[PATCH 4/6] Add EFI stub for ARM
Roy Franz
roy.franz at linaro.org
Sat Sep 28 12:23:21 EDT 2013
This patch adds EFI stub support for the ARM Linux kernel. The EFI stub
operates similarly to the x86 stub: it is a shim between the EFI firmware
and the normal zImage entry point, and sets up the environment that the
zImage is expecting. This includes loading the initrd (optionaly) and
device tree from the system partition based on the kernel command line.
The stub updates the device tree as necessary, adding entries for EFI
runtime services. The PE/COFF "MZ" header at offset 0 results in the
first instruction being an add that corrupts r5, which is not used by
the zImage interface.
Signed-off-by: Roy Franz <roy.franz at linaro.org>
---
arch/arm/boot/compressed/Makefile | 15 +-
arch/arm/boot/compressed/efi-header.S | 111 +++++++++++++
arch/arm/boot/compressed/efi-stub.c | 288 +++++++++++++++++++++++++++++++++
arch/arm/boot/compressed/efi-stub.h | 5 +
arch/arm/boot/compressed/head.S | 83 +++++++++-
5 files changed, 494 insertions(+), 8 deletions(-)
create mode 100644 arch/arm/boot/compressed/efi-header.S
create mode 100644 arch/arm/boot/compressed/efi-stub.c
create mode 100644 arch/arm/boot/compressed/efi-stub.h
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 7ac1610..5fad8bd 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -103,11 +103,22 @@ libfdt_objs := $(addsuffix .o, $(basename $(libfdt)))
$(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/%
$(call cmd,shipped)
-$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \
+$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o efi-stub.o): \
$(addprefix $(obj)/,$(libfdt_hdrs))
ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y)
-OBJS += $(libfdt_objs) atags_to_fdt.o
+OBJS += atags_to_fdt.o
+USE_LIBFDT = y
+endif
+
+ifeq ($(CONFIG_EFI_STUB),y)
+CFLAGS_efi-stub.o += -DTEXT_OFFSET=$(TEXT_OFFSET)
+OBJS += efi-stub.o
+USE_LIBFDT = y
+endif
+
+ifeq ($(USE_LIBFDT),y)
+OBJS += $(libfdt_objs)
endif
targets := vmlinux vmlinux.lds \
diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S
new file mode 100644
index 0000000..6965e0f
--- /dev/null
+++ b/arch/arm/boot/compressed/efi-header.S
@@ -0,0 +1,111 @@
+@ Copyright (C) 2013 Linaro Ltd; <roy.franz at linaro.org>
+@
+@ This file contains the PE/COFF header that is part of the
+@ EFI stub.
+@
+
+ .org 0x3c
+ @
+ @ The PE header can be anywhere in the file, but for
+ @ simplicity we keep it together with the MSDOS header
+ @ The offset to the PE/COFF header needs to be at offset
+ @ 0x3C in the MSDOS header.
+ @ The only 2 fields of the MSDOS header that are used are this
+ @ PE/COFF offset, and the "MZ" bytes at offset 0x0.
+ @
+ .long pe_header @ Offset to the PE header.
+
+ .align 3
+pe_header:
+ .ascii "PE"
+ .short 0
+
+coff_header:
+ .short 0x01c2 @ ARM or Thumb
+ .short 2 @ nr_sections
+ .long 0 @ TimeDateStamp
+ .long 0 @ PointerToSymbolTable
+ .long 1 @ NumberOfSymbols
+ .short section_table - optional_header @ SizeOfOptionalHeader
+ .short 0x306 @ Characteristics.
