valgrind-users — General discussion list for Valgrind users

Re: [Valgrind-users] Valgrind trace Memory Addresses while running?

[John R. <jr...@bi...>]

>> if we can get a list of all the physical addresses the program used, in the order the program accessed them, and whether read/write.


>  For any real world application the size of the log would be overwhelmingly huge ... (unless you only want unique addresses).

Of course this is the purpose of data compression (such as gzip, etc).
You get some/much/most of the benefit of restricting to unique addresses
while still capturing the entire stream of references.

But as Paul noted, valgrind works in virtual addresses.
Getting all the actual physical addresses is close to impossible.
If you are working in an embedded device environment
and care only about a small handful of memory-mapped
device registers, then you can (must) process the
mapping yourself.

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[John R. <jr...@bi...>]

>> Is there anything that can be done with memcheck to make it consume less memory?
> 
> No.

Well, you can use the command-line argument "--num-callers=<number>" to reduce the length
of tracebacks that are stored in the "red zones" just before and after an allocated block.
This might help enough if you have zillions of "still reachable" blocks.  But you get
shorter tracebacks, which might not give enough information to find and fix the leak
quickly.
If you do not have zillions of "still reachable" blocks, then --num-callers
will not help so much; but probably would not be needed anyway.

Re: [Valgrind-users] Valgrind trace Memory Addresses while running?

[Paul F. <pj...@wa...>]

> On 5 Aug 2022, at 20:53, G N Srinivasa Prasanna <gns...@ii...> wrote:
> 
> 
> This is the first time we are using Valgrind, and we want to know if we can get a list of all the physical addresses the program used, in the order the program accessed them, and whether read/write.
> 
> Please let us know if we can get this from Valgrind - the webpage information is not clear.
> 

Hi

Why do you need this?

I’m not sure how to translate from virtual to physical address. Do you really mean physical address? For any real world application the size of the log would be overwhelmingly huge and I suspect would very rapidly fill most disks (unless you only want unique addresses).

A+
Paul

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[John R. <jr...@bi...>]

> Does heaptrack also show  the 'still reachable' types of leaks that memcheck does?

Heaptrack intercepts malloc+free+etc, then logs the parameters, result, and
traceback; but otherwise lets the progcess-original malloc+free+etc do the work.
Heaptrack does not notice, and does not care, what you do with the result of
malloc(), except whether or not the pointer returned by malloc() ever gets
passed as an argument to free().

When heaptrack performs analysis, then any result from malloc() that has not
been free()d is a "leak" as far as heaptrack is concerned.  So that includes
what memcheck calls "still reachable" but not (yet) a leak.

> Any chance that the 'massif' tool would survive the OOM killer? This may be easier for me to get going as I already have valgrind built.

Worth a try if you have a day or so to spend.  Like all valgrind tools,
massif relies on emulating the instruction stream, so the basic ~10X
run-time slowdown applies.

> Is there anything that can be done with memcheck to make it consume less memory?

No.

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Bresalier, R. (N. - US/M. Hill) <rob...@no...>]

> > If you want to know for sure who killed it then strace it while it
> > runs and it should show you who sends the signel but my bet is that
> > it's the kernel.
> 

I tried strace -p <pid> on my process before I triggered its exit. The strace output ends saying with: "+++ killed by SIGKILL +++", but I don't find anything about who sent it.

> Or possibly watch `dmesg -w` running in another shell.
> 

I tried 'dmesg -w' but it didn't say anything about the SIGKILL. Is there something that has to be configured for dmesg to say the source of the SIGKILL?

[Valgrind-users] Valgrind trace Memory Addresses while running?

[G N S. P. <gns...@ii...>]

This is the first time we are using Valgrind, and we want to know if we can get a list of all the physical addresses the program used, in the order the program accessed them, and whether read/write.

Please let us know if we can get this from Valgrind - the webpage information is not clear.

Thanks
Prasanna

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Bresalier, R. (N. - US/M. Hill) <rob...@no...>]

Thanks Tom.

Do you think I'd have better luck using the "massif" tool? Would "massif" be able to avoid the OOM killer?

Or is there a way to reduce the amount of memory that memcheck will use?

