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[PATCH-for-4.2 v3 3/3] trace: Forbid dynamic field width in event format
From: |
Philippe Mathieu-Daudé |
Subject: |
[PATCH-for-4.2 v3 3/3] trace: Forbid dynamic field width in event format |
Date: |
Mon, 18 Nov 2019 22:04:58 +0100 |
Since not all trace backends support dynamic field width in
format (dtrace via stap does not), forbid them.
Add a check to refuse field width in new formats:
$ make
[...]
GEN hw/block/trace.h
Traceback (most recent call last):
File "scripts/tracetool.py", line 152, in <module>
main(sys.argv)
File "scripts/tracetool.py", line 143, in main
events.extend(tracetool.read_events(fh, arg))
File "scripts/tracetool/__init__.py", line 371, in read_events
event = Event.build(line)
File "scripts/tracetool/__init__.py", line 285, in build
raise ValueError("Event format must not contain field width '%*'")
ValueError: Error at hw/block/trace-events:11: Event format must not contain
field width '%*'
Reported-by: Eric Blake <address@hidden>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
---
v3:
- use better regex provided by Eric,
- instead of re.match(), use re.search() which takes unanchored regex,
- added a comment in tracing.txt
---
docs/devel/tracing.txt | 3 ++-
scripts/tracetool/__init__.py | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index 8c0376fefa..6c01ce801e 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -113,7 +113,8 @@ Format strings should reflect the types defined in the
trace event. Take
special care to use PRId64 and PRIu64 for int64_t and uint64_t types,
respectively. This ensures portability between 32- and 64-bit platforms.
Format strings must not end with a newline character. It is the responsibility
-of backends to adapt line ending for proper logging.
+of backends to adapt line ending for proper logging. Format strings must not
+use numeric field width dynamic precision (SystemTap does not support them).
Each event declaration will start with the event name, then its arguments,
finally a format string for pretty-printing. For example:
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 44c118bc2a..ec7fe9fa4a 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -206,6 +206,7 @@ class Event(object):
"\s*"
"(?:(?:(?P<fmt_trans>\".+),)?\s*(?P<fmt>\".+))?"
"\s*")
+ _DFWRE = re.compile(r"%[\d\.\- +#']*\*") # dynamic width precision
_VALID_PROPS = set(["disable", "tcg", "tcg-trans", "tcg-exec", "vcpu"])
@@ -280,6 +281,8 @@ class Event(object):
if fmt.endswith(r'\n"'):
raise ValueError("Event format must not end with a newline "
"character")
+ if Event._DFWRE.search(fmt):
+ raise ValueError("Event format must not contain field width '%*'")
if len(fmt_trans) > 0:
fmt = [fmt_trans, fmt]
--
2.21.0