mirror of https://gitee.com/openkylin/linux.git
127 lines
4.2 KiB
Plaintext
127 lines
4.2 KiB
Plaintext
libtraceevent(3)
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================
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NAME
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----
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tep_print_field, tep_print_fields, tep_print_num_field, tep_print_func_field -
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Print the field content.
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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*#include <trace-seq.h>*
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void *tep_print_field*(struct trace_seq pass:[*]_s_, void pass:[*]_data_, struct tep_format_field pass:[*]_field_);
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void *tep_print_fields*(struct trace_seq pass:[*]_s_, void pass:[*]_data_, int _size_, struct tep_event pass:[*]_event_);
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int *tep_print_num_field*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int _err_);
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int *tep_print_func_field*(struct trace_seq pass:[*]_s_, const char pass:[*]_fmt_, struct tep_event pass:[*]_event_, const char pass:[*]_name_, struct tep_record pass:[*]_record_, int _err_);
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--
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DESCRIPTION
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-----------
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These functions print recorded field's data, according to the field's type.
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The _tep_print_field()_ function extracts from the recorded raw _data_ value of
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the _field_ and prints it into _s_, according to the field type.
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The _tep_print_fields()_ prints each field name followed by the record's field
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value according to the field's type:
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[verse]
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--
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"field1_name=field1_value field2_name=field2_value ..."
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--
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It iterates all fields of the _event_, and calls _tep_print_field()_ for each of
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them.
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The _tep_print_num_field()_ function prints a numeric field with given format
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string. A search is performed in the _event_ for a field with _name_. If such
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field is found, its value is extracted from the _record_ and is printed in the
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_s_, according to the given format string _fmt_. If the argument _err_ is
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non-zero, and an error occures - it is printed in the _s_.
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The _tep_print_func_field()_ function prints a function field with given format
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string. A search is performed in the _event_ for a field with _name_. If such
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field is found, its value is extracted from the _record_. The value is assumed
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to be a function address, and a search is perform to find the name of this
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function. The function name (if found) and its address are printed in the _s_,
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according to the given format string _fmt_. If the argument _err_ is non-zero,
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and an error occures - it is printed in _s_.
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RETURN VALUE
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------------
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The _tep_print_num_field()_ and _tep_print_func_field()_ functions return 1
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on success, -1 in case of an error or 0 if the print buffer _s_ is full.
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EXAMPLE
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-------
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[source,c]
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--
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#include <event-parse.h>
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#include <trace-seq.h>
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...
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struct tep_handle *tep = tep_alloc();
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...
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struct trace_seq seq;
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trace_seq_init(&seq);
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struct tep_event *event = tep_find_event_by_name(tep, "timer", "hrtimer_start");
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...
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void process_record(struct tep_record *record)
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{
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struct tep_format_field *field_pid = tep_find_common_field(event, "common_pid");
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trace_seq_reset(&seq);
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/* Print the value of "common_pid" */
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tep_print_field(&seq, record->data, field_pid);
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/* Print all fields of the "hrtimer_start" event */
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tep_print_fields(&seq, record->data, record->size, event);
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/* Print the value of "expires" field with custom format string */
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tep_print_num_field(&seq, " timer expires in %llu ", event, "expires", record, 0);
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/* Print the address and the name of "function" field with custom format string */
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tep_print_func_field(&seq, " timer function is %s ", event, "function", record, 0);
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}
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...
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--
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FILES
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-----
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[verse]
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--
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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*trace-seq.h*
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Header file to include in order to have access to trace sequences related APIs.
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Trace sequences are used to allow a function to call several other functions
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to create a string of data to use.
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*-ltraceevent*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtraceevent(3)_, _trace-cmd(1)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtraceevent is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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