watch-var

#! /usr/bin/env perl

# Copyright (C) YangBingwu (detailyang)

use 5.006001;
use strict;
use warnings;
use Getopt::Std qw ( getopts );

sub usage();


my %opts;

getopts("ht:a:df:v:p:", \%opts) or die usage();

if ($opts{h}) {
    print usage();
    exit;
}

my $function = $opts{f}
    or die "no function name specified by the -f option.\n";

my $vars = $opts{v}
    or die "no var name specified by the -v option.\n";

my $time = $opts{t} || '10000';

if ($time !~ /^\d+$/) {
    die "Bad -t option value \"$time\": not look like a time.\n";
}

my $pid = $opts{p}
    or die "No process pid specified by the -p option.\n";

if ($pid !~ /^\d+$/) {
    die "Bad -p option value \"$pid\": not look like a pid.\n";
}


my $preamble = <<_EOC_;
probe begin {
    warn(sprintf("Tracing vars $function $vars in $pid...\\n"))
}
_EOC_
chomp $preamble;

my $stap_src =<<_EOC_;
$preamble

global vars%

probe \$1 {
    if (pid() != target()) next
    if (\@defined(\$2)) {
        newvar = \$2
        if (vars[tid()] != newvar) {
            printf("%s[%d] %s %s: \\"%s\\" => \\"%s\\" \\n", execname(), tid(), pp(), \@2, vars[tid()], newvar);
            vars[tid()] = newvar;
        }
    }
}

probe timer.ms($time) {
    exit()
}
_EOC_

if ($opts{d}) {
    print $stap_src;
    exit();
}

open my $in, "| stap --skip-badvars -x $pid - '$function' '$vars'";

print $in $stap_src;

close $in;

sub usage() {
    return <<_EOS_;
Usage:
    watch-var [optoins]
Options:
    -a <args>           Pass extra arguments to the stap utility.
    -t <time>(ms)       Time(ms) to execute.
    -p <pid>            Process id to trace.
    -f <function>       Function name to trace like syscall.connect.
    -v <vars>           vars to trace like \$\$params filename.
    -d                  Dump out the systemtap script source.
    -h                  Print this usage.
Examples:
    watch-var -t 20000 -f "syscall.open" -v filename -p 123
_EOS_
}