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

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> 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.

Could we not declare:

      g_autofree uint8_t *data = NULL;

and drop the cleanup?

>
>> +    }
>> +
>>      if (bytes < 0) {
>>          fprintf(stderr, "failed to decompress EFI zboot image\n");
>>          g_free(data);
>
> Otherwise I think this looks OK.
>
> thanks
> -- PMM

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro