[Qemu-devel] [PATCH for-2.10 v2 1/2] trace: use static event ID mapping in simpletrace.stp

[Stefan Hajnoczi <stefanha@redhat.com>]

This is a partial revert of commit
7f1b588f20d027730676e627713ae3bbf6baab04 ("trace: emit name <-> ID
mapping in simpletrace header"), which broke the SystemTap flight
recorder because event mapping records may not be present in the ring
buffer when the trace is analyzed.  This means simpletrace.py
--no-header does not know the event ID mapping needed to pretty-print
the trace.

Instead of numbering events dynamically, use a static event ID mapping
as dictated by the event order in the trace-events-all file.

The simpletrace.py script also uses trace-events-all so the next patch
will fix the simpletrace.py --no-header option to take advantage of this
knowledge.

Cc: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 scripts/tracetool/format/simpletrace_stap.py | 31 ++--------------------------
 1 file changed, 2 insertions(+), 29 deletions(-)

diff --git a/scripts/tracetool/format/simpletrace_stap.py b/scripts/tracetool/format/simpletrace_stap.py
index 144b704bcd..e7e44842ca 100644
--- a/scripts/tracetool/format/simpletrace_stap.py
+++ b/scripts/tracetool/format/simpletrace_stap.py
@@ -22,33 +22,8 @@ def global_var_name(name):
     return probeprefix().replace(".", "_") + "_" + name
 
 def generate(events, backend, group):
-    id_map = global_var_name("event_name_to_id_map")
-    next_id = global_var_name("event_next_id")
-    map_func = global_var_name("simple_trace_map_event")
     out('/* This file is autogenerated by tracetool, do not edit. */',
-        '',
-        'global %(id_map)s',
-        'global %(next_id)s',
-        'function %(map_func)s(name)',
-        '',
-        '{',
-        '    if (!([name] in %(id_map)s)) {',
-        '        %(id_map)s[name] = %(next_id)s',
-        '        name_len = strlen(name)',
-        '        printf("%%8b%%8b%%4b%%.*s", 0, ',
-        '               %(next_id)s, name_len, name_len, name)',
-        '        %(next_id)s = %(next_id)s + 1',
-        '    }',
-        '    return %(id_map)s[name]',
-        '}',
-        'probe begin',
-        '{',
-        '    printf("%%8b%%8b%%8b", 0xffffffffffffffff, 0xf2b177cb0aa429b4, 4)',
-        '}',
-        '',
-        id_map=id_map,
-        next_id=next_id,
-        map_func=map_func)
+        '')
 
     for event_id, e in enumerate(events):
         if 'disable' in e.properties:
@@ -56,9 +31,7 @@ def generate(events, backend, group):
 
         out('probe %(probeprefix)s.simpletrace.%(name)s = %(probeprefix)s.%(name)s ?',
             '{',
-            '    id = %(map_func)s("%(name)s")',
             probeprefix=probeprefix(),
-            map_func=map_func,
             name=e.name)
 
         # Calculate record size
@@ -77,7 +50,7 @@ def generate(events, backend, group):
         sizestr = ' + '.join(sizes)
 
         # Generate format string and value pairs for record header and arguments
-        fields = [('8b', 'id'),
+        fields = [('8b', str(event_id)),
                   ('8b', 'gettimeofday_ns()'),
                   ('4b', sizestr),
                   ('4b', 'pid()')]
-- 
2.13.4