-----Original Message-----
From: Tom Hughes <to...@co...> 
Sent: Friday, August 5, 2022 10:08 AM
To: Bresalier, Rob (Nokia - US/Murray Hill) <rob...@no...>; val...@li...
Subject: Re: memcheck is getting SIGKILLed before leak report is output

On 05/08/2022 14:09, Bresalier, Rob (Nokia - US/Murray Hill) wrote:

> When running memcheck on a massive monolith embedded executable (237MB 
> stripped, 1.8GiB unstripped), after I stop the executable under 
> valgrind I see the “HEAP SUMMARY” but then valgrind dies before any 
> leak reports are printed. The parent process sees that the return 
> status of memcheck is that it was SIGKILLed (status returned in 
> waitpid call is ‘9’). I am 99.9% sure that the parent process is not the one sending the SIGKILL.
> Is it possible that valgrind SIGKILLs itself? Is there a reason that 
> the linux kernel (Wind River Linux) could be sending a SIGKILL to 
> valgrind/memcheck? I do not see any messages about Out of Memory/OOM 
> killer killing valgrind. Previous experience with this executable is 
> that there are almost 3 million leak reports (most of them are “still 
> reachable”), could that be occupying too much memory. Any ideas/advice 
> to figure out what is going on?

Almost certainly the kernel OOM kiied it.

If you want to know for sure who killed it then strace it while it runs and it should show you who sends the signel but my bet is that it's the kernel.

> One thing I see in the logs is about “unhandled ioctl 0xa5 with no 
> size/direction hints”. Could this be a trigger for this crash/sigkill?

Not really, no.

Tom

--
Tom Hughes (to...@co...)
http://compton.nu/

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Bresalier, R. (N. - US/M. Hill) <rob...@no...>]

> If finding memory leaks is the only goal (for instance, if you are satisfied that
> memcheck has found all the overrun blocks, uninitialized reads, etc.) then
> https://github.com/KDE/heaptrack  is the best tool.  

Thanks! I didn't know about heaptrack. I will look definitely into that. Does heaptrack also show  the 'still reachable' types of leaks that memcheck does?

Any chance that the 'massif' tool would survive the OOM killer? This may be easier for me to get going as I already have valgrind built.

Is there anything that can be done with memcheck to make it consume less memory?

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Julian S. <jse...@gm...>]

On 05/08/2022 16:08, Tom Hughes via Valgrind-users wrote:

> If you want to know for sure who killed it then strace it while
> it runs and it should show you who sends the signel but my bet is
> that it's the kernel.

Or possibly watch `dmesg -w` running in another shell.

J

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[John R. <jr...@bi...>]

> When running memcheck on a massive monolith embedded executable (237MB stripped, 1.8GiB unstripped), after I stop the executable under valgrind I see the “HEAP SUMMARY” but then valgrind dies before any leak reports are printed.
If finding memory leaks is the only goal (for instance, if you are satisfied
that memcheck has found all the overrun blocks, uninitialized reads, etc.)
then https://github.com/KDE/heaptrack  is the best tool.  The data-gathering
phase runs in any Linux process using LD_PRELOAD and libunwind.  The analysis
phase runs a GUI under KDE, and/or generates *useful* text reports: leaks by
individual size, leaks by total size for a given traceback, allocations
(leaked or not) by frequency or total size, etc.  I like the text-only
analysis, which avoids the requirement for KDE.  Heaptrack CPU overhead
tends to be around 20% or less, so it does not take forever.  Heaptrack
does require disk space to record data (sequential access only),
so you may need several gigabytes (locally or via network.)

Re: [Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Tom H. <to...@co...>]

On 05/08/2022 14:09, Bresalier, Rob (Nokia - US/Murray Hill) wrote:

> When running memcheck on a massive monolith embedded executable (237MB 
> stripped, 1.8GiB unstripped), after I stop the executable under valgrind 
> I see the “HEAP SUMMARY” but then valgrind dies before any leak reports 
> are printed. The parent process sees that the return status of memcheck 
> is that it was SIGKILLed (status returned in waitpid call is ‘9’). I am 
> 99.9% sure that the parent process is not the one sending the SIGKILL. 
> Is it possible that valgrind SIGKILLs itself? Is there a reason that the 
> linux kernel (Wind River Linux) could be sending a SIGKILL to 
> valgrind/memcheck? I do not see any messages about Out of Memory/OOM 
> killer killing valgrind. Previous experience with this executable is 
> that there are almost 3 million leak reports (most of them are “still 
> reachable”), could that be occupying too much memory. Any ideas/advice 
> to figure out what is going on?