+ @ IMAGE_FILE_32BIT_MACHINE |
+ @ IMAGE_FILE_DEBUG_STRIPPED |
+ @ IMAGE_FILE_EXECUTABLE_IMAGE |
+ @ IMAGE_FILE_LINE_NUMS_STRIPPED
+
+optional_header:
+ .short 0x10b @ PE32 format
+ .byte 0x02 @ MajorLinkerVersion
+ .byte 0x14 @ MinorLinkerVersion
+
+ .long _edata - efi_stub_entry @ SizeOfCode
+
+ .long 0 @ SizeOfInitializedData
+ .long 0 @ SizeOfUninitializedData
+
+ .long efi_stub_entry @ AddressOfEntryPoint
+ .long efi_stub_entry @ BaseOfCode
+ .long 0 @ data
+
+extra_header_fields:
+ .long 0 @ ImageBase
+ .long 0x20 @ SectionAlignment
+ .long 0x20 @ FileAlignment
+ .short 0 @ MajorOperatingSystemVersion
+ .short 0 @ MinorOperatingSystemVersion
+ .short 0 @ MajorImageVersion
+ .short 0 @ MinorImageVersion
+ .short 0 @ MajorSubsystemVersion
+ .short 0 @ MinorSubsystemVersion
+ .long 0 @ Win32VersionValue
+
+ .long _edata @ SizeOfImage
+
+ @ Everything before the entry point is considered part of the header
+ .long efi_stub_entry @ SizeOfHeaders
+ .long 0 @ CheckSum
+ .short 0xa @ Subsystem (EFI application)
+ .short 0 @ DllCharacteristics
+ .long 0 @ SizeOfStackReserve
+ .long 0 @ SizeOfStackCommit
+ .long 0 @ SizeOfHeapReserve
+ .long 0 @ SizeOfHeapCommit
+ .long 0 @ LoaderFlags
+ .long 0x0 @ NumberOfRvaAndSizes
+
+ # 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 - efi_stub_entry @ VirtualSize
+ .long efi_stub_entry @ VirtualAddress
+ .long _edata - efi_stub_entry @ SizeOfRawData
+ .long efi_stub_entry @ 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)
diff --git a/arch/arm/boot/compressed/efi-stub.c b/arch/arm/boot/compressed/efi-stub.c
new file mode 100644
index 0000000..a77cc4f
--- /dev/null
+++ b/arch/arm/boot/compressed/efi-stub.c
@@ -0,0 +1,288 @@
+/*
+ * linux/arch/arm/boot/compressed/efi-stub.c
+ *
+ * Copyright (C) 2013 Linaro Ltd; <roy.franz at linaro.org>
+ *
+ * This file implements the EFI boot stub for the ARM kernel
+ *
+ * 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 <libfdt.h>
+#include "efi-stub.h"
+
+/* EFI function call wrappers. These are not required for
+ * ARM, but wrappers are required for X86 to convert between
+ * ABIs. These wrappers are provided to allow code sharing
+ * between X86 and ARM. Since these wrappers directly invoke the
+ * EFI function pointer, the function pointer type must be properly
+ * defined, which is not the case for X86 One advantage of this is
+ * it allows for type checking of arguments, which is not
+ * possible with the X86 wrappers.
+ */
+#define efi_call_phys0(f) f()
+#define efi_call_phys1(f, a1) f(a1)
+#define efi_call_phys2(f, a1, a2) f(a1, a2)
+#define efi_call_phys3(f, a1, a2, a3) f(a1, a2, a3)
+#define efi_call_phys4(f, a1, a2, a3, a4) f(a1, a2, a3, a4)
+#define efi_call_phys5(f, a1, a2, a3, a4, a5) f(a1, a2, a3, a4, a5)
+
+/* The maximum uncompressed kernel size is 32 MBytes, so we will reserve
+ * that for the decompressed kernel. We have no easy way to tell what
+ * the actuall size of code + data the uncompressed kernel will use.
+ */
+#define MAX_UNCOMP_KERNEL_SIZE 0x02000000
+
+/* The kernel zImage should be located between 32 Mbytes
+ * and 128 MBytes from the base of DRAM. The min
+ * address leaves space for a maximal size uncompressed image,
+ * and the max address is due to how the zImage decompressor
+ * picks a destination address.
