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| -rw-r--r-- | Documentation/libtracefs-error.txt | 137 |
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diff --git a/Documentation/libtracefs-error.txt b/Documentation/libtracefs-error.txt new file mode 100644 index 0000000..a45332d --- /dev/null +++ b/Documentation/libtracefs-error.txt @@ -0,0 +1,137 @@ +libtracefs(3) +============= + +NAME +---- +tracefs_error_last, tracefs_error_all, tracefs_error_clear - +functions to read and clear the tracefs error log. + +SYNOPSIS +-------- +[verse] +-- +*#include <tracefs.h>* + +char pass:[*]*tracefs_error_last*(struct tracefs_instance pass:[*]_instance_); +char pass:[*]*tracefs_error_all*(struct tracefs_instance pass:[*]_instance_); +int *tracefs_error_clear*(struct tracefs_instance pass:[*]_instance_); +-- + +DESCRIPTION +----------- +The *tracefs_error_last*() returns the last error message in the tracefs +error log. Several actions that require proper syntax written into the +tracefs file system may produce error messages in the error log. This +function will show the most recent error in the error log. + +The *tracefs_error_all*() returns all messages saved in the error log. +Note, this may not be all messages that were ever produced, as the kernel +only keeps a limited amount of messages, and older ones may be discarded +by the kernel. + +The *tracefs_error_clear*() will clear the error log. + +RETURN VALUE +------------ +Both *tracefs_error_last*() and *tracefs_error_all*() will return an allocated +string an error exists in the log, otherwise NULL is returned. If an error +occurs, errno will be set, otherwise if there is no error messages to display +then errno is not touched. + +*tracefs_error_clear*() returns 0 on success or -1 on error. + +EXAMPLE +------- +[source,c] +-- +#include <stdlib.h> +#include <unistd.h> +#include <errno.h> + +#include <tracefs.h> + +int main (int argc, char **argv, char **env) +{ + struct tracefs_dynevent *kevent; + char *system = NULL; + char *kprobe; + char *format; + char *addr; + int arg = 1; + int ret; + + if (argc < 4) { + printf("usage: %s [system] kprobe addr fmt\n", argv[0]); + exit(-1); + } + + if (argc > 5) + system = argv[arg++]; + + kprobe = argv[arg++]; + addr = argv[arg++]; + format = argv[arg++]; + + tracefs_error_clear(NULL); + kevent = tracefs_dynevent_get(TRACEFS_DYNEVENT_KPROBE, system, kprobe); + if (kevent) { + tracefs_dynevent_destroy(kevent, true); + tracefs_dynevent_free(kevent); + } + + ret = tracefs_kprobe_raw(system, kprobe, addr, format); + if (ret < 0) { + char *err; + + perror("Failed creating kprobe"); + errno = 0; + err = tracefs_error_last(NULL); + if (err) + fprintf(stderr, "%s\n", err); + else if (errno) + perror("Failed reading error log"); + free(err); + } + + exit(ret); +} +-- +FILES +----- +[verse] +-- +*tracefs.h* + Header file to include in order to have access to the library APIs. +*-ltracefs* + Linker switch to add when building a program that uses the library. +-- + +SEE ALSO +-------- +*libtracefs*(3), +*libtraceevent*(3), +*trace-cmd*(1) + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org> +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com> +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtracefs is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ + +COPYING +------- +Copyright \(C) 2020 VMware, Inc. Free use of this software is granted under +the terms of the GNU Public License (GPL). |