Hi, folks
Just made Kexec work on 32bit system[o32] with 32bit kernel on
Loongson, which means Linux for Loongson is ready as bootloader.
If you have interest, please read the quick start steps and advantage
introductions.
1. Quickstart
1.1 Get a kernel image which supports Kexec on Loongson
Clone, pull or fetch the latest tiny36 branch from our LLC git repo[1]
$ mkdir tiny36 && cd tiny36 && git init
$ git fetch git://dev.lemote.com/linux-loongson-community.git tiny36
Compile it with the default yeeloong_kexec_defconfig, please ensure
KEXEC is enabled.
Then, Boot into the new kernel
1.2. Prepare a user-space kexec tool for Loongson
Download the latest kexec-tools from the mainline
$ git clone git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
Remove the redefined virt_to_phys() function from kexec/virt_to_phys.c
+ #if 0
.... virt_to_phys()
+ #endif
Configure, compile and install it, please refer to the INSTALL file
$ autoconf && configure && make && make install
1.3. Load a new kernel image from the kernel who supports kexec
Ensure your are running the kernel with kexec support
Then, copy a kernel image to your machine. both vmlinux and vmlinuz should work.
Load it:
$ kexec -l /path/to/vmlinux --command-line="$(</proc/cmdline)"
(If no command line passed, the default command line from the original
bootloader will be used)
Execute the new kernel:
$ kexec -e
Then, you will find the new kernel boots quickly and then, you will
get a new kernel, that's cool.
2. About Kexec on Loongson
The 64bit support and the crash/kdump support are still in progress.
With this kexec support on Loongson, we may get:
2.1. Run Linux as bootloader
The kexec-bootloader of course is available as a new bootloader for
Loongson, although I didn't touch it, but you can get a try at first:
git://git.linuxtogo.org/home/groups/kexecboot/kexecboot.git
This is the most important feature, in the future, perhaps we can put
Linux into 512K EEPROM and use it as our bootloader, this is my
long-term plan ;-) In reality, with the help of the tiny36 project, I
have gotten 400k image booting well on YeeLoong. More efforts are in
progress. a new bootloader(X-loader) may be ported to Loongson
platform and work as the 1st stage bootloader, the size of this 1st
stage bootloader can be limited to about several KiloBytes(e.g. 20kb).
This 1st stage bootloader did the necessary initialization and then
enter into Linux as fast as it can, I guess, including the 1st stage
bootloader, the kernel may start in about 5s, and then, this kernel
can enter into X system(TinyX is needed) directly or provide a menu to
start the other full-feature kernel.
2.2. Will be more convenient to develop/test a new kernel feature or driver
New kernel can be quickly loaded from the current kernel without the
old bootloader reboot. with my test, it is really very fast.
2.3. With the coming crash/kdump support, the recover from panic will
be supported, then Loongson will get the CGL feature
** The tiny36(Linux-Tiny for MIPS/Loongson, currently, only for
2.6.36, so, I name it tiny36) project is an open & free project
launched by myself in my spare time, any good idea, suggestion,
patches and even sponsors are welcome. This should be a long-term
project, the aim is making Linux as tiny/fast as possible on
MIPS/Loongson platform. **
Enjoy it!
Wu Zhangjin
-------------
[1] http://dev.lemote.com/code/linux-loongson-community
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