+ */
+#define ZIMAGE_OFFSET_LIMIT 0x08000000
+#define MIN_ZIMAGE_OFFSET MAX_UNCOMP_KERNEL_SIZE
+
+#define PRINTK_PREFIX "EFIstub: "
+
+struct fdt_region {
+ u64 base;
+ u64 size;
+};
+
+
+/* Include shared EFI stub code */
+#include "../../../../drivers/firmware/efi/efi-stub-helper.c"
+
+
+int efi_entry(void *handle, efi_system_table_t *sys_table,
+ unsigned long *zimage_addr)
+{
+ efi_loaded_image_t *image;
+ int status;
+ unsigned long nr_pages;
+ const struct fdt_region *region;
+
+ void *fdt;
+ int err;
+ int node;
+ unsigned long zimage_size = 0;
+ unsigned long dram_base;
+ /* addr/point and size pairs for memory management*/
+ unsigned long initrd_addr;
+ unsigned long initrd_size = 0;
+ unsigned long fdt_addr;
+ unsigned long fdt_size = 0;
+ efi_physical_addr_t kernel_reserve_addr;
+ unsigned long kernel_reserve_size = 0;
+ char *cmdline_ptr;
+ int cmdline_size = 0;
+
+ unsigned long map_size, desc_size;
+ u32 desc_ver;
+ unsigned long mmap_key;
+ efi_memory_desc_t *memory_map;
+
+ unsigned long new_fdt_size;
+ unsigned long new_fdt_addr;
+
+ efi_guid_t proto = LOADED_IMAGE_PROTOCOL_GUID;
+
+ /* Check if we were booted by the EFI firmware */
+ if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
+ goto fail;
+
+ efi_printk(sys_table, PRINTK_PREFIX"Booting Linux using EFI stub.\n");
+
+
+ /* get the command line from EFI, using the LOADED_IMAGE protocol */
+ status = efi_call_phys3(sys_table->boottime->handle_protocol,
+ handle, &proto, (void *)&image);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Failed to get handle for LOADED_IMAGE_PROTOCOL.\n");
+ goto fail;
+ }
+
+ /* We are going to copy the command line into the device tree,
+ * so this memory just needs to not conflict with boot protocol
+ * requirements.
+ */
+ cmdline_ptr = efi_convert_cmdline_to_ascii(sys_table, image,
+ &cmdline_size);
+ if (!cmdline_ptr) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to allocate memory for command line.\n");
+ goto fail;
+ }
+
+ /* We first load the device tree, as we need to get the base address of
+ * DRAM from the device tree. The zImage, device tree, and initrd
+ * have address restrictions that are relative to the base of DRAM.
+ */
+ status = handle_cmdline_files(sys_table, image, cmdline_ptr, "dtb=",
+ 0xffffffff, &fdt_addr, &fdt_size);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to load device tree blob.\n");
+ goto fail_free_cmdline;
+ }
+
+ err = fdt_check_header((void *)fdt_addr);
+ if (err != 0) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Device tree header not valid.\n");
+ goto fail_free_fdt;
+ }
+ if (fdt_totalsize((void *)fdt_addr) > fdt_size) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Incomplete device tree.\n");
+ goto fail_free_fdt;
+
+ }
+
+
+ /* Look up the base of DRAM from the device tree. */
+ fdt = (void *)fdt_addr;
+ node = fdt_subnode_offset(fdt, 0, "memory");
+ region = fdt_getprop(fdt, node, "reg", NULL);
+ if (region) {
+ dram_base = fdt64_to_cpu(region->base);
+ } else {
+ /* There is no way to get amount or addresses of physical
+ * memory installed using EFI calls. If the device tree
+ * we read from disk doesn't have this, there is no way
+ * for us to construct this informaion.
+ */
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: No 'memory' node in device tree.\n");
+ goto fail_free_fdt;
+ }
+
+ /* Reserve memory for the uncompressed kernel image. This is
+ * all that prevents any future allocations from conflicting
+ * with the kernel. Since we can't tell from the compressed
+ * image how much DRAM the kernel actually uses (due to BSS
+ * size uncertainty) we allocate the maximum possible size.
+ */
+ kernel_reserve_addr = dram_base;
+ kernel_reserve_size = MAX_UNCOMP_KERNEL_SIZE;
+ nr_pages = round_up(kernel_reserve_size, EFI_PAGE_SIZE) / EFI_PAGE_SIZE;
+ status = efi_call_phys4(sys_table->boottime->allocate_pages,
+ EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
+ nr_pages, &kernel_reserve_addr);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to allocate memory for uncompressed kernel.\n");
+ goto fail_free_fdt;
+ }
+
+ /* Relocate the zImage, if required. ARM doesn't have a
+ * preferred address, so we set it to 0, as we want to allocate
+ * as low in memory as possible.
