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Date: Wed, 10 Oct 2018 10:59:09 +0900
From: AKASHI Takahiro <takahiro.akashi@...aro.org>
To: Mark Rutland <mark.rutland@....com>
Cc: catalin.marinas@....com, will.deacon@....com, dhowells@...hat.com,
vgoyal@...hat.com, herbert@...dor.apana.org.au,
davem@...emloft.net, dyoung@...hat.com, bhe@...hat.com,
arnd@...db.de, schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
prudo@...ux.ibm.com, ard.biesheuvel@...aro.org,
james.morse@....com, bhsharma@...hat.com,
kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v15 07/16] arm64: add image head flag definitions
Mark,
On Tue, Oct 09, 2018 at 04:04:05PM +0100, Mark Rutland wrote:
> On Tue, Oct 02, 2018 at 04:59:40PM +0900, AKASHI Takahiro wrote:
> > Hi Mark,
> >
> > On Mon, Oct 01, 2018 at 01:52:26PM +0100, Mark Rutland wrote:
> > > On Fri, Sep 28, 2018 at 03:48:32PM +0900, AKASHI Takahiro wrote:
> > > > Those image head's flags will be used later by kexec_file loader.
> > > >
> > > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> > > > Cc: Catalin Marinas <catalin.marinas@....com>
> > > > Cc: Will Deacon <will.deacon@....com>
> > > > Acked-by: James Morse <james.morse@....com>
> > > > ---
> > > > arch/arm64/include/asm/boot.h | 15 +++++++++++++++
> > > > arch/arm64/kernel/head.S | 2 +-
> > > > 2 files changed, 16 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/arm64/include/asm/boot.h b/arch/arm64/include/asm/boot.h
> > > > index 355e552a9175..0bab7eed3012 100644
> > > > --- a/arch/arm64/include/asm/boot.h
> > > > +++ b/arch/arm64/include/asm/boot.h
> > > > @@ -5,6 +5,21 @@
> > > >
> > > > #include <asm/sizes.h>
> > > >
> > > > +#define ARM64_MAGIC "ARM\x64"
> > > > +
> > > > +#define HEAD_FLAG_BE_SHIFT 0
> > > > +#define HEAD_FLAG_PAGE_SIZE_SHIFT 1
> > > > +#define HEAD_FLAG_BE_MASK 0x1
> > > > +#define HEAD_FLAG_PAGE_SIZE_MASK 0x3
> > > > +
> > > > +#define HEAD_FLAG_BE 1
> > >
> > > These already exist in some form in arch/arm64/kernel/image.h; can we
> > > please factor those out rather than duplicating them?
> >
> > Sure.
> >
> > > I'd be happy if you'd update image.h to use the new HEAD_FLAG_* names,
> > > and removed the old definitions.
> >
> > I want to make sure two things;
> >
> > 1. Do you assume all the existing __HEAD_FLAG_xyz's NOT be renamed
> > (say, to HEAD_FLAG_xyz)?
>
> I'm perfectly happy for them to be renamed, I just don't want duplicate
> definitions.
IMO, it's not duplication.
HEAD_FLAG_xyz is a definition of a specific field. On the other hand,
__HEAD_FLAG_xyz is a value to be put in a kernel header.
To be clear, please look at my current code attached below.
> Let's rename them to ARM64_IMAGE_FLAG_<foo>, and place them in a new
> header, arch/arm64/include/asm/image.h, which arch/arm64/kernel/image.h
> can include and make use of.
Okay.
> > 2. Do you mind removing this check in image.h?
> > (we also need to manage 'CONFIG_EFI' part of image.h.)
>
> What exactly do we need from that? AFAICT that's all linker script
> stuff that shouldn't matter for kexec.
You're right if all the definitions, as you suggested above,
are moved to a new header, asm/image.h.
-Takahiro Akashi
> Thanks,
> Mark.
arch/arm64/kernel/image.h
---8<---
/*
* Linker script macros to generate Image header fields.
*
* Copyright (C) 2014 ARM Ltd.
*
* 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.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_IMAGE_H
#define __ASM_IMAGE_H
#define HEAD_FLAG_BE_SHIFT 0
#define HEAD_FLAG_PAGE_SIZE_SHIFT (HEAD_FLAG_BE_SHIFT + 1)
#define HEAD_FLAG_PHYS_BASE_SHIFT (HEAD_FLAG_PAGE_SIZE_SHIFT + 2)
#define HEAD_FLAG_BE_MASK 0x1
#define HEAD_FLAG_PAGE_SIZE_MASK 0x3
#define HEAD_FLAG_PHYS_BASE_MASK 0x1
#define HEAD_FLAG_LE 0
#define HEAD_FLAG_BE 1
#define HEAD_FLAG_PAGE_SIZE_4K 1
#define HEAD_FLAG_PAGE_SIZE_16K 2
#define HEAD_FLAG_PAGE_SIZE_64K 3
#define HEAD_FLAG_PHYS_BASE 1
#define head_flag_field(flags, field) \
(((flags) >> field##_SHIFT) & field##_MASK)
#ifdef LINKER_SCRIPT
/*
* There aren't any ELF relocations we can use to endian-swap values known only
* at link time (e.g. the subtraction of two symbol addresses), so we must get
* the linker to endian-swap certain values before emitting them.
