Implement a minimal EFI app that decompresses the real kernel image and
launches it using the firmware's LoadImage and StartImage boot services.
This removes the need for any arch-specific hacks.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
drivers/firmware/efi/Kconfig | 6 ++
drivers/firmware/efi/libstub/Makefile | 2 +
drivers/firmware/efi/libstub/zboot-header.S | 88 ++++++++++++++++++++
drivers/firmware/efi/libstub/zboot.c | 86 +++++++++++++++++++
drivers/firmware/efi/libstub/zboot.lds | 44 ++++++++++
5 files changed, 226 insertions(+)
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 4720ba98cec3..5fc986f66505 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -116,6 +116,12 @@ config EFI_RUNTIME_WRAPPERS
config EFI_GENERIC_STUB
bool
+config EFI_ZBOOT
+ bool "Enable the generic EFI decompressor"
+ depends on EFI_GENERIC_STUB
+ depends on !ARM && !X86
+ select HAVE_KERNEL_GZIP
+
config EFI_ARMSTUB_DTB_LOADER
bool "Enable the DTB loader"
depends on EFI_GENERIC_STUB && !RISCV
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 475224be08e1..71bd877077b1 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -111,8 +111,10 @@ STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
# a verification pass to see if any absolute relocations exist in any of the
# object files.
#
+lib-$(CONFIG_EFI_ZBOOT) += zboot.o
extra-y := $(lib-y)
lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
+lib-$(CONFIG_EFI_ZBOOT) += zboot-header.o
STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
--prefix-symbols=__efistub_
diff --git a/drivers/firmware/efi/libstub/zboot-header.S b/drivers/firmware/efi/libstub/zboot-header.S
new file mode 100644
index 000000000000..8f471866081a
--- /dev/null
+++ b/drivers/firmware/efi/libstub/zboot-header.S
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/pe.h>
+
+ .section ".head", "a"
+ .globl __efistub_efi_zboot_header
+__efistub_efi_zboot_header:
+.Ldoshdr:
+ .long MZ_MAGIC
+ .org .Ldoshdr + 0x3c
+ .long .Lpehdr - .Ldoshdr
+
+.Lpehdr:
+ .long PE_MAGIC
+ .short pe_machine_type
+ .short .Lsection_count
+ .long 0
+ .long 0
+ .long 0
+ .short .Lsection_table - .Loptional_header
+ .short IMAGE_FILE_DEBUG_STRIPPED | \
+ IMAGE_FILE_EXECUTABLE_IMAGE | \
+ IMAGE_FILE_LINE_NUMS_STRIPPED
+
+.Loptional_header:
+#ifdef CONFIG_64BIT
+ .short PE_OPT_MAGIC_PE32PLUS
+#else
+ .short PE_OPT_MAGIC_PE32
+#endif
+ .byte 0, 0
+ .long _etext - .Lefi_header_end
+ .long __data_size
+ .long 0
+ .long __efistub_efi_zboot_entry - .Ldoshdr
+ .long .Lefi_header_end - .Ldoshdr
+
+#ifdef CONFIG_64BIT
+ .quad 0
+#else
+ .long _etext - .Lhead
+ .long 0
+#endif
+ .long 4096
+ .long 512
+ .short 0, 0, 0, 0, 0, 0
+ .long 0
+ .long _end - .Ldoshdr
+
+ .long .Lefi_header_end - .Ldoshdr
+ .long 0
+ .short IMAGE_SUBSYSTEM_EFI_APPLICATION
+ .short 0
+ .quad 0, 0, 0, 0
+ .long 0
+ .long (.Lsection_table - .) / 8
+ .quad 0, 0, 0, 0, 0, 0
+
+.Lsection_table:
+ .ascii ".text\0\0\0"
+ .long _etext - .Lefi_header_end
+ .long .Lefi_header_end - .Ldoshdr
+ .long _etext - .Lefi_header_end
+ .long .Lefi_header_end - .Ldoshdr
+
+ .long 0, 0
+ .short 0, 0
+ .long IMAGE_SCN_CNT_CODE | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_EXECUTE
+
+ .ascii ".data\0\0\0"
+ .long __data_size
+ .long _etext - .Ldoshdr
+ .long __data_rawsize
+ .long _etext - .Ldoshdr
+
+ .long 0, 0
+ .short 0, 0
+ .long IMAGE_SCN_CNT_INITIALIZED_DATA | \
+ IMAGE_SCN_MEM_READ | \
+ IMAGE_SCN_MEM_WRITE
+
+ .set .Lsection_count, (. - .Lsection_table) / 40
