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 <eblake@redhat.com>
Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
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
On 11/18/19 3:04 PM, 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:
>
> $ 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 <eblake@redhat.com>
> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> +++ 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).
Reads awkwardly - a dynamic precision is not numeric in the format
string (but '*' instead). Better might be:
Format strings must not use dynamic field width or precision ('*'), as
at least SystemTap does not support them.
Or even:
Format strings may use numeric field width or precision, but must not
use dynamic forms ('*') as at least SystemTap does not support that.
>
> 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
The comment is slightly off - this catches both dynamic field width (any
'*' before '.') and dynamic precision (any '*' after '.'), maybe the fix
is just s/width/width or/
>
> _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 '%*'")
and I don't know if you want to tweak the error message, maybe:
Event format must not use dynamic '*'
If we're trying to get stuff in 4.2-rc2, patch 1 and 2 are actual bug
fixes and deserve to go in; patch 3 is nice-to-have but doesn't affect
the build if it is omitted (as there are no other offenders left), so
slipping it into 5.0 for a v4 to clean it up slightly doesn't hurt. I
don't know who would send the pull request, though, and slipping 1 and 2
into -rc3 just because of 3 is not ideal.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
On 11/18/19 10:26 PM, Eric Blake wrote:
> On 11/18/19 3:04 PM, 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:
>>
>> $ 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 <eblake@redhat.com>
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1844817
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>
>> +++ 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).
>
> Reads awkwardly - a dynamic precision is not numeric in the format
> string (but '*' instead). Better might be:
>
> Format strings must not use dynamic field width or precision ('*'), as
> at least SystemTap does not support them.
>
> Or even:
>
> Format strings may use numeric field width or precision, but must not
> use dynamic forms ('*') as at least SystemTap does not support that.
>
>> 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
>
> The comment is slightly off - this catches both dynamic field width (any
> '*' before '.') and dynamic precision (any '*' after '.'), maybe the fix
> is just s/width/width or/
>
>> _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 '%*'")
>
> and I don't know if you want to tweak the error message, maybe:
> Event format must not use dynamic '*'
>
> If we're trying to get stuff in 4.2-rc2, patch 1 and 2 are actual bug
> fixes and deserve to go in; patch 3 is nice-to-have but doesn't affect
> the build if it is omitted (as there are no other offenders left), so
> slipping it into 5.0 for a v4 to clean it up slightly doesn't hurt. I
> don't know who would send the pull request, though, and slipping 1 and 2
> into -rc3 just because of 3 is not ideal.
Wise thought. I'll respin 1-2 with the Fixes: tag in case qemu-block@ or
qemu-trivial@ have pending pull-request for tomorrow, they can queue it.
Else they can go via the mips-next tree, since both patch affect the
Malta board.
Thanks!
Phil.
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