Re: [PATCH] hw/loongarch/boot: Support Linux raw boot image

[bibo mao]

On 2024/12/23 上午8:30, Jiaxun Yang wrote:
> Many distros are shipping raw kernel images (i.e. vmlinux.efi).
>
> Support booting such image by parsing header as per Linux's
> specification [1].
>
> [1]: https://docs.kernel.org/arch/loongarch/booting.html
>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
> It is based on my previous booting protocol patch
> ---
>   hw/loongarch/boot.c         | 45 +++++++++++++++++++++++++++++++++++++++++++++
>   include/hw/loongarch/boot.h | 17 +++++++++++++++++
>   2 files changed, 62 insertions(+)
>
> diff --git a/hw/loongarch/boot.c b/hw/loongarch/boot.c
> index 
> 93847b0eaf8e50ce1a990b91267780e6785e1c2f..5bc889c51fafa9c6d37426b9bee9709c12183927
>  100644
> --- a/hw/loongarch/boot.c
> +++ b/hw/loongarch/boot.c
> @@ -260,6 +260,43 @@ static uint64_t cpu_loongarch_virt_to_phys(void *opaque, 
> uint64_t addr)
>       return addr & MAKE_64BIT_MASK(0, TARGET_PHYS_ADDR_SPACE_BITS);
>   }
>   
> +static int64_t get_linux_image_info(struct loongarch_boot_info *info,
> +                                    uint64_t *kernel_entry,
> +                                    uint64_t *kernel_low,
> +                                    uint64_t *kernel_high)
> +{
> +    int fd;
> +    struct loongarch_linux_hdr hdr;
> +    int64_t kernel_size = -1;
> +
> +    fd = open(info->kernel_filename, O_RDONLY | O_BINARY);
> +    if (fd < 0) {
> +        return -1;
> +    }
> +
> +    if (read(fd, &hdr, sizeof(hdr)) != sizeof(hdr)) {
> +        close(fd);
> +        return -1;
> +    }
> +
> +    if ((le32_to_cpu(hdr.mz_magic) & 0xffff) != MZ_MAGIC ||
> +        le32_to_cpu(hdr.linux_pe_magic) != LINUX_PE_MAGIC) {
> +        close(fd);
> +        return -1;
> +    }
> +
> +    *kernel_entry = le64_to_cpu(hdr.kernel_entry);
> +    /* Early kernel versions may have those fields in virtual address */
> +    *kernel_entry &= MAKE_64BIT_MASK(0, TARGET_PHYS_ADDR_SPACE_BITS);
> +    *kernel_low = le64_to_cpu(hdr.load_offset);
> +    *kernel_low &= MAKE_64BIT_MASK(0, TARGET_PHYS_ADDR_SPACE_BITS);
> +    kernel_size = le64_to_cpu(hdr.kernel_size);
> +    *kernel_high = *kernel_low + kernel_size;
> +
> +    close(fd);
> +    return kernel_size;
> +}
> +
>   static int64_t load_kernel_info(struct loongarch_boot_info *info)
>   {
>       uint64_t kernel_entry, kernel_low, kernel_high;
> @@ -270,6 +307,14 @@ static int64_t load_kernel_info(struct loongarch_boot_info 
> *info)
>                              &kernel_entry, &kernel_low,
>                              &kernel_high, NULL, 0,
>                              EM_LOONGARCH, 1, 0);
> +    if (kernel_size < 0) {
> +        kernel_size = get_linux_image_info(info, &kernel_entry,
> +                                           &kernel_low, &kernel_high);
> +        if (kernel_size >= 0) {
> +            kernel_size = load_image_targphys(info->kernel_filename,
> +                                              kernel_low, kernel_size);
> +        }
Can we read file header file firstly?
If it is ELFMAG, load_elf is called.

If it is EFI_PE_MSDOS_MAGIC, check zimg magic in linux_efi_zboot_header, 
else loongarch_linux_hdr for plain image if zimg does not match.

Regards
Bibo Mao

> +    }
>   
>       if (kernel_size < 0) {
>           error_report("could not load kernel '%s': %s",
> diff --git a/include/hw/loongarch/boot.h b/include/hw/loongarch/boot.h
> index 
> 96ec15016a314499acf65c6c47e0c4932aa99d01..5e8bd4dd73bbb27abccfa1fa577df52aed15b6a2
>  100644
> --- a/include/hw/loongarch/boot.h
> +++ b/include/hw/loongarch/boot.h
> @@ -8,6 +8,23 @@
>   #ifndef HW_LOONGARCH_BOOT_H
>   #define HW_LOONGARCH_BOOT_H
>   
> +/* Linux Image Format */
> +#define LINUX_PE_MAGIC  0x818223cd
> +#define MZ_MAGIC        0x5a4d /* "MZ" */
> +
> +struct loongarch_linux_hdr {
> +    uint32_t mz_magic;
> +    uint32_t res0;
> +    uint64_t kernel_entry;
> +    uint64_t kernel_size;
> +    uint64_t load_offset;
> +    uint64_t res1;
> +    uint64_t res2;
> +    uint64_t res3;
> +    uint32_t linux_pe_magic;
> +    uint32_t pe_header_offset;
> +} QEMU_PACKED;
> +
>   /* UEFI 2.10 */
>   #define EFI_SYSTEM_TABLE_SIGNATURE       0x5453595320494249
>   #define EFI_2_100_SYSTEM_TABLE_REVISION  ((2<<16) | (100))
>
> ---
> base-commit: c69612063e1844b76ac01e3a781b979548c3585c
> change-id: 20241222-la-direct-kernel-boot-c598264710e7
>
> Best regards,