Re: [Crash-utility] [PATCH] extensions/trace.so: fix MEMBER_OFFSET usage
Hi Rabin,
I am still waiting for Fujitsu to name a new maintainer for the trace.c
extension module (given that Qiao Nuohan has apparently abandoned it).
I have been told by Fujitsu that they would resolve the maintainership
issue some time this week.
Until such time, there is still this patch proposal outstanding:
[Crash-utility] [Crash-Utility] extensions/trace: Add support for multiple ftrace
buffers
https://www.redhat.com/archives/crash-utility/2016-August/msg00000.html
And now this one...
In any case, it seems counter-productive to fix this issue by essentially
going backwards and using ANON_MEMBER_OFFSET(), which was a kludge to
begin with.
Would it be possible to fix this in different manner while continuing to
use the new-and-improved MEMBER_OFFSET()?
Dave
----- Original Message -----
From: Rabin Vincent <rabinv(a)axis.com>
In Linux v3.15 the name field of ftrace_event_fall moved into an
anonymous union (along with a new tp field). The trace extension
attempt to handle this by first checking if the offset can be
determined by MEMBER_OFFSET, and if that's the case, assuming that the
name is not in an anonymous union and thus that the kernel is pre-v3.15.
This used to work, but since the following commit, MEMBER_OFFSET seems
to even find fields inside anonymous unions, so the code always hits the
pre-v3.15 path even on newer kernels, preventing the trace extension
from successfully loading.
Fix this by reworking the checks to check for the tp field first and
using the presence of that field to identify a post-v3.15 kernel.
commit 5e6fbde738b827e2575aa9ec9ba4b3eb02ac65c5
Author: Dave Anderson <anderson(a)redhat.com>
Date: Thu Aug 25 14:26:58 2016 -0400
Enhancement to determine structure member data if the member is
contained within an anonymous structure or union. Without the patch,
it is necessary to parse the output of a discrete gdb "printf"
command to determine the offset of such a structure member.
(Alexandr_Terekhov(a)epam.com)
---
extensions/trace.c | 39 ++++++++++++++++++---------------------
1 file changed, 18 insertions(+), 21 deletions(-)
diff --git a/extensions/trace.c b/extensions/trace.c
index f8ccd91..b5901c4 100644
--- a/extensions/trace.c
+++ b/extensions/trace.c
@@ -1030,30 +1030,27 @@ int ftrace_get_event_type_name(ulong call, char
*name, int len)
if (inited)
goto work;
- inited = 1;
- name_offset = MAX(MEMBER_OFFSET("ftrace_event_call", "name"),
- MEMBER_OFFSET("trace_event_call", "name"));
- if (name_offset >= 0)
- goto work;
-
- name_offset = MAX(ANON_MEMBER_OFFSET("ftrace_event_call", "name"),
- ANON_MEMBER_OFFSET("trace_event_call", "name"));
- if (name_offset < 0)
- return -1;
-
- flags_offset = MAX(MEMBER_OFFSET("ftrace_event_call", "flags"),
- MEMBER_OFFSET("trace_event_call", "flags"));
- if (flags_offset < 0)
- return -1;
+ name_offset = MAX(ANON_MEMBER_OFFSET("ftrace_event_call", "tp"),
+ ANON_MEMBER_OFFSET("trace_event_call", "tp"));
+ if (name_offset >= 0) {
+ flags_offset = MAX(MEMBER_OFFSET("ftrace_event_call", "flags"),
+ MEMBER_OFFSET("trace_event_call", "flags"));
+ if (flags_offset < 0)
+ return -1;
- tp_name_offset = MEMBER_OFFSET("tracepoint", "name");
- if (tp_name_offset < 0)
- return -1;
+ tp_name_offset = MEMBER_OFFSET("tracepoint", "name");
+ if (tp_name_offset < 0)
+ return -1;
- if (!enumerator_value("TRACE_EVENT_FL_TRACEPOINT", &tracepoint_flag))
- return -1;
+ if (!enumerator_value("TRACE_EVENT_FL_TRACEPOINT", &tracepoint_flag))
+ return -1;
- inited = 2;
+ inited = 2;
+ } else {
+ name_offset = MAX(MEMBER_OFFSET("ftrace_event_call", "name"),
+ MEMBER_OFFSET("trace_event_call", "name"));
+ inited = 1;
+ }
work:
if (name_offset < 0)
--
2.1.4
--
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