[Qemu-devel] [PATCH v3] aarch64: Allow -kernel option to take a gzip-compressed kernel.

[Richard W.M. Jones]

On aarch64 it is the bootloader's job to uncompress the kernel.  UEFI
and u-boot bootloaders do this automatically when the kernel is
gzip-compressed.

However the qemu -kernel option does not do this.  The following
command does not work:

  qemu-system-aarch64 [...] -kernel /boot/vmlinuz

because it tries to execute the gzip-compressed data.

This commit lets gzip-compressed kernels be uncompressed
transparently.

Currently this is only done when emulating aarch64.

Signed-off-by: Richard W.M. Jones <address@hidden>
---
 hw/arm/boot.c       |  9 +++++++++
 hw/core/loader.c    | 43 +++++++++++++++++++++++++++++++++++++++++++
 include/hw/loader.h |  1 +
 3 files changed, 53 insertions(+)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 3d1f4a2..1d541db 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -444,6 +444,7 @@ static void do_cpu_reset(void *opaque)
 void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
 {
     CPUState *cs = CPU(cpu);
+    int allow_compressed_kernels = 0;
     int kernel_size;
     int initrd_size;
     int is_linux = 0;
@@ -465,6 +466,7 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
*info)
         primary_loader = bootloader_aarch64;
         kernel_load_offset = KERNEL64_LOAD_ADDR;
         elf_machine = EM_AARCH64;
+        allow_compressed_kernels = 1;
     } else {
         primary_loader = bootloader;
         kernel_load_offset = KERNEL_LOAD_ADDR;
@@ -510,6 +512,13 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info 
*info)
         kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
                                   &is_linux);
     }
+    /* On aarch64, it's the bootloader's job to uncompress the kernel. */
+    if (allow_compressed_kernels && kernel_size < 0) {
+        entry = info->loader_start + kernel_load_offset;
+        kernel_size = load_image_gzipped(info->kernel_filename, entry,
+                                         info->ram_size - kernel_load_offset);
+        is_linux = 1;
+    }
     if (kernel_size < 0) {
         entry = info->loader_start + kernel_load_offset;
         kernel_size = load_image_targphys(info->kernel_filename, entry,
diff --git a/hw/core/loader.c b/hw/core/loader.c
index 2bf6b8f..1cbe733 100644
--- a/hw/core/loader.c
+++ b/hw/core/loader.c
@@ -577,6 +577,49 @@ int load_ramdisk(const char *filename, hwaddr addr, 
uint64_t max_sz)
     return load_uboot_image(filename, NULL, &addr, NULL, IH_TYPE_RAMDISK);
 }
 
+/* Load a gzip-compressed kernel (currently used by aarch64). */
+int load_image_gzipped(const char *filename, hwaddr addr, uint64_t max_sz)
+{
+    uint8_t *compressed_data = NULL;
+    uint8_t *data = NULL;
+    gsize len;
+    size_t max_bytes;
+    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;
+    }
+
+    max_bytes = UBOOT_MAX_GUNZIP_BYTES;
+    if (max_bytes > max_sz) {
+        max_bytes = max_sz;
+    }
+    data = g_malloc(max_bytes);
+    bytes = gunzip(data, max_bytes, 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
-- 
2.0.1