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Message-ID: <CAMj1kXENi6rGK5tuU5ny5gAXMGLErx3o8ci3stazq0HJO5QArg@mail.gmail.com>
Date: Fri, 7 Oct 2022 09:20:46 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Cc: Atish Patra <atishp@...osinc.com>,
Daniel Kiper <daniel.kiper@...cle.com>,
Fu Wei <tekkamanninja@...il.com>,
Leif Lindholm <quic_llindhol@...cinc.com>,
Nikita Ermakov <arei@...linux.org>,
Atish Patra <atishp@...shpatra.org>,
Julian Andres Klode <julian.klode@...onical.com>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [v4 PATCH 2/3] RISC-V: Update image header
On Fri, 7 Oct 2022 at 01:51, Heinrich Schuchardt
<heinrich.schuchardt@...onical.com> wrote:
>
>
>
> On 10/7/22 01:00, Atish Patra wrote:
> > Update the RISC-V Linux kernel image headers as per the current header.
> >
> > Reference:
> > <Linux kernel source>/Documentation/riscv/boot-image-header.rst
> >
> > 474efecb65dc: ("riscv: modify the Image header to improve compatibility with the ARM64 header")
> >
> > Signed-off-by: Atish Patra <atishp@...osinc.com>
> > ---
> > include/grub/riscv32/linux.h | 15 ++++++++-------
> > include/grub/riscv64/linux.h | 21 +++++++++++++--------
> > 2 files changed, 21 insertions(+), 15 deletions(-)
> >
> > diff --git a/include/grub/riscv32/linux.h b/include/grub/riscv32/linux.h
> > index 512b777c8a41..de0dbdcd1be5 100644
> > --- a/include/grub/riscv32/linux.h
> > +++ b/include/grub/riscv32/linux.h
> > @@ -19,20 +19,21 @@
> > #ifndef GRUB_RISCV32_LINUX_HEADER
> > #define GRUB_RISCV32_LINUX_HEADER 1
> >
> > -#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x52534356 /* 'RSCV' */
> > +#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x05435352 /* 'RSC\0x5' */
>
> Thanks for following up on this series.
>
> Considering 69edb312056 ("loader/arm64/linux: Remove magic number header
> field check") why should this constant exist in GRUB at all?
>
> In a follow up patch we could remove it together with
> GRUB_LINUX_ARM_MAGIC_SIGNATURE, GRUB_LINUX_ARMXX_MAGIC_SIGNATURE, and
> GRUB_LINUX_ARMXX_MAGIC_SIGNATURE.
>
Indeed.
But by the same reasoning, why do we need per-arch kernel header
typedefs at all? The only fields we access are generic PE/COFF header
fields.
> >
> > -/* From linux/Documentation/riscv/booting.txt */
> > +/* From linux/Documentation/riscv/boot-image-header.rst */
> > struct linux_riscv_kernel_header
> > {
> > grub_uint32_t code0; /* Executable code */
> > grub_uint32_t code1; /* Executable code */
> > - grub_uint64_t text_offset; /* Image load offset */
> > - grub_uint64_t res0; /* reserved */
> > - grub_uint64_t res1; /* reserved */
> > + grub_uint64_t text_offset; /* Image load offset, little endian */
> > + grub_uint64_t image_size; /* Effective Image size, little endian */
> > + grub_uint64_t flags; /* kernel flags, little endian */
> > + grub_uint32_t version; /* Version of this header */
> > + grub_uint32_t res1; /* reserved */
> > grub_uint64_t res2; /* reserved */
> > grub_uint64_t res3; /* reserved */
>
> According to tag next-20221006 of
> Documentation/riscv/boot-image-header.rst and of
> arch/riscv/include/asm/image.h this field is called 'magic' and filled
> it with the string 'RISCV\0\0\0'.
>
> > - grub_uint64_t res4; /* reserved */
> > - grub_uint32_t magic; /* Magic number, little endian, "RSCV" */
> > + grub_uint32_t magic; /* Magic number, little endian, "RSC\x05" */
>
> The Linux kernel documentation calls this field magic2.
>
> Of course this is functionally irrelevant as we don't care about the
> content of both fields.
>
> > grub_uint32_t hdr_offset; /* Offset of PE/COFF header */
> > };
> >
> > diff --git a/include/grub/riscv64/linux.h b/include/grub/riscv64/linux.h
> > index 3630c30fbf1a..ea77f8718222 100644
> > --- a/include/grub/riscv64/linux.h
> > +++ b/include/grub/riscv64/linux.h
> > @@ -19,23 +19,28 @@
> > #ifndef GRUB_RISCV64_LINUX_HEADER
> > #define GRUB_RISCV64_LINUX_HEADER 1
> >
> > -#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x52534356 /* 'RSCV' */
> > +#include <grub/efi/pe32.h>
> > +
> > +#define GRUB_LINUX_RISCV_MAGIC_SIGNATURE 0x05435352 /* 'RSC\0x5' */
>
> to be removed in future
>
> Best regards
>
> Heinrich
>
> >
> > #define GRUB_EFI_PE_MAGIC 0x5A4D
> >
> > -/* From linux/Documentation/riscv/booting.txt */
> > +/* From linux/Documentation/riscv/boot-image-header.rst */
> > struct linux_riscv_kernel_header
> > {
> > grub_uint32_t code0; /* Executable code */
> > grub_uint32_t code1; /* Executable code */
> > - grub_uint64_t text_offset; /* Image load offset */
> > - grub_uint64_t res0; /* reserved */
> > - grub_uint64_t res1; /* reserved */
> > + grub_uint64_t text_offset; /* Image load offset, little endian */
> > + grub_uint64_t image_size; /* Effective Image size, little endian */
> > + grub_uint64_t flags; /* kernel flags, little endian */
> > + grub_uint32_t version; /* Version of this header */
> > + grub_uint32_t res1; /* reserved */
> > grub_uint64_t res2; /* reserved */
> > - grub_uint64_t res3; /* reserved */
> > - grub_uint64_t res4; /* reserved */
> > - grub_uint32_t magic; /* Magic number, little endian, "RSCV" */
> > + grub_uint64_t magic; /* magic (RISC-V specifc, deprecated)*/
> > + grub_uint32_t magic2; /* Magic number 2 (to match the ARM64 'magic' field pos) */
> > grub_uint32_t hdr_offset; /* Offset of PE/COFF header */
> > +
> > + struct grub_coff_image_header coff_image_header;
> > };
> >
> > #define linux_arch_kernel_header linux_riscv_kernel_header
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