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After commit3087c61ed2("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN"), the content of the format file under /sys/kernel/tracing/events/task/task_newtask was changed from field:char comm[16]; offset:12; size:16; signed:0; to field:char comm[TASK_COMM_LEN]; offset:12; size:16; signed:0; John reported that this change breaks older versions of perfetto. Then Mathieu pointed out that this behavioral change was caused by the use of __stringify(_len), which happens to work on macros, but not on enum labels. And he also gave the suggestion on how to fix it: :One possible solution to make this more robust would be to extend :struct trace_event_fields with one more field that indicates the length :of an array as an actual integer, without storing it in its stringified :form in the type, and do the formatting in f_show where it belongs. The result as follows after this change, $ cat /sys/kernel/tracing/events/task/task_newtask/format field:char comm[16]; offset:12; size:16; signed:0; Link: https://lore.kernel.org/lkml/Y+QaZtz55LIirsUO@google.com/ Link: https://lore.kernel.org/linux-trace-kernel/20230210155921.4610-1-laoar.shao@gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20230212151303.12353-1-laoar.shao@gmail.com Cc: stable@vger.kernel.org Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Kajetan Puchalski <kajetan.puchalski@arm.com> CC: Qais Yousef <qyousef@layalina.io> Fixes:3087c61ed2("tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN") Reported-by: John Stultz <jstultz@google.com> Debugged-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
193 lines
5.2 KiB
C
193 lines
5.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* trace_export.c - export basic ftrace utilities to user space
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*
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* Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
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*/
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#include <linux/stringify.h>
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#include <linux/kallsyms.h>
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#include <linux/seq_file.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include "trace_output.h"
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/* Stub function for events with triggers */
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static int ftrace_event_register(struct trace_event_call *call,
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enum trace_reg type, void *data)
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{
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return 0;
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}
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#undef TRACE_SYSTEM
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#define TRACE_SYSTEM ftrace
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/*
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* The FTRACE_ENTRY_REG macro allows ftrace entry to define register
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* function and thus become accessible via perf.
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*/
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#undef FTRACE_ENTRY_REG
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#define FTRACE_ENTRY_REG(name, struct_name, id, tstruct, print, regfn) \
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FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print))
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/* not needed for this file */
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#undef __field_struct
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#define __field_struct(type, item)
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#undef __field
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#define __field(type, item) type item;
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#undef __field_fn
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#define __field_fn(type, item) type item;
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#undef __field_desc
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#define __field_desc(type, container, item) type item;
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#undef __field_packed
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#define __field_packed(type, container, item) type item;
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#undef __array
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#define __array(type, item, size) type item[size];
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#undef __array_desc
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#define __array_desc(type, container, item, size) type item[size];
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#undef __dynamic_array
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#define __dynamic_array(type, item) type item[];
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#undef F_STRUCT
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#define F_STRUCT(args...) args
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#undef F_printk
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#define F_printk(fmt, args...) fmt, args
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#undef FTRACE_ENTRY
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#define FTRACE_ENTRY(name, struct_name, id, tstruct, print) \
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struct ____ftrace_##name { \
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tstruct \
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}; \
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static void __always_unused ____ftrace_check_##name(void) \
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{ \
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struct ____ftrace_##name *__entry = NULL; \
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\
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/* force compile-time check on F_printk() */ \
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printk(print); \
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}
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#undef FTRACE_ENTRY_DUP
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#define FTRACE_ENTRY_DUP(name, struct_name, id, tstruct, print) \
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FTRACE_ENTRY(name, struct_name, id, PARAMS(tstruct), PARAMS(print))
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#include "trace_entries.h"
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#undef __field_ext
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#define __field_ext(_type, _item, _filter_type) { \
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.type = #_type, .name = #_item, \
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.size = sizeof(_type), .align = __alignof__(_type), \
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is_signed_type(_type), .filter_type = _filter_type },
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#undef __field_ext_packed
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#define __field_ext_packed(_type, _item, _filter_type) { \
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.type = #_type, .name = #_item, \
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.size = sizeof(_type), .align = 1, \
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is_signed_type(_type), .filter_type = _filter_type },
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#undef __field
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#define __field(_type, _item) __field_ext(_type, _item, FILTER_OTHER)
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#undef __field_fn
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#define __field_fn(_type, _item) __field_ext(_type, _item, FILTER_TRACE_FN)
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#undef __field_desc
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#define __field_desc(_type, _container, _item) __field_ext(_type, _item, FILTER_OTHER)
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#undef __field_packed
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#define __field_packed(_type, _container, _item) __field_ext_packed(_type, _item, FILTER_OTHER)
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#undef __array
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#define __array(_type, _item, _len) { \
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.type = #_type"["__stringify(_len)"]", .name = #_item, \
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.size = sizeof(_type[_len]), .align = __alignof__(_type), \
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is_signed_type(_type), .filter_type = FILTER_OTHER, \
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.len = _len },
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#undef __array_desc
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#define __array_desc(_type, _container, _item, _len) __array(_type, _item, _len)
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#undef __dynamic_array
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#define __dynamic_array(_type, _item) { \
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.type = #_type "[]", .name = #_item, \
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.size = 0, .align = __alignof__(_type), \
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is_signed_type(_type), .filter_type = FILTER_OTHER },
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#undef FTRACE_ENTRY
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#define FTRACE_ENTRY(name, struct_name, id, tstruct, print) \
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static struct trace_event_fields ftrace_event_fields_##name[] = { \
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tstruct \
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{} };
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#include "trace_entries.h"
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#undef __entry
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#define __entry REC
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#undef __field
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#define __field(type, item)
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#undef __field_fn
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#define __field_fn(type, item)
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#undef __field_desc
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#define __field_desc(type, container, item)
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#undef __field_packed
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#define __field_packed(type, container, item)
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#undef __array
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#define __array(type, item, len)
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#undef __array_desc
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#define __array_desc(type, container, item, len)
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#undef __dynamic_array
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#define __dynamic_array(type, item)
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#undef F_printk
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#define F_printk(fmt, args...) __stringify(fmt) ", " __stringify(args)
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#undef FTRACE_ENTRY_REG
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#define FTRACE_ENTRY_REG(call, struct_name, etype, tstruct, print, regfn) \
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static struct trace_event_class __refdata event_class_ftrace_##call = { \
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.system = __stringify(TRACE_SYSTEM), \
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.fields_array = ftrace_event_fields_##call, \
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.fields = LIST_HEAD_INIT(event_class_ftrace_##call.fields),\
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.reg = regfn, \
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}; \
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\
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struct trace_event_call __used event_##call = { \
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.class = &event_class_ftrace_##call, \
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{ \
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.name = #call, \
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}, \
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.event.type = etype, \
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.print_fmt = print, \
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.flags = TRACE_EVENT_FL_IGNORE_ENABLE, \
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}; \
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static struct trace_event_call __used \
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__section("_ftrace_events") *__event_##call = &event_##call;
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#undef FTRACE_ENTRY
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#define FTRACE_ENTRY(call, struct_name, etype, tstruct, print) \
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FTRACE_ENTRY_REG(call, struct_name, etype, \
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PARAMS(tstruct), PARAMS(print), NULL)
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bool ftrace_event_is_function(struct trace_event_call *call)
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{
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return call == &event_function;
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}
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#include "trace_entries.h"
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