[dev][kernel][kexec]

Last Update : August, 19, 2014
Hi,

I'm still try to bypass the MMU protection.
I have fixe a lot of bug, like memory misalignment, bad adresses allocation, dtb correction, etc...
Last sources and binaries here :
kexec-tools V11.zip : http://xdaforums.com/attachment.php?attachmentid=2902912&stc=1&d=1408401794
kexec-tools binaries V11.zip : http://xdaforums.com/attachment.php?attachmentid=2902913&stc=1&d=1408401794

Sorry, i have always 13 sec reboot after new kernel boot.
"cpu_proc_fin" use a "mcr p15" to init cache and proc that cause freeze.
I try to find solution for that.


Last Update : June, 22, 2014
Hi,

My sources are horrible... but i give something new.

This kexec is for stock kernel only (tested on .757). I thinks theses sources work on other kernel too.

In "kexec-tools V10.zip", you have all my sources. It's highly recommended to mod them to have something OK.

In "kexec binaries.zip", you have binaries to install
=> "kexec_load.ko" and "procfs_rw.ko" must be placed in "/system/lib/modules" folder with "chmod 777"
=> "kexec" must be placed in /system/bin" folder with "chmod 777"
=> cd /system/lib/modules
=> insmod kexec_load.ko

For sources :
Mod and adapt all you want, it's free.
You have 2 scripts in Zip : "./compil-kexec" in "kexec-tools" folder to rebuild and send in device directly (install Adbtcp on device and send by tcp with : adb connect xxx.xxx.xxx.xxx) = work perfectly with me.
"scriptZ1" is for compil stock kernel or another kernel (doomlord kernel for eg)
You must rename "custom_final_files" folder after compil to "final_file" manually ; You can have guest kernel in "custom_final_files" and stock kernel in "final_files" for "kexec-tools" path ... Don't mix a guest and host kernel please ^^

I am tired... i let you test and say if it's ok for you...

Thank a lot to munjeni for his help.

kexec-tools V10.zip : http://xdaforums.com/attachment.php?attachmentid=2811994&stc=1&d=1403456181
kexec binaries.zip : http://xdaforums.com/attachment.php?attachmentid=2811995&stc=1&d=1403456181


Last Update : November, 23, 2013
Hi,
For few days now, i haven't no more kernel panic with my kexec.
I have fixed few stuffs into sources, and add a lot.

These adds are, to include a "dt.img" image file into kexec load process.

This image file is a "device_tree" image to match hardware to software.

So, i assume to don't include atags into boot process, but pass bootloader informations by this DT.
I have programmed a little scan memory to found dynamicly all magic tags, because i found 3 device_tree into memory (magic is "0xd00dfeed").
These 2 device_tree are echo from first and nice structure.

The boot process need to have informations from this DT, and need all informations to initialize hardware (no HDW initialisation by the kernel)
I must first fix issues ; Regroup zImage and dt.img into memory to load a solid bloc to kexec_load module to boot into, and second, fix an offset i can't explain, 0x800 in memory causing misalignment memory

Keep tuned..



Last Update : November, 17, 2013

Hi everybody,

My kexec-tools work for Sony Xperia Z1 stock kernel "3.4.0-perf"
This tools can work on all locked bootloader for all locked device, not only Sony or Z1 models.
This kexec-tools add a kexec_load kernel module (LKM) and use a driver to grant a communication between "kexec" user program and kexec_load.ko module

what is for ?
"kexec" user program load in memory a custom kernel in zImage format, but can load ".tar" image too
This user tool load ramdisk in memory if necessary
This tool is for this purpose only, and don't keep in memory the custom kernel at device reboot.
It is a "user" program, not a "kernel" extension... So, to really do the magic, we need the host kernel (stock sony locked kernel) have a kexec_load capability to reboot in a new gest kernel (custom kernel).

Infortuntly, stock kernel don't have kexec_load capability.
Sony have compiled his stock kernel without this option, and "standard" kexec-tools "need" this option to work.

To see all system call capability of kernel, you can run theses command :
Do all grep you want here.
The "echo 0" "restrict" is here to unmask logical adresses to "system calls"
Like you can see, "__NR_kexec_load" capability isn't here.

To add kexec_load capability in stock locked kernel, we need to add manualy a kernel module wich add this function into the kernel.
Why ? Because the way to keep in memory a custom kernel need to know a lot of parameters, and keep a specific memory range alive at reboot.
Only kernel can do this.
All user program will be terminated at reboot.

"Standard" kexec_load.ko module use a method to implement the "__NR_kexec_load" function in system call table.
Since 2.6.0 kernel, linux for security reason, have locked in memory the "system_call_table" ; No more add or modification is authorized.
If kexec tool try to add a value, "kexec_load" for us, we causes a kernel panic, and reboot device.

