Re: [PATCH v2 3/3] trace: Forbid dynamic field width in event format
On 11/8/19 10:07 AM, Eric Blake wrote:
On 11/8/19 8:40 AM, Philippe Mathieu-Daudé wrote:
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:
+++ b/scripts/tracetool/__init__.py
@@ -206,6 +206,7 @@ class Event(object):
"\s*"
"(?:(?:(?P\".+),)?\s*(?P\".+))?"
"\s*")
+ _DFWRE = re.compile(".*(%0?\*).*")
The use of leading and trailing .* is pointless if the RE itself is used
unanchored and where you only care if the () matched.
Following up on this (based on an IRC conversation):
re.match _is_ anchored by default, while re.search is unanchored
This doesn't catch all valid uses of * in a printf format. Better might
be something like:
_DFWRE = re.compile("%[\d\.\- +#']*\*")
which matches only if there is a %, any number of characters that can
form a printf flag, as well as a numeric field width but dynamic precision.
+ if Event._DFWRE.match(fmt):
Or put differently, if you want to drop the .* from the compiled regex,
then you need to use .search(fmt) here rather than .match(fmt).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
Re: [PATCH v2 3/3] trace: Forbid dynamic field width in event format
On 11/8/19 8:40 AM, Philippe Mathieu-Daudé wrote:
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:
+++ b/scripts/tracetool/__init__.py
@@ -206,6 +206,7 @@ class Event(object):
"\s*"
"(?:(?:(?P\".+),)?\s*(?P\".+))?"
"\s*")
+_DFWRE = re.compile(".*(%0?\*).*")
The use of leading and trailing .* is pointless if the RE itself is used
unanchored and where you only care if the () matched.
This doesn't catch all valid uses of * in a printf format. Better might
be something like:
_DFWRE = re.compile("%[\d\.\- +#']*\*")
which matches only if there is a %, any number of characters that can
form a printf flag, as well as a numeric field width but dynamic precision.
+if Event._DFWRE.match(fmt):
+raise ValueError("Event format must not contain field width '%*'")
if len(fmt_trans) > 0:
fmt = [fmt_trans, fmt]
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
[PATCH v2 3/3] trace: Forbid dynamic field width in event format
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
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
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé
---
scripts/tracetool/__init__.py | 3 +++
1 file changed, 3 insertions(+)
diff --git a/scripts/tracetool/__init__.py b/scripts/tracetool/__init__.py
index 44c118bc2a..e239be602b 100644
--- a/scripts/tracetool/__init__.py
+++ b/scripts/tracetool/__init__.py
@@ -206,6 +206,7 @@ class Event(object):
"\s*"
"(?:(?:(?P\".+),)?\s*(?P\".+))?"
"\s*")
+_DFWRE = re.compile(".*(%0?\*).*")
_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.match(fmt):
+raise ValueError("Event format must not contain field width '%*'")
if len(fmt_trans) > 0:
fmt = [fmt_trans, fmt]
--
2.21.0
