[PATCH 17/22] arm64: add EFI stub

From: Leif Lindholm
Date: Wed Feb 05 2014 - 12:08:18 EST

From: Mark Salter <msalter@xxxxxxxxxx>

This patch adds PE/COFF header fields to the start of the Image
so that it appears as an EFI application to EFI firmware. An EFI
stub is included to allow direct booting of the kernel Image.
Support in the COFF header for signed images was provided by
Ard Biesheuvel.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Mark Salter <msalter@xxxxxxxxxx>
Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
---
arch/arm64/Kconfig | 10 ++++
arch/arm64/kernel/Makefile | 3 ++
arch/arm64/kernel/efi-entry.S | 93 ++++++++++++++++++++++++++++++++++
arch/arm64/kernel/efi-stub.c | 67 ++++++++++++++++++++++++
arch/arm64/kernel/head.S | 112 +++++++++++++++++++++++++++++++++++++++++
5 files changed, 285 insertions(+)
create mode 100644 arch/arm64/kernel/efi-entry.S
create mode 100644 arch/arm64/kernel/efi-stub.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0e7b443..355f87c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -258,6 +258,16 @@ config CMDLINE_FORCE
This is useful if you cannot or don't want to change the
command-line options your boot loader passes to the kernel.

+config EFI_STUB
+ bool "EFI stub support"
+ depends on OF
+ select LIBFDT
+ default y
+ help
+ This kernel feature allows an Image to be loaded directly
+ by EFI firmware without the use of a bootloader.
+ See Documentation/efi-stub.txt for more information.
+
endmenu

menu "Userspace binary formats"
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 2d4554b..0f60b45 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -4,6 +4,8 @@

CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET)
AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
+CFLAGS_efi-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) \
+ -I$(src)/../../../scripts/dtc/libfdt

# Object file lists.
arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \
@@ -20,6 +22,7 @@ arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
arm64-obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
arm64-obj-$(CONFIG_ARM64_CPU_SUSPEND) += sleep.o suspend.o
arm64-obj-$(CONFIG_JUMP_LABEL) += jump_label.o
+arm64-obj-$(CONFIG_EFI_STUB) += efi-stub.o efi-entry.o

