Re: [PATCH] Add support for zboot images compressed with zstd

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 8 Oct 2025 at 20:17, Daan De Meyer <daan.j.demeyer@gmail.com> wrote:
>
> Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
> ---
>  hw/arm/boot.c       |  2 +-
>  hw/core/loader.c    | 36 ++++++++++++++++++++++++------------
>  hw/nvram/fw_cfg.c   |  2 +-
>  include/hw/loader.h |  2 +-
>  4 files changed, 27 insertions(+), 15 deletions(-)
>
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index e77d8679d8..c0dec0343a 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -826,7 +826,7 @@ static uint64_t load_aarch64_image(const char *filename, hwaddr mem_base,
>      ssize_t size;
>
>      /* On aarch64, it's the bootloader's job to uncompress the kernel. */
> -    size = load_image_gzipped_buffer(filename, LOAD_IMAGE_MAX_GUNZIP_BYTES,
> +    size = load_image_gzipped_buffer(filename, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES,
>                                       &buffer);

I would either not bother renaming this constant, or else do
it in a preliminary patch of its own in the series. (That
makes the part of the patch which is making the functional
change easier to read and review.)

> @@ -882,14 +887,6 @@ ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
>          return 0;
>      }
>
> -    if (strcmp(header->compression_type, "gzip") != 0) {
> -        fprintf(stderr,
> -                "unable to handle EFI zboot image with \"%.*s\" compression\n",
> -                (int)sizeof(header->compression_type) - 1,
> -                header->compression_type);
> -        return -1;
> -    }
> -
>      ploff = ldl_le_p(&header->payload_offset);
>      plsize = ldl_le_p(&header->payload_size);
>
> @@ -898,8 +895,23 @@ ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
>          return -1;
>      }
>
> -    data = g_malloc(LOAD_IMAGE_MAX_GUNZIP_BYTES);
> -    bytes = gunzip(data, LOAD_IMAGE_MAX_GUNZIP_BYTES, *buffer + ploff, plsize);
> +    data = g_malloc(LOAD_IMAGE_MAX_DECOMPRESSED_BYTES);
> +
> +    if (strcmp(header->compression_type, "gzip") == 0) {
> +        bytes = gunzip(data, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, *buffer + ploff, plsize);
> +#ifdef CONFIG_ZSTD
> +    } else if (strcmp(header->compression_type, "zstd") == 0) {
> +        size_t ret = ZSTD_decompress(data, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, *buffer + ploff, plsize);
> +        bytes = ZSTD_isError(ret) ? -1 : (ssize_t) ret;
> +#endif
> +    } else {
> +        fprintf(stderr,
> +                "unable to handle EFI zboot image with \"%.*s\" compression\n",
> +                (int)sizeof(header->compression_type) - 1,
> +                header->compression_type);
> +        return -1;

Moving the "unrecognized compression type" error path down to
here means that we have moved it below the g_malloc() of the
data buffer, so we now need to g_free() to avoid a leak.

> +    }
> +
>      if (bytes < 0) {
>          fprintf(stderr, "failed to decompress EFI zboot image\n");
>          g_free(data);

Otherwise I think this looks OK.

thanks
-- PMM