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    SubjectRe: [PATCH] perf symbols/KCORE: Rebuild rbtree when adjusting symbols for kcore
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    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.


    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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