Almost certainly the kernel OOM kiied it.

If you want to know for sure who killed it then strace it while
it runs and it should show you who sends the signel but my bet is
that it's the kernel.

> One thing I see in the logs is about “unhandled ioctl 0xa5 with no 
> size/direction hints”. Could this be a trigger for this crash/sigkill?

Not really, no.

Tom

-- 
Tom Hughes (to...@co...)
http://compton.nu/

[Valgrind-users] memcheck is getting SIGKILLed before leak report is output

[Bresalier, R. (N. - US/M. Hill) <rob...@no...>]

When running memcheck on a massive monolith embedded executable (237MB stripped, 1.8GiB unstripped), after I stop the executable under valgrind I see the "HEAP SUMMARY" but then valgrind dies before any leak reports are printed. The parent process sees that the return status of memcheck is that it was SIGKILLed (status returned in waitpid call is '9'). I am 99.9% sure that the parent process is not the one sending the SIGKILL. Is it possible that valgrind SIGKILLs itself? Is there a reason that the linux kernel (Wind River Linux) could be sending a SIGKILL to valgrind/memcheck? I do not see any messages about Out of Memory/OOM killer killing valgrind. Previous experience with this executable is that there are almost 3 million leak reports (most of them are "still reachable"), could that be occupying too much memory. Any ideas/advice to figure out what is going on?

We don't seem to get the sigkill if valgrind/memcheck is stopped earlier in the life of this executable. But to find the leak I need it to run past that point.

I've tried many different versions of valgrind that have worked to find leaks on this executable in the past (3.16.1, 3.18.1, 3.19.0) but they all have this same issue of being sigkilled before any leaks get printed.

One thing I see in the logs is about "unhandled ioctl 0xa5 with no size/direction hints". Could this be a trigger for this crash/sigkill?

Would appreciate any ideas/advice.

Thanks,
Rob

Re: [Valgrind-users] [SGCheck][Array overrun detection] seems found nothing in multiple version

[Paul F. <pj...@wa...>]

Hi

Sgcheck never got beyond experimental and was removed from Valgrind a few versions ago. My advice is simply to not use it.

A+
Paul

> On 4 Aug 2022, at 07:45, Pahome Chen via Valgrind-users <val...@li...> wrote:
> 
> 
> Dear all,
>  
> I read the sgcheck’s doc and know it’s a experimental tool, but it seems found no error even a very simple program.
> Does this still work or need to wait for another version?
>  
> Below is from my script and experiment, and fail in Valgrind-3.8.1/3.9.0/3.10.0/3.11.0/3.12.0
> E.g.
> >$ cat test_valgrind.c
> #include<stdio.h>
> #include<stdlib.h>
> int main()
> {
>     int val[10] = {0};
>     int tmp = val[1], i = 0;
>     tmp += val[15]; // array overrun
>     tmp *= val[20]; // array overrun
>     for (i=0; i<20; ++i) { int tmp = val[i]; } // array overrun
>     return 0;
> }
>  
> When I run above version of Valgrind mentioned, it always comes out following message.
>  
> ==11673== exp-sgcheck, a stack and global array overrun detector
> ==11673== NOTE: This is an Experimental-Class Valgrind Tool
> ==11673== Copyright (C) 2003-2015, and GNU GPL'd, by OpenWorks Ltd et al.
> ==11673== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
> ==11673== Command: ./run
> ==11673==
>  
> exp-sgcheck: sg_main.c:2332 (sg_instrument_IRStmt): the 'impossible' happened.
>  
> host stacktrace:
> ==11673==    at 0x3800CC09: show_sched_status_wrk (m_libcassert.c:343)
> ==11673==    by 0x3800CEF4: report_and_quit (m_libcassert.c:415)
> ==11673==    by 0x3800D127: vgPlain_assert_fail (m_libcassert.c:481)
> ==11673==    by 0x38004A03: sg_instrument_IRStmt (sg_main.c:2332)
> ==11673==    by 0x380003B3: h_instrument (h_main.c:683)
> ==11673==    by 0x3802968D: tool_instrument_then_gdbserver_if_needed (m_translate.c:238)
> ==11673==    by 0x380D3290: LibVEX_Translate (main_main.c:934)
> ==11673==    by 0x380271BF: vgPlain_translate (m_translate.c:1765)
> ==11673==    by 0x3805F857: vgPlain_scheduler (scheduler.c:1048)
> ==11673==    by 0x38090445: run_a_thread_NORETURN (syswrap-linux.c:102)
>  
> sched status:
>   running_tid=1
>  
> Thread 1: status = VgTs_Runnable (lwpid 11673)
> ==11673==    at 0x40169EA: _dl_runtime_resolve_xsave (in /usr/lib64/ld-2.17.so)
> ==11673==    by 0x1B: ???
> ==11673==    by 0x40057F: ??? (in /PATH/peihung/test/run)
> ==11673==    by 0xFFEFFF517: ???
>  
>  
> Note: see also the FAQ in the source distribution.
> It contains workarounds to several common problems.
> In particular, if Valgrind aborted or crashed after
> identifying problems in your program, there's a good chance
> that fixing those problems will prevent Valgrind aborting or
> crashing, especially if it happened in m_mallocfree.c.
>  
> My machine environment is Centos7 and x86_64
>  
>  
>  
>  
> Thanks.
> Best regards,
> Pahome
>  
> _______________________________________________
> Valgrind-users mailing list
> Val...@li...
> https://lists.sourceforge.net/lists/listinfo/valgrind-users

