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tracing: Fix showing of TASK_COMM_LEN instead of its value

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The TASK_COMM_LEN was converted from a macro into an enum so that BTF
 would have access to it. But this unfortunately caused TASK_COMM_LEN to
 display in the format fields of trace events, as they are created by the
 TRACE_EVENT() macro and such, macros convert to their values, where as
 enums do not.
 
 To handle this, instead of using the field itself to be display, save the
 value of the array size as another field in the trace_event_fields
 structure, and use that instead. Not only does this fix the issue, but
 also converts the other trace events that have this same problem (but were
 not breaking tooling). With this change, the original work around
 b3bc8547d3 ("tracing: Have TRACE_DEFINE_ENUM affect trace event types
 as well") could be reverted (but that should be done in the merge window).
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Merge tag 'trace-v6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fix from Steven Rostedt:
 "Fix showing of TASK_COMM_LEN instead of its value

  The TASK_COMM_LEN was converted from a macro into an enum so that BTF
  would have access to it. But this unfortunately caused TASK_COMM_LEN
  to display in the format fields of trace events, as they are created
  by the TRACE_EVENT() macro and such, macros convert to their values,
  where as enums do not.

  To handle this, instead of using the field itself to be display, save
  the value of the array size as another field in the trace_event_fields
  structure, and use that instead.

  Not only does this fix the issue, but also converts the other trace
  events that have this same problem (but were not breaking tooling).

  With this change, the original work around b3bc8547d3 ("tracing:
  Have TRACE_DEFINE_ENUM affect trace event types as well") could be
  reverted (but that should be done in the merge window)"

* tag 'trace-v6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Fix TASK_COMM_LEN in trace event format file
This commit is contained in:
Linus Torvalds 2023-02-12 13:52:17 -08:00
commit 5e98e916f9
5 changed files with 36 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/trace_events.h
View File

@ -270,6 +270,7 @@ struct trace_event_fields {
const int align;
const int is_signed;
const int filter_type;
const int len;
};
int (*define_fields)(struct trace_event_call *);
};

3
include/trace/stages/stage4_event_fields.h
View File

@ -26,7 +26,8 @@
#define __array(_type, _item, _len) { \
.type = #_type"["__stringify(_len)"]", .name = #_item, \
.size = sizeof(_type[_len]), .align = ALIGN_STRUCTFIELD(_type), \
.is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER },
.is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER,\
.len = _len },
#undef __dynamic_array
#define __dynamic_array(_type, _item, _len) { \

1
kernel/trace/trace.h
View File

@ -1282,6 +1282,7 @@ struct ftrace_event_field {
int offset;
int size;
int is_signed;
int len;
};
struct prog_entry;

39
kernel/trace/trace_events.c
View File

@ -114,7 +114,7 @@ trace_find_event_field(struct trace_event_call *call, char *name)
static int __trace_define_field(struct list_head *head, const char *type,
const char *name, int offset, int size,
int is_signed, int filter_type)
int is_signed, int filter_type, int len)
{
struct ftrace_event_field *field;
@ -133,6 +133,7 @@ static int __trace_define_field(struct list_head *head, const char *type,
field->offset = offset;
field->size = size;
field->is_signed = is_signed;
field->len = len;
list_add(&field->link, head);
@ -150,14 +151,28 @@ int trace_define_field(struct trace_event_call *call, const char *type,
head = trace_get_fields(call);
return __trace_define_field(head, type, name, offset, size,
is_signed, filter_type);
is_signed, filter_type, 0);
}
EXPORT_SYMBOL_GPL(trace_define_field);
int trace_define_field_ext(struct trace_event_call *call, const char *type,
const char *name, int offset, int size, int is_signed,
int filter_type, int len)
{
struct list_head *head;
if (WARN_ON(!call->class))
return 0;
head = trace_get_fields(call);
return __trace_define_field(head, type, name, offset, size,
is_signed, filter_type, len);
}
#define __generic_field(type, item, filter_type) \
ret = __trace_define_field(&ftrace_generic_fields, #type, \
#item, 0, 0, is_signed_type(type), \
filter_type); \
filter_type, 0); \
if (ret) \
return ret;
@ -166,7 +181,7 @@ EXPORT_SYMBOL_GPL(trace_define_field);
"common_" #item, \
offsetof(typeof(ent), item), \
sizeof(ent.item), \
is_signed_type(type), FILTER_OTHER); \
is_signed_type(type), FILTER_OTHER, 0); \
if (ret) \
return ret;
@ -1588,12 +1603,17 @@ static int f_show(struct seq_file *m, void *v)
seq_printf(m, "\tfield:%s %s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
field->type, field->name, field->offset,
field->size, !!field->is_signed);
else
seq_printf(m, "\tfield:%.*s %s%s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
else if (field->len)
seq_printf(m, "\tfield:%.*s %s[%d];\toffset:%u;\tsize:%u;\tsigned:%d;\n",
(int)(array_descriptor - field->type),
field->type, field->name,
array_descriptor, field->offset,
field->len, field->offset,
field->size, !!field->is_signed);
else
seq_printf(m, "\tfield:%.*s %s[];\toffset:%u;\tsize:%u;\tsigned:%d;\n",
(int)(array_descriptor - field->type),
field->type, field->name,
field->offset, field->size, !!field->is_signed);
return 0;
}
@ -2379,9 +2399,10 @@ event_define_fields(struct trace_event_call *call)
}
offset = ALIGN(offset, field->align);
ret = trace_define_field(call, field->type, field->name,
ret = trace_define_field_ext(call, field->type, field->name,
offset, field->size,
field->is_signed, field->filter_type);
field->is_signed, field->filter_type,
field->len);
if (WARN_ON_ONCE(ret)) {
pr_err("error code is %d\n", ret);
break;

3
kernel/trace/trace_export.c
View File

@ -111,7 +111,8 @@ static void __always_unused ____ftrace_check_##name(void) \
#define __array(_type, _item, _len) { \
.type = #_type"["__stringify(_len)"]", .name = #_item, \
.size = sizeof(_type[_len]), .align = __alignof__(_type), \
is_signed_type(_type), .filter_type = FILTER_OTHER },
is_signed_type(_type), .filter_type = FILTER_OTHER, \
.len = _len },
#undef __array_desc
#define __array_desc(_type, _container, _item, _len) __array(_type, _item, _len)