linux-kernel - Re: [PATCHv2] perf probe: Fix failure to add multiple probes without debuginfo

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Date:	Fri, 20 Mar 2015 16:42:46 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	He Kuang <hekuang@...wei.com>
CC:	acme@...nel.org, a.p.zijlstra@...llo.nl, mingo@...hat.com,
	namhyung@...nel.org, wangnan0@...wei.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] perf probe: Fix failure to add multiple probes without
 debuginfo

(2015/03/20 10:56), He Kuang wrote:
> Perf tries to find probe function addresses from map when debuginfo
> could not be found.
> 
> To the first added function, the value of ref_reloc_sym was set in
> maps__set_kallsyms_ref_reloc_sym() and can be obtained from
> host_machine->kmaps->maps. After that, new maps are added to
> host_machine->kmaps->maps in dso__load_kcore(), all these new added maps
> do not have a valid ref_reloc_sym.
> 
> When adding a second function, get_target_map() may get a map without
> valid ref_reloc_sym, and raise the error "Relocated base symbol is not
> found".
> 
> Fix this by using kernel_get_ref_reloc_sym() to get ref_reloc_sym.
> 
> This problem can be reproduced as following:
> 
>   $ perf probe --add='sys_write' --add='sys_open'
>   Relocated base symbol is not found!
>     Error: Failed to add events.
> 
> After this patch:
> 
>   $ perf probe --add='sys_write' --add='sys_open'
>   Added new event:
>     probe:sys_write      (on sys_write)
> 
>   You can now use it in all perf tools, such as:
> 
>       perf record -e probe:sys_write -aR sleep 1
> 
>   Added new event:
>     probe:sys_open       (on sys_open)
> 
>   You can now use it in all perf tools, such as:
> 
>       perf record -e probe:sys_open -aR sleep 1
> 

OK, I've checked that this solve the problem :)

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>


Thank you!

> Signed-off-by: He Kuang <hekuang@...wei.com>
> ---
>  tools/perf/util/probe-event.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index c5e1338..c1ccd6a 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2507,7 +2507,6 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  					    int max_tevs, const char *target)
>  {
>  	struct map *map = NULL;
> -	struct kmap *kmap = NULL;
>  	struct ref_reloc_sym *reloc_sym = NULL;
>  	struct symbol *sym;
>  	struct probe_trace_event *tev;
> @@ -2540,8 +2539,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  	}
>  
>  	if (!pev->uprobes && !pp->retprobe) {
> -		kmap = map__kmap(map);
> -		reloc_sym = kmap->ref_reloc_sym;
> +		reloc_sym = kernel_get_ref_reloc_sym();
>  		if (!reloc_sym) {
>  			pr_warning("Relocated base symbol is not found!\n");
>  			ret = -EINVAL;
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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