[Valgrind-users] [SGCheck][Array overrun detection] seems found nothing in multiple version

[Pahome C. <Pei...@sy...>]

Dear all,

I read the sgcheck's doc and know it's a experimental tool, but it seems found no error even a very simple program.
Does this still work or need to wait for another version?

Below is from my script and experiment, and fail in Valgrind-3.8.1/3.9.0/3.10.0/3.11.0/3.12.0
E.g.
>$ cat test_valgrind.c
#include<stdio.h>
#include<stdlib.h>
int main()
{
    int val[10] = {0};
    int tmp = val[1], i = 0;
    tmp += val[15]; // array overrun
    tmp *= val[20]; // array overrun
    for (i=0; i<20; ++i) { int tmp = val[i]; } // array overrun
    return 0;
}

When I run above version of Valgrind mentioned, it always comes out following message.

==11673== exp-sgcheck, a stack and global array overrun detector
==11673== NOTE: This is an Experimental-Class Valgrind Tool
==11673== Copyright (C) 2003-2015, and GNU GPL'd, by OpenWorks Ltd et al.
==11673== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==11673== Command: ./run
==11673==

exp-sgcheck: sg_main.c:2332 (sg_instrument_IRStmt): the 'impossible' happened.

host stacktrace:
==11673==    at 0x3800CC09: show_sched_status_wrk (m_libcassert.c:343)
==11673==    by 0x3800CEF4: report_and_quit (m_libcassert.c:415)
==11673==    by 0x3800D127: vgPlain_assert_fail (m_libcassert.c:481)
==11673==    by 0x38004A03: sg_instrument_IRStmt (sg_main.c:2332)
==11673==    by 0x380003B3: h_instrument (h_main.c:683)
==11673==    by 0x3802968D: tool_instrument_then_gdbserver_if_needed (m_translate.c:238)
==11673==    by 0x380D3290: LibVEX_Translate (main_main.c:934)
==11673==    by 0x380271BF: vgPlain_translate (m_translate.c:1765)
==11673==    by 0x3805F857: vgPlain_scheduler (scheduler.c:1048)
==11673==    by 0x38090445: run_a_thread_NORETURN (syswrap-linux.c:102)

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable (lwpid 11673)
==11673==    at 0x40169EA: _dl_runtime_resolve_xsave (in /usr/lib64/ld-2.17.so)
==11673==    by 0x1B: ???
==11673==    by 0x40057F: ??? (in /PATH/peihung/test/run)
==11673==    by 0xFFEFFF517: ???


Note: see also the FAQ in the source distribution.
It contains workarounds to several common problems.
In particular, if Valgrind aborted or crashed after
identifying problems in your program, there's a good chance
that fixing those problems will prevent Valgrind aborting or
crashing, especially if it happened in m_mallocfree.c.

My machine environment is Centos7 and x86_64




Thanks.
Best regards,
Pahome

Re: [Valgrind-users] new error message from Valgrind

[Mark W. <ma...@kl...>]

Hi,

On Wed, Aug 03, 2022 at 05:32:56PM +0100, Tom Hughes wrote:
> No, it's clone3:
> 
> https://bugs.kde.org/show_bug.cgi?id=420906

So please upgrade to valgrind 3.18.0 or higher (latest is 3.19.0).