+ */
+ zimage_size = image->image_size;
+ status = efi_relocate_kernel(sys_table, zimage_addr, zimage_size,
+ zimage_size, 0, 0);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Failed to relocate kernel.\n");
+ goto fail_free_kernel_reserve;
+ }
+
+ /* Check to see if we were able to allocate memory low enough
+ * in memory.
+ */
+ if (*zimage_addr + zimage_size > dram_base + ZIMAGE_OFFSET_LIMIT) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Failed to relocate kernel, no low memory available.\n");
+ goto fail_free_zimage;
+ }
+ status = handle_cmdline_files(sys_table, image, cmdline_ptr, "initrd=",
+ dram_base + ZIMAGE_OFFSET_LIMIT,
+ &initrd_addr, &initrd_size);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to load initrd.\n");
+ goto fail_free_zimage;
+ }
+
+ /* Estimate size of new FDT, and allocate memory for it. We
+ * will allocate a bigger buffer if this ends up being too
+ * small, so a rough guess is OK here.*/
+ new_fdt_size = fdt_size + cmdline_size + 0x800;
+ while (1) {
+ status = efi_high_alloc(sys_table, new_fdt_size, 0,
+ &new_fdt_addr,
+ dram_base + ZIMAGE_OFFSET_LIMIT);
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to allocate memory for new device tree.\n");
+ goto fail_free_initrd;
+ }
+
+ /* Now that we have done our final memory allocation (and free)
+ * we can get the memory map key needed for
+ * exit_boot_services().
+ */
+ status = efi_get_memory_map(sys_table, &memory_map, &map_size,
+ &desc_size, &desc_ver, &mmap_key);
+ if (status != EFI_SUCCESS)
+ goto fail_free_new_fdt;
+
+ status = update_fdt(sys_table,
+ fdt, (void *)new_fdt_addr, new_fdt_size,
+ cmdline_ptr,
+ initrd_addr, initrd_size,
+ memory_map, map_size, desc_size, desc_ver);
+
+ /* Succeeding the first time is the expected case. */
+ if (status == EFI_SUCCESS)
+ break;
+
+ if (status == EFI_BUFFER_TOO_SMALL) {
+ /* We need to allocate more space for the new
+ * device tree, so free existing buffer that is
+ * too small. Also free memory map, as we will need
+ * to get new one that reflects the free/alloc we do
+ * on the device tree buffer. */
+ efi_free(sys_table, new_fdt_size, new_fdt_addr);
+ efi_call_phys1(sys_table->boottime->free_pool,
+ memory_map);
+ new_fdt_size += new_fdt_size / 4;
+ } else {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to constuct new device tree.\n");
+ goto fail_free_mmap;
+ }
+ }
+
+ /* Now we are ready to exit_boot_services.*/
+ status = efi_call_phys2(sys_table->boottime->exit_boot_services,
+ handle, mmap_key);
+
+ if (status != EFI_SUCCESS) {
+ efi_printk(sys_table, PRINTK_PREFIX"ERROR: Exit boot services failed.\n");
+ goto fail_free_mmap;
+ }
+
+
+ /* Now we need to return the FDT address to the calling
+ * assembly to this can be used as part of normal boot.
+ */
+ return new_fdt_addr;
+
+fail_free_mmap:
+ efi_call_phys1(sys_table->boottime->free_pool, memory_map);
+
+fail_free_new_fdt:
+ efi_free(sys_table, new_fdt_size, new_fdt_addr);
+
+fail_free_initrd:
+ efi_free(sys_table, initrd_size, initrd_addr);
+
+fail_free_zimage:
+ efi_free(sys_table, zimage_size, *zimage_addr);
+
+fail_free_kernel_reserve:
+ efi_free(sys_table, kernel_reserve_size, kernel_reserve_addr);
+
+fail_free_fdt:
+ efi_free(sys_table, fdt_size, fdt_addr);
+
+fail_free_cmdline:
+ efi_free(sys_table, cmdline_size, (u32)cmdline_ptr);
+
+fail:
+ return EFI_STUB_ERROR;
+}
diff --git a/arch/arm/boot/compressed/efi-stub.h b/arch/arm/boot/compressed/efi-stub.h
new file mode 100644
index 0000000..0fe9376
--- /dev/null
+++ b/arch/arm/boot/compressed/efi-stub.h
@@ -0,0 +1,5 @@
+#ifndef _ARM_EFI_STUB_H
+#define _ARM_EFI_STUB_H
+/* Error code returned to ASM code instead of valid FDT address. */
+#define EFI_STUB_ERROR (~0)
+#endif
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 75189f1..aae3c75 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -10,6 +10,7 @@
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
+#include "efi-stub.h"
.arch armv7-a
/*
@@ -120,21 +121,92 @@
*/
.align
.arm @ Always enter in ARM state
+ .text
start:
.type start,#function
- .rept 7
+#ifdef CONFIG_EFI_STUB
+ @ Magic MSDOS signature for PE/COFF + ADD opcode
+ @ the EFI stub only supports little endian, as the EFI functions
+ @ it invokes are little endian.
