How to trace all events for a shell command using ftrace?

Question

How can I trace the the command like cp file1 file2 using the ftrace tool?

I want to see all the functions that been called when I used cp file1 file2 but I don't know how to do it. Can anyone help me and write down the exact command in the terminal that does it?

Answer 1

Take the following script, you can use it to ftrace any command you want. Taken from here, I've modified slightly, you can get traced output at /tmp/mytrace.txt. Example usage: script.sh cp file1 file2

#!/bin/bash     
DPATH="/sys/kernel/debug/tracing"
PID=$$
TEMP="/tmp/mytrace.txt"
## Quick basic checks
[ `id -u` -ne 0  ]  &&  { echo "needs to be root" ; exit 1; }  # check for root permissions
[ -z $1 ] && { echo "needs process name as argument" ; exit 1; } # check for args to this function
mount | grep -i debugfs &> /dev/null
[ $? -ne 0 ] && { echo "debugfs not mounted, mount it first"; exit 1; } #checks for debugfs mount

# flush existing trace data
echo nop > $DPATH/current_tracer

# set function tracer
echo function_graph > $DPATH/current_tracer

# enable the current tracer
#echo 1 > $DPATH/tracing_on

# write current process id to set_ftrace_pid file
echo $PID > $DPATH/set_ftrace_pid

# start the tracing
echo 1 > $DPATH/tracing_on
# execute the process
exec $* > /dev/null 2>&1 &
#echo "$*"

`cat $DPATH/trace > $TEMP`

echo 0 > $DPATH/tracing_on

echo nop > $DPATH/current_tracer