Debugging is the process of finding and resolving or defects that prevent correct operation of computer software or a system. Debugging tends to be harder when various subsystems are tightly coupled, as changes in one may cause bugs to emerge in another.
root@edison:~# mount -t debugfs none /sys/kernel/debug
mount: none is already mounted or /sys/kernel/debug busy
none is already mounted on /tmp/temptmpfs
root@edison:~# ls /sys/kernel/debug/
asoc gpio_debug pmu_sync_d0ix
bdi hid pwm
bluetooth hsu regmap
boot_params ieee80211 regulator
c_states_stat ignore_add remoteproc
cstate_ignore_add ignore_remove s3_ctrl
cstate_ignore_remove iio sched_features
debug_feature intel_scu_oshob soc_thermal
disable_emmc_ipanic kprobes sst
dma_buf mce suspend_stats
dri mid_pmu_states tracing
dump_cmd mmc0 usb
dump_output mmc1 wakeup_sources
dwc3-device.1 mmc2 watchdog
dynamic_debug pmic_ccsm x86
emmc_ipanic pmu_force_d0i0
gpio pmu_force_d0i3
root@edison:~#
Linux Magic System Request Key Hacks
Ftrace
root@edison:~# cd /sys/kernel/debug/tracing
root@edison:/sys/kernel/debug/tracing# cat available_tracers
blk function_graph wakeup_rt wakeup preemptirqsoff preemptoff irqsoff function nop
root@edison:/sys/kernel/debug/tracing# echo function > current_tracer
root@edison:/sys/kernel/debug/tracing# cat current_tracer
function
Applications / Libraries
Programs
None
Debugfs exists as a simple way for kernel developers to make information available to user space. Unlike /proc, which is only meant for information about a process, or sysfs, which has strict one-value-per-file rules, debugfs has no rules at all.
It is a 'magical' key combo you can hit which the kernel will respond to regardless of whatever else it is doing, unless it is completely locked up.