For this reason, i have modify kexec user program and kexec_load module to implement a driver to talk to each other.

this driver replace syscall method, and we no more need to use a system call table.
For this reason, this tool is now compatible with modern kernel like our "3.4.0"
For this reason, this tool must work for other device (Xperia X, P, S, etc...) and another brand
For this reason, if kernel is locked, we can bootstrap to run a new kernel.


Installation
First, you can compil your own kexec tool
Here, sources : http://xdaforums.com/attachment.php?attachmentid=2397299&stc=1&d=1384689174

And here, the binaries : http://xdaforums.com/attachment.php?attachmentid=2397305&stc=1&d=1384689406
(it's not a cwm zip, i have no time to create an installer for now ; use "./compil-kexec" if you want an automatic install)
Install *.ko in /system/lib/modules
Install kexec and kdump in /system/bin
Grant with "chmod 777"


Unzip in kexec-tools folder
Install a toolchain (sudo apt-get install gcc-arm-linux-gnueabi)
launch => ./compil-kexec

what's all
This script can do everythinks for you
- Compilation of tools
- Compilation of modules
- installation in device
This script can compil for every brand you have.
Except you must remove or adapt the patch (see below why)


Patch ??
This patch is because a module must be compiled in the same time the kernel himself.
For this reason a "vermagic", an identifier, is used by system to block every module not compil with kernel
Some custom kernel bypass this to authorize every modules.
But for stock kernel, it is not allowed.
You can easely strapp this by busybox.
"busybox modprobe" for help
"-f" to force load without vermagic

To see this vermagic :
This "uname -r" must be the same that
If you want use automaticaly this vermagic, you can modify into the custom kernel this file :
This file will be use at module compil to match the vermagic.


Infortunatly, it is not enought. :silly:

The infamous "no symbol version for module_layout"
When a module compil is created, it use symbols link to system call function, translate by adresses
Theses symbols are not at same physical adresses in stock kernel and modules (compiled from DooMLoRD kernel).
So, theses adresses must be convert into modules itself to match with stock symbols adress.
A patch is needed.
If you use my script, modules are automatically patched.

Here patches :
You can use hexedit or hexdump to see these adresses :
how does it work ?
# kexec --help
For kexec help... nothing more to say.

# lsmod
List loaded modules... You must see
kexec_load 31369 0 - Live 0x00000000 (O)

# rmmod kexec_load.ko
Remove kexec_load module from memory.

# grep kexec /proc/device
To see installed driver.
You must see :
100 kexec_driver

First number is "major" number to identify your driver in system.

# mknod /dev/kexec_driver c 100 0
Install driver.
Major number (here 100), is important for module.
This Major must be the same between module and driver.
By default, 100 is used.

# insmod kexec_load.ko
To install "LKM", kexec_load kernel module.
If another Major is needed, you can use "insmod kexec_load.ko 101" for Major 101
You can use "modprob" if you want, but you must configure the module folder.


How kexec and module exchange informations ?
By the driver.
Normal output for a kernel module is to write in "dmsg" file.
To see kernel output, launch this command :
To see last kernel log, see in :
For kexec module, this normal way still exist, and give a lot of informations, but to speak with, you must use the driver.
/dev/kexec_driver

You can yourself test communication:
Every command send into driver is receive by kexec_load.ko module and running into the kernel.
The answer can by read thru the driver

Here, you can see that normal way to see messages is allway dmesg.

I have add a lot of informations to help to configure kexec.



rdtags, atags ??
Not sure for this part of kernel.
"atags" is the most used method to bootloader to parse commands and informations to kernel at boot.
"atags" is a form of structure in memory to organise informations.
At boot, a address chain is created and can be compulse in /proc/atags file.
This file is read only system.
"rdtags" is another way to bootloader to parse information to kernel.
"rdtags" is not stocked in "/proc"
But, as i see, stock kernel can use "atags" from bootloader.
kexec can substitute bootloader function to create fromscratch a atags chain, and parse to new kernel.
I have change this part to stock atags in "/data/atags", and reuse or change if need.

If this don't work, i must create a rdtags chain to replace atags ; It's not a hard work.


Status

For the moment, kexec tools works.
=> Phase one OK.

I can start Phase Two : new kernel patch.
If you want to help me...

Actually, load a custom kernel and boot into with kexec tools work.
But at boot into, a kernel panic occurs.

It seems, a part of kexec patch is missing in custom kernel.

king960 said:

Attempts on Xperia P (sorry IF i noob-ed with this post)

http://xdaforums.com/showthread.php?t=2053466

Sent from my LT22i using xda app-developers app

Click to expand...

