Commands

Useful commands

• find
• grep

You use find to search your system for files, but you use grep to search files for strings.

GNU toolchain tuple:

gcc -dumpmachine
arm-linux-gnueabi-gcc -dumpmachine

Cross-compile:

arm-linux-gnueabi-gcc hello_world.c -o hello_world

Confirm the type of the file, i.e., check that the c file was cross-compiled for your target architecture:

file hello_world

Display information about the contents of ELF format files:

readelf -a libtest.a
readelf -a hello_world

Check which libraries have been linked in a program:

arm-linux-gnueabi-readelf -a hello_world | grep "Shared library"

Check runtime linker

arm-linux-gnueabi-readelf -a hello_world | grep "program interpreter"

Link all the libraries statically (size of binary is bigger than dynamic linking):

gcc -static hello_world.c -o hello_world-static

Create static library (as simple as creating an archive of objects files using the ar command). Example: If you have two source files “test1.c” and “test2.c”, and you want to create a static library named “libtest.a”, then:

gcc -c test1.c
gcc -c test2.c
ar rc libtest.a test1.o test2.o

Note: gcc -c option compile and assemble the translation unit, but do not link

Link statically compiled library “libtest.a” into “hello_world” program:

gcc hello_world.c -ltest -L../libs -I../libs -o hello_world

Create shared library (-fPIC stands for position independent):

arm-linux-gnueabi-gcc -fPIC -c test1.c
arm-linux-gnueabi-gcc -fPIC -c test2.c
arm-linux-gnueabi-gcc -shared -o libtest.so test1.o test2.o

Link application to dynamic library:

arm-linux-gnueabi-gcc hello_world.c -ltest -L../libs -I../libs -o hello_world

Cross-Compile Linux Kernel - BeagleBoneBlack

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabi-
make omap2plus_defconfig
make -j32

Display all running processes

ps aux | less
ps aux

Apply patches:

patch -p1 < file.patch

git apply --index file.patch

note: Prefer git apply in order to track new files that may be contained in the git patch.

Compiling a single source file: make path/file.o

make drivers/media/test-drivers/vimc/vimc-core.o

Compiling at the directory level: make path

make drivers/media/test-drivers/vimc/

Compile file as module, e.g., vimc:

make M=drivers/media/test-drivers/vimc

note: It’s better to use make menuconfig to configure the file as a module because of all the dependencies.

Useful commands for modules:

sudo insmod <module>.ko
sudo insmod args_module.ko name=roberto
sudo modprobe <module>
sudo rmmod <module>
sudo dmesg | tail

Count context switches:

sudo perf stat -e sched:sched_switch --timeout 1000