+
+ .align 12
+.Lefi_header_end:
+
diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
new file mode 100644
index 000000000000..edb3390c808c
--- /dev/null
+++ b/drivers/firmware/efi/libstub/zboot.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+#define STATIC static
+
+static unsigned char zboot_heap[SZ_64K] __aligned(64);
+static unsigned long free_mem_ptr, free_mem_end_ptr;
+
+#ifdef CONFIG_KERNEL_GZIP
+#include "../../../../lib/decompress_inflate.c"
+#endif
+
+const efi_system_table_t *efi_system_table;
+
+extern char _gzdata_start[], _gzdata_end[];
+extern u32 uncompressed_size __aligned(1);
+
+static void error(char *x)
+{
+ efi_err("%s\n", x);
+}
+
+efi_status_t __efiapi efi_zboot_entry(efi_handle_t handle,
+ efi_system_table_t *systab)
+{
+ efi_guid_t loaded_image = LOADED_IMAGE_PROTOCOL_GUID;
+ efi_loaded_image_t *parent, *child;
+ efi_handle_t child_handle = NULL;
+ unsigned long image_buffer;
+ efi_status_t status;
+
+ free_mem_ptr = (unsigned long)&zboot_heap;
+ free_mem_end_ptr = free_mem_ptr + sizeof(zboot_heap);
+
+ efi_system_table = systab;
+
+ efi_info("Entering EFI decompressor\n");
+
+ status = efi_bs_call(handle_protocol, handle, &loaded_image,
+ (void **)&parent);
+ if (status != EFI_SUCCESS) {
+ efi_err("Failed to locate parent's loaded image protocol\n");
+ return status;
+ }
+
+ status = efi_allocate_pages(uncompressed_size, &image_buffer, ULONG_MAX);
+ if (status != EFI_SUCCESS) {
+ efi_err("Failed to allocate memory\n");
+ return status;
+ }
+
+ if (__decompress(_gzdata_start, _gzdata_end - _gzdata_start, NULL,
+ NULL, (unsigned char *)image_buffer, 0, NULL,
+ error) < 0)
+ return EFI_LOAD_ERROR;
+
+ status = efi_bs_call(load_image, true, handle, NULL,
+ (void *)image_buffer, uncompressed_size,
+ &child_handle);
+ if (status != EFI_SUCCESS) {
+ efi_err("Failed to load image: %lx\n", status);
+ return status;
+ }
+
+ status = efi_bs_call(handle_protocol, child_handle, &loaded_image,
+ (void **)&child);
+ if (status != EFI_SUCCESS) {
+ efi_err("Failed to locate child's loaded image protocol\n");
+ return status;
+ }
+
+ // Copy the kernel command line
+ child->load_options = parent->load_options;
+ child->load_options_size = parent->load_options_size;
+
+ status = efi_bs_call(start_image, child_handle, NULL, NULL);
+ if (status != EFI_SUCCESS) {
+ efi_err("Failed to start image: %lx\n", status);
+ return status;
+ }
+ return EFI_SUCCESS;
+}
diff --git a/drivers/firmware/efi/libstub/zboot.lds b/drivers/firmware/efi/libstub/zboot.lds
new file mode 100644
index 000000000000..56777b5f2668
--- /dev/null
+++ b/drivers/firmware/efi/libstub/zboot.lds
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+ENTRY(__efistub_efi_zboot_header);
+
+SECTIONS
+{
+ .text : ALIGN(4096) {
+ *(.head)
+ *(.text* .init.text*)
+ }
+
+ .rodata : ALIGN(8) {
+ __efistub__gzdata_start = .;
+ *(.gzdata)
+ __efistub__gzdata_end = . - 4;
+ __efistub_uncompressed_size = . - 4;
+ *(.rodata* .init.rodata*)
+ _etext = ALIGN(4096);
+ . = _etext;
+ }
+
+ .data : ALIGN(4096) {
+ *(.data* .init.data*)
+ _edata = ALIGN(512);
+ . = _edata;
+ }
+
+ .bss : {
+ *(.bss* .init.bss*)
+ _end = ALIGN(512);
+ . = _end;
+ }
+
+ /DISCARD/ : {
+ *(__ksymtab_strings ___ksymtab+*)
+ }
+}
+
+PROVIDE(__data_rawsize = ABSOLUTE(_edata - _etext));
+PROVIDE(__data_size = ABSOLUTE(_end - _etext));
+
+PROVIDE(__efistub_memcpy = __pi_memcpy);
+PROVIDE(__efistub_memset = __pi_memset);
+PROVIDE(__efistub_strnlen = __pi_strnlen);
--
2.30.2
