tools lib traceevent: Use str_error_r()

To make it portable to non-glibc systems, that follow the XSI variant
instead of the GNU specific one that gets in place when _GNU_SOURCE is
defined.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-c1gn8x978qfop65m510wy43o@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
[ Updated to have include/linux/string.h too ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

4 files changed, 36 insertions, 8 deletions

diff --git a/Makefile b/Makefile
index 62cb25b6..0a9c1952 100644
--- a/Makefile
+++ b/Makefile
@@ -226,7 +226,7 @@ export Q VERBOSE
 TRACECMD_VERSION = $(TC_VERSION).$(TC_PATCHLEVEL).$(TC_EXTRAVERSION)
 KERNELSHARK_VERSION = $(KS_VERSION).$(KS_PATCHLEVEL).$(KS_EXTRAVERSION)
 
-INCLUDES = -I. -I $(srctree)/../../include $(CONFIG_INCLUDES)
+INCLUDES = -I. -I ./include -I $(srctree)/../../include $(CONFIG_INCLUDES)
 
 include $(src)/features.mk
 
@@ -339,7 +339,7 @@ TRACE_GRAPH_MAIN_OBJS = trace-graph-main.o $(TRACE_GRAPH_OBJS) $(TRACE_GUI_OBJS)
 KERNEL_SHARK_OBJS = $(TRACE_VIEW_OBJS) $(TRACE_GRAPH_OBJS) $(TRACE_GUI_OBJS) \
 	trace-capture.o kernel-shark.o
 
-PEVENT_LIB_OBJS = event-parse.o trace-seq.o parse-filter.o parse-utils.o
+PEVENT_LIB_OBJS = event-parse.o trace-seq.o parse-filter.o parse-utils.o str_error_r.o
 TCMD_LIB_OBJS = $(PEVENT_LIB_OBJS) trace-util.o trace-input.o trace-ftrace.o \
 			trace-output.o trace-record.o trace-recorder.o \
 			trace-restore.o trace-usage.o trace-blk-hack.o \
diff --git a/event-parse.c b/event-parse.c
index 82400ead..d6ca5225 100644
--- a/event-parse.c
+++ b/event-parse.c
@@ -31,6 +31,7 @@
 #include <errno.h>
 #include <stdint.h>
 #include <limits.h>
+#include <linux/string.h>
 
 #include <netinet/ip6.h>
 #include "event-parse.h"
@@ -6157,12 +6158,7 @@ int pevent_strerror(struct pevent *pevent __maybe_unused,
 	const char *msg;
 
 	if (errnum >= 0) {
-		msg = strerror_r(errnum, buf, buflen);
-		if (msg != buf) {
-			size_t len = strlen(msg);
-			memcpy(buf, msg, min(buflen - 1, len));
-			*(buf + min(buflen - 1, len)) = '\0';
-		}
+		str_error_r(errnum, buf, buflen);
 		return 0;
 	}
 
diff --git a/include/linux/string.h b/include/linux/string.h
new file mode 100644
index 00000000..8052d80f
--- /dev/null
+++ b/include/linux/string.h
@@ -0,0 +1,6 @@
+#ifndef __LINUX_STRING_H_
+#define __LINUX_STRING_H_
+
+char *str_error_r(int errnum, char *buf, size_t buflen);
+
+#endif
diff --git a/str_error_r.c b/str_error_r.c
new file mode 100644
index 00000000..503ae072
--- /dev/null
+++ b/str_error_r.c
@@ -0,0 +1,26 @@
+#undef _GNU_SOURCE
+#include <string.h>
+#include <stdio.h>
+#include <linux/string.h>
+
+/*
+ * 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.
+ */
+char *str_error_r(int errnum, char *buf, size_t buflen)
+{
+	int err = strerror_r(errnum, buf, buflen);
+	if (err)
+		snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);
+	return buf;
+}