obj-y += $(arm64-obj-y) vdso/
obj-m += $(arm64-obj-m)
diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
new file mode 100644
index 0000000..83bfb72
--- /dev/null
+++ b/arch/arm64/kernel/efi-entry.S
@@ -0,0 +1,93 @@
+/*
+ * EFI entry point.
+ *
+ * Copyright (C) 2013 Red Hat, Inc.
+ * Author: Mark Salter <msalter@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/linkage.h>
+#include <linux/init.h>
+
+#include <asm/assembler.h>
+
+#define EFI_LOAD_ERROR 0x8000000000000001
+
+ __INIT
+
+ /*
+ * We arrive here from the EFI boot manager with:
+ *
+ * * MMU on with identity-mapped RAM.
+ * * Icache and Dcache on
+ *
+ * We will most likely be running from some place other than where
+ * we want to be. The kernel image wants to be placed at TEXT_OFFSET
+ * from start of RAM.
+ */
+ENTRY(efi_stub_entry)
+ stp x29, x30, [sp, #-32]!
+
+ /*
+ * Call efi_entry to do the real work.
+ * x0 and x1 are already set up by firmware. Current runtime
+ * address of image is calculated and passed via *image_addr.
+ *
+ * unsigned long efi_entry(void *handle,
+ * efi_system_table_t *sys_table,
+ * unsigned long *image_addr) ;
+ */
+ adrp x8, _text
+ add x8, x8, #:lo12:_text
+ add x2, sp, 16
+ str x8, [x2]
+ bl efi_entry
+ cmn x0, #1
+ b.eq efi_load_fail
+
+ /*
+ * efi_entry() will have relocated the kernel image if necessary
+ * and we return here with device tree address in x0 and the kernel
+ * entry point stored at *image_addr. Save those values in registers
+ * which are preserved by __flush_dcache_all.
+ */
+ ldr x1, [sp, #16]
+ mov x20, x0
+ mov x21, x1
+
+ /* Turn off Dcache and MMU */
+ mrs x0, CurrentEL
+ cmp x0, #PSR_MODE_EL2t
+ ccmp x0, #PSR_MODE_EL2h, #0x4, ne
+ b.ne 1f
+ mrs x0, sctlr_el2
+ bic x0, x0, #1 << 0 // clear SCTLR.M
+ bic x0, x0, #1 << 2 // clear SCTLR.C
+ msr sctlr_el2, x0
+ isb
+ b 2f
+1:
+ mrs x0, sctlr_el1
+ bic x0, x0, #1 << 0 // clear SCTLR.M
+ bic x0, x0, #1 << 2 // clear SCTLR.C
+ msr sctlr_el1, x0
+ isb
+2:
+ bl __flush_dcache_all
+
+ /* Jump to real entry point */
+ mov x0, x20
+ mov x1, xzr
+ mov x2, xzr
+ mov x3, xzr
+ br x21
+
+efi_load_fail:
+ mov x0, #EFI_LOAD_ERROR
+ ldp x29, x30, [sp], #32
+ ret
+
+ENDPROC(efi_stub_entry)
diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
new file mode 100644
index 0000000..17f5cc3
--- /dev/null
+++ b/arch/arm64/kernel/efi-stub.c
@@ -0,0 +1,67 @@
+/*
+ * linux/arch/arm/boot/compressed/efi-stub.c
+ *
+ * Copyright (C) 2013, 2014 Linaro Ltd; <roy.franz@xxxxxxxxxx>
+ *
+ * This file implements the EFI boot stub for the arm64 kernel.
+ * Adapted from ARM version by Mark Salter <msalter@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/efi.h>
+#include <linux/libfdt.h>
+#include <asm/sections.h>
+#include <generated/compile.h>
+#include <generated/utsrelease.h>
+
+/*
+ * AArch64 requires the DTB to be 8-byte aligned in the first 512MiB from
+ * start of kernel and may not cross a 2MiB boundary. We set alignment to
+ * 2MiB so we know it won't cross a 2MiB boundary.
+ */
+#define EFI_FDT_ALIGN SZ_2M /* used by allocate_new_fdt_and_exit_boot() */
+#define MAX_FDT_OFFSET SZ_512M
+
+/* Include shared EFI stub code */
+#include "../../../drivers/firmware/efi/efi-stub-helper.c"
+#include "../../../drivers/firmware/efi/fdt.c"
+#include "../../../drivers/firmware/efi/arm-stub.c"
+
+
+static efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
+ unsigned long *image_addr,
+ unsigned long *image_size,
+ unsigned long *reserve_addr,
+ unsigned long *reserve_size,
+ unsigned long dram_base,
+ efi_loaded_image_t *image)
+{
+ efi_status_t status;
+ unsigned long kernel_size, kernel_memsize = 0;
+
+ /* Relocate the image, if required. */
+ kernel_size = _edata - _text;
+ if (*image_addr != (dram_base + TEXT_OFFSET)) {
+ kernel_memsize = kernel_size + (_end - _edata);
+ status = efi_relocate_kernel(sys_table, image_addr,
+ kernel_size, kernel_memsize,
+ dram_base + TEXT_OFFSET,
+ PAGE_SIZE);
+ if (status != EFI_SUCCESS) {
