linux-kernel - Re: [PATCH v3 2/2] Support interactive annotation of code without symbols

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Message-ID: <20200224123526.GF16664@krava>
Date:   Mon, 24 Feb 2020 13:35:26 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jin Yao <yao.jin@...ux.intel.com>
Cc:     acme@...nel.org, jolsa@...nel.org, peterz@...radead.org,
        mingo@...hat.com, alexander.shishkin@...ux.intel.com,
        Linux-kernel@...r.kernel.org, ak@...ux.intel.com,
        kan.liang@...el.com, yao.jin@...el.com
Subject: Re: [PATCH v3 2/2] Support interactive annotation of code without
 symbols

On Mon, Feb 24, 2020 at 10:22:25AM +0800, Jin Yao wrote:
> For perf report on stripped binaries it is currently impossible to do
> annotation. The annotation state is all tied to symbols, but there are
> either no symbols, or symbols are not covering all the code.
> 
> We should support the annotation functionality even without symbols.
> 
> This patch fakes a symbol and the symbol name is the string of address.
> After that, we just follow current annotation working flow.
> 
> For example,
> 
> 1. perf report
> 
> Overhead  Command  Shared Object     Symbol
>   20.67%  div      libc-2.27.so      [.] __random_r
>   17.29%  div      libc-2.27.so      [.] __random
>   10.59%  div      div               [.] 0x0000000000000628
>    9.25%  div      div               [.] 0x0000000000000612
>    6.11%  div      div               [.] 0x0000000000000645
> 
> 2. Select the line of "10.59%  div      div               [.] 0x0000000000000628" and ENTER.
> 
> Annotate 0x0000000000000628
> Zoom into div thread
> Zoom into div DSO (use the 'k' hotkey to zoom directly into the kernel)
> Browse map details
> Run scripts for samples of symbol [0x0000000000000628]
> Run scripts for all samples
> Switch to another data file in PWD
> Exit
> 
> 3. Select the "Annotate 0x0000000000000628" and ENTER.
> 
> Percent│
>        │
>        │
>        │     Disassembly of section .text:
>        │
>        │     0000000000000628 <.text+0x68>:
>        │       divsd %xmm4,%xmm0
>        │       divsd %xmm3,%xmm1
>        │       movsd (%rsp),%xmm2
>        │       addsd %xmm1,%xmm0
>        │       addsd %xmm2,%xmm0
>        │       movsd %xmm0,(%rsp)
> 
> Now we can see the dump of object starting from 0x628.
> 
>  v3:
>  ---
>  Keep just the ANNOTATION_DUMMY_LEN, and remove the
>  opts->annotate_dummy_len since it's the "maybe in future
>  we will provide" feature.
> 
>  v2:
>  ---
>  Fix a crash issue when annotating an address in "unknown" object.
> 
>  The steps to reproduce this issue:
> 
>  perf record -e cycles:u ls
>  perf report
> 
>     75.29%  ls       ld-2.27.so        [.] do_lookup_x
>     23.64%  ls       ld-2.27.so        [.] __GI___tunables_init
>      1.04%  ls       [unknown]         [k] 0xffffffff85c01210
>      0.03%  ls       ld-2.27.so        [.] _start
> 
>  When annotating 0xffffffff85c01210, the crash happens.
> 
>  v2 adds checking for ms->map in add_annotate_opt(). If the object is
>  "unknown", ms->map is NULL.
> 
> Signed-off-by: Jin Yao <yao.jin@...ux.intel.com>
> ---
>  tools/perf/ui/browsers/hists.c | 43 +++++++++++++++++++++++++++++-----
>  tools/perf/util/annotate.h     |  1 +
>  2 files changed, 38 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> index f36dee499320..2f07680559c4 100644
> --- a/tools/perf/ui/browsers/hists.c
> +++ b/tools/perf/ui/browsers/hists.c
> @@ -2465,13 +2465,41 @@ do_annotate(struct hist_browser *browser, struct popup_action *act)
>  	return 0;
>  }
>  
> +static struct symbol *new_annotate_sym(u64 addr, struct map *map)
> +{
> +	struct symbol *sym;
> +	struct annotated_source *src;
> +	char name[64];
> +
> +	snprintf(name, sizeof(name), "%-#.*lx", BITS_PER_LONG / 4, addr);
> +
> +	sym = symbol__new(addr, ANNOTATION_DUMMY_LEN, 0, 0, name);
> +	if (sym) {
> +		src = symbol__hists(sym, 1);
> +		if (!src) {
> +			symbol__delete(sym);
> +			return NULL;
> +		}

hi,
I like the patchset:

Acked-by: Jiri Olsa <jolsa@...hat.com>

could you please also check if we can do this earlier,
so the dummy symbol is actualy collecting all the hits?

like within the symbol__inc_addr_samples function,
but I mght be missing something..

thanks,
jirka