On Thu, Oct 29, 2020 at 1:16 PM Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > On Thu, Oct 29, 2020 at 9:11 AM Ian Rogers <irogers@xxxxxxxxxx> wrote: > > > > If bits is 0, the case when the map is empty, then the >> is the size of > > the register which is undefined behavior - on x86 it is the same as a > > shift by 0. Fix by handling the 0 case explicitly when running with > > address sanitizer. > > > > A variant of this patch was posted previously as: > > https://lore.kernel.org/lkml/20200508063954.256593-1-irogers@xxxxxxxxxx/ > > > > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx> > > --- > > tools/lib/bpf/hashmap.h | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h > > index d9b385fe808c..27d0556527d3 100644 > > --- a/tools/lib/bpf/hashmap.h > > +++ b/tools/lib/bpf/hashmap.h > > @@ -12,9 +12,23 @@ > > #include <stddef.h> > > #include <limits.h> > > > > +#ifdef __has_feature > > +#define HAVE_FEATURE(f) __has_feature(f) > > +#else > > +#define HAVE_FEATURE(f) 0 > > +#endif > > + > > static inline size_t hash_bits(size_t h, int bits) > > { > > /* shuffle bits and return requested number of upper bits */ > > +#if defined(ADDRESS_SANITIZER) || HAVE_FEATURE(address_sanitizer) > > + /* > > + * If the requested bits == 0 avoid undefined behavior from a > > + * greater-than bit width shift right (aka invalid-shift-exponent). > > + */ > > + if (bits == 0) > > + return -1; > > +#endif > > Oh, just too much # magic here :(... If we want to prevent hash_bits() > from being called with bits == 0 (despite the result never used), > let's just adjust hashmap__for_each_key_entry and > hashmap__for_each_key_entry_safe macros: > > diff --git a/tools/lib/bpf/hashmap.h b/tools/lib/bpf/hashmap.h > index d9b385fe808c..488e0ef236cb 100644 > --- a/tools/lib/bpf/hashmap.h > +++ b/tools/lib/bpf/hashmap.h > @@ -174,9 +174,9 @@ bool hashmap__find(const struct hashmap *map, > const void *key, void **value); > * @key: key to iterate entries for > */ > #define hashmap__for_each_key_entry(map, cur, _key) \ > - for (cur = ({ size_t bkt = hash_bits(map->hash_fn((_key), map->ctx),\ > - map->cap_bits); \ > - map->buckets ? map->buckets[bkt] : NULL; }); \ > + for (cur = map->buckets \ > + ? map->buckets[hash_bits(map->hash_fn((_key), > map->ctx), map->cap_bits)] \ > + : NULL; \ > cur; \ > cur = cur->next) \ > if (map->equal_fn(cur->key, (_key), map->ctx)) > > Either way it's a bit ugly and long, but at least we don't have extra > #-driven ugliness. This can work with the following changes in hashmap.c. I'll resend this as a whole patch. Thanks, Ian --- a/tools/lib/bpf/hashmap.c +++ b/tools/lib/bpf/hashmap.c @@ -156,7 +156,7 @@ int hashmap__insert(struct hashmap *map, const void **old_key, void **old_value) { struct hashmap_entry *entry; - size_t h; + size_t h = 0; int err; if (old_key) @@ -164,7 +164,9 @@ int hashmap__insert(struct hashmap *map, if (old_value) *old_value = NULL; - h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits); + if (map->buckets) + h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits); + if (strategy != HASHMAP_APPEND && hashmap_find_entry(map, key, h, NULL, &entry)) { if (old_key) @@ -208,6 +210,9 @@ bool hashmap__find(const struct hashmap struct hashmap_entry *entry; size_t h; + if (!map->buckets) + return false; + h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits); if (!hashmap_find_entry(map, key, h, NULL, &entry)) return false; @@ -223,6 +228,9 @@ bool hashmap__delete(struct hashmap *map struct hashmap_entry **pprev, *entry; size_t h; + if (!map->buckets) + return false; + h = hash_bits(map->hash_fn(key, map->ctx), map->cap_bits); if (!hashmap_find_entry(map, key, h, &pprev, &entry)) return false; > > #if (__SIZEOF_SIZE_T__ == __SIZEOF_LONG_LONG__) > > /* LP64 case */ > > return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits); > > -- > > 2.29.1.341.ge80a0c044ae-goog > >