+ pr_efi_err(sys_table, "Failed to relocate kernel\n");
+ return status;
+ }
+ if (*image_addr != (dram_base + TEXT_OFFSET)) {
+ pr_efi_err(sys_table, "Failed to alloc kernel memory\n");
+ efi_free(sys_table, kernel_memsize, *image_addr);
+ return EFI_ERROR;
+ }
+ *image_size = kernel_memsize;
+ }
+
+
+ return EFI_SUCCESS;
+}
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index c86bfdf..2f07979 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -107,8 +107,18 @@
/*
* DO NOT MODIFY. Image header expected by Linux boot-loaders.
*/
+#ifdef CONFIG_EFI_STUB
+ /*
+ * Magic "MZ" signature for PE/COFF
+ * Little Endian: add x13, x18, #0x16
+ */
+efi_head:
+ .long 0x91005a4d
+ b stext
+#else
b stext // branch to kernel start, magic
.long 0 // reserved
+#endif
.quad TEXT_OFFSET // Image load offset from start of RAM
.quad 0 // reserved
.quad 0 // reserved
@@ -119,7 +129,109 @@
.byte 0x52
.byte 0x4d
.byte 0x64
+#ifdef CONFIG_EFI_STUB
+ .long pe_header - efi_head // Offset to the PE header.
+#else
.word 0 // reserved
+#endif
+
+#ifdef CONFIG_EFI_STUB
+ .align 3
+pe_header:
+ .ascii "PE"
+ .short 0
+coff_header:
+ .short 0xaa64 // AArch64
+ .short 2 // nr_sections
+ .long 0 // TimeDateStamp
+ .long 0 // PointerToSymbolTable
+ .long 1 // NumberOfSymbols
+ .short section_table - optional_header // SizeOfOptionalHeader
+ .short 0x206 // Characteristics.
+ // IMAGE_FILE_DEBUG_STRIPPED |
+ // IMAGE_FILE_EXECUTABLE_IMAGE |
+ // IMAGE_FILE_LINE_NUMS_STRIPPED
+optional_header:
+ .short 0x20b // PE32+ format
+ .byte 0x02 // MajorLinkerVersion
+ .byte 0x14 // MinorLinkerVersion
+ .long _edata - stext // SizeOfCode
+ .long 0 // SizeOfInitializedData
+ .long 0 // SizeOfUninitializedData
+ .long efi_stub_entry - efi_head // AddressOfEntryPoint
+ .long stext - efi_head // BaseOfCode
+
+extra_header_fields:
+ .quad 0 // ImageBase
+ .long 0x20 // SectionAlignment
+ .long 0x8 // FileAlignment
+ .short 0 // MajorOperatingSystemVersion
+ .short 0 // MinorOperatingSystemVersion
+ .short 0 // MajorImageVersion
+ .short 0 // MinorImageVersion
+ .short 0 // MajorSubsystemVersion
+ .short 0 // MinorSubsystemVersion
+ .long 0 // Win32VersionValue
+
+ .long _edata - efi_head // SizeOfImage
+
+ // Everything before the kernel image is considered part of the header
+ .long stext - efi_head // SizeOfHeaders
+ .long 0 // CheckSum
+ .short 0xa // Subsystem (EFI application)
+ .short 0 // DllCharacteristics
+ .quad 0 // SizeOfStackReserve
+ .quad 0 // SizeOfStackCommit
+ .quad 0 // SizeOfHeapReserve
+ .quad 0 // SizeOfHeapCommit
+ .long 0 // LoaderFlags
+ .long 0x6 // NumberOfRvaAndSizes
+
+ .quad 0 // ExportTable
+ .quad 0 // ImportTable
+ .quad 0 // ResourceTable
+ .quad 0 // ExceptionTable
+ .quad 0 // CertificationTable
+ .quad 0 // BaseRelocationTable
+
+ // Section table
+section_table:
+
+ /*
+ * The EFI application loader requires a relocation section
+ * because EFI applications must be relocatable. This is a
+ * dummy section as far as we are concerned.
+ */
+ .ascii ".reloc"
+ .byte 0
+ .byte 0 // end of 0 padding of section name
+ .long 0
+ .long 0
+ .long 0 // SizeOfRawData
+ .long 0 // PointerToRawData
+ .long 0 // PointerToRelocations
+ .long 0 // PointerToLineNumbers
+ .short 0 // NumberOfRelocations
+ .short 0 // NumberOfLineNumbers
+ .long 0x42100040 // Characteristics (section flags)
+
+
+ .ascii ".text"
+ .byte 0
+ .byte 0
+ .byte 0 // end of 0 padding of section name
+ .long _edata - stext // VirtualSize
+ .long stext - efi_head // VirtualAddress
+ .long _edata - stext // SizeOfRawData
+ .long stext - efi_head // PointerToRawData
+
+ .long 0 // PointerToRelocations (0 for executables)
+ .long 0 // PointerToLineNumbers (0 for executables)
+ .short 0 // NumberOfRelocations (0 for executables)
+ .short 0 // NumberOfLineNumbers (0 for executables)
+ .long 0xe0500020 // Characteristics (section flags)
+ .align 5
+#endif

ENTRY(stext)
mov x21, x0 // x21=FDT
--
1.7.10.4

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