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bpf loader - finish support for kernel version conditional loading

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bpf program section names must be unique to prevent programs from
appending to each other, so instead the bpf loader will strip
everything past the final $ symbol when actually pinning
the program into the filesystem.

While at it add a little bit more logging.

Example on aosp cuttlefish 5.4.30 virtual device:
  D LibBpfLoader: bpf_prog_load lib call for /system/etc/bpf/offload.o (schedcls_ingress_tether_ether) returned fd: 8 (no error)
  D LibBpfLoader: cs[1].name:schedcls_ingress_tether_rawip$stub min_kver:0 .max_kver:40e00 (kvers:5041e)
  D LibBpfLoader: cs[2].name:schedcls_ingress_tether_rawip$4_14 min_kver:40e00 .max_kver:ffffffff (kvers:5041e)
  D LibBpfLoader: bpf_prog_load lib call for /system/etc/bpf/offload.o (schedcls_ingress_tether_rawip$4_14) returned fd: 9 (no error)
  I bpfloader: Attempted load object: /system/etc/bpf/offload.o, ret: Success

  $ adb shell ls -l /sys/fs/bpf | egrep offload
  -rw-rw---- 1 root network_stack 0 2020-04-22 01:27 map_offload_tether_ingress_map
  -rw-rw---- 1 root network_stack 0 2020-04-22 01:27 map_offload_tether_stats_map
  -r--r----- 1 root root          0 2020-04-22 01:27 prog_offload_schedcls_ingress_tether_ether
  -r--r----- 1 root root          0 2020-04-22 01:27 prog_offload_schedcls_ingress_tether_rawip

Test: builds, atest, proper program loaded on 5.4.30 aosp cuttlefish
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Id3fcb8e2a6b0087f704e77726e9961efc6145739
This commit is contained in:
Maciej Żenczykowski 2020-04-21 15:34:18 -07:00
commit 681f604b2e
1 changed files with 18 additions and 9 deletions
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27
libbpf_android/Loader.cpp
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@ -540,27 +540,36 @@ static int loadCodeSections(const char* elfPath, vector<codeSection>& cs, const
string fname = pathToFilename(string(elfPath), true);
for (int i = 0; i < (int)cs.size(); i++) {
string progPinLoc;
bool reuse = false;
string name = cs[i].name;
if (cs[i].prog_def.has_value()) {
if (kvers < cs[i].prog_def->min_kver) continue;
if (kvers >= cs[i].prog_def->max_kver) continue;
unsigned min_kver = cs[i].prog_def->min_kver;
unsigned max_kver = cs[i].prog_def->max_kver;
ALOGD("cs[%d].name:%s min_kver:%x .max_kver:%x (kvers:%x)\n", i, name.c_str(), min_kver,
max_kver, kvers);
if (kvers < min_kver) continue;
if (kvers >= max_kver) continue;
}
// strip any potential $foo suffix
// this can be used to provide duplicate programs
// conditionally loaded based on running kernel version
name = name.substr(0, name.find_last_of("$"));
bool reuse = false;
// Format of pin location is
// /sys/fs/bpf/prog_<filename>_<mapname>
progPinLoc = string(BPF_FS_PATH) + "prog_" + fname + "_" + cs[i].name;
string progPinLoc = string(BPF_FS_PATH) + "prog_" + fname + "_" + name;
if (access(progPinLoc.c_str(), F_OK) == 0) {
fd = bpf_obj_get(progPinLoc.c_str());
ALOGD("New bpf prog load reusing prog %s, ret: %d\n", cs[i].name.c_str(), fd);
ALOGD("New bpf prog load reusing prog %s, ret: %d\n", progPinLoc.c_str(), fd);
reuse = true;
} else {
vector<char> log_buf(BPF_LOAD_LOG_SZ, 0);
fd = bpf_prog_load(cs[i].type, cs[i].name.c_str(), (struct bpf_insn*)cs[i].data.data(),
cs[i].data.size(), license.c_str(), kvers, 0,
log_buf.data(), log_buf.size());
fd = bpf_prog_load(cs[i].type, name.c_str(), (struct bpf_insn*)cs[i].data.data(),
cs[i].data.size(), license.c_str(), kvers, 0, log_buf.data(),
log_buf.size());
ALOGD("bpf_prog_load lib call for %s (%s) returned fd: %d (%s)\n", elfPath,
cs[i].name.c_str(), fd, (fd < 0 ? std::strerror(errno) : "no error"));