Debugging Linux Kernel using ftrace Part15 - trace_options

-
'trace_options' file allows user to control the level of information displayed when we do cat on 'trace' or 'trace_file'


You can see from the above screenshot, There are 26 options available for the user to control. There are some tracer specific options which are not listed in this file and are present in 'options' directory.

The words which begin with "no" represents trace options that are disabled.

To enable an option.

$ echo 'sym-offset' > trace_options

To disable an option, add "no"

$ echo 'nosym-offset' > trace_options.

Let's try some of the options.

1. sym-offset: Enabling this option, you will see function name plus offset in the function. By default, this is disabled.


2. print-parent: This option displays the calling function. By default, this option is disabled.




3. function-fork: This option enables tracing the children when set_ftrace_pid is set.
4. irq-info: Displays the interrupt, preempt count, need resched data information in the trace


5. context-info: Disabling this option, will hide the Task-PID, CPU, Timestamp and other useful information.


Comments

Post a Comment

Popular posts from this blog

bb.utils.contains yocto

-
Image
bb.utils.contains  is most commonly used function in Yocto. grep in poky directory returned with 696 count. $ grep -nr 'bb.utils.contains' poky/ | wc -l 696 It's definition is present in 'poky/bitbake/lib/bb/utils.py' file This function returns third argument if the second argument is subset of the first argument else returns fourth argument Let's take an example to understand this. You can see from the above screenshot, when the second argument is a subset of first argument, "present" was returned, else "notpresent" was returned We can also use bb.utils.contains inside if loop. This we can use inside a recipe. if ${@bb.utils.contains('SOMEFLAG','NEWVALUE3','true','false',d)}; then     FOO = 'HELLO' fi
Read more

Difference between RDEPENDS and DEPENDS in Yocto

-
We normally observe these two (RDEPENDS and DEPENDS) whenever we open any recipe. What should we choose when we write our own recipe. DEPENDS -> Build Time Dependency RDEPENDS -> Run Time Dependency DEPENDS: When a recipe 'A' is DEPENDS on recipe 'B'. In this case, Bitbake first builds recipe 'B' and then recipe 'A' E.g. You need 'dbus' to be built before 'wpa_supplicant'. RDEPENDS: When a recipe 'A' is RDEPENDS on recipe 'B'. In this case, Bitbake deploys 'B' on the target system when it deploys 'A'.  E.g. 'perf' RDEPENDS on 'bash' In other words, DEPENDS are those set of packages that should be available while building package, whereas RDEPENDS are set of packages that should be available during execution of the program.
Read more

make config vs oldconfig vs defconfig vs menuconfig vs savedefconfig

-
Image
Building the Linux Kernel is a two-step process: Configuring the Kernel options Building the Kernel with those options. There are many methods available for configuring the kernel. make config: Text-based Configuration.  Options are prompted one after another. All options need to be answered Access to former options is not possible make menuconfig: Menu-driven user interface Allows to navigate forwards and backward directly between features Allows to load and save files with filenames different from ".config" Provides search feature It uses ncurses library for GUI. If the ncurses library is not installed, make menuconfig option fails. To install ncurses library on Ubuntu: sudo apt-get install libncurses5-dev make defconfig: Creates a ".config" file with default options from the ARCH supplied defconfig Configurations are generally stored in the directory: arch/$(ARCH)/configs $ ls arch/x86/configs/ i386_defconfi
Read more