Cheers,

Mark

Re: [Valgrind-users] new error message from Valgrind

[Mark R. <ma...@cs...>]

Just tried running the Valgrind test suite on WSL2 (win 10, Ubuntu 22.04).
I'm not surprised that there were lots of failures.  But the majority were:
WARNING: unhandled amd64-linux syscall: 435

I suspect WSL is not a platform you care much about, but looking at syswrap
for Darwin I see this might be pid hibernate?  Would it be difficult to add
support for this?

Thank you,
Mark

-----Original Message-----
From: Mark Wielaard [mailto:ma...@kl...]
Sent: Monday, August 1, 2022 4:56 AM
To: Tom Hughes <to...@co...>; Mark Roberts <ma...@cs...>;
val...@li...
Subject: Re: [Valgrind-users] new error message from Valgrind

On Thu, 2022-07-28 at 22:22 +0100, Tom Hughes via Valgrind-users wrote:
> On 28/07/2022 21:39, Mark Roberts wrote:
> > I recently upgraded from Ubutu 20.04 to 22.04 and am now getting a
> > new error message from Valgrind:
> >
> > --915-- WARNING: unhandled amd64-linux syscall: 334
> >
> > --915-- You may be able to write your own handler.
> >
> > --915-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
> >
> > --915-- Nevertheless we consider this a bug.  Please report
> >
> > --915-- it at http://valgrind.org/support/bug_reports.html
> > <http://valgrind.org/support/bug_reports.html>.
> >
> > Using same version of Valgrind as before (3.17).
> >
> > Any ideas as to what’s happening?
>
> Yes, your libc has started trying to use rseq.
>
> It's harmless - the next version of valgrind will silently reject it
> with ENOSYS which is what is happening now anyway just with a warning.

Where the next version of valgrind is 3.19.0 which is already released (in
April).  So you might just want to upgrade your valgrind.

If you want to backport to older versions then the commit that got rid of
the warning was:

commit 1024237358f01009fe233cb1294f3b8211304eaa
Author: Mark Wielaard <ma...@kl...>
Date:   Fri Dec 10 17:41:59 2021 +0100

    Implement linux rseq syscall as ENOSYS

    This implements rseq for amd64, arm, arm64, ppc32, ppc64,
    s390x and x86 linux as ENOSYS (without warning).

    glibc will start using rseq to accelerate sched_getcpu, if
    available. This would cause a warning from valgrind every
    time a new thread is started.

    Real rseq (restartable sequences) support is pretty hard, so
    for now just explicitly return ENOSYS (just like we do for clone3).


https://sourceware.org/pipermail/libc-alpha/2021-December/133656.html

Cheers,

Mark

Re: [Valgrind-users] new error message from Valgrind

[Tom H. <to...@co...>]

No, it's clone3:

