linux-kernel - Re: [PATCH] perf symbols/KCORE: Rebuild rbtree when adjusting symbols for kcore

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Date:	Wed, 11 Nov 2015 15:02:35 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Adrian Hunter <adrian.hunter@...el.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	<namhyung@...nel.org>, <lizefan@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>, <jolsa@...nel.org>,
	<masami.hiramatsu.pt@...achi.com>
Subject: Re: [PATCH] perf symbols/KCORE: Rebuild rbtree when adjusting symbols
 for kcore



On 2015/11/6 21:59, Adrian Hunter wrote:
> On 06/11/15 15:19, Arnaldo Carvalho de Melo wrote:
>> Em Fri, Nov 06, 2015 at 09:46:12AM +0000, Wang Nan escreveu:
>>> In dso__split_kallsyms_for_kcore(), current code adjusts symbol's
>>> address but only reinsert it into rbtree if the symbol belongs to
>>> another map. However, the expression for adjusting symbol (pos->start -=
>>> curr_map->start - curr_map->pgoff) can change the relative order between
>>> two symbols (even if the affected symbols are in different maps, in
>>> kcore case they are possible to share one same dso), which damages the
>>> rbtree.
>> Right, some code does change the symbol values it gets from whatever
>> symtab (kallsyms, ELF, JIT maps, etc) when it should instead use the per
>> map data structure (struct map) and its ->{map,unmap}_ip, ->pgoff,
>> ->reloc, members for that :-\
>>
>> I.e. 'struct dso' should be just what comes from the symtab, while
>> 'struct map' should be about where that DSO is in memory.
>>
>> With that in mind, do you still think your fix is the correct one?
>>
>> Adrian?
> The problem is when the order in memory (in kallsyms) is different
> to the order on the dso (kcore).
>
> I think to make it more general it needs to insert to a new tree.
> e.g.
>

I have tested this patch and it works for me.

Thank you.

> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index b4cc7662677e..09343a880c0b 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -654,19 +654,24 @@ static int dso__split_kallsyms_for_kcore(struct dso *dso, struct map *map,
>   	struct map_groups *kmaps = map__kmaps(map);
>   	struct map *curr_map;
>   	struct symbol *pos;
> -	int count = 0, moved = 0;
> +	int count = 0;
> +	struct rb_root old_root = dso->symbols[map->type];
>   	struct rb_root *root = &dso->symbols[map->type];
>   	struct rb_node *next = rb_first(root);
>   
>   	if (!kmaps)
>   		return -1;
>   
> +	*root = RB_ROOT;
> +
>   	while (next) {
>   		char *module;
>   
>   		pos = rb_entry(next, struct symbol, rb_node);
>   		next = rb_next(&pos->rb_node);
>   
> +		rb_erase_init(&pos->rb_node, &old_root);
> +
>   		module = strchr(pos->name, '\t');
>   		if (module)
>   			*module = '\0';
> @@ -674,28 +679,21 @@ static int dso__split_kallsyms_for_kcore(struct dso *dso, struct map *map,
>   		curr_map = map_groups__find(kmaps, map->type, pos->start);
>   
>   		if (!curr_map || (filter && filter(curr_map, pos))) {
> -			rb_erase_init(&pos->rb_node, root);
>   			symbol__delete(pos);
> -		} else {
> -			pos->start -= curr_map->start - curr_map->pgoff;
> -			if (pos->end)
> -				pos->end -= curr_map->start - curr_map->pgoff;
> -			if (curr_map->dso != map->dso) {
> -				rb_erase_init(&pos->rb_node, root);
> -				symbols__insert(
> -					&curr_map->dso->symbols[curr_map->type],
> -					pos);
> -				++moved;
> -			} else {
> -				++count;
> -			}
> +			continue;
>   		}
> +
> +		pos->start -= curr_map->start - curr_map->pgoff;
> +		if (pos->end)
> +			pos->end -= curr_map->start - curr_map->pgoff;
> +		symbols__insert(&curr_map->dso->symbols[curr_map->type], pos);
> +		++count;
>   	}
>   
>   	/* Symbols have been adjusted */
>   	dso->adjust_symbols = 1;
>   
> -	return count + moved;
> +	return count;
>   }
>   
>   /*
>


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