To prevent device drivers from attaching to device or memory regions
owned by the firmware, register all UEFI reserved regions in the iomem
resource table at init time.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
arch/arm64/kernel/efi.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index d2f483a7cffe..ba5fe66c3634 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -305,6 +305,50 @@ void efi_virtmap_unload(void)
efi_set_pgd(current->active_mm);
}
+static __init void efi_reserve_iomem_resource(efi_memory_desc_t *md)
+{
+ struct resource *res;
+
+ res = alloc_bootmem_low(sizeof(*res));
+ res->start = md->phys_addr;
+ res->end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT) - 1;
+ res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+ if (!is_reserve_region(md)) {
+ /*
+ * Non-RAM regions with the EFI_MEMORY_RUNTIME attribute
+ * are owned by the UEFI firmware, so make sure they are
+ * tagged as exclusive: this will prevent device drivers
+ * from binding to the memory region, and will also prevent
+ * access via /dev/mem if CONFIG_STRICT_DEVMEM is in effect.
+ */
+ res->name = "UEFI Runtime [MMIO]";
+ res->flags |= IORESOURCE_EXCLUSIVE;
+ } else if (md->type == EFI_RUNTIME_SERVICES_DATA) {
+ /*
+ * UEFI Runtime Services Data regions may be used to store
+ * configuration tables such as SMBIOS, which are often
+ * accessed using userland tools such as 'dmidecode', that
+ * are /dev/mem based. So don't set the exclusive flag in
+ * this case.
+ */
+ res->name = "UEFI Runtime [Data]";
+ } else {
+ /*
+ * Register all remaining reserved RAM regions as both busy
+ * and exclusive in the iomem resource table. This prevents
+ * drivers from claiming the region, and also disallows
+ * /dev/mem access.
+ */
+ if (md->type == EFI_RUNTIME_SERVICES_CODE)
+ res->name = "UEFI Runtime [Code]";
+ else
+ res->name = "UEFI Reserved";
+ res->flags |= IORESOURCE_EXCLUSIVE;
+ }
+ request_resource(&iomem_resource, res);
+}
+
void __init efi_virtmap_init(void)
{
efi_memory_desc_t *md;
@@ -316,6 +360,8 @@ void __init efi_virtmap_init(void)
u64 paddr, npages, size;
pgprot_t prot;
+ if (is_reserve_region(md) || md->attribute & EFI_MEMORY_RUNTIME)
+ efi_reserve_iomem_resource(md);
if (!(md->attribute & EFI_MEMORY_RUNTIME))
continue;
if (WARN(md->virt_addr == 0,
--
1.8.3.2
--
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