Thread: Clara HD Crosscompile a web browser for the KOReader terminal
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Old 02-07-2024, 03:41 PM   #13
elinkser
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Posts: 242
Karma: 146236
Join Date: Oct 2022
Device: Kobo Clara HD
DBSERVER AND VALGRIND (USE AT OWN RISK - SEE WARNING)
***

GDBSERVER
(This is mainly for minimalists - you can get full gdb from NiLuJe kobostuff developer suite.)


The GNU Debugger - gdbserver

The gdb app has only the following dependencies:

Depends (9)
gmp
libexpat
libgcc
libstdc++**
musl*
ncurses-libs
python3
readline
zlib

*already got it from elinks/nano install in Post #3
**gdbserver has this additional dependency


RUN THESE COMMANDS FROM LINUX DESKTOP:

DOWNLOAD THE REQUIRED PACKAGES:

$ cd myalpine/


$ wget https://dl-cdn.alpinelinux.org/alpin...db-12.1-r2.apk

$ wget https://dl-cdn.alpinelinux.org/alpin...0220924-r4.apk

$ tar zxvf gdb-12.1-r2.apk

$ mv usr/bin/gdbserver scripts/

$ tar zxvf libstdc++-12.2.1_git20220924-r4.apk

$ mv usr/lib/libstdc++.so.6.0.30 libs/libstdc++.so.6


On your PC recompile fbpad2 with -g option:

$ cd fbpad-eink-master/

$ source ~/koxtoolchain/refs/x-compile.sh kobo env bare

$ nano -l Makefile
Code:
  1 CFLAGS += -Wall -O2  -g
$ make

$ file fbpad2
fbpad2: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 2.6.33, with debug_info, not stripped


NOW CONNECT YOUR KOBO TO YOUR PC:

Copy your gdbserver binary from the scripts/ folder on the PC to the /mnt/onboard/.adds/koreader/scripts/ folder on the kobo.

Copy fbpad2 to /mnt/onboard/.adds/koreader/scripts/ folder on your Kobo.

***

***Backup the existing libstdc++.so.6 in the
/mnt/onboard/.adds/koreader/libs/ folder on the kobo.***

Copy libstdc++.so.6 from the libs/ folder on the PC to the /mnt/onboard/.adds/koreader/libs/ folder on the kobo.

Make sure KOReader can still run.
If not, restore the original libstdc++.so.6 to the /mnt/onboard/.adds/koreader/libs/ folder.

***

$ sudo apt install gdb-multiarch

$ sudo ufw allow proto tcp from 192.168.2.1 to 192.168.2.2 port 2345

From SSH shell run (after first running ". /korenv.sh" as was done in Post #4):

# gdbserver host:2345 fbpad2 -p 58 0</dev/tty1 &
# Process fbpad2 created; pid = 1532
Listening on port 2345


From host desktop run:

$ gdb-multiarch fbpad2
GNU gdb (Debian 8.2.1-2+b3) 8.2.1
...
Reading symbols from fbpad2...done.
(gdb)

Connect to gdbserver:

(gdb) target remote 192.168.2.2:2345
Remote debugging using 192.168.2.2:2345
...
Reading symbols from target:/lib/ld-linux-armhf.so.3...(no debugging symbols found)...done.
0x76fcfb00 in ?? () from target:/lib/ld-linux-armhf.so.3

(gdbserver response: Remote debugging from host 192.168.2.1, port 51944)

(gdb) b main
Breakpoint 1 at 0x10de1

(gdb) continue
Continuing.
Reading /lib/libarmmem-v7l.so from remote target...
Reading /lib/libutil.so.1 from remote target...
Reading /lib/libc.so.6 from remote target...
Breakpoint 1, 0x00010dec in main ()


From a second SSH shell to Kobo run:

# fbkeyboard2

Enter ALT-c and you get the shell prompt on the Kobo display.
(may have to issue "continue" command again from gdb.)

Enter ALT-p <Ret> to see tag list.

CTRL-ALT-q to end the fbpad session.

CTRL-ALT-x to end the fbkeyboard session.



***

Do NOT attempt the following on your Kobo.
Having valgrind is NOT worth the risk of having to factory wipe your device.

I had a replaceable sdcard-based system with multiple backups, previous proof that the substitute build environment was compatible, and an SFTP-capable filemanager running on my desktop with an already loaded SSH server in Kobo memory.

Spoiler:



*** WARNING - DO NOT ATTEMPT THIS ***

Valgrind is a tool to help find memory-management problems in programs


The valgrind app has only the following dependencies:

Depends (1)
musl*

*already got it from elinks/nano install in Post #3.


RUN THESE COMMANDS FROM LINUX DESKTOP:

DOWNLOAD THE REQUIRED PACKAGES:

$ cd myalpine/

$ wget https://dl-cdn.alpinelinux.org/alpin...-3.20.0-r0.apk

$ wget https://dl-cdn.alpinelinux.org/alpin...g-1.2.3-r5.apk


$ tar zxvf valgrind-3.20.0-r0.apk

$ mv usr/bin/valgrind scripts/

$ mkdir libexec

$ mkdir libexec/valgrind

$ mv usr/libexec/valgrind/default.supp libexec/valgrind/

$ mv usr/libexec/valgrind/memcheck-arm-linux libexec/valgrind/

$ mv usr/libexec/valgrind/vgpreload_core-arm-linux.so libexec/valgrind/


Get alternate dynamic linker/loader from Linaro toolchain.

