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Commit bbbab191 authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware) Committed by Arnaldo Carvalho de Melo
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tools lib traceevent: Separate out tep_strerror() for strerror_r() issues 



While working on having PowerTop use libtracevent as a shared object
library, Tzvetomir hit "str_error_r not defined". This was added by commit
c3cec9e6 ("tools lib traceevent: Use str_error_r()") because
strerror_r() has two definitions, where one is GNU specific, and the other
is XSI complient. The strerror_r() is in a wrapper str_error_r() to keep the
code from having to worry about which compiler is being used.

The problem is that str_error_r() is external to libtraceevent, and not part
of the library. If it is used as a shared object then the tools using it
will need to define that function. I do not want that function defined in
libtraceevent itself, as it is out of scope for that library.

As there's only a single instance of this call, and its in the traceevent
library's own tep_strerror() function, we can copy what was done in perf,
and create yet another external file that undefs _GNU_SOURCE to use the more
portable version of the function. We don't need to worry about the errors
that strerror_r() returns. If the buffer isn't big enough, we simply
truncate it.

Reported-by: default avatarTzvetomir Stoyanov <tstoyanov@vmware.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Cc: linux trace devel <linux-trace-devel@vger.kernel.org>
Link: http://lkml.kernel.org/r/20181005121816.484e654f@gandalf.local.home


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 8b2f245f

tools/lib/traceevent/Build

+1 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ libtraceevent-y += trace-seq.o 
libtraceevent-y += parse-filter.o

libtraceevent-y += parse-utils.o

libtraceevent-y += kbuffer-parse.o

libtraceevent-y += tep_strerror.o



plugin_jbd2-y         += plugin_jbd2.o

plugin_hrtimer-y      += plugin_hrtimer.o

tools/lib/traceevent/event-parse.c

+0 −30
Original line number Diff line number Diff line
@@ -18,7 +18,6 @@ 
#include <errno.h>

#include <stdint.h>

#include <limits.h>

#include <linux/string.h>

#include <linux/time64.h>



#include <netinet/in.h>
@@ -6201,35 +6200,6 @@ enum tep_errno tep_parse_event(struct tep_handle *pevent, const char *buf, 
	return __parse_event(pevent, &event, buf, size, sys);

}



#undef _PE

#define _PE(code, str) str

static const char * const tep_error_str[] = {

	TEP_ERRORS

};

#undef _PE



int tep_strerror(struct tep_handle *pevent __maybe_unused,

		 enum tep_errno errnum, char *buf, size_t buflen)

{

	int idx;

	const char *msg;



	if (errnum >= 0) {

		str_error_r(errnum, buf, buflen);

		return 0;

	}



	if (errnum <= __TEP_ERRNO__START ||

	    errnum >= __TEP_ERRNO__END)

		return -1;



	idx = errnum - __TEP_ERRNO__START - 1;

	msg = tep_error_str[idx];

	snprintf(buf, buflen, "%s", msg);



	return 0;

}



int get_field_val(struct trace_seq *s, struct tep_format_field *field,

		  const char *name, struct tep_record *record,

		  unsigned long long *val, int err)

tools/lib/traceevent/tep_strerror.c

0 → 100644
+53 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: LGPL-2.1

#undef _GNU_SOURCE

#include <string.h>

#include <stdio.h>



#include "event-parse.h"



#undef _PE

#define _PE(code, str) str

static const char * const tep_error_str[] = {

	TEP_ERRORS

};

#undef _PE



/*

 * The tools so far have been using the strerror_r() GNU variant, that returns

 * a string, be it the buffer passed or something else.

 *

 * But that, besides being tricky in cases where we expect that the function

 * using strerror_r() returns the error formatted in a provided buffer (we have

 * to check if it returned something else and copy that instead), breaks the

 * build on systems not using glibc, like Alpine Linux, where musl libc is

 * used.

 *

 * So, introduce yet another wrapper, str_error_r(), that has the GNU

 * interface, but uses the portable XSI variant of strerror_r(), so that users

 * rest asured that the provided buffer is used and it is what is returned.

 */

int tep_strerror(struct tep_handle *tep __maybe_unused,

		 enum tep_errno errnum, char *buf, size_t buflen)

{

	const char *msg;

	int idx;



	if (!buflen)

		return 0;



	if (errnum >= 0) {

		int err = strerror_r(errnum, buf, buflen);

		buf[buflen - 1] = 0;

		return err;

	}



	if (errnum <= __TEP_ERRNO__START ||

	    errnum >= __TEP_ERRNO__END)

		return -1;



	idx = errnum - __TEP_ERRNO__START - 1;

	msg = tep_error_str[idx];

	snprintf(buf, buflen, "%s", msg);



	return 0;

}