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    Subject[PATCH 4.9 086/153] perf callchain: Reference count maps
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Krister Johansen <kjlx@templeofstupid.com>

    commit aa33b9b9a2ebb00d33c83a5312d4fbf2d5aeba36 upstream.

    If dso__load_kcore frees all of the existing maps, but one has already
    been attached to a callchain cursor node, then we can get a SIGSEGV in
    any function that happens to try to use this invalid cursor. Use the
    existing map refcount mechanism to forestall cleanup of a map until the
    cursor iterates past the node.

    Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Fixes: 84c2cafa2889 ("perf tools: Reference count struct map")
    Link: http://lkml.kernel.org/r/20170106062331.GB2707@templeofstupid.com
    Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    tools/perf/util/callchain.c | 11 +++++++++--
    tools/perf/util/callchain.h | 6 ++++++
    tools/perf/util/hist.c | 7 +++++++
    3 files changed, 22 insertions(+), 2 deletions(-)

    --- a/tools/perf/util/callchain.c
    +++ b/tools/perf/util/callchain.c
    @@ -437,7 +437,7 @@ fill_node(struct callchain_node *node, s
    }
    call->ip = cursor_node->ip;
    call->ms.sym = cursor_node->sym;
    - call->ms.map = cursor_node->map;
    + call->ms.map = map__get(cursor_node->map);
    list_add_tail(&call->list, &node->val);

    callchain_cursor_advance(cursor);
    @@ -462,6 +462,7 @@ add_child(struct callchain_node *parent,

    list_for_each_entry_safe(call, tmp, &new->val, list) {
    list_del(&call->list);
    + map__zput(call->ms.map);
    free(call);
    }
    free(new);
    @@ -730,6 +731,7 @@ merge_chain_branch(struct callchain_curs
    callchain_cursor_append(cursor, list->ip,
    list->ms.map, list->ms.sym);
    list_del(&list->list);
    + map__zput(list->ms.map);
    free(list);
    }

    @@ -778,7 +780,8 @@ int callchain_cursor_append(struct callc
    }

    node->ip = ip;
    - node->map = map;
    + map__zput(node->map);
    + node->map = map__get(map);
    node->sym = sym;

    cursor->nr++;
    @@ -945,11 +948,13 @@ static void free_callchain_node(struct c

    list_for_each_entry_safe(list, tmp, &node->parent_val, list) {
    list_del(&list->list);
    + map__zput(list->ms.map);
    free(list);
    }

    list_for_each_entry_safe(list, tmp, &node->val, list) {
    list_del(&list->list);
    + map__zput(list->ms.map);
    free(list);
    }

    @@ -1013,6 +1018,7 @@ int callchain_node__make_parent_list(str
    goto out;
    *new = *chain;
    new->has_children = false;
    + map__get(new->ms.map);
    list_add_tail(&new->list, &head);
    }
    parent = parent->parent;
    @@ -1033,6 +1039,7 @@ int callchain_node__make_parent_list(str
    out:
    list_for_each_entry_safe(chain, new, &head, list) {
    list_del(&chain->list);
    + map__zput(chain->ms.map);
    free(chain);
    }
    return -ENOMEM;
    --- a/tools/perf/util/callchain.h
    +++ b/tools/perf/util/callchain.h
    @@ -5,6 +5,7 @@
    #include <linux/list.h>
    #include <linux/rbtree.h>
    #include "event.h"
    +#include "map.h"
    #include "symbol.h"

    #define HELP_PAD "\t\t\t\t"
    @@ -174,8 +175,13 @@ int callchain_merge(struct callchain_cur
    */
    static inline void callchain_cursor_reset(struct callchain_cursor *cursor)
    {
    + struct callchain_cursor_node *node;
    +
    cursor->nr = 0;
    cursor->last = &cursor->first;
    +
    + for (node = cursor->first; node != NULL; node = node->next)
    + map__zput(node->map);
    }

    int callchain_cursor_append(struct callchain_cursor *cursor, u64 ip,
    --- a/tools/perf/util/hist.c
    +++ b/tools/perf/util/hist.c
    @@ -1,6 +1,7 @@
    #include "util.h"
    #include "build-id.h"
    #include "hist.h"
    +#include "map.h"
    #include "session.h"
    #include "sort.h"
    #include "evlist.h"
    @@ -1019,6 +1020,10 @@ int hist_entry_iter__add(struct hist_ent
    int max_stack_depth, void *arg)
    {
    int err, err2;
    + struct map *alm = NULL;
    +
    + if (al && al->map)
    + alm = map__get(al->map);

    err = sample__resolve_callchain(iter->sample, &callchain_cursor, &iter->parent,
    iter->evsel, al, max_stack_depth);
    @@ -1058,6 +1063,8 @@ out:
    if (!err)
    err = err2;

    + map__put(alm);
    +
    return err;
    }


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