hw/loader: Add support for zboot images compressed with zstd

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com>
Message-ID: <20251124123521.1058183-5-daan.j.demeyer@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

hw/core/loader.c

@@ -68,6 +68,11 @@
 
 #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 */
@@ -916,14 +921,6 @@ 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);
 
@@ -933,7 +930,22 @@ ssize_t unpack_efi_zboot_image(uint8_t **buffer, ssize_t *size)
     }
 
     data = g_malloc(max_bytes);
-    bytes = gunzip(data, max_bytes, *buffer + ploff, plsize);
+
+    if (strcmp(header->compression_type, "gzip") == 0) {
+        bytes = gunzip(data, max_bytes, *buffer + ploff, plsize);
+#ifdef CONFIG_ZSTD
+    } else if (strcmp(header->compression_type, "zstd") == 0) {
+        size_t ret = ZSTD_decompress(data, max_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;