FM / tapset

/usr/share/systemtap/tapset

Name	Size	Mode	Actions
arm/	-	0755	rm
arm64/	-	0755	rm
bpf/	-	0755	rm
dyninst/	-	0755	rm
i386/	-	0755	rm
ia64/	-	0755	rm
linux/	-	0755	rm
mips/	-	0755	rm
powerpc/	-	0755	rm
riscv/	-	0755	rm
s390/	-	0755	rm
x86_64/	-	0755	rm
ansi.stp	4178	0644	edit dl rm
argv.stp	2721	0644	edit dl rm
choose_defined.stpm	208	0644	edit dl rm
container_of.stpm	235	0644	edit dl rm
context.stp	6103	0644	edit dl rm
errno.stp	9118	0644	edit dl rm
floatingpoint.stp	6936	0644	edit dl rm
indent-default.stp	59	0644	edit dl rm
indent.stp	4590	0644	edit dl rm
init.stp	269	0644	edit dl rm
input.stp	263	0644	edit dl rm
java.stp	1346	0644	edit dl rm
libperl5.26.3-64.stp	1339	0644	edit dl rm
libpython2.7-64.stp	522	0644	edit dl rm
livepatch.stp	3006	0644	edit dl rm
logging.stp	4132	0644	edit dl rm
macros.stpm	562	0644	edit dl rm
null.stp	17	0644	edit dl rm
offsetof.stpm	183	0644	edit dl rm
oneshot.stp	38	0644	edit dl rm
pn.stp	1588	0644	edit dl rm
print_stats.stpm	1719	0644	edit dl rm
private30.stpm	80	0644	edit dl rm
prometheus.stp	129	0644	edit dl rm
prometheus.stpm	8380	0644	edit dl rm
python.stp	474	0644	edit dl rm
python2.stp	29435	0644	edit dl rm
python3.stp	36655	0644	edit dl rm
queue_stats.stp	9487	0644	edit dl rm
random.stp	432	0644	edit dl rm
README	371	0644	edit dl rm
regex.stp	4107	0644	edit dl rm
registers.stp	11081	0644	edit dl rm
sizeof.stpm	212	0644	edit dl rm
speculative.stp	1746	0644	edit dl rm
sreg_arch.stpm	263	0644	edit dl rm
stap_staticmarkers.stp	9670	0644	edit dl rm
stopwatch.stp	3063	0644	edit dl rm
string.stp	7514	0644	edit dl rm
switchfile.stp	612	0644	edit dl rm
system.stp	593	0644	edit dl rm
this.stp	160	0644	edit dl rm
timers.stp	924	0644	edit dl rm
tls.stp	8099	0644	edit dl rm
tokenize.stp	2124	0644	edit dl rm
try_assign.stpm	768	0644	edit dl rm
type_defined.stpm	374	0644	edit dl rm
tzinfo.stp	930	0644	edit dl rm
uconversions-guru.stp	6078	0644	edit dl rm
uconversions.stp	36640	0644	edit dl rm

Edit: /usr/share/systemtap/tapset/regex.stp (4107B)

// Regular expression subexpression tapset
// Copyright (C) 2017 Serhei Makarov
// Copyright (C) 2013 Red Hat, Inc.
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.

%{
#define STAP_NEED_CONTEXT_SUBEXPRESSION 1
%}

/**
 * sfunction matched_str - Return the last matched string.
 *
 * Description: returns the string matched by the last successful
 * use of the =~ regexp matching operator. Returns an error if the
 * last use of =~ led to a failed match.
 */
function matched_str:string() { return matched(0) }

/**
 * sfunction matched - Return a given matched subexpression.
 *
 * @n: index to the subexpression to return. 0 corresponds to the
 * entire regular expression.
 *
 * Description: returns the content of the n'th subexpression of the
 * last successful use of the =~ regex matching operator. Returns an
 * empty string if the n'th subexpression was not matched (e.g. due to
 * alternation). Throws an error if the last use of =~ was a failed
 * match, or if fewer than n subexpressions are present in the
 * original regexp.
 */
function matched:string(n:long)
%{ /* pure */ /* unprivileged */ /* pragma:tagged_dfa */
  int start_ix, end_ix; // indices into tag buffer
  int start, end, length; // actual coordinate values

if (!CONTEXT->last_match.result) {
    snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
             "Attempted to get subexpression %lld from failed match", (long long) STAP_ARG_n);
    CONTEXT->last_error = CONTEXT->error_buffer;
  }

start_ix = 2 * STAP_ARG_n, end_ix = start_ix + 1;

if (end_ix >= CONTEXT->last_match.num_final_tags) {
    snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
             "Attempted to get nonexistent subexpression %lld", (long long) STAP_ARG_n);
    CONTEXT->last_error = CONTEXT->error_buffer;
  }

start = CONTEXT->last_match.tag_vals[start_ix];
  end = CONTEXT->last_match.tag_vals[end_ix];
  // _stp_printf ("**DEBUG** Extracted subexpression #%lld:(%d,%d) from %d to %d\n", STAP_ARG_n, start_ix, end_ix, start, end);

if (start < 0 || end < 0) {
    // If indices are negative, the group was not matched. Return empty string:
    start = end = 0;
    // snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
    //          "Unknown coordinates for subexpression %lld", STAP_ARG_n);
    // CONTEXT->last_error = CONTEXT->error_buffer;
  }

if (start > end) {
    // This should not happen.
    snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
             "BUG: inverted coordinates for subexpression %lld", (long long) STAP_ARG_n);
    CONTEXT->last_error = CONTEXT->error_buffer;
  }

length = end - start;

// TODOXXX assert (start <= strlen(matched_str)) ??
  // XXX: Must add 1 to length to account for NUL byte in strlcpy().
  strlcpy(STAP_RETVALUE, CONTEXT->last_match.matched_str + start, length + 1);
%}

/**
 * sfunction ngroups - Number of subexpressions in the last match.
 *
 * Description: returns the number of subexpressions from the
 * last successful use of the =~ regex matching operator.
 *
 * Note that this number includes subexpressions which are present in
 * the regex but did not match any string; for example, given the
 * regex "a|(b)", the subexpressions will count the group for (b)
 * regardless of whether it matched a string or not. Throws an error
 * if the last use of =~ was a failed match.
 */
function ngroups:long()
%{ /* pure */ /* unprivileged */ /* pragma:tagged_dfa */
  if (!CONTEXT->last_match.result) {
    snprintf(CONTEXT->error_buffer, sizeof(CONTEXT->error_buffer),
             "Attempted to get subexpression count from failed match");
    CONTEXT->last_error = CONTEXT->error_buffer;
  }

STAP_RETVALUE = CONTEXT->last_match.num_final_tags / 2;
%}

// XXX: perhaps implement matched_start, matched_end to get indices?
// XXX: some kind of find-replace functionality?
// XXX: some kind of splitting / multiple-match functionality?

cmd: