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Date: Tue, 13 Aug 2013 19:07:57 -0700
From: Roy Franz <roy.franz@...aro.org>
To: Dave Martin <Dave.Martin@....com>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, matt.fleming@...el.com,
Russell King - ARM Linux <linux@....linux.org.uk>,
Leif Lindholm <leif.lindholm@...aro.org>,
Mark Salter <msalter@...hat.com>
Subject: Re: [PATCH 15/16] Add EFI stub for ARM
On Tue, Aug 13, 2013 at 6:44 PM, Roy Franz <roy.franz@...aro.org> wrote:
>
> Thanks Dave - comments inline, and I have an updated head.S diff at the end.
>
> Roy
>
>
> On Tue, Aug 13, 2013 at 7:19 AM, Dave Martin <Dave.Martin@....com> wrote:
>>
>> On Fri, Aug 09, 2013 at 04:26:16PM -0700, Roy Franz wrote:
>> > This patch adds EFI stub support for the ARM Linux kernel. The EFI stub
>> > operations 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, including adding reserved
>> > memory regions and 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.
>>
>> Thanks for the update -- a few more comments, nothing major.
>>
>> > Signed-off-by: Roy Franz <roy.franz@...aro.org>
>> > ---
>> > arch/arm/boot/compressed/Makefile | 15 +-
>> > arch/arm/boot/compressed/efi-header.S | 111 ++++++++
>
> ...
>>
>>
>> > + goto fdt_set_fail;
>> > +
>> > + return EFI_SUCCESS;
>>
>> This looks better.
>>
>> > +
>> > +fdt_set_fail:
>> > + if (status == -FDT_ERR_NOSPACE)
>> > + return EFI_BUFFER_TOO_SMALL;
>> > +
>> > + return EFI_LOAD_ERROR;
>> > +}
>> > +
>> > +
>> > +
>>
>> Maybe add a comment to indicate that this returns the address of the
>> relocated fdt, or EFI_LOAD_ERROR.
>>
>> By default "int" feels more likely to return a status code.
>>
>> It is not common to return pointers using the "int" type: it may be
>> preferable to use unsigned long of void * instead. This won't
>> change the functionality.
>>
>> Casts to (int) which could overflow the signed range can cause GCC
>> to generate bizarre code in some situations, because C doesn't
>> have to guarantee wrapping when casting to signed types. Since we
>> just pass that value through without doing any arithmetic I think we're
>> unlikely to hit that here, but it's best avoided anyhow.
>
>
> The function now returns only status, not the FDT address, so I have changed
> it to an int.
> When I changed the function to no longer do the memory allocation for the
> new FDT this changed,
> but I missed changing the return type to int.
>
>
>>
>>
>> > +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*/
>> > + u64 initrd_addr;
>> > + u64 initrd_size = 0;
>> > + u64 fdt_addr;
>> > + u64 fdt_size = 0;
>> > + u64 kernel_reserve_addr;
>> > + u64 kernel_reserve_size = 0;
>> > + char *cmdline_ptr;
>> > + unsigned long cmdline_size = 0;
>> > +
>> > + unsigned long map_size, desc_size;
>> > + 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 this into device tree, so we don't care
>> > where in
>> > + * memory it is.
>> > + */
>> > + cmdline_ptr = convert_cmdline_to_ascii(sys_table, image,
>> > + &cmdline_size, 0xFFFFFFFF);
>> > + if (!cmdline_ptr) {
>> > + efi_printk(sys_table, PRINTK_PREFIX"ERROR: converting
>> > command line to ascii failed.\n");
>>
>> The real reason for this failure is failure to allocate memory: there's
>> no other way it can fail.
>>
>> So, the error message could be "Unable to allocate memory for command
>> line"
>
>
> done.
>>
>>
>> > + 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 *)(unsigned long)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 *)(unsigned long)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 *)(u32)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 {
>> > + 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. */
>> > + 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. */
>> > + zimage_size = image->image_size;
>> > + status = relocate_kernel(sys_table, zimage_addr, zimage_size,
>> > + dram_base + MIN_ZIMAGE_OFFSET,
>> > + dram_base + ZIMAGE_OFFSET_LIMIT);
>> > + if (status != EFI_SUCCESS) {
>> > + efi_printk(sys_table, PRINTK_PREFIX"ERROR: Failed to
>> > relocate kernel\n");
>> > + goto fail_free_kernel_reserve;
>> > + }
>> > +
>> > + 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 + 0x200;
>> > +
>> > +fdt_alloc_retry:
>>
>> Minor stylistic thing, but looping using goto is not too readable.
