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

[Ard Biesheuvel]

On Fri, 7 Oct 2022 at 01:51, Heinrich Schuchardt
<heinrich.schuchardt@xxxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> > ---
> >   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