https://bugs.kde.org/show_bug.cgi?id=420906

Tom

On 03/08/2022 17:30, Mark Roberts wrote:
> Just tried running the Valgrind test suite on WSL2 (win 10, Ubuntu 22.04).
> I'm not surprised that there were lots of failures.  But the majority were:
> WARNING: unhandled amd64-linux syscall: 435
> 
> I suspect WSL is not a platform you care much about, but looking at syswrap
> for Darwin I see this might be pid hibernate?  Would it be difficult to add
> support for this?
> 
> Thank you,
> Mark
> 
> -----Original Message-----
> From: Mark Wielaard [mailto:ma...@kl...]
> Sent: Monday, August 1, 2022 4:56 AM
> To: Tom Hughes <to...@co...>; Mark Roberts <ma...@cs...>;
> val...@li...
> Subject: Re: [Valgrind-users] new error message from Valgrind
> 
> On Thu, 2022-07-28 at 22:22 +0100, Tom Hughes via Valgrind-users wrote:
>> On 28/07/2022 21:39, Mark Roberts wrote:
>>> I recently upgraded from Ubutu 20.04 to 22.04 and am now getting a
>>> new error message from Valgrind:
>>>
>>> --915-- WARNING: unhandled amd64-linux syscall: 334
>>>
>>> --915-- You may be able to write your own handler.
>>>
>>> --915-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
>>>
>>> --915-- Nevertheless we consider this a bug.  Please report
>>>
>>> --915-- it at http://valgrind.org/support/bug_reports.html
>>> <http://valgrind.org/support/bug_reports.html>.
>>>
>>> Using same version of Valgrind as before (3.17).
>>>
>>> Any ideas as to what’s happening?
>>
>> Yes, your libc has started trying to use rseq.
>>
>> It's harmless - the next version of valgrind will silently reject it
>> with ENOSYS which is what is happening now anyway just with a warning.
> 
> Where the next version of valgrind is 3.19.0 which is already released (in
> April).  So you might just want to upgrade your valgrind.
> 
> If you want to backport to older versions then the commit that got rid of
> the warning was:
> 
> commit 1024237358f01009fe233cb1294f3b8211304eaa
> Author: Mark Wielaard <ma...@kl...>
> Date:   Fri Dec 10 17:41:59 2021 +0100
> 
>      Implement linux rseq syscall as ENOSYS
> 
>      This implements rseq for amd64, arm, arm64, ppc32, ppc64,
>      s390x and x86 linux as ENOSYS (without warning).
> 
>      glibc will start using rseq to accelerate sched_getcpu, if
>      available. This would cause a warning from valgrind every
>      time a new thread is started.
> 
>      Real rseq (restartable sequences) support is pretty hard, so
>      for now just explicitly return ENOSYS (just like we do for clone3).
> 
> 
> https://sourceware.org/pipermail/libc-alpha/2021-December/133656.html
> 
> Cheers,
> 
> Mark


-- 
Tom Hughes (to...@co...)
http://compton.nu/

Re: [Valgrind-users] new error message from Valgrind

[Mark W. <ma...@kl...>]

On Thu, 2022-07-28 at 22:22 +0100, Tom Hughes via Valgrind-users wrote:
> On 28/07/2022 21:39, Mark Roberts wrote:
> > I recently upgraded from Ubutu 20.04 to 22.04 and am now getting a
> > new 
> > error message from Valgrind:
> > 
> > --915-- WARNING: unhandled amd64-linux syscall: 334
> > 
> > --915-- You may be able to write your own handler.
> > 
> > --915-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
> > 
> > --915-- Nevertheless we consider this a bug.  Please report
> > 
> > --915-- it at http://valgrind.org/support/bug_reports.html 
> > <http://valgrind.org/support/bug_reports.html>.
> > 
> > Using same version of Valgrind as before (3.17).
> > 
> > Any ideas as to what’s happening?
> 
> Yes, your libc has started trying to use rseq.
> 
> It's harmless - the next version of valgrind will silently
> reject it with ENOSYS which is what is happening now anyway
> just with a warning.

Where the next version of valgrind is 3.19.0 which is already released
(in April).  So you might just want to upgrade your valgrind.

If you want to backport to older versions then the commit that got rid
of the warning was:

commit 1024237358f01009fe233cb1294f3b8211304eaa
Author: Mark Wielaard <ma...@kl...>
Date:   Fri Dec 10 17:41:59 2021 +0100

    Implement linux rseq syscall as ENOSYS
    
    This implements rseq for amd64, arm, arm64, ppc32, ppc64,
    s390x and x86 linux as ENOSYS (without warning).
    
    glibc will start using rseq to accelerate sched_getcpu, if
    available. This would cause a warning from valgrind every
    time a new thread is started.
    
    Real rseq (restartable sequences) support is pretty hard, so
    for now just explicitly return ENOSYS (just like we do for clone3).
    
    
https://sourceware.org/pipermail/libc-alpha/2021-December/133656.html

Cheers,

Mark

Re: [Valgrind-users] new error message from Valgrind

[Tom H. <to...@co...>]

On 28/07/2022 21:39, Mark Roberts wrote:
> I recently upgraded from Ubutu 20.04 to 22.04 and am now getting a new 
> error message from Valgrind:
> 
> --915-- WARNING: unhandled amd64-linux syscall: 334
> 
> --915-- You may be able to write your own handler.
> 
> --915-- Read the file README_MISSING_SYSCALL_OR_IOCTL.
> 
> --915-- Nevertheless we consider this a bug.  Please report
> 
> --915-- it at http://valgrind.org/support/bug_reports.html 
> <http://valgrind.org/support/bug_reports.html>.
> 
> Using same version of Valgrind as before (3.17).
> 
> Any ideas as to what’s happening?