$ cp ../gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf/arm-linux-gnueabihf/libc/lib/ld-2.19-2014.08-1-git.so .


NOW CONNECT YOUR KOBO TO YOUR PC:

Copy your valgrind binary from the scripts/ folder on the PC to the /mnt/onboard/.adds/koreader/scripts/ folder on the kobo.

Create a /usr/libexec folder on the Kobo.

Copy valgrind/ folder from libexec on the PC to the /mnt/onboard/.adds/ folder on the kobo.

# ln -s /mnt/onboard/.adds/valgrind/ /usr/libexec/valgrind

Copy ld-2.19-2014.08-1-git.so to root directory / of Kobo.



# valgrind /mnt/onboard/.adds/koreader/scripts/nano
(works)


# valgrind /bin/ls
Fatal error at startup:
A must-be-redirected function valgrind:
whose name matches the pattern: index
in an object with soname matching: ld-linux-armhf.so.3
was not found whilst processing

See source of problem:
https://sourceforge.net/p/valgrind/m...m/#msg30887009


# cd /lib

# ls -l ld*
-rwxr-xr-x 134412 ld-2.11.1.so
lrwxrwxrwx 13 ld-linux-armhf.so.3 -> ld-linux.so.3
lrwxrwxrwx 12 ld-linux.so.3 -> ld-2.11.1.so
-rwxr-xr-x 525980 ld-musl-armhf.so.1

Check if the stock ld-linux.so.3 includes the memcpy function:

# readelf --symbols /lib/ld-linux.so.3 | grep mem
12: 000176bc 332 FUNC WEAK DEFAULT 10 __libc_memalign@@GLIBC_2.4


Check if the alternate /ld-2.19-2014.08-1-git.so includes the memcpy function:

# readelf --symbols /ld-2.19-2014.08-1-git.so | grep memcpy
804: 00000000 0 FILE LOCAL DEFAULT ABS rtld-memcpy.os
907: 00012700 1056 FUNC LOCAL DEFAULT 11 memcpy
1097: 000132e9 16 FUNC LOCAL DEFAULT 11 __memcpy_from_thumb



**********************************************
***CRITICAL STEP***
* MAKE SURE YOU HAVE SSH CONNECTION TO KOBO ALREADY LOADED IN MEMORY *
* AND AN SFTP-CAPABLE FILEMANAGER RUNNING ON DESKTOP ABLE TO RESTORE DYNAMIC LINKER/LOADER FILE REMOTELY*
* AND AN SDCARD-BASED FILESYSTEM ON KOBO, BACKED UP
* YOU WILL BE REPLACING LINKER WHICH MAY CAUSE COMMANDS TO STOP WORKING ON KOBO *
* YOU WILL BE REPLACING LINKER WHICH MAY CAUSE COMMANDS TO STOP WORKING ON KOBO *
* YOU WILL BE REPLACING LINKER WHICH MAY CAUSE COMMANDS TO STOP WORKING ON KOBO *

Back up stock dynamic linker/loader:

# cp -P ld-linux-armhf.so.3 /

Check that it is backed up:

# ls -l /ld-linux-armhf.so.3
lrwxrwxrwx 13 /ld-linux-armhf.so.3 -> ld-linux.so.3

Copy alternate linker over the stock linker:

# cp /ld-2.19-2014.08-1-git.so ld-linux-armhf.so.3

Check if commands still work:

# pwd
/lib

* IF COMMANDS DON'T WORK, RESTORE /lib/ld-linux-armhf.so.3 FROM YOUR BACKUP USING YOUR SSH CONNECTION *

**********************************************

Now let's retry valgrind with the new linker:

# valgrind /bin/ls
(works)


On your PC recompile fbpad2 with -g option:

$ cd fbpad-eink-master/

$ source ~/koxtoolchain/refs/x-compile.sh kobo env bare

$ nano -l Makefile
Code:
  1 CFLAGS += -Wall -O2  -g
$ make

Copy fbpad2 to /mnt/onboard/.adds/koreader/scripts/ folder on your Kobo.

From SSH shell run (after first running ". /korenv.sh" as was done in Post #4):

# valgrind fbpad2 -p 58 0</dev/tty1 &
<Ret>
# fbkeyboard2

Enter ALT-c and you get the shell prompt on the Kobo display.

Enter ALT-p <Ret> to see tag list.

CTRL-ALT-q to end the fbpad session.

CTRL-ALT-x to end the fbkeyboard session.

Output:
==2059== Memcheck, a memory error detector
==2059== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==2059== Using Valgrind-3.20.0 and LibVEX; rerun with -h for copyright info
==2059== Command: fbpad2 -p 58
...
==2059==
==2059== All heap blocks were freed -- no leaks are possible
==2059==
==2059== Use --track-origins=yes to see where uninitialised values come from
==2059== For lists of detected and suppressed errors, rerun with: -s
==2059== ERROR SUMMARY: 4 errors from 3 contexts (suppressed: 0 from 0)
[1]+ Segmentation fault valgrind fbpad2 -p 58 0</dev/tty1


**********************************************
***CRITICAL STEP***

* RESTORE /lib/ld-linux-armhf.so.3 FROM YOUR BACKUP USING YOUR SSH CONNECTION *

Check if commands still work:

# pwd
/lib

**********************************************

***
Attached Files
File Type: zip fbpad2-debug.zip (118.5 KB, 426 views)
Last edited by elinkser; 02-08-2024 at 03:31 AM. Reason: warning
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