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033c55fe2e
The fields of ftrace specific events (events used to save ftrace internal
events like function traces and trace_printk) are generated similarly to
how normal trace event fields are generated. That is, the fields are added
to a trace_events_fields array that saves the name, offset, size,
alignment and signness of the field. It is used to produce the output in
the format file in tracefs so that tooling knows how to parse the binary
data of the trace events.
The issue is that some of the ftrace event structures are packed. The
function graph exit event structures are one of them. The 64 bit calltime
and rettime fields end up 4 byte aligned, but the algorithm to show to
userspace shows them as 8 byte aligned.
The macros that create the ftrace events has one for embedded structure
fields. There's two macros for theses fields:
__field_desc() and __field_packed()
The difference of the latter macro is that it treats the field as packed.
Rename that field to __field_desc_packed() and create replace the
__field_packed() to be a normal field that is packed and have the calltime
and rettime use those.
This showed up on 32bit architectures for function graph time fields. It
had:
~# cat /sys/kernel/tracing/events/ftrace/funcgraph_exit/format
[..]
field:unsigned long func; offset:8; size:4; signed:0;
field:unsigned int depth; offset:12; size:4; signed:0;
field:unsigned int overrun; offset:16; size:4; signed:0;
field:unsigned long long calltime; offset:24; size:8; signed:0;
field:unsigned long long rettime; offset:32; size:8; signed:0;
Notice that overrun is at offset 16 with size 4, where in the structure
calltime is at offset 20 (16 + 4), but it shows the offset at 24. That's
because it used the alignment of unsigned long long when used as a
declaration and not as a member of a structure where it would be aligned
by word size (in this case 4).
By using the proper structure alignment, the format has it at the correct
offset:
~# cat /sys/kernel/tracing/events/ftrace/funcgraph_exit/format
[..]
field:unsigned long func; offset:8; size:4; signed:0;
field:unsigned int depth; offset:12; size:4; signed:0;
field:unsigned int overrun; offset:16; size:4; signed:0;
field:unsigned long long calltime; offset:20; size:8; signed:0;
field:unsigned long long rettime; offset:28; size:8; signed:0;
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reported-by: "jempty.liang" <imntjempty@163.com>
Link: https://patch.msgid.link/20260204113628.53faec78@gandalf.local.home
Fixes: 04ae87a520 ("ftrace: Rework event_create_dir()")
Closes: https://lore.kernel.org/all/20260130015740.212343-1-imntjempty@163.com/
Closes: https://lore.kernel.org/all/20260202123342.2544795-1-imntjempty@163.com/
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
211 lines
5.7 KiB
C
211 lines
5.7 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_packed
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#define __field_packed(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_desc_packed
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#define __field_desc_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 __stack_array
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#define __stack_array(type, item, size, field) __array(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_packed
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#define __field_packed(_type, _item) __field_ext_packed(_type, _item, FILTER_OTHER)
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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_desc_packed
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#define __field_desc_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 __stack_array
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#define __stack_array(_type, _item, _len, _field) __array(_type, _item, _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_packed
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#define __field_packed(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_desc_packed
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#define __field_desc_packed(type, container, item)
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#undef __array
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#define __array(type, item, len)
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#undef __stack_array
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#define __stack_array(type, item, len, field)
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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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