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Bug 1366574 - dyninst: Installs breakpoints even in read-only mode
Summary: dyninst: Installs breakpoints even in read-only mode
Alias: None
Product: Fedora
Classification: Fedora
Component: dyninst
Version: 24
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Stan Cox
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2016-08-12 11:20 UTC by Florian Weimer
Modified: 2017-08-08 16:30 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2017-08-08 16:30:06 UTC

Attachments (Terms of Use)
trace-only.cpp (deleted)
2016-08-12 11:56 UTC, Florian Weimer
no flags Details

System ID Priority Status Summary Last Updated
Github dyninst dyninst issues 181 None None None 2016-09-20 19:50:57 UTC

Description Florian Weimer 2016-08-12 11:20:44 UTC
Description of problem:

Dyninst, even when using read-only interfaces, installs a breakpoint in the target process, on the _dl_debug_state function.

If the tracer crashes or exits abnormally, the breakpoint will persist, and the traced program may hit and crash as a result.  This means that it is impossible to write non-invasive tools using Dyninst at present.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Compile the attached file and link it against Dyninst.
2. Run: strace -f -eptrace ./trace-only $$
3. Observe the use of PTRACE_POKETEXT

Actual results:

[pid 28892] ptrace(PTRACE_POKETEXT, 28832, 0x7fb297d2de80, 0x2e6666666666c3cc) = 0

Expected results:


Comment 1 Florian Weimer 2016-08-12 11:56:59 UTC
Created attachment 1190350 [details]

Comment 2 Josh Stone 2016-08-12 18:58:37 UTC
You can turn off library tracking by default:

  #include <dyninst/PlatFeatures.h>

Then for a given Process, you can refresh manually with:


Does that suffice for you?

AFAICS the various "tracking" APIs are not discussed at all in proccontrol.pdf though, so that's probably worth raising upstream.

Comment 3 Florian Weimer 2016-08-15 14:46:20 UTC
A global variable?  Not really nice, but it works for me.

Comment 4 Florian Weimer 2016-09-05 10:05:25 UTC
Sorry, it seems that


at the start of the program is not fully effective.  I still see

30217 ptrace(PTRACE_PEEKTEXT, 28519, 0x7fb3508500a0, [0x2e6666666666c3f3]) = 0
30217 ptrace(PTRACE_POKETEXT, 28519, 0x7fb3508500a0, 0x2e6666666666c3cc) = 0

with it.  This is not related to library tracking, but something else.  GDB shows this as the location of the crash:

Dump of assembler code for function __nptl_create_event:
   0x00007fb3508500a0 <+0>:	int3   
=> 0x00007fb3508500a1 <+1>:	retq   

Looking at the Dyninst sources, this does not appear to be optional.

(The Dyninst manual could also be a bit more explicit and describe how to deallocate a Process object so that the traced process does not crash later on.)

Comment 5 Josh Stone 2016-09-20 19:50:58 UTC
Those new breakpoints are coming from thread_db_process::initThreadDB() for TD_CREATE and TD_DESTROY events.

I filed an upstream bug about wanting a true read-only mode.

Comment 6 Josh Stone 2016-10-04 22:35:02 UTC
As just pointed out in upstream 181, there actually is a control for threads too:


And manual refresh is similarly:


I'm not sure how we both overlooked that.  It seems to work for me -- I now see no calls to ptrace(PTRACE_POKETEXT,...) nor to process_vm_writev(...).

Comment 7 Fedora Admin XMLRPC Client 2017-05-15 19:58:41 UTC
This package has changed ownership in the Fedora Package Database.  Reassigning to the new owner of this component.

Comment 8 Fedora End Of Life 2017-07-25 22:24:12 UTC
This message is a reminder that Fedora 24 is nearing its end of life.
Approximately 2 (two) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 24. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as EOL if it remains open with a Fedora  'version'
of '24'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version'
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Comment 9 Fedora End Of Life 2017-08-08 16:30:06 UTC
Fedora 24 changed to end-of-life (EOL) status on 2017-08-08. Fedora 24 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

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