[Qemu-devel] [PATCH v5 1/2] loader: Add load_image_gzipped function.

["Richard W.M. Jones" <rjones@redhat.com>]

As the name suggests this lets you load a ROM/disk image that is
gzipped.  It is uncompressed before storing it in guest memory.

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 hw/core/loader.c    | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/hw/loader.h |  1 +
 2 files changed, 49 insertions(+)

diff --git a/hw/core/loader.c b/hw/core/loader.c
index 2bf6b8f..e773aab 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -577,6 +577,54 @@ int load_ramdisk(const char *filename, hwaddr addr, uint64_t max_sz)
     return load_uboot_image(filename, NULL, &addr, NULL, IH_TYPE_RAMDISK);
 }
 
+/* This simply prevents g_malloc in the function below from allocating
+ * a huge amount of memory, by placing a limit on the maximum
+ * uncompressed image size that load_image_gzipped will read.
+ */
+#define LOAD_IMAGE_MAX_GUNZIP_BYTES (256 << 20)
+
+/* Load a gzip-compressed kernel. */
+int load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz)
+{
+    uint8_t *compressed_data = NULL;
+    uint8_t *data = NULL;
+    gsize len;
+    ssize_t bytes;
+    int ret = -1;
+
+    if (!g_file_get_contents(filename, (char **) &compressed_data, &len,
+                             NULL)) {
+        goto out;
+    }
+
+    /* Is it a gzip-compressed file? */
+    if (len < 2 ||
+        compressed_data[0] != '\x1f' ||
+        compressed_data[1] != '\x8b') {
+        goto out;
+    }
+
+    if (max_sz > LOAD_IMAGE_MAX_GUNZIP_BYTES) {
+        max_sz = LOAD_IMAGE_MAX_GUNZIP_BYTES;
+    }
+
+    data = g_malloc(max_sz);
+    bytes = gunzip(data, max_sz, compressed_data, len);
+    if (bytes < 0) {
+        fprintf(stderr, "%s: unable to decompress gzipped kernel file\n",
+                filename);
+        goto out;
+    }
+
+    rom_add_blob_fixed(filename, data, bytes, addr);
+    ret = bytes;
+
+ out:
+    g_free(compressed_data);
+    g_free(data);
+    return ret;
+}
+
 /*
  * Functions for reboot-persistent memory regions.
  *  - used for vga bios and option roms.
diff --git a/include/hw/loader.h b/include/hw/loader.h
index 796cbf9..00c9117 100644
--- a/include/hw/loader.h
+++ b/include/hw/loader.h
@@ -15,6 +15,7 @@ int get_image_size(const char *filename);
 int load_image(const char *filename, uint8_t *addr); /* deprecated */
 int load_image_targphys(const char *filename, hwaddr,
                         uint64_t max_sz);
+int load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz);
 
 #define ELF_LOAD_FAILED       -1
 #define ELF_LOAD_NOT_ELF      -2
-- 
2.0.4