1 files changed, 100 insertions, 0 deletions
diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
new file mode 100644
index 000000000000..c47ace06f010
--- /dev/null
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <linux/pe.h>
+#include <asm/efi.h>
+#include <linux/unaligned.h>
+
+#include "efistub.h"
+
+static unsigned long alloc_preferred_address(unsigned long alloc_size)
+{
+#ifdef EFI_KIMG_PREFERRED_ADDRESS
+	efi_physical_addr_t efi_addr = EFI_KIMG_PREFERRED_ADDRESS;
+
+	if (efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
+			alloc_size / EFI_PAGE_SIZE, &efi_addr) == EFI_SUCCESS)
+		return efi_addr;
+#endif
+	return ULONG_MAX;
+}
+
+void __weak efi_cache_sync_image(unsigned long image_base,
+				 unsigned long alloc_size)
+{
+	// Provided by the arch to perform the cache maintenance necessary for
+	// executable code loaded into memory to be safe for execution.
+}
+
+struct screen_info *alloc_screen_info(void)
+{
+	return __alloc_screen_info();
+}
+
+asmlinkage efi_status_t __efiapi
+efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
+{
+	char *cmdline_ptr __free(efi_pool) = NULL;
+	unsigned long image_base, alloc_size;
+	efi_loaded_image_t *image;
+	efi_status_t status;
+
+	WRITE_ONCE(efi_system_table, systab);
+
+	status = efi_bs_call(handle_protocol, handle,
+			     &LOADED_IMAGE_PROTOCOL_GUID, (void **)&image);
+	if (status != EFI_SUCCESS) {
+		efi_err("Failed to locate parent's loaded image protocol\n");
+		return status;
+	}
+
+	status = efi_handle_cmdline(image, &cmdline_ptr);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	efi_info("Decompressing Linux Kernel...\n");
+
+	status = efi_zboot_decompress_init(&alloc_size);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	 // If the architecture has a preferred address for the image,
+	 // try that first.
+	image_base = alloc_preferred_address(alloc_size);
+	if (image_base == ULONG_MAX) {
+		unsigned long min_kimg_align = efi_get_kimg_min_align();
+		u32 seed = U32_MAX;
+
+		if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
+			// Setting the random seed to 0x0 is the same as
+			// allocating as low as possible
+			seed = 0;
+		} else if (efi_nokaslr) {
+			efi_info("KASLR disabled on kernel command line\n");
+		} else {
+			status = efi_get_random_bytes(sizeof(seed), (u8 *)&seed);
+			if (status == EFI_NOT_FOUND) {
+				efi_info("EFI_RNG_PROTOCOL unavailable\n");
+				efi_nokaslr = true;
+			} else if (status != EFI_SUCCESS) {
+				efi_err("efi_get_random_bytes() failed (0x%lx)\n",
+					status);
+				efi_nokaslr = true;
+			}
+		}
+
+		status = efi_random_alloc(alloc_size, min_kimg_align, &image_base,
+					  seed, EFI_LOADER_CODE, 0, EFI_ALLOC_LIMIT);
+		if (status != EFI_SUCCESS) {
+			efi_err("Failed to allocate memory\n");
+			return status;
+		}
+	}
+
+	// Decompress the payload into the newly allocated buffer
+	status = efi_zboot_decompress((void *)image_base, alloc_size) ?:
+	         efi_stub_common(handle, image, image_base, cmdline_ptr);
+
+	efi_free(alloc_size, image_base);
+	return status;
+}