>>
>> The following while loop might be a bit clearer, but I leave it
>> up to you.
>>
>> 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
>> > + * forexit_boot_services.*/
>> > + status = efi_get_memory_map(sys_table, &memory_map, &map_size,
>> > + &desc_size, &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);
>>
>> if (status == EFI_SUCCESS)
>> break;
>>
>> instead of
>>
>> > +
>> > + if (status != EFI_SUCCESS) {
>>
>> then
>>
>> if (status != EFI_BUFFER_TOO_SMALL)
>> > + efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to
>> > constuct new device tree.\n");
>> > + goto fail_free_initrd;
>>
>> instead of
>>
>> > + if (status == EFI_BUFFER_TOO_SMALL) {
>>
>> then
>>
>> > + /* 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;
>>
>> And then just loop
>> }
>>
>> instead of the rest:
>>
> I have replaced the allocation retry with a while loop as suggested.
>
>> > + goto fdt_alloc_retry;
>> > + }
>> > + efi_printk(sys_table, PRINTK_PREFIX"ERROR: Unable to
>> > constuct new device tree.\n");
>> > + goto fail_free_initrd;
>> > + }
>> > +
>> > + /* 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_addr, kernel_reserve_size);
>> > +
>> > +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..5401a3a 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 +121,99 @@
>> > */
>> > .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
>> > + .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 return of new entry point of
>> > + @ zImage, as EFI stub may copy the kernel. Pass address
>> > + @ of space in r2 - EFI stub will fill in the pointer.
>> > +
>> > + sub sp, sp, #8 @ we only need 4 bytes,
>> > + @ but keep stack 8 byte
>> > aligned.
>> > + mov r2, sp
>>
>> You can save an instruction here: skip these two instructions, and see
>> below just before the call to efi_entry [1]
>>
>> > + @ Pass our actual runtime start address in pointer data
>> > + adr r11, LC0 @ address of LC0 at run
>> > time
>> > + ldr r12, [r11, #0] @ address of LC0 at link
>> > time
>>
>> Can we just move this delta calculation after efi_entry?
>>
>> You don't need to specifiy an explicit offset if it's zero, btw:
>>
>> ldr r12, [r11]
>>
>> works just as well. Same for the other instances.
>
>
> So after looking at this it was pretty messed up. The LC0 business was to
> compute the
> linktime/runtime offset, which I had used to lookup the uncompressed kernel
> size.
> That ended up not being useful, but this code stayed around. I've reworked
> this
> section of code to remove that cruft and incorporate your suggestions.
>
> I've put an updated diff of just head.S at the end of the email.
>
>>
>> > +
>> > + sub r3, r11, r12 @ calculate the delta
>> > offset
>> > + str r3, [r2, #0]
>>
>> I think r2 is still equal to sp, so
>>
>> str r3, [sp]
>>
>> should be OK.
>>
>> [1]Or, combine this with the modification of sp:
>>
>> str r3, [sp, #-8]!
>> mov r2, sp
>>
>> > + bl efi_entry
>> > +
>> > + @ get new zImage entry address from stack, put into r3
>> > + ldr r3, [sp, #0]
>> > + add sp, sp, #8 @ restore stack
>>
>> ldr r3, [sp], #8
>>
>> > +
>> > + @ Check for error return from EFI stub
>> > + mov r1, #EFI_STUB_ERROR
>> > + cmp r0, r1
>>
>> cmp r0, #EFI_STUB_ERROR
>>
>> probably works. The assembler will turn this into a cmn as necessary.
>>
>> > + 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
>> > + ldr r0, =0x80000001
>> > + ldmfd sp!, {fp, 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 +246,6 @@ 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
>> >
>> >
>> > _______________________________________________
>> > linux-arm-kernel mailing list
>> > linux-arm-kernel@...ts.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
>
> diff --git a/arch/arm/boot/compressed/head.S
> b/arch/arm/boot/compressed/head.S
> index 75189f1..820a238 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]!
above line should be:
str r3, [sp, #-8]!
that - sign is really hard to see in gmail :)
> + 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
>
--
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