Re: [PATCH v3 1/7 UPDATE] perf tools: Find vdso with the consider of cross-platform

[Adrian Hunter]

On 13/05/16 11:51, He Kuang wrote:
> There's a problem in machine__findnew_vdso(), vdso buildid generated
> by a 32-bit machine stores it with the name 'vdso', but when
> processing buildid on a 64-bit machine with the same 'perf.data', perf
> will search for vdso named as 'vdso32' and get failed.
> 
> This patch tries to find the exsiting dsos in machine->dsos by thread
> dso_type. 64-bit thread tries to find vdso with name 'vdso', because
> all 64-bit vdso is named as that. 32-bit thread first tries to find
> vdso with name 'vdso32' if this thread was run on 64-bit machine, if
> failed, then it tries 'vdso' which indicates that the thread was run
> on 32-bit machine when recording.
> 
> Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
> ---
>  tools/perf/util/vdso.c | 40 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 37 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c
> index 44d440d..99f4a3d 100644
> --- a/tools/perf/util/vdso.c
> +++ b/tools/perf/util/vdso.c
> @@ -134,8 +134,6 @@ static struct dso *__machine__addnew_vdso(struct machine *machine, const char *s
>  	return dso;
>  }
>  
> -#if BITS_PER_LONG == 64
> -
>  static enum dso_type machine__thread_dso_type(struct machine *machine,
>  					      struct thread *thread)
>  {
> @@ -156,6 +154,8 @@ static enum dso_type machine__thread_dso_type(struct machine *machine,
>  	return dso_type;
>  }
>  
> +#if BITS_PER_LONG == 64
> +
>  static int vdso__do_copy_compat(FILE *f, int fd)
>  {
>  	char buf[4096];
> @@ -283,8 +283,38 @@ static int __machine__findnew_vdso_compat(struct machine *machine,
>  
>  #endif
>  
> +static struct dso *machine__find_vdso(struct machine *machine,
> +				      struct thread *thread)
> +{
> +	struct dso *dso = NULL;
> +	enum dso_type dso_type;
> +
> +	dso_type = machine__thread_dso_type(machine, thread);
> +	switch (dso_type) {
> +	case DSO__TYPE_32BIT:
> +		dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO32, true);
> +		if (!dso)
> +			dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO,
> +					   true);

So if we have not yet added the 32-bit vdso but have added the 64-bit vdso,
we will return the wrong one.

Can we check it? e.g.

		if (!dso)
			dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO,
					   true);
			if (dso_type != dso__type(dso, machine))
				dso = NULL;

> +		break;
> +	case DSO__TYPE_X32BIT:
> +		dso = __dsos__find(&machine->dsos, DSO__NAME_VDSOX32, true);
> +		if (!dso)
> +			dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO,
> +					   true);

The x32 vdso is never called DSO__NAME_VDSO so this is not correct, but for
the same reason we don't need this __dsos__find() anyway.

> +		break;
> +	case DSO__TYPE_64BIT:
> +	case DSO__TYPE_UNKNOWN:
> +	default:
> +		dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO, true);
> +		break;
> +	}
> +
> +	return dso;
> +}
> +
>  struct dso *machine__findnew_vdso(struct machine *machine,
> -				  struct thread *thread __maybe_unused)
> +				  struct thread *thread)
>  {
>  	struct vdso_info *vdso_info;
>  	struct dso *dso = NULL;
> @@ -297,6 +327,10 @@ struct dso *machine__findnew_vdso(struct machine *machine,
>  	if (!vdso_info)
>  		goto out_unlock;
>  
> +	dso = machine__find_vdso(machine, thread);
> +	if (dso)
> +		goto out_unlock;
> +
>  #if BITS_PER_LONG == 64
>  	if (__machine__findnew_vdso_compat(machine, thread, vdso_info, &dso))
>  		goto out_unlock;
>