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NetBpfLoad: fix empty log_buf detection logic

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log_buf.size() was always BPF_LOAD_LOG_SZ and thus != 0

After changing ALOGD to ALOGI you now see (for example):
  NetBpfLoad: BPF_PROG_LOAD call for /apex/com.android.tethering/etc/bpf/net_shared/block.o (bind4_block_port) returned 'processed 55 insns (limit 1000000) max_states_per_insn 0 total_states 4 peak_states 4 mark_read 1' fd: 6 (ok)

(ALOGV/ALOGD's are effectively silently dropped by the KernelLogger we use)

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I4a296976ae3f1e2217c46d81ed48850fdfa95a3c
This commit is contained in:
Maciej Żenczykowski 2024-09-05 09:38:14 -07:00
commit ea1d8f6376
1 changed files with 18 additions and 10 deletions
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28
bpf/loader/NetBpfLoad.cpp
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@ -141,9 +141,6 @@ inline bool isUserdebug() {
#define BPF_FS_PATH "/sys/fs/bpf/"
// Size of the BPF log buffer for verifier logging
#define BPF_LOAD_LOG_SZ 0xfffff
static unsigned int page_size = static_cast<unsigned int>(getpagesize());
constexpr const char* lookupSelinuxContext(const domain d) {
@ -1006,7 +1003,7 @@ static int loadCodeSections(const char* elfPath, vector<codeSection>& cs, const
(!fd.ok() ? std::strerror(errno) : "no error"));
reuse = true;
} else {
vector<char> log_buf(BPF_LOAD_LOG_SZ, 0);
static char log_buf[1 << 20]; // 1 MiB logging buffer
union bpf_attr req = {
.prog_type = cs[i].type,
@ -1014,8 +1011,8 @@ static int loadCodeSections(const char* elfPath, vector<codeSection>& cs, const
.insns = ptr_to_u64(cs[i].data.data()),
.license = ptr_to_u64(license.c_str()),
.log_level = 1,
.log_size = static_cast<__u32>(log_buf.size()),
.log_buf = ptr_to_u64(log_buf.data()),
.log_size = sizeof(log_buf),
.log_buf = ptr_to_u64(log_buf),
.kern_version = kvers,
.expected_attach_type = cs[i].attach_type,
};
@ -1023,12 +1020,23 @@ static int loadCodeSections(const char* elfPath, vector<codeSection>& cs, const
strlcpy(req.prog_name, cs[i].name.c_str(), sizeof(req.prog_name));
fd.reset(bpf(BPF_PROG_LOAD, req));
ALOGD("BPF_PROG_LOAD call for %s (%s) returned fd: %d (%s)", elfPath,
cs[i].name.c_str(), fd.get(), (!fd.ok() ? std::strerror(errno) : "no error"));
// Kernel should have NULL terminated the log buffer, but force it anyway for safety
log_buf[sizeof(log_buf) - 1] = 0;
// Strip out final newline if present
int log_chars = strlen(log_buf);
if (log_chars && log_buf[log_chars - 1] == '\n') log_buf[--log_chars] = 0;
bool log_oneline = !strchr(log_buf, '\n');
ALOGD("BPF_PROG_LOAD call for %s (%s) returned '%s' fd: %d (%s)", elfPath,
cs[i].name.c_str(), log_oneline ? log_buf : "{multiline}",
fd.get(), (!fd.ok() ? std::strerror(errno) : "ok"));
if (!fd.ok()) {
if (log_buf.size()) {
vector<string> lines = Split(log_buf.data(), "\n");
// kernel NULL terminates log_buf, so this checks for non-empty string
if (log_buf[0]) {
vector<string> lines = Split(log_buf, "\n");
ALOGW("BPF_PROG_LOAD - BEGIN log_buf contents:");
for (const auto& line : lines) ALOGW("%s", line.c_str());