Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64...

[cascardo/linux.git] / drivers / firmware / efi / libstub / arm-stub.c

diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 2b38147..dcae482 100644 (file)
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -295,3 +295,62 @@ fail_free_image:
 fail:
        return EFI_ERROR;
 }
+
+/*
+ * This is the base address at which to start allocating virtual memory ranges
+ * for UEFI Runtime Services. This is in the low TTBR0 range so that we can use
+ * any allocation we choose, and eliminate the risk of a conflict after kexec.
+ * The value chosen is the largest non-zero power of 2 suitable for this purpose
+ * both on 32-bit and 64-bit ARM CPUs, to maximize the likelihood that it can
+ * be mapped efficiently.
+ */
+#define EFI_RT_VIRTUAL_BASE    0x40000000
+
+/*
+ * efi_get_virtmap() - create a virtual mapping for the EFI memory map
+ *
+ * This function populates the virt_addr fields of all memory region descriptors
+ * in @memory_map whose EFI_MEMORY_RUNTIME attribute is set. Those descriptors
+ * are also copied to @runtime_map, and their total count is returned in @count.
+ */
+void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
+                    unsigned long desc_size, efi_memory_desc_t *runtime_map,
+                    int *count)
+{
+       u64 efi_virt_base = EFI_RT_VIRTUAL_BASE;
+       efi_memory_desc_t *out = runtime_map;
+       int l;
+
+       for (l = 0; l < map_size; l += desc_size) {
+               efi_memory_desc_t *in = (void *)memory_map + l;
+               u64 paddr, size;
+
+               if (!(in->attribute & EFI_MEMORY_RUNTIME))
+                       continue;
+
+               /*
+                * Make the mapping compatible with 64k pages: this allows
+                * a 4k page size kernel to kexec a 64k page size kernel and
+                * vice versa.
+                */
+               paddr = round_down(in->phys_addr, SZ_64K);
+               size = round_up(in->num_pages * EFI_PAGE_SIZE +
+                               in->phys_addr - paddr, SZ_64K);
+
+               /*
+                * Avoid wasting memory on PTEs by choosing a virtual base that
+                * is compatible with section mappings if this region has the
+                * appropriate size and physical alignment. (Sections are 2 MB
+                * on 4k granule kernels)
+                */
+               if (IS_ALIGNED(in->phys_addr, SZ_2M) && size >= SZ_2M)
+                       efi_virt_base = round_up(efi_virt_base, SZ_2M);
+
+               in->virt_addr = efi_virt_base + in->phys_addr - paddr;
+               efi_virt_base += size;
+
+               memcpy(out, in, desc_size);
+               out = (void *)out + desc_size;
+               ++*count;
+       }
+}