Click to collapse

It's a dead thread.
Because, it's a epic failed (for now).

********

Status of my attempts :

Modules loads : OK for two modules (kexec_load and procfs_rw)
- procfs_rw.ko => create "/proc/atags" => ok, but bad buf... it must be fix (easy part)
- kexec_load.ko => Loaded => ok but, the way to use is "syscall" add for kexec_load function => failed
why ? Because after 2.6 kernel (Z1 have 3.4.0 kernel), syscall_table is read only and had fixed size. So if i attempt to add value (kexec_load in our case), we have kernel panic.

But i have a solution to add function in LKM, is to add a "real" module call.

I have add a "kexec_driver" in "/dev" structure by :

Driver is in alpha stage and highty experimental

To be continue...

delewer said:

just for information...
compressed kernel with lzma his bigger than no lzma lol
4,1 Vs 4,15

so, i thave try :
kexec --load zImage.lzma --mem-min=0x0f00000000 --command-line="$(cat /proc/cmdline)"
debug: Focus 1 - argc '5' ; argv 'bea96754' ; kernel_buf 'b6bdf008' ; kernel_size '3f5414' ; info 'bea96528' ; i '1' ; file_type.name 'zImage'
debug: malloc - xmalloc mem_range '4511824'
Could not find a free area of memory of 3fd414 bytes...

lol ... if you could find a way to reduced size ??

Click to expand...

Click to collapse

Did you reserved and freed memory for kexec? Something like:

+#if defined(CONFIG_KEXEC_HARDBOOT)
+static void kexec_hardboot_reserve(void)
+{
+ if (memblock_reserve(KEXEC_HARDBOOT_START, KEXEC_HARDBOOT_SIZE)) {
+ printk(KERN_ERR "Failed to reserve memory for KEXEC_HARDBOOT: "
+ "%dM@0x%.8X\n",
+ KEXEC_HARDBOOT_SIZE / SZ_1M, KEXEC_HARDBOOT_START);
+ return;
+ }
+ memblock_free(KEXEC_HARDBOOT_START, KEXEC_HARDBOOT_SIZE);
+ memblock_remove(KEXEC_HARDBOOT_START, KEXEC_HARDBOOT_SIZE);
+
+ kexec_hardboot_device.num_resources = ARRAY_SIZE(kexec_hardboot_resources);
+ kexec_hardboot_device.resource = kexec_hardboot_resources;
+}
+#endif

Click to expand...

Click to collapse

Standard kexec not working and allso kexec can boot only kexec patched kernels, so I get them only working using hard kexec, hard worked on them and finaly I had a fully working kexec for Sony Xperia Go, Sola, P and U, maybe this help -> https://github.com/munjeni/android_kernel_xperiago/commits/jb-dev?page=2

I will start working on your work after I get Xperia Z1 Mini! You made a realy interesting thread, I am realy interested in this! Hope we get some progress. :good:

And one more thing, I will backport my Boot Menu to Z1 and Z1S soon as we get kexec working! More info here -> http://xdaforums.com/showthread.php?t=2418241

ikenley said:

Excellent work Delewer!

So is it currently functional but with bugs or does it still need work before others can start testing it?

Are your tests at the moment with Sony stock kernel (i,e, DooMKernel) or with AOSP kernel (i.e. CM kernel running CM10 or equivalent)?

Click to expand...

Click to collapse

It's not a fonctionnal kexec ; all i see in my sources say it work, but it is not yet, it's frustating to me to be so close.

I test only with DoomKernel, to be sure when ok, to see it is.
When ok, aosp will be kexeced immediatly after... for sure !!!

Most important for now it's to have log from new kernel to debug the first crash ; if i have a log, we win the battle.

Hi new thread created for kernel kexec development.

Status: not working: wrong values for mem defines under the kernel is giving segmentation fault as its attempting to write to memory areas that are currently being used byyyyy the system


Instructions:
Make kernel compatible?:
1. Download kernel diff patch from below
2. Terminal - diff patch > diff.txt

How to use:
1. Download kexec-tools (kexec binary) from below
2. Copy into system/bin directory and give it executable permission
3. Download compatible kernel
4. Terminal - kexec --load-hardboot zImage --initrd=initrd.img --mem-min=0x20000000 --command-line="$(cat /proc/cmdline)"
kexec -e

Download links:
Kexec tool- https://db.tt/8DZXQ9eV
Ramdisk firmware 1.548 : https://db.tt/8DZXQ9eV
zImage (kernel):


Source code:
Kernel diff patch: https://db.tt/Xi2htT7Q (currently contains wrong values for mem defines)
Kexec-tools: https://db.tt/I22ofr3b


Special thanks: @delewer @krabappel2548