linux-kernel - Re: [BUG PATCH] perf: kvm - finding struct machine fails for PERF_RECORD

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4F8343CA.7050208@gmail.com>
Date:	Mon, 09 Apr 2012 14:17:14 -0600
From:	David Ahern <dsahern@...il.com>
To:	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	acme@...stprotocols.net
CC:	mingo@...hat.com, a.p.zijlstra@...llo.nl, paulus@...ba.org,
	fweisbec@...il.com, eranian@...gle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG PATCH] perf: kvm - finding struct machine fails for PERF_RECORD_MMAP

On 4/9/12 2:22 AM, Nikunj A. Dadhania wrote:
> From: Nikunj A. Dadhania<nikunj@...ux.vnet.ibm.com>
>
> Running 'perf kvm --host --guest --guestmount /tmp/guestmount record -a -g -- sleep 2'
>
> Was resulting in a segfault. For event type PERF_RECORD_MMAP,
> event->ip.pid is being used in perf_session__find_machine_for_cpumode,
> which is not correct.

I'm not getting the segfault with latest tip/perf/urgent, but I am 
getting a hang.

It's stuck on buildid:

(gdb) bt
#0  0x00007fabf53e79da in mmap64 () from /lib64/libc.so.6
#1  0x0000000000454656 in __perf_session__process_events 
(session=0x1e06110,
     data_offset=<value optimized out>, data_size=<value optimized out>, 
file_size=37328,
     tool=0x75db40) at util/session.c:1192
#2  0x00000000004102e6 in process_buildids (status=<value optimized 
out>, arg=0x75cc00)
     at builtin-record.c:320
#3  perf_record__exit (status=<value optimized out>, arg=0x75cc00) at 
builtin-record.c:333
#4  0x00007fabf53419c9 in exit () from /lib64/libc.so.6
#5  0x0000000000406b84 in handle_internal_command (argc=9, 
argv=0x7fff3f14d6c0) at perf.c:345
#6  run_argv (argc=9, argv=0x7fff3f14d6c0) at perf.c:389
#7  main (argc=9, argv=0x7fff3f14d6c0) at perf.c:487


Adding -B works around it and proves something is not right regarding 
buildid's and perf-kvm. I'll dig into it as time allows, but wanted to 
send this out in case Arnaldo understands the problem now.

David

>
> event->ip.pid happens to be 0 in this case and results in returning a
> NULL machine object. Finally, access to self->pid in
> machine__mmap_name, results in a segfault later.
>
> For PERF_RECORD_MMAP type, pass event->mmap.pid.
>
> Signed-off-by: Nikunj A. Dadhania<nikunj@...ux.vnet.ibm.com>
> ---
>
>   tools/perf/util/session.c |   12 ++++++++++--
>   1 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index 9412e3b..00923cd 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -826,8 +826,16 @@ static struct machine *
>   {
>   	const u8 cpumode = event->header.misc&  PERF_RECORD_MISC_CPUMODE_MASK;
>
> -	if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL&&  perf_guest)
> -		return perf_session__find_machine(session, event->ip.pid);
> +	if (cpumode == PERF_RECORD_MISC_GUEST_KERNEL&&  perf_guest) {
> +		u32 pid;
> +
> +		if (event->header.type == PERF_RECORD_MMAP)
> +			pid = event->mmap.pid;
> +		else
> +			pid = event->ip.pid;
> +
> +		return perf_session__find_machine(session, pid);
> +	}
>
>   	return perf_session__find_host_machine(session);
>   }
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/