From patchwork Fri Oct 5 16:18:16 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 10759473 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:56386 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729546AbeJEXRo (ORCPT ); Fri, 5 Oct 2018 19:17:44 -0400 Date: Fri, 5 Oct 2018 12:18:16 -0400 From: Steven Rostedt To: Arnaldo Carvalho de Melo Cc: LKML , Jiri Olsa , Ingo Molnar , Namhyung Kim , Tzvetomir Stoyanov , Linux Trace Devel Subject: [PATCH v4] tools/lib/traceevent: Separate out tep_strerror() for strerror_r() issues Message-ID: <20181005121816.484e654f@gandalf.local.home> MIME-Version: 1.0 Sender: linux-trace-devel-owner@vger.kernel.org List-ID: Content-Length: 5005 From: "Steven Rostedt (VMware)" While working on having PowerTop use libtracevent as a shared object library, Tzvetomir hit "str_error_r not defined". This was added by commit c3cec9e68f12d ("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. Link: http://lkml.kernel.org/r/20181002175539.2ac894c7@gandalf.local.home Reported-by: Tzvetomir Stoyanov Signed-off-by: Steven Rostedt (VMware) --- tools/lib/traceevent/Build | 1 + tools/lib/traceevent/event-parse.c | 30 --------------------- tools/lib/traceevent/tep_strerror.c | 53 +++++++++++++++++++++++++++++++++++++ 3 files changed, 54 insertions(+), 30 deletions(-) create mode 100644 tools/lib/traceevent/tep_strerror.c diff --git a/tools/lib/traceevent/Build b/tools/lib/traceevent/Build index c681d0575d16..0050c145d806 100644 --- a/tools/lib/traceevent/Build +++ b/tools/lib/traceevent/Build @@ -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 diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c index 7980fc6c3bac..233179a712d6 100644 --- a/tools/lib/traceevent/event-parse.c +++ b/tools/lib/traceevent/event-parse.c @@ -18,7 +18,6 @@ #include #include #include -#include #include #include @@ -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) diff --git a/tools/lib/traceevent/tep_strerror.c b/tools/lib/traceevent/tep_strerror.c new file mode 100644 index 000000000000..4ac26445b2f6 --- /dev/null +++ b/tools/lib/traceevent/tep_strerror.c @@ -0,0 +1,53 @@ +// SPDX-License-Identifier: LGPL-2.1 +#undef _GNU_SOURCE +#include +#include + +#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; +}