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Currently the trace_event structures are placed in the _ftrace_events section, and at link time, the linker makes one large array of all the trace_event structures. On boot up, this array is read (much like the initcall sections) and the events are processed. The problem is that there is no guarantee that gcc will place complex structures nicely together in an array format. Two structures in the same file may be placed awkwardly, because gcc has no clue that they are suppose to be in an array. A hack was used previous to force the alignment to 4, to pack the structures together. But this caused alignment issues with other architectures (sparc). Instead of packing the structures into an array, the structures' addresses are now put into the _ftrace_event section. As pointers are always the natural alignment, gcc should always pack them tightly together (otherwise initcall, extable, etc would also fail). By having the pointers to the structures in the section, we can still iterate the trace_events without causing unnecessary alignment problems with other architectures, or depending on the current behaviour of gcc that will likely change in the future just to tick us kernel developers off a little more. The _ftrace_event section is also moved into the .init.data section as it is now only needed at boot up. Suggested-by: David Miller <davem@davemloft.net> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
174 lines
4.5 KiB
C
174 lines
4.5 KiB
C
/*
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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/debugfs.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 <linux/fs.h>
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#include "trace_output.h"
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#undef TRACE_SYSTEM
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#define TRACE_SYSTEM ftrace
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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_desc
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#define __field_desc(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
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#define __field(type, item) \
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ret = trace_define_field(event_call, #type, #item, \
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offsetof(typeof(field), item), \
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sizeof(field.item), \
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is_signed_type(type), FILTER_OTHER); \
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if (ret) \
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return ret;
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#undef __field_desc
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#define __field_desc(type, container, item) \
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ret = trace_define_field(event_call, #type, #item, \
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offsetof(typeof(field), \
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container.item), \
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sizeof(field.container.item), \
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is_signed_type(type), FILTER_OTHER); \
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if (ret) \
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return ret;
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#undef __array
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#define __array(type, item, len) \
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do { \
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BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
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mutex_lock(&event_storage_mutex); \
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snprintf(event_storage, sizeof(event_storage), \
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"%s[%d]", #type, len); \
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ret = trace_define_field(event_call, event_storage, #item, \
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offsetof(typeof(field), item), \
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sizeof(field.item), \
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is_signed_type(type), FILTER_OTHER); \
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mutex_unlock(&event_storage_mutex); \
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if (ret) \
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return ret; \
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} while (0);
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#undef __array_desc
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#define __array_desc(type, container, item, len) \
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BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \
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ret = trace_define_field(event_call, #type "[" #len "]", #item, \
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offsetof(typeof(field), \
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container.item), \
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sizeof(field.container.item), \
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is_signed_type(type), FILTER_OTHER); \
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if (ret) \
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return ret;
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#undef __dynamic_array
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#define __dynamic_array(type, item) \
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ret = trace_define_field(event_call, #type, #item, \
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offsetof(typeof(field), item), \
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0, is_signed_type(type), FILTER_OTHER);\
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if (ret) \
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return ret;
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#undef FTRACE_ENTRY
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#define FTRACE_ENTRY(name, struct_name, id, tstruct, print) \
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int \
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ftrace_define_fields_##name(struct ftrace_event_call *event_call) \
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{ \
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struct struct_name field; \
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int ret; \
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\
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tstruct; \
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\
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return ret; \
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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_desc
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#define __field_desc(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...) #fmt ", " __stringify(args)
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#undef FTRACE_ENTRY
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#define FTRACE_ENTRY(call, struct_name, etype, tstruct, print) \
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\
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struct ftrace_event_class event_class_ftrace_##call = { \
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.system = __stringify(TRACE_SYSTEM), \
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.define_fields = ftrace_define_fields_##call, \
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.fields = LIST_HEAD_INIT(event_class_ftrace_##call.fields),\
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}; \
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\
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struct ftrace_event_call __used event_##call = { \
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.name = #call, \
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.event.type = etype, \
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.class = &event_class_ftrace_##call, \
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.print_fmt = print, \
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}; \
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struct ftrace_event_call __used \
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__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call;
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#include "trace_entries.h"
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