[PATCH v3 0/3] Add support for zboot images compressed with zstd

[PATCH v3 0/3] Add support for zboot images compressed with zstd

[Daan De Meyer]

Fedora arm64 has an EFI_ZBOOT kernel image compressed
with zstd. Let's make sure we can use it for direct kernel
boot with qemu.

Daan De Meyer (3):
  Rename LOAD_IMAGE_MAX_GUNZIP_BYTES to
    LOAD_IMAGE_MAX_DECOMPRESSED_BYTES
  Use g_autofree in unpack_efi_zboot_image()
  Add support for zboot images compressed with zstd

 hw/arm/boot.c       |  2 +-
 hw/core/loader.c    | 41 ++++++++++++++++++++++++++---------------
 hw/nvram/fw_cfg.c   |  2 +-
 include/hw/loader.h |  2 +-
 4 files changed, 29 insertions(+), 18 deletions(-)

-- 
2.51.0

[PATCH v3 1/3] Rename LOAD_IMAGE_MAX_GUNZIP_BYTES to LOAD_IMAGE_MAX_DECOMPRESSED_BYTES

[Daan De Meyer]

Preparation for adding support for zstd compressed efi zboot kernel
images.

Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
---
 hw/arm/boot.c       | 2 +-
 hw/core/loader.c    | 8 ++++----
 hw/nvram/fw_cfg.c   | 2 +-
 include/hw/loader.h | 2 +-
 4 files changed, 7 insertions(+), 7 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);
 
     if (size < 0) {
diff --git a/hw/core/loader.c b/hw/core/loader.c
index 477661a025..42edcf2d98 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -796,8 +796,8 @@ ssize_t load_image_gzipped_buffer(const char *filename, uint64_t max_sz,
         goto out;
     }
 
-    if (max_sz > LOAD_IMAGE_MAX_GUNZIP_BYTES) {
-        max_sz = LOAD_IMAGE_MAX_GUNZIP_BYTES;
+    if (max_sz > LOAD_IMAGE_MAX_DECOMPRESSED_BYTES) {
+        max_sz = LOAD_IMAGE_MAX_DECOMPRESSED_BYTES;
     }
 
     data = g_malloc(max_sz);
@@ -898,8 +898,8 @@ 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);
+    bytes = gunzip(data, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, *buffer + ploff, plsize);
     if (bytes < 0) {
         fprintf(stderr, "failed to decompress EFI zboot image\n");
         g_free(data);
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index aa24050493..af3b112524 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1115,7 +1115,7 @@ void load_image_to_fw_cfg(FWCfgState *fw_cfg, uint16_t size_key,
 
     if (try_decompress) {
         size = load_image_gzipped_buffer(image_name,
-                                         LOAD_IMAGE_MAX_GUNZIP_BYTES, &data);
+                                         LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, &data);
     }
 
     if (size == (size_t)-1) {
diff --git a/include/hw/loader.h b/include/hw/loader.h
index c96b5e141c..24b91ba02b 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -80,7 +80,7 @@ ssize_t load_image_mr(const char *filename, MemoryRegion *mr);
  * load_image_gzipped_buffer() will read. It prevents
  * g_malloc() in those functions from allocating a huge amount of memory.
  */
-#define LOAD_IMAGE_MAX_GUNZIP_BYTES (256 << 20)
+#define LOAD_IMAGE_MAX_DECOMPRESSED_BYTES (256 << 20)
 
 ssize_t load_image_gzipped_buffer(const char *filename, uint64_t max_sz,
                                   uint8_t **buffer);
-- 
2.51.0

Re: [PATCH v3 1/3] Rename LOAD_IMAGE_MAX_GUNZIP_BYTES to LOAD_IMAGE_MAX_DECOMPRESSED_BYTES

[Daniel P. Berrangé]

On Sat, Oct 11, 2025 at 10:15:51AM +0200, Daan De Meyer wrote:
> Preparation for adding support for zstd compressed efi zboot kernel
> images.
> 
> Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
> ---
>  hw/arm/boot.c       | 2 +-
>  hw/core/loader.c    | 8 ++++----
>  hw/nvram/fw_cfg.c   | 2 +-
>  include/hw/loader.h | 2 +-
>  4 files changed, 7 insertions(+), 7 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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[PATCH v3 2/3] Use g_autofree in unpack_efi_zboot_image()

[Daan De Meyer]

Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
---
 hw/core/loader.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 42edcf2d98..a511888aa3 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -864,7 +864,7 @@ struct linux_efi_zboot_header {
 ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
 {
     const struct linux_efi_zboot_header *header;
-    uint8_t *data = NULL;
+    g_autofree uint8_t *data = NULL;
     ssize_t ploff, plsize;
     ssize_t bytes;
 
@@ -902,12 +902,11 @@ ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
     bytes = gunzip(data, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, *buffer + ploff, plsize);
     if (bytes < 0) {
         fprintf(stderr, "failed to decompress EFI zboot image\n");
-        g_free(data);
         return -1;
     }
 
     g_free(*buffer);
-    *buffer = g_realloc(data, bytes);
+    *buffer = g_realloc(g_steal_pointer(&data), bytes);
     *size = bytes;
     return bytes;
 }
-- 
2.51.0

Re: [PATCH v3 2/3] Use g_autofree in unpack_efi_zboot_image()

[Daniel P. Berrangé]

On Sat, Oct 11, 2025 at 10:15:52AM +0200, Daan De Meyer wrote:
> Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
> ---
>  hw/core/loader.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
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[PATCH v3 3/3] Add support for zboot images compressed with zstd

[Daan De Meyer]

Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
---
 hw/core/loader.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index a511888aa3..c1611cc960 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -67,6 +67,11 @@
 
 #include <zlib.h>
 
+#ifdef CONFIG_ZSTD
+#include <zstd.h>
+#include <zstd_errors.h>
+#endif
+
 static int roms_loaded;
 
 /* return the size or -1 if error */
@@ -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);
 
@@ -899,7 +896,22 @@ ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
     }
 
     data = g_malloc(LOAD_IMAGE_MAX_DECOMPRESSED_BYTES);
-    bytes = gunzip(data, LOAD_IMAGE_MAX_DECOMPRESSED_BYTES, *buffer + ploff, plsize);
+
+    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;
+    }
+
     if (bytes < 0) {
         fprintf(stderr, "failed to decompress EFI zboot image\n");
         return -1;
-- 
2.51.0

Re: [PATCH v3 3/3] Add support for zboot images compressed with zstd

[Daniel P. Berrangé]

On Sat, Oct 11, 2025 at 10:15:53AM +0200, Daan De Meyer wrote:
> Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
> ---
>  hw/core/loader.c | 30 +++++++++++++++++++++---------
>  1 file changed, 21 insertions(+), 9 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
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