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arm64: efi: add EFI stub
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This patch adds PE/COFF header fields to the start of the kernel
Image so that it appears as an EFI application to UEFI firmware.
An EFI stub is included to allow direct booting of the kernel
Image.

Signed-off-by: Mark Salter <[email protected]>
[Add support in PE/COFF header for signed images]
Signed-off-by: Ard Biesheuvel <[email protected]>
Signed-off-by: Leif Lindholm <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Signed-off-by: Matt Fleming <[email protected]>
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mosalter authored and Matt Fleming committed Apr 30, 2014
1 parent e197746 commit 3c7f255
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Showing 6 changed files with 555 additions and 3 deletions.
5 changes: 3 additions & 2 deletions arch/arm64/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -290,8 +290,9 @@ config EFI
help
This option provides support for runtime services provided
by UEFI firmware (such as non-volatile variables, realtime
clock, and platform reset). This is only useful on systems
that have UEFI firmware.
clock, and platform reset). A UEFI stub is also provided to
allow the kernel to be booted as an EFI application. This
is only useful on systems that have UEFI firmware.

endmenu

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4 changes: 3 additions & 1 deletion arch/arm64/kernel/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -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 \
Expand All @@ -22,7 +24,7 @@ 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_KGDB) += kgdb.o
arm64-obj-$(CONFIG_EFI) += efi.o
arm64-obj-$(CONFIG_EFI) += efi.o efi-stub.o efi-entry.o

obj-y += $(arm64-obj-y) vdso/
obj-m += $(arm64-obj-m)
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109 changes: 109 additions & 0 deletions arch/arm64/kernel/efi-entry.S
Original file line number Diff line number Diff line change
@@ -0,0 +1,109 @@
/*
* EFI entry point.
*
* Copyright (C) 2013, 2014 Red Hat, Inc.
* Author: Mark Salter <[email protected]>
*
* 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:
*
* * CPU in little-endian mode
* * 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)
/*
* Create a stack frame to save FP/LR with extra space
* for image_addr variable passed to efi_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 callee preserved.
*/
mov x20, x0 // DTB address
ldr x0, [sp, #16] // relocated _text address
mov x21, x0

/*
* Flush dcache covering current runtime addresses
* of kernel text/data. Then flush all of icache.
*/
adrp x1, _text
add x1, x1, #:lo12:_text
adrp x2, _edata
add x2, x2, #:lo12:_edata
sub x1, x2, x1

bl __flush_dcache_area
ic ialluis

/* 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:
/* Jump to kernel 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)
81 changes: 81 additions & 0 deletions arch/arm64/kernel/efi-stub.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,81 @@
/*
* Copyright (C) 2013, 2014 Linaro Ltd; <[email protected]>
*
* This file implements the EFI boot stub for the arm64 kernel.
* Adapted from ARM version by Mark Salter <[email protected]>
*
* 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

#define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)

static void efi_char16_printk(efi_system_table_t *sys_table_arg,
efi_char16_t *str);

static efi_status_t efi_open_volume(efi_system_table_t *sys_table,
void *__image, void **__fh);
static efi_status_t efi_file_close(void *handle);

static efi_status_t
efi_file_read(void *handle, unsigned long *size, void *addr);

static efi_status_t
efi_file_size(efi_system_table_t *sys_table, void *__fh,
efi_char16_t *filename_16, void **handle, u64 *file_sz);

/* 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;
}
112 changes: 112 additions & 0 deletions arch/arm64/kernel/head.S
Original file line number Diff line number Diff line change
Expand Up @@ -108,8 +108,18 @@
/*
* DO NOT MODIFY. Image header expected by Linux boot-loaders.
*/
#ifdef CONFIG_EFI
efi_head:
/*
* This add instruction has no meaningful effect except that
* its opcode forms the magic "MZ" signature required by UEFI.
*/
add x13, x18, #0x16
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
Expand All @@ -120,7 +130,109 @@
.byte 0x52
.byte 0x4d
.byte 0x64
#ifdef CONFIG_EFI
.long pe_header - efi_head // Offset to the PE header.
#else
.word 0 // reserved
#endif

#ifdef CONFIG_EFI
.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
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