFI_BOOT_SERVICES_DATA)
continue;
- /* Only reserve where possible:
- * - Not within any already allocated areas
- * - Not over any memory area (really needed, if above?)
- * - Not within any part of the kernel
- * - Not the bios reserved area
- */
- if ((start + size > __pa_symbol(_text)
- && start <= __pa_symbol(_end)) ||
- !e820_all_mapped(start, start+size, E820_RAM) ||
- memblock_is_region_reserved(start, size)) {
- /* Could not reserve, skip it */
- md->num_pages = 0;
- memblock_dbg("Could not reserve boot range [0x%010llx-0x%010llx]\n",
- start, start+size-1);
- } else
+
+ already_reserved = memblock_is_region_reserved(start, size);
+
+ /*
+ * Because the following memblock_reserve() is paired
+ * with free_bootmem_late() for this region in
+ * efi_free_boot_services(), we must be extremely
+ * careful not to reserve, and subsequently free,
+ * critical regions of memory (like the kernel image) or
+ * those regions that somebody else has already
+ * reserved.
+ *
+ * A good example of a critical region that must not be
+ * freed is page zero (first 4Kb of memory), which may
+ * contain boot services code/data but is marked
+ * E820_RESERVED by trim_bios_range().
+ */
+ if (!already_reserved) {
memblock_reserve(start, size);
+
+ /*
+ * If we are the first to reserve the region, no
+ * one else cares about it. We own it and can
+ * free it later.
+ */
+ if (can_free_region(start, size))
+ continue;
+ }
+
+ /*
+ * We don't own the region. We must not free it.
+ *
+ * Setting this bit for a boot services region really
+ * doesn't make sense as far as the firmware is
+ * concerned, but it does provide us with a way to tag
+ * those regions that must not be paired with
+ * free_bootmem_late().
+ */
+ md->attribute |= EFI_MEMORY_RUNTIME;
}
}
@@ -183,8 +228,8 @@ void __init efi_free_boot_services(void)
md->type != EFI_BOOT_SERVICES_DATA)
continue;
- /* Could not reserve boot area */
- if (!size)
+ /* Do not free, someone else owns it: */
+ if (md->attribute & EFI_MEMORY_RUNTIME)
continue;
free_bootmem_late(start, size);