+ .word 0x62805a4d
+#else
+ mov r0, r0
+#endif
+ .rept 5
mov r0, r0
.endr
- ARM( mov r0, r0 )
- ARM( b 1f )
- THUMB( adr r12, BSYM(1f) )
- THUMB( bx r12 )
+
+ adrl r12, BSYM(zimage_continue)
+ ARM( mov pc, r12 )
+ THUMB( bx r12 )
+ @ zimage_continue will be in ARM or thumb mode as configured
.word 0x016f2818 @ Magic numbers to help the loader
.word start @ absolute load/run zImage address
.word _edata @ zImage end address
+
+#ifdef CONFIG_EFI_STUB
+ @ Portions of the MSDOS file header must be at offset
+ @ 0x3c from the start of the file. All PE/COFF headers
+ @ are kept contiguous for simplicity.
+#include "efi-header.S"
+
+efi_stub_entry:
+ @ The EFI stub entry point is not at a fixed address, however
+ @ this address must be set in the PE/COFF header.
+ @ EFI entry point is in A32 mode, switch to T32 if configured.
+ THUMB( adr r12, BSYM(1f) )
+ THUMB( bx r12 )
THUMB( .thumb )
1:
+ @ Save lr on stack for possible return to EFI firmware.
+ @ Don't care about fp, but need 64 bit alignment....
+ stmfd sp!, {fp, lr}
+
+ @ allocate space on stack for passing current zImage address
+ @ and for the EFI stub to return of new entry point of
+ @ zImage, as EFI stub may copy the kernel. Pointer address
+ @ is passed in r2. r0 and r1 are passed through from the
+ @ EFI firmware to efi_entry
+ adr r3, start
+ str r3, [sp, #-8]!
+ mov r2, sp @ pass pointer in r2
+ bl efi_entry
+ ldr r3, [sp], #8 @ get new zImage address from stack
+
+ @ Check for error return from EFI stub. r0 has FDT address
+ @ or EFI_STUB_ERROR error code.
+ cmp r0, #EFI_STUB_ERROR
+ beq efi_load_fail
+
+ @ Save return values of efi_entry
+ stmfd sp!, {r0, r3}
+ bl cache_clean_flush
+ bl cache_off
+ ldmfd sp!, {r0, r3}
+
+ @ Set parameters for booting zImage according to boot protocol
+ @ put FDT address in r2, it was returned by efi_entry()
+ @ r1 is FDT machine type, and r0 needs to be 0
+ mov r2, r0
+ mov r1, #0xFFFFFFFF
+ mov r0, #0
+
+ @ Branch to (possibly) relocated zImage that is in r3
+ @ Make sure we are in A32 mode, as zImage requires
+ THUMB( bx r3 )
+ ARM( mov pc, r3 )
+
+efi_load_fail:
+ @ Return EFI_LOAD_ERROR to EFI firmware on error.
+ @ Switch back to ARM mode for EFI is done based on
+ @ return address on stack in case we are in THUMB mode
+ ldr r0, =0x80000001
+ ldmfd sp!, {fp, pc} @ put lr from stack into pc
+#endif
+
+ THUMB( .thumb )
+zimage_continue:
mrs r9, cpsr
#ifdef CONFIG_ARM_VIRT_EXT
bl __hyp_stub_install @ get into SVC mode, reversibly
@@ -167,7 +239,6 @@ not_angel:
* by the linker here, but it should preserve r7, r8, and r9.
*/
- .text
#ifdef CONFIG_AUTO_ZRELADDR
@ determine final kernel image address
--
1.7.10.4
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