Fix: lttng: placing probe on symbol starting with `_`

Issue
=====
The lttng CLI tool does not parse `--probe` symbol name properly if the
name has an underscore at the beginning.
For example, the following command fails
  lttng enable-event -k --probe _do_fork my_do_fork_event

This happens because the `parse_probe_opts()` function looks if the
first character of the symbol field is an alphabetic character to
determine if a symbol was provided. The problem is that some kernel
symbols such as `_do_fork` start with an underscore.

Solution
========
check if the first character is an alphabetic character OR an
underscore.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I3ee6c26641ceee508ee78e895d372c6b09fe90fb
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng/commands/enable_events.c b/src/bin/lttng/commands/enable_events.c
index 6889b63d73eb12cacc8db055c4bd0d2a0bcc1fd1..84bcb20814233c8928a53b9fd8e1d93e88b453d5 100644 (file)
--- a/src/bin/lttng/commands/enable_events.c
+++ b/src/bin/lttng/commands/enable_events.c
@@ -143,7 +143,7 @@ static int parse_probe_opts(struct lttng_event *ev, char *opt)
        }
 
        /* Check for symbol */
        }
 
        /* Check for symbol */

-       if (isalpha(name[0])) {
+       if (isalpha(name[0]) || name[0] == '_') {

                match = sscanf(opt, "%" LTTNG_SYMBOL_NAME_LEN_SCANF_IS_A_BROKEN_API "s",
                        name);
                if (match == 1) {
                match = sscanf(opt, "%" LTTNG_SYMBOL_NAME_LEN_SCANF_IS_A_BROKEN_API "s",
                        name);
                if (match == 1) {