loader: Add bzImage support

Reimplement KernelLoader trait against structure BzImage to add bzImage
loader support.

Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>

Author: bjzhjing

DESIGN.md

@@ -35,4 +35,58 @@ be used to fill boot parameters, vmm is totally responsible for the construction
 
 - GDT must be configured and loaded
 
+# bzImage
+
+The boot process is also explained from the following two sides.
+
+## Loader side
+
+### What will be returned from loader
+
+bzImage includes two parts, the setup and the compressed kernel. The compressed
+kernel part will be loaded into guest memory, and the following three parts
+will be returned to the VMM by the loader.
+
+- The start address of loaded kernel
+
+- The offset of memory where kernel is end of loading
+
+- The setup header begin at the offset 0x01f1 of bzImage, this one is an extra
+  compared to the return of ELF loader.
+
+### Where kernel is loaded
+
+The same as ELF image loader, there are two ways for deciding where the
+compressed kernel will be loaded.
+
+- VMM specify where to load kernel image.
+
+- Load into code32_start (Boot load address) by default.
+
+### Additional checking
+
+As what the boot protocol said, the kernel is a bzImage kernel if the
+protocol >= 2.00 and the 0x01 bit(LOAD_HIGH) is the loadflags field is set. Add
+this checking to validate the bzImage.
+
+## VMM side
+
+### Construct zero page
+
+While vmm build "zero page" with e820 table and other stuff, bzImage loader will
+return the setup header to fill the boot parameters. Meanwhile,
+setup_header.init_size is a must to be filled into zero page, which will be used
+during head_64.S boot process.
+
+### Configure vCPU
+
+- RIP, the start address of loaded 64-bit kernel returned from loader + 0x200.
+  Regarding to the 64-bit boot protocol, kernel is started by jumping to the
+  64-bit kernel entry point, which is the start address of loaded 64-bit kernel
+  plus 0x200.
+
+- 64 bit mode with paging enabled
+
+- GDT must be configured and loaded
+
 

README.md

@@ -13,12 +13,29 @@ cd linux-loader
 cargo build
 ```
 
-## How to run test
+## How to run test for Elf loader
 
+```shell
+# Assuming your linux-loader is under $HOME
+$ cd linux-loader
+$ cargo test
+$ cargo test -- --nocapture
 ```
-cd linux-loader
-cargo test
-cargo test -- --nocapture
+
+## How to run test for bzImage loader
+
+As we don't want to distribute an entire kernel bzImage, the `load_bzImage` test is ignored by
+default. In order to test the bzImage support, one needs to locally build a bzImage, copy it
+to the `src/loader` directory and run the ignored test:
+
+```shell
+# Assuming your linux-loader and linux-stable are both under $LINUX_LOADER
+$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git $LINUX_LOADER/linux-stable
+$ cd linux-stable
+$ make bzImage 
+$ cp linux-stable/arch/x86/boot/bzImage $LINUX_LOADER/linux-loader/src/loader/
+$ cd $LINUX_LOADER/linux-loader
+$ cargo test -- --ignored
 ```
 
 ## Platform Support