```python
from bcc import BPF
import ctypes
import time

# BPF program for counting return values
bpf_program_count = """
#include <uapi/linux/ptrace.h>

BPF_HISTOGRAM(hist);

int count_return(struct pt_regs *ctx) {
    u64 ret = PT_REGS_RC(ctx);
    hist.increment(bpf_log2l(ret));
    return 0;
}
"""

# BPF program for submitting addresses
bpf_program_submit = """
#include <uapi/linux/ptrace.h>

BPF_HASH(addresses, u64, u64);

int submit_addresses(struct pt_regs *ctx, u64 resolver, u64 implementation) {
    addresses.update(&resolver, &implementation);
    return 0;
}
"""

# Load BPF programs
bpf_count = BPF(text=bpf_program_count)
bpf_submit = BPF(text=bpf_program_submit)

def get_symbol_address(symbol):
    """Get the address of a symbol."""
    return BPF.ksymname(symbol)

def set_addresses(resolver, implementation):
    """Set the addresses of the resolver and implementation functions."""
    resolver_addr = ctypes.c_ulonglong(resolver)
    implementation_addr = ctypes.c_ulonglong(implementation)
    bpf_submit["addresses"][resolver_addr] = implementation_addr

def find_implementation_offset():
    """Find the offset of the implementation function."""
    for k, v in bpf_submit["addresses"].items():
        return v.value - k.value
    return None

def main():
    strlen_symbol = get_symbol_address("strlen")
    if not strlen_symbol:
        print("Failed to get strlen symbol address.")
        return

    strlen_offset = find_implementation_offset()
    if strlen_offset is None:
        print("Failed to find the implementation offset.")
        return

    strlen_impl_address = strlen_symbol + strlen_offset

    bpf_count.attach_uretprobe(name="c", sym="strlen", fn_name="count_return", addr=strlen_impl_address)

    print("Counting strlen return values. Press Ctrl+C to stop.")

    try:
        while True:
            time.sleep(1)
            print("Histogram of strlen return values:")
            bpf_count["hist"].print_log2_hist("strlen return values")
            bpf_count["hist"].clear()
    except KeyboardInterrupt:
        print("Detaching BPF program and exiting.")
        exit()

if __name__ == "__main__":
    main()
```