linux-kernel - Re: [v4 PATCH 2/3] RISC-V: Update image header

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Message-ID: <CAOnJCULKVMMMtxdWgeLb=3Au+yXUmoD9eK8Lowin8WdDGvhiew@mail.gmail.com>
Date:   Fri, 7 Oct 2022 00:54:02 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        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>,
        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, Oct 7, 2022 at 12:50 AM Heinrich Schuchardt
<heinrich.schuchardt@...onical.com> wrote:
>
>
>
> On 10/7/22 09:20, Ard Biesheuvel wrote:
> > 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?
> >>

Yes. Those are not required. I will remove those.

> >> 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.
> >>
> >
GRUB_LINUX_ARM_MAGIC_SIGNATURE is still being used in ARM32 loaders.
The other one can be removed.

> > 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.
>
> That said I would suggest to put the series in without any further
> iterations and clean up afterwards.
>
> Acked-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
>
> >
> >>>
> >>> -/* 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.
> >>

Yes. I forgot to update this one for rv32. RV64 header file has the
correct fields.

> >> 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' */
> >>

Done.

> >> 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



-- 
Regards,
Atish