Lets try recovering a file from rm *

By mistake I deleted a source code which I spend around a day to develop. With the help of extundelete utility it is possible to recover file if same space is not reallocated by file system.

Here is what I did to recover my deleted file info_bootimg.c

sudo src/extundelete --restore-file  workspace/utils/helper_utills/bootinfo/info_bootimg.c  /dev/mapper/vg00-lv_local_mnt

"workspace/utils/helper_utills/bootinfo/" is the path relative to the root of partition

This is where the partition is mounted,

/dev/mapper/vg00-lv_local_mnt on /local/mnt type ext4 (rw)

File's absolute path is "/local/mnt/workspace/utils/helper_utills/bootinfo/info_bootimg.c"

But you have to strip "/local/mnt" to get it working.

Download extundelete from,
http://extundelete.sourceforge.net/

./configure and make

Debugging using T32 on a Multi cores/cpus

Contemporary processors are multi core/cpus. This has made life of a developer bit tougher. For eg, for the break point to hit, you need to set it on all the cpus, because you never know where the code is going to run. Another instance is to stop all the core at the same time.

Below is a set of scritps which helps you to make your job easier.

For eg we will consider working on a 4 core processor.

You need to create few cmm files. Contents and file names as shown below,

1) main.cmm
=========
GLOBAL &ScriptPath &vmlinuxPath

&ScriptPath="Z:\deleteme\T32"
&vmlinuxPath="Z:\kdevs\3.18\kdev\kobj"

globalon cmd i do &ScriptPath\initcore_all.cmm
globalon cmd pos do &ScriptPath\pos.cmm
globalon cmd load do &ScriptPath\load_all.cmm
globalon cmd ball do &ScriptPath\break_all.cmm

==========

2) initcore_all.cmm

============

intercom.execute localhost:15370 do &ScriptPath\initcore.cmm

intercom.execute localhost:15371 do &ScriptPath\initcore.cmm

intercom.execute localhost:15372 do &ScriptPath\initcore.cmm

intercom.execute localhost:15373 do &ScriptPath\initcore.cmm

============

3) initcore.cmm

==========

sys.m.a

snoop.pc ON

b.d

b.s die  /Onchip

b.s panic  /Onchip

===========

4) loadall.cmm

=========

intercom.execute localhost:15370 do &ScriptPath\load.cmm &vmlinuxPath

intercom.execute localhost:15371 do &ScriptPath\load.cmm &vmlinuxPath

intercom.execute localhost:15372 do &ScriptPath\load.cmm &vmlinuxPath

intercom.execute localhost:15373 do &ScriptPath\load.cmm &vmlinuxPath

==========

5) load.cmm

========

ENTRY &vmlinuxPath

d.load.elf &vmlinuxPath\vmlinux /NOCODE

========

6) pos.cmm
=======
intercom.execute localhost:15370 framepos 0 0 65 13
intercom.execute localhost:15371 framepos 75 0 65 13
intercom.execute localhost:15372 framepos 0 25 65 13
intercom.execute localhost:15373 framepos 75 25 65 13
========

7) break_all.cmm
===========
intercom.execute localhost:15370 break
intercom.execute localhost:15371 break
intercom.execute localhost:15372 break
intercom.execute localhost:15373 break

===========

Open four instances of T32. run main.cmm on T32 associated with core 0.

then type the i in the command line to run intercore_all.cmm

Using GDB to find structure info

As usual  load elf file

$gdb vmlinux

We are going to inspect the address layout of structure platform_device,

struct platform_device {
        const char      *name;
        int             id;
        bool            id_auto;
        struct device   dev;
        u32             num_resources;
        struct resource *resource;

        const struct platform_device_id *id_entry;
        char *driver_override; /* Driver name to force a match */

        /* MFD cell pointer */
        struct mfd_cell *mfd_cell;

        /* arch specific additions */
        struct pdev_archdata    archdata;
};


(gdb) p &((struct platform_device *)0)->name
$2 = (const char **) 0x0
(gdb) p &((struct platform_device *)0)->id
$3 = (int *) 0x8
(gdb) p &((struct platform_device *)0)->id_auto
$4 = (bool *) 0xc
(gdb) p &((struct platform_device *)0)->dev
$5 = (struct device *) 0x10

Above output shows the offset of different variables in the structure.