Re: [PATCH] perf, report: use properly build_id kernel binaries

[Jiri Olsa]

hi, any feedback?

thanks,
jirka

On Wed, Jun 01, 2011 at 09:43:46PM +0200, Jiri Olsa wrote:
> If we bring the recorded perf data together with kernel
> binary from another machine using:
> 
> 	on server A:
> 	perf archive
> 
> 	on server B:
> 	tar xjvf perf.data.tar.bz2 -C ~/.debug
> 
> the build_id kernel dso is not properly recognized during
> the "perf report" command on server B.
> 
> The reason is, that build_id dsos are added during the session initialization,
> while the kernel maps are created during the sample event processing.
> 
> The machine__create_kernel_maps functions ends up creating new dso object
> for kernel, but it does not check if we already have one added by build_id
> processing.
> 
> 
> Also the build_id reading ABI quirk added in commit:
> 
>  - commit b25114817a73bbd2b84ce9dba02ee1ef8989a947
>    perf build-id: Add quirk to deal with perf.data file format breakage
> 
> populates the "struct build_id_event::pid" with 0, which
> is later interpreted as DEFAULT_GUEST_KERNEL_ID.
> 
> This is not always correct, so it's better to guess the pid
> value based on the "struct build_id_event::header::misc" value.
> 
> 
> - Tested with data generated on x86 kernel version v2.6.34
>   and reported back on x86_64 current kernel.
> - Not tested for guest kernel case.
> 
> 
> Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
> does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
> misinterpreted within the current perf code. Probably there's not much we
> can do about that.
> 
> 
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
>  tools/perf/util/header.c |   11 ++++++++-
>  tools/perf/util/symbol.c |   57 +++++++++++++++++++++++++--------------------
>  tools/perf/util/symbol.h |    1 -
>  3 files changed, 42 insertions(+), 27 deletions(-)
> 
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index afb0849..a0d90b1 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -726,7 +726,16 @@ static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
>  			return -1;
>  
>  		bev.header = old_bev.header;
> -		bev.pid	   = 0;
> +
> +		/*
> +		 * As the pid is the missing value, we need to fill
> +		 * it properly. The header.misc value give us nice hint.
> +		 */
> +		bev.pid	= HOST_KERNEL_ID;
> +		if (bev.header.misc == PERF_RECORD_MISC_GUEST_USER ||
> +		    bev.header.misc == PERF_RECORD_MISC_GUEST_KERNEL)
> +			bev.pid	= DEFAULT_GUEST_KERNEL_ID;
> +
>  		memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
>  		__event_process_build_id(&bev, filename, session);
>  
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index eec1963..c307121 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -2170,27 +2170,22 @@ size_t machines__fprintf_dsos_buildid(struct rb_root *machines,
>  	return ret;
>  }
>  
> -struct dso *dso__new_kernel(const char *name)
> +static struct dso*
> +dso__kernel_findnew(struct machine *machine, const char *name,
> +		    const char *short_name, int dso_type)
>  {
> -	struct dso *dso = dso__new(name ?: "[kernel.kallsyms]");
> -
> -	if (dso != NULL) {
> -		dso__set_short_name(dso, "[kernel]");
> -		dso->kernel = DSO_TYPE_KERNEL;
> -	}
> -
> -	return dso;
> -}
> +	/*
> +	 * The kernel dso could be created by build_id processing.
> +	 */
> +	struct dso *dso = __dsos__findnew(&machine->kernel_dsos, name);
>  
> -static struct dso *dso__new_guest_kernel(struct machine *machine,
> -					const char *name)
> -{
> -	char bf[PATH_MAX];
> -	struct dso *dso = dso__new(name ?: machine__mmap_name(machine, bf,
> -							      sizeof(bf)));
> +	/*
> +	 * We need to run this in all cases, since during the build_id
> +	 * processing we had no idea this was the kernel dso.
> +	 */
>  	if (dso != NULL) {
> -		dso__set_short_name(dso, "[guest.kernel]");
> -		dso->kernel = DSO_TYPE_GUEST_KERNEL;
> +		dso__set_short_name(dso, short_name);
> +		dso->kernel = dso_type;
>  	}
>  
>  	return dso;
> @@ -2208,24 +2203,36 @@ void dso__read_running_kernel_build_id(struct dso *dso, struct machine *machine)
>  		dso->has_build_id = true;
>  }
>  
> -static struct dso *machine__create_kernel(struct machine *machine)
> +static struct dso *machine__get_kernel(struct machine *machine)
>  {
>  	const char *vmlinux_name = NULL;
>  	struct dso *kernel;
>  
>  	if (machine__is_host(machine)) {
>  		vmlinux_name = symbol_conf.vmlinux_name;
> -		kernel = dso__new_kernel(vmlinux_name);
> +		if (!vmlinux_name)
> +			vmlinux_name = "[kernel.kallsyms]";
> +
> +		kernel = dso__kernel_findnew(machine, vmlinux_name,
> +					     "[kernel]",
> +					     DSO_TYPE_KERNEL);
>  	} else {
> +		char bf[PATH_MAX];
> +
>  		if (machine__is_default_guest(machine))
>  			vmlinux_name = symbol_conf.default_guest_vmlinux_name;
> -		kernel = dso__new_guest_kernel(machine, vmlinux_name);
> +		if (!vmlinux_name)
> +			vmlinux_name = machine__mmap_name(machine, bf,
> +							  sizeof(bf));
> +
> +		kernel = dso__kernel_findnew(machine, vmlinux_name,
> +					     "[guest.kernel]",
> +					     DSO_TYPE_GUEST_KERNEL);
>  	}
>  
> -	if (kernel != NULL) {
> +	if (kernel != NULL && (!kernel->has_build_id))
>  		dso__read_running_kernel_build_id(kernel, machine);
> -		dsos__add(&machine->kernel_dsos, kernel);
> -	}
> +
>  	return kernel;
>  }
>  
> @@ -2329,7 +2336,7 @@ void machine__destroy_kernel_maps(struct machine *machine)
>  
>  int machine__create_kernel_maps(struct machine *machine)
>  {
> -	struct dso *kernel = machine__create_kernel(machine);
> +	struct dso *kernel = machine__get_kernel(machine);
>  
>  	if (kernel == NULL ||
>  	    __machine__create_kernel_maps(machine, kernel) < 0)
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 325ee36..4f377d9 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -155,7 +155,6 @@ struct dso {
>  };
>  
>  struct dso *dso__new(const char *name);
> -struct dso *dso__new_kernel(const char *name);
>  void dso__delete(struct dso *dso);
>  
>  int dso__name_len(const struct dso *dso);
> -- 
> 1.7.1
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