efi: libstub: Factor out EFI stub entrypoint into separate file

In preparation for allowing the EFI zboot decompressor to reuse most of
the EFI stub machinery, factor out the actual EFI PE/COFF entrypoint
into a separate file.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/firmware/efi/libstub/efi-stub-entry.c b/drivers/firmware/efi/libstub/efi-stub-entry.c
new file mode 100644
index 000000000000..5245c4f031c0
--- /dev/null
+++ b/drivers/firmware/efi/libstub/efi-stub-entry.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+/*
+ * EFI entry point for the generic EFI stub used by ARM, arm64, RISC-V and
+ * LoongArch. This is the entrypoint that is described in the PE/COFF header
+ * of the core kernel.
+ */
+efi_status_t __efiapi efi_pe_entry(efi_handle_t handle,
+				   efi_system_table_t *systab)
+{
+	efi_loaded_image_t *image;
+	efi_status_t status;
+	unsigned long image_addr;
+	unsigned long image_size = 0;
+	/* addr/point and size pairs for memory management*/
+	char *cmdline_ptr = NULL;
+	efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
+	unsigned long reserve_addr = 0;
+	unsigned long reserve_size = 0;
+
+	WRITE_ONCE(efi_system_table, systab);
+
+	/* Check if we were booted by the EFI firmware */
+	if (efi_system_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
+		return EFI_INVALID_PARAMETER;
+
+	/*
+	 * Get a handle to the loaded image protocol.  This is used to get
+	 * information about the running image, such as size and the command
+	 * line.
+	 */
+	status = efi_bs_call(handle_protocol, handle, &loaded_image_proto,
+			     (void *)&image);
+	if (status != EFI_SUCCESS) {
+		efi_err("Failed to get loaded image protocol\n");
+		return status;
+	}
+
+	status = efi_handle_cmdline(image, &cmdline_ptr);
+	if (status != EFI_SUCCESS)
+		return status;
+
+	efi_info("Booting Linux Kernel...\n");
+
+	status = handle_kernel_image(&image_addr, &image_size,
+				     &reserve_addr,
+				     &reserve_size,
+				     image, handle);
+	if (status != EFI_SUCCESS) {
+		efi_err("Failed to relocate kernel\n");
+		return status;
+	}
+
+	status = efi_stub_common(handle, image, image_addr, cmdline_ptr);
+
+	efi_free(image_size, image_addr);
+	efi_free(reserve_size, reserve_addr);
+
+	return status;
+}