*
* Note that, in order for this to work when building the ELF64 PIE executable
* (for KASLR), these values should not be referenced via R_AARCH64_ABS64
* relocations, since these are fixed up at runtime rather than at build time
* when PIE is in effect. So we need to split them up in 32-bit high and low
* words.
*/
#ifdef CONFIG_CPU_BIG_ENDIAN
#define DATA_LE32(data) \
((((data) & 0x000000ff) << 24) | \
(((data) & 0x0000ff00) << 8) | \
(((data) & 0x00ff0000) >> 8) | \
(((data) & 0xff000000) >> 24))
#else
#define DATA_LE32(data) ((data) & 0xffffffff)
#endif
#define DEFINE_IMAGE_LE64(sym, data) \
sym##_lo32 = DATA_LE32((data) & 0xffffffff); \
sym##_hi32 = DATA_LE32((data) >> 32)
#define __HEAD_FLAG(field) (__HEAD_FLAG_##field << \
HEAD_FLAG_##field##_SHIFT)
#ifdef CONFIG_CPU_BIG_ENDIAN
#define __HEAD_FLAG_BE HEAD_FLAG_BE
#else
#define __HEAD_FLAG_BE HEAD_FLAG_LE
#endif
#define __HEAD_FLAG_PAGE_SIZE ((PAGE_SHIFT - 10) / 2)
#define __HEAD_FLAG_PHYS_BASE HEAD_FLAG_PHYS_BASE
#define __HEAD_FLAGS (__HEAD_FLAG(BE) | \
__HEAD_FLAG(PAGE_SIZE) | \
__HEAD_FLAG(PHYS_BASE))
/*
* These will output as part of the Image header, which should be little-endian
* regardless of the endianness of the kernel. While constant values could be
* endian swapped in head.S, all are done here for consistency.
*/
#define HEAD_SYMBOLS \
DEFINE_IMAGE_LE64(_kernel_size_le, _end - _text); \
DEFINE_IMAGE_LE64(_kernel_offset_le, TEXT_OFFSET); \
DEFINE_IMAGE_LE64(_kernel_flags_le, __HEAD_FLAGS);
#ifdef CONFIG_EFI
__efistub_stext_offset = stext - _text;
/*
* Prevent the symbol aliases below from being emitted into the kallsyms
* table, by forcing them to be absolute symbols (which are conveniently
* ignored by scripts/kallsyms) rather than section relative symbols.
* The distinction is only relevant for partial linking, and only for symbols
* that are defined within a section declaration (which is not the case for
* the definitions below) so the resulting values will be identical.
*/
#define KALLSYMS_HIDE(sym) ABSOLUTE(sym)
/*
* The EFI stub has its own symbol namespace prefixed by __efistub_, to
* isolate it from the kernel proper. The following symbols are legally
* accessed by the stub, so provide some aliases to make them accessible.
* Only include data symbols here, or text symbols of functions that are
* guaranteed to be safe when executed at another offset than they were
* linked at. The routines below are all implemented in assembler in a
* position independent manner
*/
__efistub_memcmp = KALLSYMS_HIDE(__pi_memcmp);
__efistub_memchr = KALLSYMS_HIDE(__pi_memchr);
__efistub_memcpy = KALLSYMS_HIDE(__pi_memcpy);
__efistub_memmove = KALLSYMS_HIDE(__pi_memmove);
__efistub_memset = KALLSYMS_HIDE(__pi_memset);
__efistub_strlen = KALLSYMS_HIDE(__pi_strlen);
__efistub_strnlen = KALLSYMS_HIDE(__pi_strnlen);
__efistub_strcmp = KALLSYMS_HIDE(__pi_strcmp);
__efistub_strncmp = KALLSYMS_HIDE(__pi_strncmp);
__efistub_strrchr = KALLSYMS_HIDE(__pi_strrchr);
__efistub___flush_dcache_area = KALLSYMS_HIDE(__pi___flush_dcache_area);
#ifdef CONFIG_KASAN
__efistub___memcpy = KALLSYMS_HIDE(__pi_memcpy);
__efistub___memmove = KALLSYMS_HIDE(__pi_memmove);
__efistub___memset = KALLSYMS_HIDE(__pi_memset);
#endif
__efistub__text = KALLSYMS_HIDE(_text);
__efistub__end = KALLSYMS_HIDE(_end);
__efistub__edata = KALLSYMS_HIDE(_edata);
__efistub_screen_info = KALLSYMS_HIDE(screen_info);
#endif /* CONFIG_EFI */
#endif /* LINKER_SCRIPT */
#endif /* __ASM_IMAGE_H */
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