Linux – Is ‘Sleep’ Based on the System Clock or on Time Elapsed?

You could write a function that does both:

set_both_clocks() {
  date "$@"
  hwclock -w
}

Give it the exact same arguments you'd give to date when setting the system clock.

The easiest way to do this (if your gdb has python support):

break *0xaddress
run
# target process is now stopped at breakpoint
python import time
python starttime=time.time()
continue
python print (time.time()-starttime)

If your gdb doesn't have python support but can run shell commands, then use this:

shell echo set \$starttime=$(date +%s.%N) > ~/gdbtmp
source ~/gdbtmp
continue
shell echo print $(date +%s.%N)-\$starttime > ~/gdbtmp
source ~/gdbtmp

Alternatively, you could make the target process call gettimeofday or clock_gettime, but that is a lot more tedious. These functions return the time by writing to variables in the process's address space, which you'd probably have to allocate by calling something like malloc, and that may not work if your breakpoint stopped the program in the middle of a call to another malloc or free.