Yes, your libc has started trying to use rseq.

It's harmless - the next version of valgrind will silently
reject it with ENOSYS which is what is happening now anyway
just with a warning.

Tom

-- 
Tom Hughes (to...@co...)
http://compton.nu/

[Valgrind-users] new error message from Valgrind

[Mark R. <ma...@cs...>]

I recently upgraded from Ubutu 20.04 to 22.04 and am now getting a new
error message from Valgrind:



--915-- WARNING: unhandled amd64-linux syscall: 334

--915-- You may be able to write your own handler.

--915-- Read the file README_MISSING_SYSCALL_OR_IOCTL.

--915-- Nevertheless we consider this a bug.  Please report

--915-- it at http://valgrind.org/support/bug_reports.html.



Using same version of Valgrind as before (3.17).



Any ideas as to what’s happening?



Thank you,

Mark

[Valgrind-users] Happy birthday, Valgrind!

[Mark W. <ma...@kl...>]

It has been twenty years today since Valgrind 1.0 was released.

Make sure to read Nicholas Nethercote’s Twenty years of Valgrind:
https://nnethercote.github.io/2022/07/27/twenty-years-of-valgrind.html
And learn about the early days, Valgrind "skins", the influence
Valgrind had on raising the bar when it comes to correctness for C and
C++ programs, and why a hacker on the Rust programming language still
uses Valgrind.

Happy birthday, Valgrind!

Re: [Valgrind-users] Memcheck Support For Per-Thread Caching

[John R. <jr...@bi...>]

> Does memcheck include support for per-thread caching (now enabled by default in glibc)?

Memcheck intercepts all calls on allocation and free-ing subroutines
(malloc, free, calloc, realloc, memalign, posix_memalign, brk, sbrk, mmap, ...)
and totally replaces each one with code that is internal to memcheck.
The glibc routines never are called at all.  Also, memcheck serializes
all execution, and executes code from only one thread at a time.

[Valgrind-users] Memcheck Support For Per-Thread Caching

[Glenn H. <gle...@gm...>]

Does memcheck include support for per-thread caching (now enabled by
default in glibc)?


ᐧ

Re: [Valgrind-users] Possible to suppress low block count loss records?

[Julian S. <jse...@gm...>]

On 13/07/2022 16:38, Bresalier, Rob (Nokia - US/Murray Hill) wrote:
> We are trying to track down a suspected place in our code that keeps accumulating memory in a 'still reachable'.

It sounds like you're trying to track down a "process lifetime" leak.

You'd be better off using one of the heap profiling tools for that,
either massif (--tool=massif) or dhat (--tool=dhat), but probably massif.

You'll need to ask your package manager to install the massif-visualizer GUI.

Run with --tool=massif --num-callers=12 (or 16 or whatever).  Use the GUI
to look at the resulting profile.  After a bit of poking around it should
be obvious where all your allocation is coming from.

J

Re: [Valgrind-users] Possible to suppress low block count loss records?

[John R. <jr...@bi...>]

> We are trying to track down a suspected place in our code that keeps accumulating memory in a ‘still reachable’.
> 
> When I turn on still reachable and run my process for a few hours and then stop the process to get the valgrind reports there are over 2.7 million loss records which are mostly still reachables. It would take forever for valgrind to print this out.

It would take around one hour or less to *produce* the complete report
without printing it.  Re-direct stderr to a file, or use command-line options
--xml-fd= or --xml-file=.  See "valgrind --help" and/or the user manual
for other options to control error reporting.

Using any text editor on the report file, or inserting the 'sed'
(or 'awk') stream editor into the pipeline of error output,
enables filtering the error reports.

> The large majority of “still reachable” that I want to ignore allocate just a few blocks. I would like to suppress these and only output “still reachables” that allocated 100 blocks or more.

Note that all the excluded reports (counts 1 through 99) have only 1 or 2
characters in their decimal representation, so you don't even need to
convert the field to a number to decide.

> If not possible without patching valgrind, any hints on where I could patch valgrind to accomplish this?

Find the source location which prints the instance count, and adjust the code.
This is "standard engineering effort" for a programmer who is adept at using 'grep',
even without prior experience with the source code of valgrind.