Re: [BUG PATCH] perf: kvm - finding struct machine fails for PERF_RECORD_MMAP

[David Ahern <dsahern@gmail.com>]

On 4/9/12 2:22 AM, Nikunj A. Dadhania wrote:
> From: Nikunj A. Dadhania<nikunj@linux.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.
>
> 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@linux.vnet.ibm.com>

Reviewed-by: David Ahern <dsahern@gmail.com>
Tested-by: David Ahern <dsahern@gmail.com>

David

> ---
>
>   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);
>   }
>
> --
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