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BpfMap - add pinned path based constructors

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(and remove the old straight from fd constructor)

Note that BpfMapRO is not yet truly compile time read-only,
since it still has methods that can modify things (although those
modifications will of course fail due to the map fd being r/o).

Test: build, atest with followup fixes
Bug: 129773125
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I70b511e3f0a62cd4d9d5a923e658b1086337ec4c
This commit is contained in:
Maciej Żenczykowski 2020-01-20 03:18:26 -08:00
parent 7c9a984f1d
commit dfd941f0fd
1 changed files with 17 additions and 15 deletions
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32
libbpf_android/include/bpf/BpfMap.h
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@ -46,25 +46,20 @@ template <class Key, class Value>
class BpfMap {
public:
BpfMap<Key, Value>() {};
explicit BpfMap<Key, Value>(int fd) : mMapFd(fd){};
// We could technically implement this constructor either with
// : mMapFd(dup(fd)) {} // fd valid in caller, we have our own local copy
// or
// : mMapFd(fd.release()) {} // fd no longer valid in caller, we 'stole' it
//
// However, I think we're much better off with a compile time failure, since
// it's better for whoever passes in a unique_fd to think twice about whether
// they're trying to pass in ownership or not.
explicit BpfMap<Key, Value>(base::unique_fd fd) = delete;
protected:
// flag must be within BPF_OBJ_FLAG_MASK, ie. 0, BPF_F_RDONLY, BPF_F_WRONLY
BpfMap<Key, Value>(const char* pathname, uint32_t flags) {
int map_fd = mapRetrieve(pathname, flags);
if (map_fd >= 0) mMapFd.reset(map_fd);
}
public:
explicit BpfMap<Key, Value>(const char* pathname) : BpfMap<Key, Value>(pathname, 0) {}
BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags) {
int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
if (map_fd < 0) {
mMapFd.reset(-1);
} else {
mMapFd.reset(map_fd);
}
if (map_fd >= 0) mMapFd.reset(map_fd);
}
base::Result<Key> getFirstKey() const {
@ -246,6 +241,13 @@ base::Result<void> BpfMap<Key, Value>::iterateWithValue(
return curKey.error();
}
template <class Key, class Value>
class BpfMapRO : public BpfMap<Key, Value> {
public:
explicit BpfMapRO<Key, Value>(const char* pathname)
: BpfMap<Key, Value>(pathname, BPF_F_RDONLY) {}
};
} // namespace bpf
} // namespace android