kexec/arm64: Add support for handling zlib compressed (Image.gz) image

Currently the kexec_file_load() support for arm64 doesn't allow
handling zlib compressed (i.e. Image.gz) image.

Since most distributions use 'make zinstall' rule inside
'arch/arm64/boot/Makefile' to install the arm64
Image.gz compressed file inside the boot destination directory (for e.g.
/boot), currently we cannot use kexec_file_load() to load vmlinuz (or
Image.gz):

 # file /boot/vmlinuz
   /boot/vmlinuz: gzip compressed data, was "Image", <..snip..>, max
   compression, from Unix, original size 21945120

 Now, since via kexec_file_load() we pass the 'fd' of Image.gz
 (compressed file) via the following command line ...

 # kexec -s -l /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname
   -r`.img --reuse-cmdline

... kernel returns -EINVAL error value, as it is not able to locate
the magic number =0x644d5241, which is expected in the 64-byte header
of the decompressed kernel image.

We can fix this in user-space kexec-tools, which handles an
'Image.gz' being passed via kexec_file_load(), using an approach
as follows:

a). Copy the contents of Image.gz to a temporary file.
b). Decompress (gunzip-decompress) the contents inside the
    temporary file.
c). Pass the 'fd' of the temporary file to the kernel space. So
    basically the kernel space still gets a decompressed kernel
    image to load via kexec-tools

I tested this patch for the following three use-cases:

1. Uncompressed Image file:
 #kexec -s -l Image --initrd=/boot/initramfs-`uname -r`.img --reuse-cmdline

2. Signed Image file:
 #kexec -s -l Image.signed --initrd=/boot/initramfs-`uname -r`.img --reuse-cmdline

3. zlib compressed Image.gz file:
 #kexec -s -l /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname -r`.img --reuse-cmdline

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

1 files changed, 12 insertions, 0 deletions

diff --git a/kexec/kexec.c b/kexec/kexec.c
index 8ca3b45..bc6ab3d 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -1206,8 +1206,20 @@ static int do_kexec_file_load(int fileind, int argc, char **argv,
 	kernel_buf = slurp_decompress_file(kernel, &kernel_size);
 
 	for (i = 0; i < file_types; i++) {
+#ifdef __aarch64__
+		/* handle Image.gz like cases */
+		if (is_zlib_file(kernel, &kernel_size)) {
+			if ((ret = file_type[i].probe(kernel, kernel_size)) >= 0) {
+				kernel_fd = ret;
+				break;
+			}
+		} else
+			if (file_type[i].probe(kernel_buf, kernel_size) >= 0)
+				break;
+#else
 		if (file_type[i].probe(kernel_buf, kernel_size) >= 0)
 			break;
+#endif
 	}
 
 	if (i == file_types) {