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, 7 insertions, 0 deletions

diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
index cc3419f..628de79 100644
--- a/kexec/arch/arm64/kexec-arm64.h
+++ b/kexec/arch/arm64/kexec-arm64.h
@@ -38,11 +38,18 @@ int image_arm64_probe(const char *kernel_buf, off_t kernel_size);
 int image_arm64_load(int argc, char **argv, const char *kernel_buf,
 	off_t kernel_size, struct kexec_info *info);
 void image_arm64_usage(void);
+
 int uImage_arm64_probe(const char *buf, off_t len);
 int uImage_arm64_load(int argc, char **argv, const char *buf, off_t len,
 		      struct kexec_info *info);
 void uImage_arm64_usage(void);
 
+int zImage_arm64_probe(const char *kernel_buf, off_t kernel_size);
+int zImage_arm64_load(int argc, char **argv, const char *kernel_buf,
+	off_t kernel_size, struct kexec_info *info);
+void zImage_arm64_usage(void);
+
+
 off_t initrd_base;
 off_t initrd_size;